CN1547000A - Cement mortar and concrete shrinkage stress testing method - Google Patents
Cement mortar and concrete shrinkage stress testing method Download PDFInfo
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- CN1547000A CN1547000A CNA2003101170980A CN200310117098A CN1547000A CN 1547000 A CN1547000 A CN 1547000A CN A2003101170980 A CNA2003101170980 A CN A2003101170980A CN 200310117098 A CN200310117098 A CN 200310117098A CN 1547000 A CN1547000 A CN 1547000A
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Abstract
The invention discloses a kind of contraction stress testing method for cement sand pulp and concrete, provides a direct, effective, convenient testing method for measuring the contraction stress of concrete. The project is: it includes following steps: 1) confirms the size of the sample according to the maximal particle size in cement sand pulp or concrete material; 2) the cement sand pulp or concrete material are put into the concrete limited swelling and contracting device to be formed into testing block, measures the deformation value through the swell and contraction meter, works out the stress value according to the deformation; the method integrates the swell and contraction meter and the limited welling and contracting device, solves the problem that there has no method to measure the stress. The structure is simple, and the precision is high.
Description
Technical field
The present invention relates to a kind of method of testing, specifically is a kind of sand-cement slurry, concrete shrinkage stress method of testing.Be applicable to test sand-cement slurry or concrete under the temperature and humidity conditions of regulation, the internal stress that not produced by the external force effect changes, and comprising the compressive stress of the generation of expanding and shrinking the tension that produces.
Background technology
Sand-cement slurry and concrete material are one of building materialss most widely used, the most successful in the construction work, but the characteristics that the tensile pressure ratio that anisotropy that it had and nonhomogeneity of materials cause is low have also exposed this material limitation in use, and the contraction fissure problem that therefore solves it is a traditional research topic of concrete science always.Particularly since concrete high strength and the high performance, this problem is more outstanding.The sand-cement slurry in the past and the differential contraction stress of concrete material have no idea to predict in advance that normally between the operating period after the engineering completion, sand-cement slurry or concrete ftracture, and then it are split post analysis, this is implemented safeguard or construction again again; Its effort of taking a lot of work exhausts the people and drains the treasury, and severe patient is the entail dangers to people's life security also.
Summary of the invention
Problem set forth above, the problem to be solved in the present invention just, purpose of the present invention will provide a kind of exactly and estimate concrete shrinkage cracking with stress index, can intuitively, effectively solve the differential contraction stress measuring method of practical problems, make concrete from now on various shrinkage tests simple and convenient as strength test.
To achieve these goals, the present invention adopts by the applicant's application and authorizes, the patent No. is that 00261525.8 utility model patent " sand-cement slurry expands and shrinks measuring instrument " and application number are that 03244493.1 utility model patent " concrete confined expansion constriction device " is used, a kind of sand-cement slurry, concrete shrinkage stress method of testing to sand-cement slurry and concrete deformation stress are measured may further comprise the steps:
1) determines that by the maximum particle diameter in sand-cement slurry or the concrete aggregate it tries the size of body;
2) sand-cement slurry or concrete aggregate are packed into form test block behind the concrete confined expansion constriction device, expand by sand-cement slurry and shrink measuring instrument and measure the deflection of described test block, calculate its stress value according to its deflection; Concrete operations are as follows:
A) measured before 3 hours, concrete confined expansion constriction device, sand-cement slurry expansion contraction measuring instrument and a par are put into measuring chamber, sand-cement slurry expansion contraction measuring instrument is proofreaied and correct with par;
B) initial length of its concrete confined expansion constriction device is measured in concrete confined expansion constriction device one is faced up placement, and described concrete confined expansion constriction device direction and stationkeeping in the measurement phase is constant;
C) with completing steps b) concrete confined expansion constriction device place in the die trial, pack into sand-cement slurry or concrete of gradation in die trial, its slotting puddling is real; Cover the drop cloth that one deck prevents water evaporates in its shop, surface;
D) maintenance is sent in the die trial that step c) is formed;
E) with the die trial demoulding of step d) maintenance moulding, Measuring Time is according to the rules measured the deflection of described concrete confined expansion constriction device;
F), obtain the stress σ of described test block with the elastic modulus and the following formula of bar diameter numerical value substitution of the xsect of described concrete confined expansion constriction device, described restriction reinforcing bar:
Wherein: E limits in " concrete confined expansion constriction device " to make the elastic modulus of reinforcing bar;
D limits in " concrete confined expansion constriction device " to make the bar diameter of reinforcing bar;
A is the cross-sectional area of " concrete confined expansion constriction device ";
ε is at described specifying measurement deflection of " concrete confined expansion constriction device " in the time.
Wherein the initial length value measured by step b) of deflection ε and test block can be obtained the deflection that described concrete limits constriction device length at the following formula of length value substitution that described specifying measurement recorded in the time, and described formula is as follows:
Wherein: L
2The length reading that records in experimental period for test block;
L
1Initial length for concrete restriction constriction device;
L
0Be the test block datum length, be i.e. pour into the length of cement, sand-cement slurry or concrete part in the concrete confined expansion constriction device;
G) the examination body in the different length of times is measured in described stipulated time ± 1 hour.
The sectional dimension (wide, height) of the described sand-cement slurry examination of step 1) body is 10mm～100mm, length 10mm～1000mm, and the sectional dimension (wide, height) of concrete examination body is 50mm～400mm, length 50mm～2000mm.
The service precision value that measuring instrument is shunk in described sand-cement slurry expansion is at least 0.001mm.
The described restriction bar diameter of step b) is selected according to the bar diameter of engine request.
At step e), f), g) described in the Measuring Time of regulation be to set according to experimenter's requirement, be generally 1 day, 3 days, 7 days, 14 days, measured once in 7 days by every interval later on, also can continuous coverage every day; The final time can be a couple of days, one month, several months and even several years.
The curing condition of step d) is: carry out under the standard temperature of fog room and humidity, described standard temperature is 20 ℃ ± 3 ℃, and described standard humidity is more than 90%;
The maintenance of step d) also can be carried out under the constant temperature and humidity condition, and described thermostat temperature is 20 ℃ ± 2 ℃, and described constant humidity relative humidity is 60 ± 5%.
The curing condition of step d) can also carry out under natural temperature and damp condition.
Described concrete confined expansion constriction device gauge head shrinks the measuring instrument gauge head with described sand-cement slurry expansion and contacts, and the reading exact value is greater than 0.001mm.
Described test block is by group test, and three test blocks of every composing type are got its mean value as the length variations value, and its calculated value is accurate to behind the radix point at least three, in particular cases can also keep multidigit.
The present invention is owing to adopt above method, it has the following advantages: 1, adopt sand-cement slurry expansion contraction measuring instrument and concrete confined expansion constriction device to be used, by measuring concrete confined expansion constriction device length variations, just can calculate by the derivation of equation, calculate inside concrete stress, obtain expansion, differential contraction stress changing value in the concrete, can estimate concrete cracking degree and anti-crack ability objectively, therefore solve insurmountable always for a long time concrete shrinkage stress forecasting problem.2, record vertical restrained deformation amount of concrete examination body by " sand-cement slurry expands and shrinks measuring instrument ", and collect related data, input in the connected computing machine, according to the deflection of " concrete confined expansion constriction device " reflection, synchronometer is calculated inside concrete stress situation again; Stress situation between the concrete of comparison different mixture ratio, can judge the size of concrete opposing differential contraction stress ability, and then the time and the probability in crack take place in the prediction concrete, changes the present post analysis that splits into obviate, has directly perceived, science, effectively reaches the strong characteristics of emulation.3, equipment therefor and measuring instrument are simple in structure, easy to operate and measuring accuracy is high, can be before concrete construction according to arrangement of reinforcement, the restraint condition of engineering different parts, the restriction bar diameter, select for use corresponding " concrete confined expansion constriction device " to lay the foundation, for the research and development of new material provide new platform for concrete carries out the differential contraction stress design.4, the early stage self-desiccation that chemistry reduces, low water binder ratio causes of concrete early-age shrinkage such as plastic shrinkage, aquation generation shrinks and is difficult to measure statement with existing method, reason is that the definite initial length of present method is the length behind the concrete demoulding, and concreting to the length variations of demoulding inner concrete generation during this period of time can't be measured.But these distortion can be converted to stress analysis by this method, accurately measure the STRESS VARIATION that these contractions cause.5, can compare differential contraction stress difference between the concrete of different mixture ratio under the same test conditions, also can the differential contraction stress of concrete under the different tests condition of same match ratio be compared.
Description of drawings
The concrete confined expansion constriction device structural representation that Fig. 1 adopts for the present invention
The cement and expanded contraction measuring instrument structural representation that Fig. 2 adopts for the present invention
Fig. 3 is that embodiment one concrete is measured stress curve figure
Fig. 4 is that embodiment two expansive concretes are measured stress curve figure
Fig. 5 is the measurement stress curve figure of embodiment three
Fig. 6 is the measurement stress curve figure of embodiment four
Fig. 7 is the measurement stress curve figure of embodiment five
Fig. 8 is the measurement stress curve figure of embodiment six
Embodiment
At first " sand-cement slurry expands and shrinks measuring instrument " that the present invention is adopted describes in detail with " concrete confined expansion constriction device ".
As shown in Figure 1, concrete confined expansion constriction device is made up of with spheric probe 5 a constraint reinforcing bar 1, slippage sleeve pipe 2, constraint end plate 3, anchoring piece 4, constraint reinforcing bar 1 two ends are connected with constraint end plate 3 respectively, constraint end plate 3 two ends are fixed with spheric probe 5, anchoring piece 4 is fixed on the constraint end plate 3, and slippage sleeve pipe 2 is sheathed on the middle part of constraint reinforcing bar 1.When concrete casting in concrete confined expansion constriction device, concrete setting formation one is identical with constraint end plate 3 sizes, with the identical confining region of constraint reinforcing bar 1 length, be provided with on the constraint reinforcing bar 1 of slippage sleeve pipe 2, concrete does not directly contact with constraint reinforcing bar 1, the bond stress constraint of unfettered reinforcing bar 1, and it is bigger to cause being provided with slippage sleeve pipe 2 length range inner concrete tensions, easy to crack, can in the length range of slippage sleeve pipe 2, observe concrete cracking; If concrete test block is changed the cross section in respect to slippage sleeve pipe 2 length ranges at confining region middle part, its cross section is diminished, then be easier to make stress to concentrate and produce, form observation district, crack, be the section of concrete pulling stress maximum herein, just the concrete section of easy cracking.Two spheric probes 5 are fixed in the outside of constraint end plate 3, when measuring the concrete test block contraction, the last lower plane gauge head that shrinks measuring instrument with the concrete expansion closely contacts, and forms the some face and contacts, make concrete test block axis and the instrument accurate centering of gauge head up and down, improved measuring accuracy.Inboard vertical fixing at constraint end plate 3 has several anchoring pieces 4, is equipped with the constraint rivet on each anchoring piece 4, has strengthened concrete binding effect.Constraint reinforcing bar 1 can adopt deformed bar, also can adopt plain bar, can reach the suffered binding effect of concrete in the actual engineering of simulation.
As shown in Figure 2, sand-cement slurry expand to be shunk measuring instrument and is the applicant's application and the patented technology of having authorized, and the measuring accuracy of this measuring instrument is 0.001mm, this instrument by clock gauge 6, pedestal 7, go up gauge head 8 and following gauge head 9 is formed.Pedestal 7 shown in Figure 2 is put in the test block that concrete confined expansion constriction device forms, the gauge head 8,9 at measuring instrument two ends is aimed at the spheric probe 5 at described concrete confined expansion constriction device two ends, can read measurement data by the clock gauge on its measuring instrument 6, by the automatic output record of its data of computer realization of being connected with measuring instrument
After proofreading and correct " sand-cement slurry expands and shrinks measuring instrument ", " concrete confined expansion constriction device " carried out initial length and measure the acquisition and recording measured value; To having built sand-cement slurry or the acquisition and recording measured value is measured in concrete " confined expansion constriction device " test block after the demoulding; Measuring method is consistent with the method for measuring initial length, at first the one side in the test block of concrete confined expansion constriction device is provided with numbering, one face up to place and measure what be provided with numbering, its direction and position are consistent with direction with the position of initial length, and constant to beginning.The spheric probe that the test block of confined expansion constriction device is two sections closely contacts with two plane gauge heads up and down of measuring instrument, forms the contact of some face, makes test block axis and the instrument accurate centering of gauge head up and down.
The present invention has utilized above-mentioned two instruments and device to cooperate, sand-cement slurry and concrete stress are tested, more several groups of concrete differential contraction stresses of different mixture ratio, it is little to select its differential contraction stress, the concrete that cracking resistance is good is used for construction, has improved concrete performance index and serviceable life greatly.
According to above-mentioned disclosed measurement mechanism and instrument, realization method of testing of the present invention is described further by following specific embodiment:
Embodiment one
As shown in Figure 1, tested body is for being perfused with cement or concrete " concrete confined expansion constriction device "; Before measuring 3 hours, one side is provided with the vacant concrete confined expansion constriction device of numbering, sand-cement slurry expansion contraction measuring instrument and a par with putting into a measuring chamber, clean said apparatus and measuring instrument and gauge head, sand-cement slurry expansion contraction measuring instrument is proofreaied and correct with par;
Measure initial length: " concrete confined expansion constriction device " established one of the numbering placement that faces up, before not having placing cement concrete in injection, measure initial length;
Test block is made: " the concrete confined expansion constriction device " that measure initial length placed die trial, to test the concrete gradation then and pour into die trial, insert gently in fact, when operation, can not touch the restriction reinforcing bar with tamper, otherwise can cause the reinforcing bar distortion, influence measuring accuracy.Scrape off unnecessary concrete and floating then.Test block is placed under the curing condition of regulation again and carry out maintenance, the test block surface covers with Polypropylence Sheet or wet cloth, prevents water evaporates.
The test block size is selected according to the maximum particle diameter of gathering materials in the concrete, and the sectional dimension of general test block is 4 times of maximum particle diameter size of gathering materials, and the length of test block is more than 3 times of cross-sectional width.The sectional dimension of concrete test block is 100mm * 100mm in the present embodiment, length 515mm, and the restriction bar diameter of concrete confined expansion constriction device is 28mm, the datum length of concrete test block is 485mm.
The pedestal that measuring instrument is shunk in sand-cement slurry expansion shown in Figure 2 is put in above-mentioned test block, the gauge head at measuring instrument two ends is aimed at the spheric probe at described concrete confined expansion constriction device two ends, can read measurement data by the clock gauge on its measuring instrument, by the automatic output record of its data of computer realization of being connected with measuring instrument.
Examination body after the demoulding is carried out the first time measure, compare, just can obtain the 1st day differential contraction stress by calculating with the initial length value.
To try maintenance under the curing condition that body is put in regulation then, its curing condition is determined voluntarily by the experimenter, also can determine that interval time of measurement (length of time) is also determined voluntarily by the experimenter with reference to relevant specification and standard.The initial calculation phase in the length of time is counted from building moulding day.The test temperature of present embodiment is 20 ℃ ± 2 ℃, and relative humidity is 60 ± 5%.Measuring the length of time is 1,2,3,4,5,9,12,16,19,21,23,26,29,33,35,40,42,46,49,51,52,53 day, and final Measuring Time is defined as 53 days.
Numbering 1 in the present embodiment in concrete material prescription such as the table 1 is listed, test block is measured in the length of time of setting by the afore-mentioned test method, with computing machine that " sand-cement slurry expands and shrinks measuring instrument " links to each other on just can obtain its stress curve.
As shown in Figure 3, by the concrete of numbering 1 proportioning when the 51 days length of time, its differential contraction stress reaches 2.733MPa, this moment, concrete differential contraction stress reached its ultimate tensile strength (UTS), concrete cracking, stress relaxation then takes place, and stress (2.733MPa) and time (the 53 days length of time) when producing the crack all can be obtained comparatively accurately by method of testing of the present invention.
Table 1
| Numbering | Every cubic metre of material usage (kg/m 3) | The slump (mm) | ||||||
| Cement | Flyash | Water | Swelling agent | Water reducer | Sand | Stone | ||
| ??1 | ????420 | ??80 | ??175 | ??0 | ??3 | ??655 | ??1080 | ????240 |
| ??2 | ????380 | ??70 | ??175 | ??50 | ??3 | ??655 | ??1080 | ????240 |
| ??3 | ????585 | ??0 | ??260 | ??65 | ??0 | ??1300 | ??0 | ????/ |
According to the elastic modulus of restriction reinforcing bar in the concrete confined expansion constriction device itself, the general value of elastic modulus is 2.0 * 10
5MPa, the diameter that the restriction reinforcing bar is got and the cross-sectional area of concrete confined expansion constriction device; To set and the following formula of measured value substitution, calculate the stress value of this test block, stress value be on the occasion of, then represent turgor pressure stress; Stress value is a negative value, and then tension is shunk in expression.
Stress:
Wherein: E limits in " concrete confined expansion constriction device " to make the elastic modulus of reinforcing bar; Springform measures 2.0 * 10
5MPa;
D is the diameter of above-mentioned restriction reinforcing bar;
A is the cross-sectional area of " concrete confined expansion constriction device ";
ε is at the deflection of specifying measurement time test " concrete confined expansion constriction device ".
The deflection ε of above-mentioned concrete confined expansion constriction device is calculated by following formula:
Wherein: L
2---the length reading that test block recorded in experimental period;
L
1---the initial reading of test block length;
L
0---the test block datum length is perfused with sand-cement slurry or concrete length partly in " concrete confined expansion constriction device ".
Testing three test blocks is one group of data, gets its arithmetic mean as the length variations value.Calculation requirement is accurate to behind the radix point the 3rd.
Table 2 is operation results of embodiment one." measurement length " during the 0 day length of time is initial reading L
1, then be L each length of time later on
2, L
0=485mm, D=28mm, E=2.0 * 10
5MPa calculates for example the 1 day length of time: the initial reading (L of three test blocks
1) be respectively: the reading (L after 0.064,0.053,0.009,1 day
2) be 0.056,0.047,0.004, deduct initial reading and divided by L with 1 day reading
0, i.e. (L
2-L
1)/L
0, the deflection ε that obtains three test blocks respectively is-0.00165% ,-0.00124% ,-0.00103%, and the arithmetic mean that calculates them is 0.00131%, can be in the hope of stress σ=-0.171 (MPa) with this value substitution Stress calculation formula.
Table 2 test data is calculated
| The length of time (my god) | Measure length | The absolute deformation amount | Relative deformation ε (%) | Average deformation value ε (%) | Stress σ (MPa) |
| ??0 | ????0.064 ????0.053 ????0.009 | ||||
| ??1 | ????0.056 ????0.047 ????0.004 | ????-0.008 ????-0.006 ????-0.005 | -0.00165 -0.00124 -0.00103 | -0.00131 | -0.171 |
| ??2 | ????0.049 ????0.04 ????-0.008 | ????-0.015 ????-0.013 ????-0.017 | -0.00309 -0.00268 -0.00351 | -0.00309 | -0.406 |
| ??3 | ????0.043 ????0.035 ????-0.012 | ????-0.021 ????-0.018 ????-0.021 | -0.00433 -0.00371 -0.00433 | -0.00412 | -0.541 |
| ??4 | ????0.038 ????0.03 ????-0.017 | ????-0.026 ????-0.023 ????-0.026 | -0.00536 -0.00474 -0.00536 | -0.00515 | -0.676 |
| ??5 | ????0.032 ????0.023 ????-0.024 | ????-0.032 ????-0.03 ????-0.033 | -0.00660 -0.00619 -0.00680 | -0.00653 | -0.857 |
| ??9 | ????0.024 ????0.014 ????-0.028 | ????-0.04 ????-0.039 ????-0.037 | -0.00825 -0.00804 -0.00763 | -0.00797 | -1.046 |
| ??12 | ????0.019 ????0.007 ????-0.035 | ????-0.045 ????-0.046 ????-0.044 | -0.00928 -0.00948 -0.00907 | -0.00928 | -1.218 |
| ??16 | ????0.012 ????0.001 ????-0.042 | ????-0.052 ????-0.052 ????-0.051 | -0.01072 -0.01072 -0.01052 | -0.01065 | -1.398 |
| ??19 | ????0.005 ????-0.003 ????-0.049 | ????-0.059 ????-0.056 ????-0.058 | -0.01216 -0.01155 -0.01196 | -0.01189 | -1.560 |
| ??21 | ????0 ????-0.008 ????-0.056 | ????-0.064 ????-0.061 ????-0.065 | -0.01320 -0.01258 -0.01340 | -0.01306 | -1.714 |
| ??23 | ????-0.006 ????-0.014 ????-0.063 | ????-0.07 ????-0.067 ????-0.072 | -0.01443 -0.01381 -0.01485 | -0.01436 | -1.885 |
| ??26 | ????-0.01 ????-0.018 ????-0.069 | ????-0.074 ????-0.071 ????-0.078 | -0.01526 -0.01464 -0.01608 | -0.01533 | -2.011 |
| ????29 | ??-0.015 ??-0.022 ??-0.072 | ????-0.079 ????-0.075 ????-0.081 | -0.01629 -0.01546 -0.01670 | -0.01615 | -2.120 |
| ????33 | ??-0.019 ??-0.026 ??-0.078 | ????-0.083 ????-0.079 ????-0.087 | -0.01711 -0.01629 -0.01794 | -0.01711 | -2.246 |
| ????35 | ??-0.023 ??-0.029 ??-0.081 | ????-0.087 ????-0.082 ????-0.09 | -0.01794 -0.01691 -0.01856 | -0.01780 | -2.336 |
| ????40 | ??-0.026 ??-0.033 ??-0.085 | ????-0.09 ????-0.086 ????-0.094 | -0.01856 -0.01773 -0.01938 | -0.01856 | -2.435 |
| ????42 | ??-0.028 ??-0.035 ??-0.087 | ????-0.092 ????-0.088 ????-0.096 | -0.01897 -0.01814 -0.01979 | -0.01897 | -2.489 |
| ????46 | ??-0.032 ??-0.038 ??-0.09 | ????-0.096 ????-0.091 ????-0.099 | -0.01979 -0.01876 -0.02041 | -0.01966 | -2.580 |
| ????49 | ??-0.035 ??-0.042 ??-0.093 | ????-0.099 ????-0.095 ????-0.102 | -0.02041 -0.01959 -0.02103 | -0.02034 | -2.670 |
| ????51 | ??-0.037 ??-0.044 ??-0.096 | ????-0.101 ????-0.097 ????-0.105 | -0.02082 -0.02000 -0.02165 | -0.02082 | -2.733 |
| ????52 | ??-0.01 ??-0.02 ??-0.076 | ????-0.074 ????-0.073 ????-0.085 | -0.01526 -0.01505 -0.01753 | -0.01595 | -2.092 |
| ????53 | ??0.002 ??-0.011 ??-0.063 | ????-0.062 ????-0.064 ????-0.072 | -0.01278 -0.01320 -0.01485 | -0.01361 | -1.786 |
Embodiment two
Be with embodiment one difference, described test block material difference, its concrete material prescription is shown in numbering 2 in the table 1; Test block size and method of testing are all identical with embodiment one.
Numbering 2 is for adding the expansive concrete that swelling agent is arranged owing to stored bigger compressive pre-stress in the water curing stage, enter do empty the contraction after, need to offset earlier this part compressive pre-stress, during to the 32 days length of time, concrete also is in pressured state.Therefore number the normal concrete that the 2 expansive concrete differential contraction stresses under the same conditions of mixing swelling agent are less than numbering 1.
As shown in Figure 4, with measuring instrument that computing machine links to each other on can obtain its stress curve, concrete differential expansion stress when the 32 days length of time of numbering 2 proportionings also reaches 0.07MPa, compressive stress do not occur, compare with numbering 1 match ratio, numbering 2 has good anti-crack ability.
Utilize the formula of embodiment one, can calculate turgor pressure stress and contraction tension that this concrete possesses.
Embodiment three
Be with embodiment one difference: the test block size is different, selected according to the maximum particle diameter of gathering materials in the concrete, the sectional dimension of the sectional dimension concrete examination body of concrete test block is generally 400mm * 400mm, length 2000mm, the restriction bar diameter of concrete confined expansion constriction device is 70mm, the sectional dimension datum length 1970mm of concrete test block, test temperature is 21 ℃, relative humidity 63%.Other method of testing and effect are with embodiment one.
As shown in Figure 5, with measuring instrument that computing machine links to each other on can obtain its stress curve, the result is as can be seen from figure, the concrete early-age shrinkage of this proportioning is less, and differential contraction stress sharply increases after 2 days, illustrates to shrink to accelerate, during to 15 days, differential contraction stress reaches 1.38MPa.
Embodiment four
What numbering 3 showed in the table 1 is the match ratio of a sand-cement slurry.
The sectional dimension of sand-cement slurry examination body is 100mm * 100mm, length 1000mm, and the diameter of restriction reinforcing bar is 10mm according to the bar diameter of engine request.
Get under the standard temperature of fog room and the damp condition and carry out maintenance, its standard curing room temperature is 20 ℃, is maintenance 7 days in the environment 90% or more in relative humidity earlier, changes relative humidity again over to and be 60% the interior maintenance of environment.
Cement adopts 42.5MPa cement.
Other measuring method is with embodiment one.Implementation result as shown in Figure 6 owing to, in the examination body, stored bigger compressive pre-stress in the expansion of water curing stage swelling agent, enter do empty the contraction after, need to offset earlier this part compressive pre-stress, during to the 19 days length of time, test block also is in pressured state.Therefore it is better than general mortar to number 3 sand-cement slurry anti-crack ability under the same conditions.
Embodiment five
The sectional dimension of cement paste examination body is generally 10mm * 10mm, length 10mm, and the diameter of restriction reinforcing bar is 2mm according to the bar diameter of engine request.
Get thermostatic constant wet chamber's condition maintenance, its thermostat temperature is made as 18 ℃, and relative humidity is 55%.
Cement adopts 42.5MPa cement.
Other measuring method is with embodiment one.Implementation result as shown in Figure 7, the result is presented under this restrictive condition, 19 days differential contraction stress of cement slurry is 0.7MPa.
Embodiment six
Be with embodiment one difference: the test block size is different, selected according to the maximum particle diameter of gathering materials in the concrete, the sectional dimension of the sectional dimension concrete examination body of concrete test block is 50mm * 50mm, length 200mm, the restriction bar diameter of concrete confined expansion constriction device is 6mm, the sectional dimension datum length 170mm of concrete test block, test temperature is 22 ℃, relative humidity 65%.Other method of testing and effect are with embodiment one.
Implementation result as shown in Figure 8, under this test condition, 19 days differential contraction stress of concrete is 0.49MPa.
Claims (8)
1. a sand-cement slurry, concrete shrinkage stress method of testing may further comprise the steps:
1) determines that by the maximum particle diameter in sand-cement slurry or the concrete aggregate it tries the size of body;
2) sand-cement slurry or concrete aggregate are packed into form test block behind the concrete confined expansion constriction device, expand by sand-cement slurry and shrink measuring instrument and measure the deflection of described test block, calculate its stress value according to its deflection; Concrete operations are as follows:
A) measured before 3 hours, concrete confined expansion constriction device, sand-cement slurry expansion contraction measuring instrument and a par are put into measuring chamber, sand-cement slurry expansion contraction measuring instrument is proofreaied and correct with par;
B) initial length of its concrete confined expansion constriction device is measured in concrete confined expansion constriction device one is faced up placement, and described concrete confined expansion constriction device direction and stationkeeping in the measurement phase is constant;
C) with completing steps b) concrete confined expansion constriction device place in the die trial, pack into sand-cement slurry or concrete of gradation in die trial, its slotting puddling is real; Cover the drop cloth that one deck prevents water evaporates in its shop, surface;
D) maintenance is sent in the die trial that step c) is formed;
E) with the die trial demoulding of step d) maintenance moulding, Measuring Time is according to the rules measured the deflection of described concrete confined expansion constriction device;
F), obtain the stress σ of described test block with the elastic modulus and the following formula of bar diameter numerical value substitution of the xsect of described concrete confined expansion constriction device, described restriction reinforcing bar:
Wherein: E limits in " concrete confined expansion constriction device " to make the elastic modulus of reinforcing bar;
D limits in " concrete confined expansion constriction device " to make the bar diameter of reinforcing bar;
A is the cross-sectional area of " concrete confined expansion constriction device ";
ε is at described specifying measurement deflection of " concrete confined expansion constriction device " in the time.
Wherein the initial length value measured by step b) of deflection ε and test block can be obtained the deflection that described concrete limits constriction device length at the following formula of length value substitution that described specifying measurement recorded in the time, and described formula is as follows:
Wherein: L
2The length reading that records in experimental period for test block;
L
1Initial length for concrete restriction constriction device;
L
0Be the test block datum length, be i.e. pour into the length of cement, sand-cement slurry or concrete part in the concrete confined expansion constriction device;
G) the examination body in the different length of times is measured in described stipulated time ± 1 hour.
2. sand-cement slurry according to claim 1, concrete shrinkage stress method of testing, it is characterized in that: the sectional dimension (wide, height) of the sand-cement slurry examination body of described step 1) is 10mm～100mm, length 10mm～1000mm, the sectional dimension (wide, height) of concrete examination body is 50mm～400mm, length 50mm～2000mm.
3. sand-cement slurry according to claim 1, concrete shrinkage stress method of testing is characterized in that: the service precision value that measuring instrument is shunk in described sand-cement slurry expansion is at least 0.001mm.
4. sand-cement slurry according to claim 1, concrete shrinkage stress method of testing is characterized in that: step 2 is to carry out under the standard temperature of fog room and humidity, and described standard temperature is 20 ℃ ± 3 ℃, and described standard humidity is more than 90%;
5. sand-cement slurry according to claim 1, concrete shrinkage stress method of testing is characterized in that: step 2 is carried out under the constant temperature and humidity condition, and described thermostat temperature is 20 ℃ ± 2 ℃, and described constant humidity relative humidity is 60 ± 5%.
6. sand-cement slurry according to claim 1, concrete shrinkage stress method of testing is characterized in that: step 2 is carried out under natural temperature and damp condition.
7. sand-cement slurry according to claim 1, concrete shrinkage stress method of testing is characterized in that: described concrete confined expansion constriction device gauge head shrinks the measuring instrument gauge head with described sand-cement slurry expansion and contacts, and the reading exact value is greater than 0.001mm.
8. sand-cement slurry according to claim 1, concrete shrinkage stress method of testing is characterized in that: described test block is by group test, and three test blocks of every composing type are got its mean value as the length variations value, and its calculated value is accurate to behind the radix point at least three.
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