CN104404850A

CN104404850A - Method for improving bending tensile strength and durability of cement concrete for road

Info

Publication number: CN104404850A
Application number: CN201410658840.7A
Authority: CN
Inventors: 蒋新明
Original assignee: CHUZHOU CITY HIGHWAY ADMINISTRATION
Current assignee: Jiang Xinming
Priority date: 2014-11-18
Filing date: 2014-11-18
Publication date: 2015-03-11
Also published as: CN105294005A; AU2015101897A4; AU2015349248A1; CN105294005B; WO2016078522A1

Abstract

The invention discloses a method for improving bending tensile strength and durability of cement concrete for a road. The principle of buoyancy and a dense framework gradation theory are combined, in the design of a mix proportion, the use amount of coarse aggregate is increased, cement mortar is reduced, and an aggregate framework is formed; phenomena of coarse aggregate sinking and mortar floating in the concrete vibrating process are reduced as far as possible, bleeding is reduced, and the structural strength of an interfacial transition zone is improved, so that the bending tensile strength and durability of concrete are improved. The invention provides a design method of the mix proportion of pavement concrete with main characteristics of bending tensile strength and durability. When the crushed stone gradation is determined, measured coarse aggregate gradation corresponding to the maximum concrete volume weight is taken as selected gradation; the sand ratio can be reduced by 3%-4% than the standard, and the specific surface area and wetting water of aggregate are reduced; meanwhile, the use amount of cement is reduced, and improvement of concrete strength is facilitated; the pavement concrete with good workability, strength and durability is prepared, and the technical problems of large use amount and low bending tensile strength of former pavement concrete cement are solved.

Description

A kind of method improving road cement concrete bending tensile strength and durability

Technical field

The present invention relates to technical field of concrete, be specifically related to a kind of method improving road cement concrete bending tensile strength and durability.

Background technology

Along with the high speed development of Chinese national economy and highway transportation cause, there is the feature of " heavy duty, large discharge and canalized traffic " in highway transportation, heavy goods vehicle and overloaded vehicle sharply rise, cause the sharply increase that actual accumulated standard axle is secondary, cause road surface premature failure, thus the structural strength of highway pavement and functional performance are had higher requirement.Cement concrete pavement has the advantages such as rigidity is large, intensity is high, good stability, good endurance, long service life and maintenance costs are few.And along with the development of communication, domestic high-quality heavy traffic bitumen for road use becomes shortage gradually, and price rises steadily.Compare flexible pavement, cement concrete pavement is with the obvious advantage in bearing capacity and cost.

It should be noted that the axle of many regional haulage vehicles is heavily far longer than the single shaft 100KN of national regulation, the limiting load standard of twin shaft 180KN, high capacity waggon and automobile overload define Heavy Traffic.Heavy Traffic be not merely somewhere, certain endemism economized, but nationwide, generality.According to the investigation of some Importants such as Hebei, Henan, Shanxi, the overload ratio of more than 10 tons heavy goods vehicles is more than 40%, and some section reaches 80%, and extreme overload rate reaches 300%.So serious Heavy Traffic, the premature breakdown that cement concrete pavement is produced becomes more and more obvious, the road surface in many areas does not reach design life, the use initial stage namely there is fracture, purt mud, come to nothing, the damage such as faulting of slab ends, some section panel is even completely cracked, and service life of road surface is shortened greatly, and Pavement Condition decay is accelerated, maintenance costs constantly rises, and causes larger economic loss to society and transportation department.As one of the central core of circulation of Shanxi coal transmission, the normal domestic section, (putting down) highway Jiaozhuo of Zheng (state), within 1991, be open to the traffic, 30 years projected lives, but open to traffic has been scarred less than 3 years, the half range road surface of particularly sending a car from direction, Shanxi, more so, vehicle is advanced quite difficult for disconnected plate, sinking, hole ditch.In the past few years, relevant department drops into this section maintenance cost and reaches more than 4,000 ten thousand, exceedes the nearly half of construction investment.

Although cement concrete pavement has stronger anti-heavily loaded ability, because axle for vehicle carries the absolute increase of tonnage, actual accumulated standard axle carry be far longer than design axle carry, make cement concrete pavement produce fatigue damage.Large-tonnage heavy duty probably causes the disposable limiting damage of cement concrete pavement in some cases.Heavy Traffic has become the external factor of the cement concrete pavement most critical of earlier period damage on a large scale.The direct result of cement concrete pavement fatigue damage is that the road surface traffic capacity reduces, maintenance capacity sharp increase, and maintenance difficult, maintenance cost are high.

Meanwhile, along with country strengthens new countryside construction further, highway network construction and Country Road Construction have entered into the flourish new period.It is high that cement concrete pavement has supporting capacity, and anti-disaster ability is strong, and cost is low, and maintenance is easy, can make full use of the advantages such as local sandstone material, is more and more widely used in China's common road particularly highway construction of village of counties and townships.Since 2005, Chuzhou City newly reconstruct with overhaul engineering in complete cement concrete pavement altogether more than 154 kilometers, rural highway more than 1380 kilometer substantially all adopts cement concrete pavement.Therefore, research and develop high resistance bending tensile strength and high performance pavement concrete just seem very urgent with the requirement meeting cement concrete pavement development and have important practical significance.

The research of China in cement concrete strength is based on compressive strength, in " highway cement concrete pavement construction technique normalizing " (JTGF30-2003), based on the scientific achievement still obtained by State Scientific and Technological Commission 025 project, 025 project proposes with bending tensile strength the empirical formula method of the ordinary road design of concrete being index, orthogonal experiment, and propose bending resistance and draw the relation with compressive strength, the method mainly controls based on macro-mechanical property, simple, but design objective is single, mix-design adopts stage filling theory, aggregate is continuous grading, parameter and pavement performance contact defective tightness.In addition pass by the change that road surface cement concrete type type in the more than ten years, construction technology occurred, heavy duty, the pavement performance of Overload Traffic to cement concrete pavement propose stern challenge.Therefore, still there is sizable gap by functional performance design in existing the road cement concrete mixing proportion design method distance.

Cement concrete compression strength impact is aggregate and sand glue mutually, and interfacial transition zone (referring to there is the high pore layer of one deck about 5-10 micron early origin outside aggregate Interface) is less on concrete crushing strength impact.And concrete tensile strength impact is aggregate, sand glue and interfacial transition zone mutually.Due to the existence of interfacial transition zone, directly affect the bond stress of sand glue to building stones, when concrete is subject to action of pulling stress, sand glue and building stones are easy to be peeling in interfacial transition zone, cause " contribution rate " of building stones participation bending tensile strength not high.As can be seen here, cement concrete bending tensile strength produces " short-board effect " in interfacial transition zone.How to reduce interfacial transition zone, improve the bond stress of building stones and sand glue, allowing more building stones participate in intensity contribution is the key point improving concrete tensile strength and durability.

According to test, use cement concrete aggregate void content that the local building stones in Chuzhou make according to ordinary road concrete mix about 36%, and concrete medium sand colloid amasss and accounts for 53% of cumulative volume, aggregate volume accounts for about 47%, sand glue more than needed about 17%.Aggregate certainly will be suspended in sand glue by too much " sand glue more than needed ", makes concrete after having vibrated, before initial set, in semi liquid state feature.Due to Action of Gravity Field, unnecessary or have little time to participate in the hydrone of hydration reaction and to be squeezed floatings, generation " buoyancy effect ".The most jitty floated is intercepted by aggregate or gravel, and hydrone gets up in building stones or grit bottom, side enrichment, participates in the hydration reaction of interfacial transition zone, makes interfacial transition zone porosity and looseness, form bad interfacial transition zone.Bad interfacial transition zone causes the bond stress of sand glue to building stones sharply to decline, and then affects concrete tensile strength and durability, (as shown in figure 15, in figure, stain represents hydrone, G: gravity).

Take three kinds of measures can overcome inside concrete " buoyancy effect ", reduce the formation of bad interfacial transition zone, improve cement concrete bending tensile strength and durability: in cement concrete, adopt appropriateness " sand glue more than needed ", aggregate is utilized to form framework, make the concrete mixed by partially liquid to partially solid-state transition, aggregate gravity passes to basic unit by framework, the water be wrapped in inside sand glue will not extrude by aggregate, suppress the trend that free water molecule rises, overcome the generation of " buoyancy effect " to reach, and then reduce bad interfacial transition zone; While satisfied construction, reduce outer-area in unit-quantity as far as possible, thus reduce bad interfacial transition zone probability of happening from total amount; Adjustment sand coarse aggregate ratio, makes cement concrete inside " sand glue more than needed " content more be tending towards reasonable, reduces the absolute dosage of cement and water simultaneously.

Summary of the invention

It is simple that technical problem to be solved by this invention is to provide a kind of method, is convenient to the raising road cement concrete bending tensile strength of practical application and the method for durability.

Technical problem to be solved by this invention realizes by the following technical solutions:

Improve a method for road cement concrete bending tensile strength and durability, the application overcomes the concept of " buoyancy effect " by proposing, solve the difficult problem that ordinary concrete bending tensile strength is not high, and its concrete grammar is as follows,

1) determine by reducing inside concrete " glue the sand more than needed " (implication of glue sand more than needed: except filler aggregate is produced except space by principle analysis in conjunction with lot of experiments, for meeting cement concrete workability and workability and the glue sand added) content, the mix-design thinking of optimised coagulation soil internal construction, and propose the Design of Cement Concrete Mixture Ratio method of " two subtract take out ", namely sand coarse aggregate ratio reduces to 32% from 36% of routine, single cement consumption reduces to 330 kilograms by 380 kilograms of engineering in the past, has taken out " melon seeds sheet " this one-level aggregate;

2) local raw material are joined concrete with the examination of different glue sand content, determine " the rich glue sand " content be applicable to, in this, as the guide parameters of Design of Cement Concrete Mixture Ratio;

3) mix-design cement consumption is according to " highway cement concrete pavement construction technique normalizing " (JTGF30-2003) requirement, to be not less than 300kg/m ³for radix, progressively increase 10-15kg/m depending on raw material situation ³, by Mix Ratio Test determination cement consumption; Sand coarse aggregate ratio selection range is 29-32%, and every cubic meter of concrete water supply volume is by trial mix concrete mix, and the water supply volume reaching requirement workability (being generally 30-40S) corresponding is determined;

4) after substantially determining above-mentioned parameter by parallel test, conveniently absolute volume method can determine the preliminary match ratio of cement concrete, in conjunction with trial mix test and strength test, finally draws the design mixture proportion meeting construction workability and requirement of strength;

5) parameters scope: use the rubble of more than 9.5mm as aggregate (by maximum By Measuring The Volume Density determination grating); The fineness modulus of sand is advisable with 2.7-3.0; Recommendation sand coarse aggregate ratio is 29-32%; Folk prescription concrete cement consumption is at 330-340kg/m ³; The folk prescription the reinforcement of concrete water yield is 130-145kg/m ³.

For domestic X021 Ban Zhu road, Chuzhou City Laian County, this Cement Concrete Pavement Design bending tensile strength 4.5MPa, use Nanjing conch P042.5 class g cement, Liuhe District, Nanjing produce aggregate (maximum By Measuring The Volume Density determination grating is 30:70), the river, pond, Mingguang City sand (fineness modulus 3.0) of 9.5-19.0mm and 19.0-31.5mm two kinds of specifications.According to the thinking determination match ratio of new technology be, cement: water: sand: rubble=330:142:624:1456kg/m ³; This cement concrete pavement 28d bending tensile strength average 6.15MPa, improves 17.4% than the same period with the average 5.24MPa of ground ordinary concrete project; 28d splitting tensile strength, by reaching 4.31MPa, improves 21.4% compared with the 3.55MPa of ordinary concrete; 28d contract with dry rate drops to 90 × 10-6 by 120 × 10-6, reduces by 17.5%; 28d curing age unit wear extent reduces 4.6%; 28d infiltration height drops to 10.2mm by 12.9mm; Folk prescription concrete cement consumption 380kg/m ³drop to 330kg/m ³, save cement 50 kilograms for every cubic metre.

Above-mentioned framework compact type cement concrete is adopted to carry out construction Craft:

One. transport

1) before transporting the vehicle charging of concrete, answer peace and quiet compartment, watering profit wall, drains ponding, when filling with substance should move parking stall, prevent segregation, answer mortar leakage prevention in concrete transportation, leak material and pollute road surface, must not jolt segregation, must not arbitrarily stop in way, vehicle start and parking should be steady, and must there be covering measure in summer if desired, and discharging height must not be greater than 1.5m;

2) during haulage vehicle discharging, forbid collision slab or pull bar, once collision, should inform that site operation person remeasures correction in time;

3) concrete batching system is from discharging to transport, the complete permission maximum duration of making, 0.5 ~ 1.5 hour is generally according to construction temperature, exceeding regulation to pave and allow the concrete of maximum duration to be used for pavement spread, forbidding with to add water or additive method changes the workability of compound;

Two. pave

1), before concrete batching system paves, then to the position of template with support firm situation, installing etc. of dowel bar, pull bar checks comprehensively;

2) special messenger is arranged to command tipping truck, as far as possible point accurately discharging several times;

3), when concrete mix paves, must be undertaken by the order of first template edge, Ban Jiao, seam crossing; The position that coarse aggregate is too concentrated, must be distributed in the concrete mix of uniform quality and be gone; During with spade scraper concrete mix, the method for " button spade " must be adopted, must not spade be raised;

4) scene inspects mixture quality by random samples at random, and the on-the-spot slump controls, within 20 ㎜, firmly to clear out job site to underproof compound;

5) cause for some reason and stop work or reached for 2/3 initial setting time for more than 1 hour, should arrange constuction joint in the panel termination that making is good, discarding can not by the mix of jolt ramming; For the joint of stopping work within the above-mentioned time, wet gunnysack should be covered in joint to prevent joint loss of water, as downtime is long, must remove the compound without jolt ramming initial set;

6) concrete mix should be half flow regime, and the inclined-plane of adjacent two cars is discharging and the natural inclined plane after vibrating, and must not adopt the method operation of " catching up with slurry ";

7), when making fills out grade concrete, should count according to the time of making the latest of both sides Portland Cement Concrete Surface Course, and earliest time should not be less than regulation requirement; When making fills out grade concrete, should take safeguard measure to the edge of the surface layer that both sides have been completed, prevent from damaging and mucilage, face of doing is appropriate to the occasion at the standardized neat straight line of New-old concrete joint spatula, and the mortar of edges of boards should be removed clean;

Three. vibrate

1) vibrate and to lay by being no less than 1 internal vibration rod in every meter of width in scene, composition transverse-vibration tamper group, the continuous vibration compacting along cross section, and should to note at the bottom of road slab, inner and edge must not owe to shake or leak to shake;

2) during vibrating spear operation, vibrating head is made naturally to sink to concrete, unavailable depress with sudden force, should vertically insert, accomplish " fast inserting is pulled out slowly ", fast inserting is to prevent first for surface concrete jolt ramming, and with lower-layer concrete generation layering, segregation phenomenon, pulling out slowly is fill up to make concrete have enough time the space formed when vibrating head is extracted out;

3) vibrating spear insertion depth should from basic unit 3 ~ 5cm, answer collision free template, reinforcing bar, dowel bar and pull bar simultaneously, more must not take to impel concrete to shake by the method for vibrating head vibration reinforcing bar close, otherwise will reinforcement location be made to change because of vibration, also can reduce the adhesion stress between reinforcing bar and concrete, even can mutually depart from; During operation, vibrating head insert the concrete degree of depth should not exceed rod long 2/3 ~ 3/4, otherwise vibrating head will not be drawn out easily and cause flexible pipe to damage; More flexible pipe must not be inserted in concrete, in case mortar etch and infiltrate flexible pipe and damage parts; Vibrator is in use as too high in temperature, answers hard stop to cool and checks, as parts fault, will place under repair in time, during winter low temperature, before vibrator operation, adopt and slowly heat, after the lubrication oil in barred body is thawed, and can operation;

4) completed the position of jolt ramming at vibrating spear, propose slurry jolt ramming crisscross twice with plate vibrator, first pass oscillation crosswise makes concrete compaction comprehensively, and second time longitudinal direction is vibrated, and makes surfacing;

5) vibrating plate answers step by step tray to carry out in proper order line by line, can not drag and shake, tiltedly shake, vibrating plate continuing a position, time of vibration should not be less than 15 seconds, vibrating plate must be lifted and displacement by two people, must not freely place or long-time sustained vibration, shift control is to be limited with edge bleeding thickness 3 ± 1mm bottom vibrating plate; When bleeding flows into horizontal concrete in mould, get final product failure of oscillation, must not shake again in concrete initial set state, the vibration effect of surrounding also must not be made to the concrete of initial set, in order to avoid affect concrete quality;

6) bottom walking beam, (front-axle beam) should weld or the coarse aggregate compacting tooth (oblique 45 °, spacing 2-4 ㎝) of fitting depth about 4mm, ensures the surperficial mortar thickness of (4 ± 1) mm;

7) walking beam should vertically longitudinally at the uniform velocity tow by road surface center line, makes surperficial bleeding uniform ground, drags shake in flattening course at walking beam, lacks material place and concrete batching system should be used to fill up, and not handy sharp sand slurry is filled up; The position that material is many should be rooted out;

8) when vibrating, artificial feed supplement should be aided with, the displacement of jolt ramming effect, template, pull bar, dowel bar, distortion should be checked at any time, loosen, the situation such as spillage, and to correct in time;

Four. leveling facing

1) after walking beam jolt ramming, should drag rolling bar and come and go and propose slurry leveling for 2 ~ 3 times, first pass is answered short distance slowly to push away to roll or drag and is rolled, and longer distance at the uniform velocity should drag and roll later, and caught up with all the time by cement paste in rolling bar front, superfluous water mud should be rooted out;

2) surface after rolling is dragged to adopt 3m floating rule, each several all over leveling facing in length and breadth, and check that surface evenness is until planeness meets the requirements with plaster ground;

3) wiping one's face of cement concrete is received slurry and must not be less than 3 times (slump number of times of wiping one's face more greatly should corresponding increase), first time receives slurry and carries out immediately after leveling terminates, its Main Function continues screeding concrete surface, presses down surperficial coarse aggregate simultaneously; Second time should be carried out before bleeding, and it act as screeding concrete surface; When bleeding terminates, when surface no longer includes Free water, can carry out third time and receive slurry, third time must be smeared with iron and be carried out, and complete facing, its effect prevents from bleeding from terminating rear surface occur bleeding cement and peel simultaneously;

4) all top of concrete and planeness should be controlled with the inspection of 4m ruler after each receipts slurry;

5) plucking: after the face operation of doing terminates, should according to the requirement of the design road pavement surface average texture degree of depth, in time by concrete surface wharf's pavement quality;

Five. seam joint-cutting is constructed

1) longitudinal joint should be constructed according to the regulation of design document, longitudinal joint is longitudinal constuction joint, pull bar is at formwork erection after-pouring, install before concrete, the pull bar of longitudinal constuction joint is then installed through the tie rod hole of template, and when closing up, longitudinal joint top will brush pitch, and must not to be coated on pull bar and (to be coated with one time after clearing up side during form removal, close up and be coated with one time again before noon), after form removal, longitudinal joint must be cleaned out (malthoid of particularly caulking joint and mortar), then half portion brush longitudinal joint pitch thereon; Wide, the thick transparent adhesive tape caulking joint of form joint place, and remove after form removal;

2) lateral contraction is sawn into after being sewn on concrete scleroma (with reference to desirable experience number 250 temperature hour or on-the-spot examination saw), too early unsuitable, with avoid occurring seam along uneven, hair stubble, gap, gnaw the phenomenons such as limit; Can not be too late, to prevent, concrete strength is high causes joint-cutting difficulty, more mustn't there is disconnected plate, must note during joint-cutting observing, principle is " energy Qie Zeqie, peaceful early late ", for edges of boards, due to template cause joint-cutting must supplement joint-cutting or form removal with small-sized joint cutter not as good as limit place after to mend with special joint cutter and cut, ensure that seam is through over the surface of the panel, avoid edges of boards arrisdefect;

3) horizontal expansion joint (E.J.) should be in 90 ° with Lu Zhizheng line, slotted wall iron sticks up stickfast, slotted wall must vertically, and gap width is consistent, must not even starch in seam, expansion joint plate is established in bottom, gap, top embedding sewing, expansion joint plate should be prefabricated in advance, before prefabricated expansion joint plate embeds, should make slotted wall clean dried, expansion joint plate and slotted wall are combined closely;

4) Pavement Concrete joint-cutting special machine is adopted to carry out joint-cutting, and select thick 3-5mm joint-cutting blade, joint-cutting depth design requires as 6cm, transverse contraction joint cuts: horizontal constuction joint adopts saw kerf, stitch dark 6cm, wide 5mm, must maintain sufficient water filling during cutting, underwayly will observe blade water filling situation;

Six. form removal

1) striking time should be determined according to construction temperature and concrete strength growth pattern, round the clock during temperature on average 20 DEG C, allows striking time to be 30 hours, during temperature on average 25 DEG C, allows striking time to be 24 hours, must not be collided at this moment in section;

2) should be careful during form removal, the corner angle of concrete slab, tongue and groove must not be damaged, brushing pitch after the cleaning of form removal trailing flank;

Seven. health

1) cement concrete pavement layer survive after maintenance work be divided into initial curing and late maintaining, the moisturizing watering method of curing that initial curing (leveling facing terminates to lancing time section) adopts geotextiles to cover, late maintaining (joint-cutting terminates to end to health) adopts the double-deck moisturizing watering method of curing of covered with plastic film in geotextiles, and special messenger must be established often to make an inspection tour, guarantee health situation, health is complete waters gap-grouting material at saw kerf place, should remove the interim close stifled material in seam before the cementation of fissures, seam apical side height is concordant with road surface;

2) health should focus on the wet curing of first 7 days especially, and should strengthen watering, keep enough humidity, health number of days is preferably 14 ~ 21 days, and hot weather is no less than 14 days, and microthermal climate is not less than 21 days;

3) special messenger should be had between concrete slab preserving period to check health situation, rectify a deviation at any time.

The invention has the beneficial effects as follows: to have intensity high for the cement concrete pavement that the present invention lays, good stability, good endurance, application life compared with long, routine servicing expense is few, and is conducive to the advantages such as driving at night; Decrease maintenance and the maintenance cost in later stage, be conducive to the construction of resource-conserving and environment-friendly society.

Accompanying drawing explanation

Fig. 1 is three kinds of metaling grading concrete unit weight trial curves;

Fig. 2 is cement consumption 320kg/m ³time, the flexural tensile strength value (28d) that the change of sand coarse aggregate ratio, water/binder ratio is corresponding;

Fig. 3 is cement consumption 340kg/m ³time, the flexural tensile strength value (28d) that the change of sand coarse aggregate ratio, water/binder ratio is corresponding;

Fig. 4 is cement consumption 360kg/m ³time, the flexural tensile strength value (28d) that the change of sand coarse aggregate ratio, water/binder ratio is corresponding;

Fig. 5 is cement consumption 380kg/m ³time, the flexural tensile strength value (28d) that the change of sand coarse aggregate ratio, water/binder ratio is corresponding;

Fig. 6 is sand coarse aggregate ratio when being 31%, the flexural tensile strength value (28d) that the change of cement consumption, water/binder ratio is corresponding;

Fig. 7 is sand coarse aggregate ratio when being 33%, the flexural tensile strength value (28d) that the change of cement consumption, water/binder ratio is corresponding;

Fig. 8 is sand coarse aggregate ratio when being 35%, the flexural tensile strength value (28d) that the change of cement consumption, water/binder ratio is corresponding;

To be sand coarse aggregate ratio be Fig. 9 31%, cement consumption 340kg time, the flexural tensile strength value (28d) that water/binder ratio change is corresponding

Figure 10 is that " plain edition " contrasts with " modified " cement concrete compression strength;

Figure 11 is that " plain edition " contrasts with " modified " cement concrete bending strength;

Figure 12 is that " plain edition " contrasts with " modified " cement concrete splitting tensile strength;

Figure 13 is " plain edition " and " modified " cement concrete Contrast of Wear Resistance;

Figure 14 is that " plain edition " contrasts with " modified " Anti-Penetrability of Cement Concrete;

Figure 15 is conventional pavement concrete internal dynamic schematic diagram before being initial set;

Figure 16 is that the utility model concrete aggregate forms frame construction schematic diagram.

Detailed description of the invention

The technological means realized to make the present invention, creation characteristic, reaching object and effect is easy to understand, below in conjunction with concrete diagram, setting forth the present invention further.

Improve a method for road cement concrete bending tensile strength and durability, propose the concept of " buoyancy effect ", solve the difficult problem that ordinary concrete bending tensile strength is not high, its concrete grammar is as follows,

1) to be determined by reducing inside concrete " more than needed glue sand " in conjunction with lot of experiments by principle analysis that (sand coarse aggregate ratio is excessive, cement mortar is too much had more than needed, unit consumption of water is bigger than normal, cause the flexural tensile strength of cement concrete not high) content, the mix-design thinking of optimised coagulation soil internal construction, and propose the Design of Cement Concrete Mixture Ratio method of " two subtract take out ", namely sand coarse aggregate ratio reduces to 32% from 36% of routine, single cement consumption reduces to 330 kilograms by 380 kilograms of engineering in the past, has taken out " melon seeds sheet " this one-level aggregate;

Test shows, novel pavement cement concrete aggregate void content is about about 42%, and cement concrete medium sand glue content is about 48%, sand glue more than needed about 6%, " the sand glue more than needed " of appropriateness ensure that under main aggregate forms the prerequisite of framework, have enough sand glue to fill up space, construction workability is unaffected; Also can meet (as shown in figure 16) even if aggregate makes a variation on a small quantity.

One. transport

Two. pave

Three. vibrate

6) bottom walking beam, (front-axle beam) should weld or the coarse aggregate compacting tooth (oblique 45o, spacing 2-4 ㎝) of fitting depth about 4mm, ensures the surperficial mortar thickness of (4 ± 1) mm;

Four. leveling facing

Five. seam joint-cutting is constructed

Six. form removal

Seven. health

Material selec-tion:

Cement: cement is the cementitious materials of cement concrete, the character of cement concrete depends on the quality of cement to a great extent, when selecting component materials of concrete, must rationally be selected cement type mod sum label.Selecting of cement should by regulation in JTG F30-2003 " highway cement concrete pavement construction technique normalizing ", and the quality requirement of cement should meet all standard in " general purpose portland cement examination criteria " (GB175-2007).Wherein, the intensity of cement and volume stability have the greatest impact to concrete quality: cement strength is the important computations parameter of cement concrete and Mortar Mixing Ratio Design and Experiment; The volume stability of cement is poor, the problem such as easily cause concrete structure to ftracture, to burst apart.Therefore the reliable cement of stay in grade must be selected to be vital." pearl " board P.O42.5 cement that the present embodiment selects pearl cement plant, Chuzhou to produce, concrete physical and mechanical property is in table 1.

The physical and mechanical property (place of production: pearl cement plant, Chuzhou) of table 1 cement

Coarse aggregate (rubble): coarse aggregate is concrete chief component is also one of key factor affecting concrete strength, and coarse aggregate depends primarily on kind, mechanical property, surface characteristics and the grating etc. of gathering materials on concrete impact.According to existing experience and technical specification, Class II highway and following grade highway cement concrete crushed stone nominal maximum particle diameter thereof should not be greater than 31.5mm, general employing three kinds of size coarse aggregates carry out grading composition, but according to this Project design thinking, in order to form aggregate framework, only adopting the debugging grating of gathering materials of 2.36-13.2mm, 4.75-26.5mm two kinds of specifications, cancelling 5-10mm rubble, increase concrete workability, reduce damping action.5-10mm rubble elongated particles is large, and specific area is large, and when the content of this rubble is too much, concrete mix becomes rough discrete, and workability is deteriorated, and is easy to fracture simultaneously, also affects concrete strength.

Strictly should control grating, flat-elongated particles, the crush values of coarse aggregate in mix-design well, if the flat-elongated particles gathered materials is too much or crush values is excessive, under equal match ratio, concrete intensity is lower.The present embodiment selects Dingyuan west thirty shop rubble, and specific performance is in table 2.

Table 2 rubble the performance test results (place of production: thirty shop, west, Dingyuan County)

Fine aggregate (sand): in pavement of road engineering concrete, fine aggregate generally adopts natural sand, fineness modulus is between 2.5 ~ 3.0, and mud content must not more than 2%, and sand is too thin or mud content is too much, can increase concrete shrinkage crack.This problem selects river, pond, Mingguang City sand, and specific performance is in table 3.

The performance test results (place of production: Mingguang City Chi He) of table 3 sand

Mixing water: in concrete mixing water, normally must not condense and the objectionable impurities hardened, as grease, carbohydrate etc. containing affecting cement.Every water that can drink and clean natural water, can be used for mixing concrete, and the present embodiment adopts general drinking water.

1, macadam gradating is determined

The rubble of 2.36-13.2mm, 4.75-26.5mm two kinds of specifications is sieved, with meeting coarse aggregate synthesis scope regulation in " job specfication " after the mixing of different ratios.Then by maximum By Measuring The Volume Density determination optimum gradation.According to engineering experience, the general 2.36-13.2mm of macadam gradating accounts for 25%, 4.75-26.5mm accounts for 75%.Add the sand of 35% of gross weight of gathering materials after mixing in varing proportions with above two kinds of dimension crushed stones, then add the phase application quantity cement and water determined by benchmark match ratio.Now cement mortar is as rubble sliding agent, compound is loaded jolt ramming on a vibration table in 25 ~ 30L capacity tube, shake while gather materials supernatant in press-in concrete with spatula, and multiple pressure enters some coarse aggregates as far as possible, floating till after vibration compacting volume is unchanged.Record the corresponding coarse aggregate grating of maximum concrete density for selected optimum gradation.

Coarse aggregate 4.75-26.5mm and 2.36-13.2mm carries out unit weight test with 60:40,70:30,80:20 tri-kinds of grating concrete batchings respectively, and result of the test is as shown in table 4, Fig. 1.

Table 4 three kinds of coarse aggregate grading concrete value of bulk density

Join result of the test according to mixing, the concrete density value parabolically form of three kinds of coarse aggregate grating preparations, wherein, the unit weight of 70:30 ratio is maximum, determines that optimum gradation is 70:30.Therefore, the optimum gradation of 4.75-26.5mm rubble and 2.36-13.2mm rubble should be 70:30.

2, the determination of sand coarse aggregate ratio

In existing " job specfication ", the determination of sand coarse aggregate ratio determines by rule of thumb according to road panel thickness of slab and sand fineness modulus.According to this Project design thinking, on the basis of existing specification, suitably sand coarse aggregate ratio should be reduced.The concrete sand coarse aggregate ratio determined by existing specification is 35%, and therefore, getting sand coarse aggregate ratio is respectively that 35%, 33%, 31% mixing concrete carries out concrete mix proportion experiment, thus determines optimum sand coarse aggregate ratio.Result of the test is in table 5 and Fig. 2 to Fig. 5.

Table 5 Mixture ratio design data

This serial Mix Ratio Test shows: the relation parabolically type of sand coarse aggregate ratio and flexural tensile strength, and when namely sand coarse aggregate ratio is positioned at high point or low spot, corresponding flexural tensile strength is higher, and flexural tensile strength corresponding to intermediate point is unsatisfactory.On the whole, during unit cement consumption 340kg, sand coarse aggregate ratio 31% and the corresponding 28 days flexural tensile strengths of sand coarse aggregate ratio 35% all meet design requirement, concrete 28 days flexural tensile strengths comparatively sand coarse aggregate ratio 31% height that sand coarse aggregate ratio 35% is prepared, but form skeleton better in order to ensure coarse aggregate, select the sand coarse aggregate ratio of 31% as final argument.

3, the determination of cement consumption

According to " job specfication ", in order to meet life requirement, when Class II highway adopts 42.5 class g cement, least unit cement consumption is 300kg, is 382.7kg/m by the cement consumption that calculates of preliminary match ratio simultaneously ³.According to this project thinking, the increase of coarse aggregate content causes surface of aggregate to amass decline to a certain degree, thus cement consumption is corresponding decreases.Therefore, getting cement consumption is respectively 320kg/m ³, 340kg/m ³, 360kg/m ³, 380kg/m ³carry out concrete mix proportion experiment determination cement optimum amount.Result of the test is in table 5 and Fig. 6 to Fig. 8.

In above-mentioned a series of Mix Ratio Test, when sand coarse aggregate ratio, water/binder ratio one timing, that flexural tensile strength is higher is cement consumption 340kg, 360kg.Merely increasing cement consumption is infeasible to improve concrete strength, because limit by workability, water/binder ratio remains unchanged, and the active ingredient in unit cement colloid does not increase, thus the cementing strength of cement colloid does not improve, flexural tensile strength also can not be improved naturally.

In general, intensity of test block is made when cement consumption is at 360kg higher than cement unit dose 340kg.But the two difference is limited, and the intensity results of 340kg cement consumption test block is also well beyond requirement of strength.Therefore, from the viewpoint of economy, think that unit cement consumption 340kg is suitable feasible.

4, the determination of water/binder ratio

Water/binder ratio is one of main factor affecting concrete strength.In theory, the water/binder ratio needed for the abundant aquation of cement is generally about 0.23, but during with such water/binder ratio mixing concrete mix, compound is too stiff, and under certain condition of vibrating, concrete is difficult to shaping closely knit.When actual mixing compound, often add more water to obtain necessary mobility.According to " job specfication ", in order to meet life requirement, the maximum water/binder ratio of Class II highway is 0.46, is 0.41 by the water/binder ratio that calculates of preliminary match ratio simultaneously.According to the mentality of designing of this project, gray scale of fetching water respectively is 0.41,0.43,0.45 carry out ruggedness test.Keep unit consumption of water substantially identical with benchmark match ratio, according to " fix water supply volume " rule, this change of water/binder ratio to concrete mobility without considerable influence.Result of the test is in table 5 and Fig. 9.

Can be found by a series of Mix Ratio Test: when sand coarse aggregate ratio get 31%, cement consumption be 340kg time, along with the increase of water/binder ratio, concrete 28 bending tensile strength slightly declines, but concrete 28 bending tensile strength is not very sensitive to water/binder ratio on the whole.This is because the cement concrete strength designed by this problem is mainly derived from the cage construction of coarse aggregate, the impact by water/binder ratio is less, and this also demonstrates the reasonability of this Subject Design thought further.Can find by comparing us, 28 days flexural tensile strengths of water/binder ratio 0.41,0.43,0.45 correspondence all meet design requirement.Therefore, consider from the angle of economy, the final water/binder ratio of the present embodiment gets 0.45.

According to above result of the test, according to Design of Cement Concrete Mixture Ratio principle, ensure again while taking into account economy that pavement concrete will have enough bending tensile strengths, suitable service behaviour, superior durability, final test room match ratio is defined as: cement: water: sand: rubble=340kg:153kg:608kg:1353kg.

Compressive strength test

The method (T0553-2005) of test concrete anti-compression ultimate strength in test basis " testing regulation ", test specimen is the cube of 150mm × 150mm × 150mm, test the compressive strength of two kinds of different mixture ratio concrete different larval instar, " plain edition " and " modified " grating pattern proportioning of cement concrete that design strength is F5.0 and result of the test are as shown in table 6 to 8 and Figure 10:

The common mix-design list of table 6 F5.0

Table 7 F5.0 improves mix-design list

Table 8 F5.0 match ratio compressive strength test result gathers

By relatively finding, compare and " plain edition " cement concrete, " modified " cement concrete 7d compressive strength has raising very by a small margin, and about 3.68%; But 28d compressive strength reduces 2.36% on the contrary.Therefore, comprehensive above-mentioned conclusion, can tentatively think: " modified " grating pattern is very limited to raising cement concrete 7d compressive strength, and is unfavorable for the performance of cement concrete 28d compressive strength.

Rupture strength is tested

The method (T0558-2005) of test agent on crack resistance of concrete folding ultimate strength in test basis " testing regulation ", test specimen is the corner cube prism girder of 150mm × 150mm × 550mm, three branch place two points are adopted to load and 3 free support formula experimental rigs, test the rupture strength of two kinds of different mixture ratio concrete different larval instar, " plain edition " and " modified " grating pattern proportioning of cement concrete that design strength is F5.0 and result of the test are as shown in table 9 to 11 and Figure 11:

The common mix-design list of table 9 F5.0

Table 10 F5.0 improves mix-design list

Table 11 F5.0 match ratio rupture strength result of the test gathers

Divide into groups in Figure 11 1,2 and grouping 3,4 corresponding be respectively " plain edition " and " modified " grating pattern cement concrete, known by comparing two kinds of grating pattern cement concrete 7d, 28d rupture strengths, " modified " cement concrete 7d, 28d rupture strength all has the raising of certain amplitude, compared with " plain edition " cement concrete bending strength, 7d rupture strength increase rate reaches 19.8%, and 28d rupture strength increase rate also reaches 17.9%.Therefore, comprehensive above-mentioned conclusion, can tentatively think: " modified " grating pattern is effectively to raising cement concrete 7d and 28d rupture strength, adopt " framework compact " grating pattern cement concrete can significantly improve its rupture strength, refinforced cement concrete flag is to the resistant function of vehicular impact load.

Cement concrete splitting tensile strength is tested

The method (T 0560-2005) of test concrete splitting intensity in test basis " testing regulation ", test specimen is the cube of 150mm × 150mm × 150mm, first in the middle part of test specimen, the position of splitting surface is made in line, then test specimen is placed on the center of testing machine lower platen, upper, pad with circular arc filler strip and each one of bed course between lower platen and test specimen, filler strip is vertical with end face time shaping, should uniform load continuously during test, loading velocity is 0.06MPa/s, test the cleavage strength of two kinds of different mixture ratio concrete different larval instar, the match ratio identical with rupture strength test specimen is adopted to make test specimen, " plain edition " and " modified " grating pattern cement concrete splitting tensile strength result of the test is as shown in table 12 and Figure 12:

Table 12 F5.0 match ratio splitting tensile strength result of the test gathers

With cement concrete bending strength rule similar be, " modified " cement concrete 7d, 28d splitting tensile strength all has the raising of certain amplitude, compared with " plain edition " cement concrete splitting tensile strength, 7d splitting tensile strength increase rate reaches 36.5%, and 28d splitting tensile strength increase rate reaches 43.6%.Along with the change of cement concrete grating pattern, its 7d, 28d splitting tensile strength occurs and its 7d, the phenomenon that 28d rupture strength Changing Pattern is similar, this is understandable, found by a lot of scholar's research, cement concrete bending strength and its splitting tensile strength all have stronger power exponential function correlation, this also therewith research conclusion be consistent, therefore, comprehensive above-mentioned conclusion, can reach a conclusion: adopt " framework compact " grating pattern cement concrete can significantly improve its splitting tensile strength, energy refinforced cement concrete flag is to the resistant function of vehicular impact load, improve road slab application life, advantageously in the performance of pavement performance.

Life test

Concrete durability refers to that concrete is under the effect of natural environment, environment for use and material internal factor, in the goal service life of designing requirement, do not need to spend substantial contribution consolidation process and keep the ability of its safety, using function and appearance requirement, or the effect of concrete opposing weather, chemical erosion, wearing and tearing or other destructive process any ability.Economic durable Novel cement concrete should be not only high-strength pavement concrete, and should be high performance pavement concrete, has high-durability.The durability of cement and concrete pavement is the frost resistance of abrasion resistance, dry shrinkage resistance, impermeability, northern area and fatigue-resistance characteristics mainly.Due to laboratory condition restriction, the cement concrete life test that this project is carried out comprises: abrasion test, dry shrinkage testing, impermeability test.Indoor water cement concrete fatigue test method, after test conditions maturation, being carried out supplementing, being verified the improvement of " modified " grating pattern cement concrete fatigue performance.

Cement concrete abrasion test

Generally, road surface is by when repeatedly rubbing, and what be first worn is concrete surface cement screedn.Therefore, the abrasion resistance of cement concrete surface screed wear-resistingly has very important effect to concrete.This problem adopts TNS-04 Cenmented sand wearproof tester, test specimen is 150mm × 150mm × 150mm cube standard specimen, undertaken by " testing regulation " regulation, before test, test specimen is dried to constant weight in 60 DEG C of baking ovens, then grinding 50 turns on cement mortar testing machine, wear area is 0.0125m2, and calculation testing piece unit area wear extent, describes concrete anti-wear performance in this, as standard.Result of the test is as shown in table 13 to 14 and Figure 13.

The common match ratio of table 13 F5.0 and improvement mix-design list

Table 14 F5.0 match ratio unit wear extent result of the test gathers

As can be seen from Figure 13 two kinds of grating pattern cement concrete unit wear extent Experimental Comparison results: after adopting " modified " grating pattern, 28d curing age concrete unit wear extent decreases 4.6%.

By finding the wear process research of cement concrete, the wearing and tearing of cement concrete are complicated physical mechanics processes.With regard to common vehicle abrasion condition, the key wear form of pavement concrete is fatigue wear and abrasive wear.With regard to concrete material composition, concrete wear resistance mainly with the kind of cement and admixture, cement consumption, cement strength and relevant with particle diameter with the cementitiousness gathered materials, hardness of gathering materials.Improve the measure of concrete abrasion-resistant performance, should be improve concrete fracture toughness, reduce fragility, reduce grown-in defects, improve hardness and reduce modulus of elasticity." modified " grating cement concrete water/binder ratio reduces, and structure is tending towards fine and close, therefore causes anti-wear performance to improve, but only relies on the improvement of grating pattern, can not improve concrete abrasion-resistant very significantly.

Cement concrete drying shrinkage is tested

The drying of the road cement concrete is shunk and is referred to that concrete is after stopping maintenance, the adsorbed water in internal capillary hole and gelling hole is lost and the irreversible contraction occurred in undersaturated air, data is had to show, drying shrinkage often can account for 80% ~ 90% of road concrete contraction total amount, the present embodiment carries out laboratory test research for " plain edition " and " modified " cement concrete, evaluates cement concrete grating pattern to the impact of the road cement concrete shrinkage performance.Test adopts the comparator of regulation in " testing regulation " to survey nail method and measures the air shrinkage value of cement concrete in each length of time, and evaluate concrete shrinkage performance with contract with dry rate (air shrinkage value/test specimen base is long), adopt the match ratio identical with abrasion test to make test specimen, test specimen base is long is 515mm.Two type concrete shrinkage experimental test results are as shown in Table 15.

Table 15 F5.0 match ratio dry shrinkage testing result gathers

Can find out from upper table: " plain edition " cement concrete 28d drying shrinkage is 120 × 10-6, and " modified " cement concrete 28d drying shrinkage is 99 × 10-6, reduce about 17.5% than " plain edition ", " modified " cement concrete drying shrinkage is short compared with " plain edition " for stationary phase as can be seen here.This is mainly due to after " modified " grating pattern cement concrete employing framework compact type grating, water/binder ratio and water supply volume all reduce than " plain edition " grating pattern cement concrete, pore structure of cement stone improves, more closely knit, being strengthened in interfacial transition zone, improves very significantly so the shrinkage performance of " modified " grating pattern cement concrete has compared with " plain edition " grating pattern cement concrete.

Standard Test Method for Permeation Resistance of Cement Concrete

Road concrete is the gas, liquid, solid three-phase produced by hydrated cementitious and the porous heterogeneous material deposited, and it has certain water permeability.The permeance property height of road concrete directly affects the speed that liquid (or gas) infiltrates, after harmful liquid or gas infiltrate inside concrete, series of physical chemistry and mechanical function will be produced with component materials of concrete, and water can also transport corrosion products outside concrete bodies in time, then supplement erosion ion.In addition, when road concrete suffers multigelation, the saturation water in concrete also can cause freeze-thaw damage, one of water or the condition of alkali-aggregate reaction.Therefore, impermeability is also improve and ensure the major influence factors of concrete durability.According to " testing regulation " cement concrete impermeability test T0568 method, the match ratio identical with abrasion test is adopted to make test specimen, test the seepage-resistant grade of " plain edition " and " modified " two kinds of different cement concretes respectively, evaluate cement concrete grating pattern to the impact of the road cement concrete seepage-resistant grade, result of the test is shown in table 16, and infiltration high measure result is as shown in table 17 and Figure 14.

Table 16 F5.0 match ratio impermeability test result gathers

Table 17 two kinds of different gradation pattern cement concrete infiltration height result of the tests gather

Can be found out by " plain edition " grating pattern cement concrete and " modified " cement concrete permeability resistance result of the test, " modified " cement concrete comparatively " plain edition " cement concrete seepage-resistant grade is improved to some extent, this causes seepage-resistant grade different due to the proportioning of cement concrete difference of two kinds of grating patterns, " modified " cement concrete has framework dense structure, can improve concrete permeability resistance, be one of key factor of Concrete Structure durability.

(1) " modified " grating pattern is effectively to raising cement concrete 7d and 28d rupture strength, adopt framework compact type cement concrete can significantly improve its rupture strength, refinforced cement concrete flag is to the resistant function of vehicular impact load.

(2) adopt framework compact type cement concrete can significantly improve its splitting tensile strength, can refinforced cement concrete flag to the resistant function of vehicular impact load, improve road slab application life, advantageously in the performance of pavement performance.

(3) " modified " grating pattern cement concrete water/binder ratio reduces, and structure is tending towards fine and close, therefore causes anti-wear performance to improve, but only relies on the improvement of grating pattern, can not improve concrete abrasion-resistant very significantly.

(4) " modified " grating pattern cement concrete is little compared with " plain edition " grating pattern cement concrete 28d drying shrinkage, drying shrinkage is short for stationary phase, and the shrinkage performance of " modified " grating pattern cement concrete comparatively " plain edition " grating pattern cement concrete has and improves very significantly.

(5) " modified " grating pattern cement concrete is improved to some extent compared with " plain edition " grating pattern cement concrete seepage-resistant grade.

Experiment Road overview

According to laboratory test result of study, rely on " S311 Chu determines the western thirty shop section overhaul engineering in road (Class II highway) " to be test section, this project overview is as follows:

(1) the key technical indexes:

1, road quality classification: Class II highway

2, designed driving speed: 60 kilometers/hour

3, subgrade and pavement: roadbed is wide 18 meters, road surface is wide 15 meters

4, road structure is followed successively by 26cm Portland Cement Concrete Surface Course, 18cm cement stabilized macadam base, 36cm Lime-soil subbase from top to bottom

5, design load: highway-II grade

6, designed flood frequency: large jackshaft is 1/100; Foot bridge, culvert, roadbed are 1/50

(2) unit in charge of construction and supervisor:

This engineering is constructed by Dingyuan County road and bridge engineering Co., Ltd, the management of Chuzhou City Hong Xin supervision companies.Detect Chuzhou City traffic engineering inspection center of unit.

Test section is detected and is divided into following three kinds of situations:

(1) finished product concrete inspection sample: unit in charge of construction arranges special messenger, special train every day, delivers to Chuzhou City traffic engineering inspection center by the mixed concrete that the same day gathers and detects.

(2) core detects: finished product concrete gets core by 7 days, 28 days scenes, coordinates Chuzhou City traffic engineering inspection center to detect the concrete rupture strength of finished product and compressive strength.

(3) strict Control Engineering progress, and gather finished product concrete data in time.

Experiment road section construction instructs

It is high that cement concrete pavement has intensity, good stability, good endurance, application life compared with long, routine servicing expense is few, and is conducive to the advantages such as driving at night.The raw-material selection in road surface, grating and composition design, testing inspection level, working procedure control, technological level, equipment and technical level and construction environment etc., all directly affect the quality of pavement engineering.Ensure that cement concrete pavement has good functional performance, not only well-designed, also want well construction, construction link takes charge of construction quality severely.This guidance combines " highway cement concrete pavement construction technique normalizing " (JTG F30-2003), does to simply analyse with regard to framework compact type Construction Technique of Cement Concrete Road and method of quality control.

Raw-material requirement

1, cement

The Portland cement for road that cement used should select rotary kiln to produce or Portland cement, its strength grade should match with the design rupture strength of cement concrete pavement.The by-product quality certification and laboratory test report is needed when cement is marched into the arena.Different cement uses with reference to the different mixture ratio of each code test, and the same section of same work team must not use different cement.The cement in bulk of new production, the storage period having to pass through necessity could use.Cement temperatures should not use more than 50 DEG C.Cement is by the frequency censorship of every kind 1 time/500T, and its indices should meet the regulation of " highway cement concrete pavement construction technique normalizing " (JTGF30-2003).Cement is marched into the arena more than 3 months, again must test it, meets the requirements and can use; The cement become damp and rotten must not use.

2, coarse aggregate

Coarse aggregate adopts rubble, and its quality should be hard, durable, wear-resisting, clean.Coarse aggregate nominal maximum aggregate size must not be greater than 31.5mm, and the content of stone powder of below 0.075mm must not more than 1%, and all the other indices should meet drawing and each related specifications requirement.The index such as faller gill shape, oversize granule content, formate gradation composition of coarse aggregate presses the frequency detecting of 1 crowd/1500m3; Apparent density, bulk density, void content mud content, clod content are according to the frequency detecting of 1 crowd/1000m3; Crush values and water content detect at any time depending on change of gathering materials.The indices such as the grating of coarse aggregate still answer the indices of the coarse aggregate in the code test of Pass Test room, and the deviation as the indices with the coarse aggregate in test room code test is greater than code requirement, need again do match ratio code test.

3, fine aggregate

Fine aggregate adopts medium coarse sand, and quality should be hard, durable, clean.Indices should meet drawing and each related specifications requirement.The fineness modulus of fine aggregate should between 2.3-3.2.The fineness modulus excursion of same match ratio sand more than 0.3, otherwise should should not stacked respectively, and uses after adjusting the sand coarse aggregate ratio in match ratio.In fine aggregate, more than 4.75mm and below 0.15mm content can not more than 10%, and the amount retained separately retaining in arbitrary sieve aperture must not more than 45%, and grating should meet related specifications requirement.The apparent density of fine aggregate, bulk density, void content, grating, mud content, clod content are according to the frequency detecting of 1 crowd/500m3; Fineness modulus and grating situation detect at any time depending on the situation of marching into the arena of gathering materials.

4, mixing water

In general drinking water should be adopted.Water quality need meet related specifications requirement.

1. the objectionable impurities affecting cement and normally condense and harden must not be contained in water, as oil, sugar, acid, alkali, salt etc.

2. sulfate, pH value, salt content meet index of correlation.

Mix-design

The method that Experiment Road mix-design is determined according to desk research, and can finely tune match ratio according to engineering practice, and follow the pertinent regulations of " highway cement concrete pavement construction technique normalizing " (JTGF30-2003).

The inspection of quality of framework compact type cement concrete

(1) quality inspection of framework compact type cement concrete and examination should meet the regulation of " highway bridge and culvert construction technique normalizing " (JTJ041-2000), " highway cement concrete pavement construction technique normalizing " (JTGF30-2003), " Of Road Engineering Quality Checking And Evaluation standard " (JTG F80/1-2004).

(2) framework compact type cement concrete is when final acceptance of construction, and concrete contraction, the long-term behaviour such as to creep and endurance quality should meet relevant regulations.

Experiment Road test and interpretation of result

Determine in the thirty shop section overhaul engineering of west, road at city S311 Chu, according to the consumption that gathers materials increased in folk prescription concrete, reduce cement paste consumption, reduce the thinking of unit consumption of water, when all raw material does not change, only design is optimized to concrete mix, the method that method for designing adopts test of Proportional Ratio to determine, and whole-process control detection is carried out to Experiment Road.

Experiment quantity and frequency: every day, construction section prepared concrete crushing strength test specimen 5 groups, concrete tensile strength test specimen 5 groups, measure the intensity that the length of time is 7 days, 28 days respectively.Get core to engineering entity, carry out diametral compression test to core, the length of time is 28 days, tests its splitting tensile strength and the corresponding rupture strength that converts.The data recorded and common match ratio cement concrete strength in 2007 are contrasted.

Experiment Road match ratio

Portland cement concrete match ratios in 2007 and the improvement proportioning of cement concrete of constructing for 2008 are as shown in table 18 and table 19.

The common mix-design list of table 182007

Table 192008 year improves mix-design list

Testing inspection data

(1) concrete flexural strength

The rupture strength testing result of two kinds of cement concretes is shown in table 20.

Table 20 two kinds of cement concrete bending strength result of the tests gather

(2) core splitting tensile strength

The splitting tensile strength testing result of two kinds of cement concrete pavement cores is shown in table 21, and table 22 is the concrete detection data of " modified " cement concrete core.

Table 21 two kinds of cement concrete splitting tensile strength result of the tests gather

Table 2228 day improves match ratio core result of the test and gathers

Test result analysis

1. result of the test shows, the framework compact type cement concrete bending strength of improvement and splitting tensile strength all comparatively plain edition cement concrete make moderate progress.Wherein 7d, 28d rupture strength comparatively portland cement concrete improve respectively 6.7% and 13.8%, 7d, 28d splitting tensile strength then improve 8.4% and 22.2% respectively.Same consistent with the conclusion of laboratory test gained, modified framework compact cement concrete bending strength, splitting tensile strength all comparatively plain edition cement concrete have clear improvement.This shows in practical engineering application, framework compact type cement concrete is more highly resistant to the percussion of vehicular load compared with portland cement concrete, thus extend service life of road surface, reduce maintenance cost, make cement-concrete road performance be able to better performance.

2. upper as can be seen from match ratio composition, modified cement concrete comparatively plain edition cement concrete can save cement in a large number.Match ratio after adopting this problem to optimize, more common match ratio can save cement about 15%.

3. in framework compact type cement concrete, the feature of the desirable grating of coarse aggregate is that 4.75-16.0mm small crushed stone amount ratio conventional amount is much smaller, and not only reduces construction costs like this, and effectively can alleviate various places handstone shortage problem.

4. the ratio accounted for due to coarse aggregate in modified cement concrete is large, sand coarse aggregate ratio is less, surface of aggregate is amassed little, moistening water reduces, water supply volume about 10%-20% fewer than general concrete, concrete density is improved, and concrete unit weight brings up to 2500-2550kg/m3 by 2400kg/m3, density improves respective strengths and is improved, simultaneously also highly beneficial to raising concrete durability.

5. because cement and water consumption make concrete slab drying shrinkage little less, the probability of road surface fine fisssure and disconnected plate can be reduced.

What 6. application operability and controllability became is easy, in this project implementation, 0.45 ~ 5.67 different water/binder ratio is adopted to test respectively, in table 23, testing result is indicated, the fluctuation of water/binder ratio is not too large on the impact of final rupture strength, thus just can according to construction needs in construction, relax the requirement to water/binder ratio, reach the object improving concrete construction workability, constructing operation is more prone to.

The concrete flexural strength contrast table of table 23 Different Water-Cement Ratio

Remarks: cement consumption 330Kg.

Test section road effect

After the operation nearly six months of test section, detect test section, testing result gathers in table 24.

Table 24 road surface entity detection result statistical form

(1) intensity.Get core totally 35 places in the interval representativeness of enforcement, as can be seen from the table, in test item, intensity is all qualified.

(2) the working face plate thickness inspected by random samples, width of roadway are also all qualified, and surface evenness has 3 places defective, and transverse slope has 1 place defective, and the anti-skid construction degree of depth has 1 place defective.See on the whole, the effect of test section after runing half a year is substantially better.

Achievement in research Practical Project is applied

1. Chuzhou City road network alteration work

Through laboratory test research and Experiment Road project quality inspection, prove the framework compact type mixing proportion design method that this problem proposes, can not only construction costs be reduced, and can also effectively improve cement-concrete road performance indications, there is very strong engineering promotional value.For further achievement in research being applied, by above-mentioned mixing proportion design method, Chuzhou City road network in 2008 is reconstructed, overhaul engineering each bid section Pavement Concrete Mixing Ratio carried out designing and examination auxiliary tone whole, concrete mix, the mechanical performance of concrete result of the test of different bid section are listed in table 25.

Table 25 Chuzhou City road network alteration work making section proportioning of cement concrete and mechanical property

Engineering practice shows: according to this problem mixtures optimal design method, the pavement concrete unit cement consumption ﹤ 400Kg/m of above-mentioned bid section ³, unit consumption of water ﹤ 150Kg/m ³.Workability all can meet construction requirement, and about 80%, the 28d flexural tensile strength that 7d rupture strength reaches design strength meets the requirement of preparation 28d flexural tensile strength average.Originally the framework compact type cement concrete researched and proposed obtains good application in engineering.

After theory analysis and laboratory test, the achievement in research that the present invention obtains has carried out checking and applying in Practical Project.

(1) according to the feature of dense structure of skeleton, in conjunction with corresponding construction of cement concrete road surface specification, the construction proposing framework compact type cement concrete test section is instructed, when mainly comprising making Experiment Road concrete at mix, transport, build, vibrate and answer Attention question in maintenance processes.

(2) S311 Chu is relied on to determine west, road thirty shop section overhaul engineering making Experiment Road.Get core and test performance by on-the-spot sample preparation and entity project, contrast with common match ratio, demonstrate the concrete rupture strength of modified match ratio and obtain remarkable improvement.Detect the index such as intensity, thickness, planeness, construction depth of Experiment Road after operation a period of time, the result display Experiment Road operational effect obtained is better.

(3) after the theory analysis of system, laboratory test and Experiment Road project quality inspection, the achievement in research of this problem is applied in Chuzhou City Road network analysis.Find that institute's making each bid section road surface operational effect is all better through tracing detection after a while.Thus prove the framework compact type mixing proportion design method that this problem proposes, can not only construction costs be reduced, and can also effectively improve cement-concrete road performance indications, there is very strong engineering promotional value.

Economic and Efficiency Analysis

Within 2008, the reconstruction of Chuzhou City road network, overhaul engineering amount to 8 cement concrete pavement projects, total kilometrage 76.3km.Compared with similar projects in 2007, folk prescription concrete cement consumption is reduced to 330-340kg by 375-380kg, and folk prescription concrete work cost declines about 15 yuan, amounts to and saves cement more than 9500 ton, saves engineering construction fund about 3,600,000 yuan.Chuzhou City traffic engineering inspection center carries out core detection to projects rupture strength, and testing result shows, core intensity qualification rate 100%, and average is at more than 6.0MPa, and all core conversion rupture strengths are all higher than design strength 0.5MPa.

Meanwhile, the pavement concrete of this achievement in research preparation, can extend engineering application life, thus reduces later period maintenance expense, and as extended 10-20, or reduce 1-2 time and keep in repair, its economic benefit is also very significant.

In addition, this achievement in research also will have an impact to other engineering (as municipal engineering, factories and miness construction) and likely be applied, and all will produce larger economic benefit.

More than show and describe general principle of the present invention and principal character and advantage of the present invention.The technician of the industry should understand; the present invention is not restricted to the described embodiments; what describe in above-described embodiment and manual just illustrates principle of the present invention; without departing from the spirit and scope of the present invention; the present invention also has various changes and modifications, and these changes and improvements all fall in the claimed scope of the invention.Application claims protection domain is defined by appending claims and equivalent thereof.

Claims

1. improve a method for road cement concrete bending tensile strength and durability, it is characterized in that, its concrete grammar is as follows:

1) local raw material are joined concrete with the examination of different glue sand content, determine the glue sand content be applicable to, in this, as the guide parameters of Design of Cement Concrete Mixture Ratio;

2) sand coarse aggregate ratio is reduced to 29%-32% from 36% of routine, single cement consumption reduces to 330 kilograms by 380 kilograms of engineering in the past, and the middle particle diameter 4.75mm-9.5mm dimension stone that tradition gathered materials is rejected;

3) mix-design cement consumption is according to " highway cement concrete pavement construction technique normalizing " (JTGF30-2003) requirement, to be not less than 300kg/m ³for radix, progressively increase 10-15kg/m depending on raw material situation ³, by Mix Ratio Test determination cement consumption; Sand coarse aggregate ratio selection range is 29-32%, and every cubic meter of concrete water supply volume is by trial mix concrete mix, and the water supply volume reaching requirement workability corresponding is determined;

4), after substantially determining above-mentioned parameter by parallel test, the conveniently preliminary match ratio of absolute volume method determination cement concrete, in conjunction with trial mix test and strength test, finally draws the design mixture proportion meeting construction workability and requirement of strength;

5) parameters scope: use the rubble of more than 9.5mm as aggregate, the fineness modulus of sand is advisable with 2.7-3.0; Recommendation sand coarse aggregate ratio is 29-32%; Folk prescription concrete cement consumption is at 330-340kg/m ³; The folk prescription the reinforcement of concrete water yield is 130-145kg/m ³.

2. a kind of method improving road cement concrete bending tensile strength and durability according to claim 1, is characterized in that: step is as follows,

One. transport

Two. pave

3), when concrete mix paves, must be undertaken by the order of first template edge, Ban Jiao, seam crossing; The position that coarse aggregate is too concentrated, must be distributed in the concrete mix of uniform quality and be gone;

5) cause for some reason and stop work or reached for 2/3 initial setting time for more than 1 hour, should arrange constuction joint in the panel termination that making is good, discarding can not by the mix of jolt ramming; For the joint of stopping work within the above-mentioned time, should cover wet gunnysack in joint to prevent joint loss of water, downtime is long, must remove the compound without jolt ramming initial set;

6) concrete mix should be half flow regime, and the inclined-plane of adjacent two cars is discharging and the natural inclined plane after vibrating;

Three. vibrate

3) vibrating spear insertion depth should from basic unit 3 ~ 5cm, answer collision free template, reinforcing bar, dowel bar and pull bar simultaneously, must not take to impel concrete to shake by the method for vibrating head vibration reinforcing bar close, otherwise will reinforcement location be made to change because of vibration, also can reduce the adhesion stress between reinforcing bar and concrete, even can mutually depart from; During operation, vibrating head insert the concrete degree of depth should not exceed rod long 2/3 ~ 3/4, otherwise vibrating head will not be drawn out easily and cause flexible pipe to damage; More flexible pipe must not be inserted in concrete, in case mortar etch and infiltrate flexible pipe and damage parts; Vibrator is in use as too high in temperature, answers hard stop to cool and checks, as parts fault, will place under repair in time, during winter low temperature, before vibrator operation, adopt and slowly heat, after the lubrication oil in barred body is thawed, and can operation;

6) should to weld bottom walking beam or the coarse aggregate compacting tooth of fitting depth about 4mm, ensure the surperficial mortar thickness of 4 ± 1mm;

Four. leveling facing

3) the receipts slurry of wiping one's face of cement concrete must not be less than 3 times, and first time receives slurry and carries out immediately after leveling terminates, and its Main Function is that continuation screeding concrete is surperficial, presses down surperficial coarse aggregate simultaneously; Second time should be carried out before bleeding, and it act as screeding concrete surface; When bleeding terminates, when surface no longer includes Free water, can carry out third time and receive slurry, third time must be smeared with iron and be carried out, and complete facing, its effect prevents from bleeding from terminating rear surface occur bleeding cement and peel simultaneously;

Five. seam joint-cutting is constructed

1) longitudinal joint should be constructed according to the regulation of design document, longitudinal joint is longitudinal constuction joint, pull bar is at formwork erection after-pouring, install before concrete, the pull bar of longitudinal constuction joint is then installed through the tie rod hole of template, and when closing up, longitudinal joint top will brush pitch, and must not be coated on pull bar, after form removal, longitudinal joint must be cleaned out, then half portion brush longitudinal joint pitch thereon; Wide, the thick transparent adhesive tape caulking joint of form joint place, and remove after form removal;

2) lateral contraction is sawn into after being sewn on concrete scleroma, too early unsuitable, to avoid occurring stitching along uneven, hair stubble, gap, gnawing the phenomenons such as limit; Can not be too late, to prevent, concrete strength is high causes joint-cutting difficulty, more mustn't there is disconnected plate, must note during joint-cutting observing, principle is " energy Qie Zeqie, peaceful early late ", for edges of boards, due to template cause joint-cutting must supplement joint-cutting or form removal with small-sized joint cutter not as good as limit place after to mend with special joint cutter and cut, ensure that seam is through over the surface of the panel, avoid edges of boards arrisdefect;

Six. form removal

Seven. health

1) cement concrete pavement layer survive after maintenance work be divided into initial curing and late maintaining, the moisturizing watering method of curing that initial curing adopts geotextiles to cover, late maintaining adopts the double-deck moisturizing watering method of curing of covered with plastic film in geotextiles, and special messenger must be established often to make an inspection tour, guarantee health situation, health is complete waters gap-grouting material at saw kerf place, should remove the interim close stifled material in seam before the cementation of fissures, and seam apical side height is concordant with road surface;