CN111098388A

CN111098388A - Fair-faced concrete and construction process thereof

Info

Publication number: CN111098388A
Application number: CN201911151490.4A
Authority: CN
Inventors: 付志海; 张灵童
Original assignee: China Railway Sixth Group Co Ltd
Current assignee: China Railway Sixth Group Co Ltd
Priority date: 2019-11-21
Filing date: 2019-11-21
Publication date: 2020-05-05

Abstract

The invention provides fair-faced concrete which is prepared from the following components in parts by weight: cement 385-395 parts, sand 705-715 parts, stone 1000-1010 parts, water 150-170 parts, fly ash 95-100 parts and admixture 11-12 parts; the additive is a water reducing agent, and the water reducing agent does not contain chloride. The water reducing agent provided by the invention can effectively enhance the dispersing capacity and slump retaining performance, and further enhance the success rate of one-step forming of the fair-faced concrete.

Description

Fair-faced concrete and construction process thereof

Technical Field

The invention belongs to the technical field of concrete construction, and particularly relates to fair-faced concrete and a construction process thereof.

Technical Field

The foreign high-speed railway has earlier development and more stable economic development, but the passenger flow fluctuation is gentler than that in China, so the passenger flow prediction difficulty is relatively small, and the research theory on the scale of the station house is more mature. The Japanese red soup station is located in the county mountain of Nanyang city, mountain of Japan, and has a building area of 1217.65m²And one layer above ground. The east is a new station body, and the west uses a log house rather with ancient wind. The newly-built station edutainment takes off in the future, uses the modeling inspiration from the gliding wing, and is shaped like an extended wing; adopt the steel construction, the facade is arc steelframe and supports the roof, has adopted a large amount of glass elements, has increased daylighting and inside and outside penetrating sense. As a local station, the station is small and exquisite in size and has a quick passing type space; the other function is to provide rest places for tourists and citizens for the tourists to know relevant service information, and the multifunctional and humanized design is achieved.

The German Berlin central station is built in 1996 and is built and put into use ten years later, is a five-layer steel structure glass building with the floor area of 1.5 ten thousand square meters and is also a third landmark building behind the building of the Ministry of Berlin and the Bolanden castle door. More than 1100 trains enter and exit each day, and 30 ten thousand passengers can be delivered. The station ground track is 320 meters long, the underground platform is 450 meters long, and more than 80 stores are owned. The integrated hub integrates Germany high-speed and ordinary-speed railway, subway, urban area rapid rail traffic and road traffic.

The melben south cross star station is an end station located in the center of a city, and the whole station is similar to a huge sun shade and umbrella, so that the station is very suitable for the climate environment of Australia. The waved roof made of metal and glass steel ribs covers all 14 platforms, the supported glass wall provides good lighting for the interior of the station, and the bottom of the glass wall made of metal steel does not touch the ground, so that a huge 'ventilating duct' surrounding the station is formed, and air circulation in the station is guaranteed.

The development of the high-speed railway in China is late, but along with the continuous deepening of the reform degree of China and the steady increase of economy, the high-speed railway is being rapidly built at a speed which is several times faster, and the building of a high-quality and convenient railway passenger station is imperative. The high-speed railway station is a main node for connecting urban roads and the high-speed railway, is a realization place for various contents such as passenger station entering and exiting, transfer, waiting and the like, is an important building entity for investment of the high-speed railway, and is very important for railway departments and passengers, so that the scale of station rooms has important influence on the urban roads and the high-speed railway.

The railway passenger station is the foremost direct window of the railway, is a landmark building of a place, and is highly valued by local governments and social circles all the time. The scale is too large, so that the investment and operation cost are increased, the transfer and running distance in the passenger station is too long, and too much time is consumed; the small scale is not beneficial to the development of various services of the station, so that a large amount of passengers are gathered in the peak period, and certain potential safety hazards exist in management.

Disclosure of Invention

In the construction of the station house, the underground layer is provided with a plurality of central columns and beams which need to be subjected to the bare concrete construction.

The invention adopts the following technical scheme:

the clear water concrete is prepared from the following components in parts by weight:

cement 385-395 parts, sand 705-715 parts, stone 1000-1010 parts, water 150-170 parts, fly ash 95-100 parts and admixture 11-12 parts;

the additive is a water reducing agent, and the water reducing agent does not contain chloride.

In one embodiment of the present invention, the cement is selected from the group consisting of portland cement, ordinary portland cement, portland slag cement, pozzolanic portland cement, fly ash portland cement, and composite portland cement.

In a particular embodiment of the invention, the cement is selected from p.o42.5 portland cement.

In a particular embodiment of the invention, the sand is selected from the group having one or more of the following specification characteristics:

1) medium sand with fineness modulus more than 2.6;

2) the mud content is less than 3.0 percent;

3) the content of mud lumps is less than 1.5 percent.

In a particular embodiment of the invention, the stones are selected from the group having one or more of the following specification characteristics:

1) the grain diameter is 5-25 mm;

2) the mud content is less than 1 percent;

3) the content of mud blocks is less than 0.5 percent;

4) the stone contains needle-shaped particles no more than 15%.

According to a specific embodiment of the invention, the water reducing agent is prepared from the following components in parts by weight: 25-35 parts of methyl allyl polyoxyethylene ether, 3-4 parts of acrylic acid, 0.5-2 parts of sodium polyaspartate, 5-7 parts of coconut oil and 0.5-1 part of ammonium persulfate.

The components are mixed and stirred for 1-2h at the temperature of 60-70 ℃ to obtain the water reducer.

The invention also provides a construction process of the fair-faced concrete, which comprises the following steps:

1) stirring the concrete for later use;

2) selecting a template type and installing;

3) pouring a layer of stone-removed cement mortar to the bottom in the template, pouring concrete after compacting, and vibrating by using a vibrating rod;

4) and (5) removing the mold and maintaining.

In a specific embodiment of the invention, in the step 1), the prepared spare concrete after stirring meets the requirements that the pressure bleeding rate is less than 22 percent and the slump loss is less than 30 percent after 90 min.

In the step 2), the template is strictly processed according to the design, the processing precision is strictly controlled, the surface of the template is ensured to be flat and square, and the joint is tight.

According to a specific embodiment of the invention, in the step 3), the pouring thickness of cement mortar is 30-50 mm; the vibration time of each vibration point is 20-30sec before the concrete surface does not sink and no air bubble escapes, and the over-vibration is prevented from segregation; the drawing speed of the vibrating rod is 75mm/sec, and the distance between the vibrating rod and the surface of the fair-faced concrete is kept to be not less than 50mm in the vibrating process.

In the step 4), the time for stripping the bare concrete of the vertical surface structure is 1-2 times longer than that for stripping the ordinary concrete, so that the stripping is not adhered, and the edges and corners of the finished concrete are complete. The maintenance requirement of the clear concrete is stricter than that of the common concrete; the concrete facade structure needs to be maintained immediately after being demolded, a customized plastic film sleeve is adopted for wrapping, moisturizing and maintaining, and a curing agent is not adopted for maintaining; after the concrete pouring of the beam is finished, the beam is leveled in sections, and then the beam is covered by plastic cloth in time. After the concrete is hardened, watering and curing can be carried out on the side surface, and cracks are prevented strictly.

The concrete curing time is generally not less than 14 days.

The concrete surface after the template is removed can not be directly covered by a straw curtain or a straw bag so as to avoid permanent yellow pollution, and a clean plastic film is adopted for tight covering and maintenance; if heat preservation is needed, a straw curtain or a straw bag can be covered outside the plastic film.

Compared with the prior art, the invention has the beneficial effects that:

the water reducing agent provided by the invention can effectively enhance the dispersing capacity and slump retaining performance, and further enhance the success rate of one-step forming of the fair-faced concrete.

Detailed Description

The technical solutions of the present invention will be described clearly and completely below, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

First, material preparation

The template is a 6mm thick sizing steel template produced by Beijing Auyu, the surface treatment is smooth, and the strength and the rigidity meet the construction requirements; the release agent is a marine rock industry water-based release agent.

The quality of various raw materials, additives and admixtures is tested again and meets the requirements of relevant regulations; the technical parameters of the concrete such as the mixing proportion and the like meet the relevant requirements of design and construction schemes.

The sand content is controlled within the range of 38-42% by using non-alkali active aggregate.

Slump requirement: the column concrete is 150mm plus or minus 20mm, and the beam concrete is 170 mm plus or minus 20 mm.

The mixing time of the concrete is prolonged by 20-30s compared with that of the common concrete; draining accumulated water in the charging barrel after the concrete transport vehicle is cleaned each time; and the transport time difference of the concrete is controlled, the time from the end of stirring to the time before the clear water concrete mixture enters the mold is not more than 90min, and the overlarge slump loss is avoided.

Secondly, template treatment

1. The surface finished by the last use must be cleaned before the template is used.

2. The main contents of processing the bare concrete template

(1) Determining the type of the template according to the requirements of the appearance quality of the bare concrete, the division of a construction flowing water section, the turnover frequency of the template and the like;

(2) calculating the structural design of the template and designing a template processing diagram;

(3) the method comprises the following steps of (1) designing a plane matched mould of a template, dividing a panel and arranging split bolts;

(4) detailed formwork node design and the like;

(5) the structural sealing or material sealing design of the abutted seams of the template panels and the seams of the adjacent template supporting molds.

3. The release agent is selected from

The template release agent is a high-quality water-based release agent, and is uniformly coated without brush leakage; the water-based release agent for sea rock industry is preferred through field tests.

4. Template processing and acceptance

The template is processed strictly according to the design, the processing precision is strictly controlled, the surface of the template is ensured to be flat and square, and the joint is tight (the allowable deviation is shown in table 1).

TABLE 1 tolerance for machining of integral large form

Order of item	Item	Tolerance deviation (mm)	Inspection method
				1	Height of the formwork	+2	Measuring tape quantity inspection
2	Width of the form	1	Measuring tape quantity inspection
				3	Diagonal difference of template surface	≤2	Measuring tape quantity inspection
4	Flatness of the template	2	Running rule and clearance gauge measurement check
				5	Flatness of edge rib	2	Running rule and clearance gauge measurement check
6	Height difference of abutted seams between adjacent panels	≤0.5	Ruler and clearance gage measurement
				7	Gap between adjacent panel joints	≤0.6	Feeler gauge inspection

The periphery of the steel template of the fair-faced concrete template is processed by adopting an edge milling process, and the panel is preferably polished.

Installing and dismantling a template:

the installation of the template can be carried out according to the technical regulations of large templates in building engineering JGJ74-2003 and the relevant technical regulations of the construction of reinforced concrete engineering templates.

Before the template is installed, the template is firstly installed in a trial mode, and after the template is qualified, the template can be installed formally.

The removal of the template needs to properly prolong the time for removing the template; setting protective measures for the fair-faced concrete column; and the template is required to be cleaned and repaired in time after being dismantled.

Third, concrete engineering

1. Quality requirement of raw materials

(1) Cement: the high-quality ordinary Portland cement with stable quality, low alkali content and small water demand is selected. The cement with the same manufacturer, brand and strength grade is required to meet the requirement of the cement special for the fair-faced concrete. The cement is selected from portland cement, ordinary portland cement, portland slag cement, pozzolanic portland cement, portland fly ash cement and composite portland cement; preferably p.o42.5 portland cement.

(2) Blending materials: the first-grade fly ash is selected, the manufacturer is fixed, the quality and the color are fixed, and impurities are not contained. The loss on ignition of the fly ash is less than 5 percent, the fineness is 8-12 percent, and the water demand ratio is less than 95 percent.

(3) Aggregate: all stones should be produced in the same place of production, the same stone source and the same specification. The stones are graded continuously, the color is uniform, the particle size is 5-25mm, the mud content is less than 1%, the mud block content is less than 0.5%, and the needle-shaped particles are not more than 15%. The medium sand with fineness modulus more than 2.6 is selected, the mud content is less than 3.0, preferably 1.5%, the mud block content is less than 1.5%, the texture is hard, the gradation is good, and the color is uniform and consistent (the alkali active aggregate is forbidden).

(4) Additive: the high-efficiency water reducing agent is adopted and contains proper air entraining components, so that introduced bubbles are uniform and fine, and if the introduced bubbles are large, communicated large bubbles are easily formed, and pitted surfaces appear on the surface of concrete. The concrete is required to have good cohesiveness and water retention, so that segregation or bleeding phenomenon is avoided in the vibrating process, and the difficulty in discharging bubbles caused by too high viscosity of the concrete is avoided. The admixture containing the chloride salt is not required to be used, the color of the concrete is not changed by the admixture, and the surface of the hardened concrete can not cause the phenomena of frost formation or moisture regain.

(5) Design of mix proportion

a. Identical components perform exactly the same mix ratio.

b. The water consumption is reduced as much as possible to improve the compactness, the strength and the durability.

c. The cement consumption is reduced as much as possible under the condition of ensuring the strength, the hydration heat is reduced, and the shrinkage is reduced.

d. The proper sand rate and water-cement ratio are selected, and the sand rate and the water-cement ratio are not too large or too small (the sand rate is 38-42 percent, and the water-cement ratio is 0.4-0.6).

2. Concrete mixing, transportation and inspection in the field

(1) The mixing time of the concrete is prolonged by 20-30s compared with that of the common concrete; the concrete transport vehicle is cleaned each time, and then the accumulated water in the charging barrel is drained; and the transport time difference of the concrete is controlled, and overlarge slump loss is avoided.

(2) The color of the concrete mixture should be uniform, and the concrete in the same visual space can be ensured to have no visible color difference.

(3) The entering concrete is delivered to the field inspection personnel by vehicles by the personnel in the mixing plant, the delivered content has visual concrete appearance color and whether bleeding segregation phenomenon exists, the tester performs sampling test (180 plus 200mm) on the concrete slump of each vehicle, and the slump is not required to be used.

(4) The concrete mixture has excellent working performance and no segregation and bleeding phenomenon, the pressure bleeding rate is less than 22 percent, and the slump loss after 90min is less than 30 percent over time.

3. Pouring of concrete

(1) Before pouring, the garbage in the template needs to be cleaned, and the interior of the mold is kept clean and free of accumulated water.

(2) During concrete pouring, the concrete can meet the requirement of a template under the condition of lighter vibration than that of common concrete construction, and the leveling and compacting degrees are achieved.

(3) When the vibrating rod is adopted for vibrating, the vibration points of the concrete are distributed from the middle to the edge, the rod distribution is uniform, the hasps are buckled layer by layer, and the concrete is continuously poured.

(4) The inserting depth of the vibrating rod is larger than the pouring thickness, and the vibrating rod is inserted into the lower layer concrete by 50-100mm, so that the poured concrete is uniform and compact in form.

(5) The interval time of the two successive concreting is not more than 30 minutes, before the second concreting, a concrete layer with the thickness of 150mm on the top of the concrete of the previous time needs to be vibrated again, so that the concretes poured twice are combined into a compact whole; before vibrating again, the concrete layer can be penetrated by the dead weight of the vibrating rod to confirm that the concrete is not initially set last time. If the time interval between two concrete pouring is 30min, or if the time interval does not exceed 30min, the second layer of concrete can not be directly poured because the self weight of the vibrating rod can not penetrate into the concrete layer, and the concrete is treated according to the contact.

(6) The template and the reinforcing steel bar are prevented from being prized and vibrated in the vibrating process, the vibration time of each vibration point is controlled to be 20-30 seconds until no air bubbles escape and the concrete surface does not sink any more, and the segregation caused by over-vibration is avoided. The drawing speed of the vibrating rod is 75mm/sec, the distance between the vibrating rod and the surface of the fair-faced concrete is kept to be not less than 50mm in the vibrating process, and the influence of the vibrating rod on the surface is reduced.

(7) Before the column is poured, the stone-removed cement mortar with the same strength grade as the concrete is poured by 30-50mm at the root part, and after the concrete is compacted, the concrete is poured, so that the strength after pouring is enhanced; the vibration is required to be poured together with the wall body. If the drop height of the concrete is more than 2m, a hose is connected to the blanking pipe and extends into the column mould, and the blanking height is kept to be not more than 2 m.

(8) In the vibrating process, the splashing of the mortar is reduced as much as possible, and the mortar splashed on the inner side of the template is cleaned in time.

(9) The same column is preferably cast with concrete from the same tanker.

4. Concrete curing

(1) The concrete should be cured from the beginning before initial setting, and the same maturity is ensured, avoiding the surface color difference of the concrete formed thereby.

(2) The time for stripping the bare concrete of the facade structure is 1-2 times longer than that for stripping the ordinary concrete, so that the stripping is not adhered, and the edges and corners of the finished concrete are complete. The maintenance requirement of the clear concrete is stricter than that of the common concrete; the concrete facade structure needs to be maintained immediately after being demolded, a customized plastic film sleeve is adopted for wrapping, moisturizing and maintaining, and a curing agent is not adopted for maintaining; after the concrete pouring of the beam is finished, the beam is leveled in sections, and then the beam is covered by plastic cloth in time. After the concrete is hardened, watering and curing can be carried out on the side surface, and cracks are prevented strictly.

(3) The concrete curing time is generally not less than 14 days.

(4) The concrete surface after the template is removed can not be directly covered by a straw curtain or a straw bag so as to avoid permanent yellow pollution, and a clean plastic film is adopted for tight covering and maintenance; if heat preservation is needed, a straw curtain or a straw bag can be covered outside the plastic film.

5. Concrete form removal

(1) The bare concrete formwork dismantling process is strictly carried out according to the technical regulations of large formworks in constructional engineering JGJ74-2003 and the relevant technical regulations of reinforced concrete engineering construction, and concrete finished products cannot be damaged in the formwork dismantling process.

(2) The form removal must be carried out when the structural concrete strength meets the design requirements, and when no design requirements exist, the concrete should reach the strength level that the surface and edges of the concrete cannot be damaged due to form removal.

(3) The dismounting sequence of the template is carried out according to the design requirement of the template, and after the fasteners are dismounted in sequence, the template is slightly pried away; the formwork must be lifted without colliding with the finished concrete product after confirming that there is no connection between the formwork and the concrete structure.

Maintenance and form removal need strict operation, and the one-step forming rate of the facing fair-faced concrete is improved by matching with concrete used for pouring.

In accordance with the above design requirements, the present application provides the following examples, and provides corresponding comparative examples.

Example 1

A construction process of fair-faced concrete comprises the following steps:

1) taking 385-395 parts of cement, 705-715 parts of sand, 1000-1010 parts of stones, 150-170 parts of water, 95-100 parts of fly ash and 11-12 parts of a water reducing agent of each component of concrete, and stirring for later use; 389 parts of cement, 709 parts of sand, 1005 parts of stone, 160 parts of water, 97 parts of fly ash and 11.2 parts of additive

2) Processing according to the design, controlling the processing precision, and selecting a template with a flat and square surface and a tight joint for installation;

3) firstly pouring a layer of stone-removed cement mortar with the thickness of 30mm to the bottom in the template, pouring concrete after compaction, and vibrating by using a vibrating rod, wherein the vibration time of each vibration point is 20-30sec generally until no air bubbles escape and the concrete surface does not sink, and the phenomenon of segregation caused by over-vibration is avoided;

4) the concrete is cured before initial setting, the same maturity is ensured, and the surface color difference of the concrete formed by the curing is avoided.

Example 2

A construction process of fair-faced concrete comprises the following steps:

1) mixing 389 parts of cement, 709 parts of sand, 1005 parts of stones, 160 parts of water, 97 parts of fly ash and 11.2 parts of additives for later use;

3) pouring a layer of stone-removed cement mortar with the thickness of 40mm to the bottom in the template, pouring concrete after compaction, and vibrating by using a vibrating rod, wherein the vibration time of each vibration point is 20-30 seconds generally until no air bubbles escape and the concrete surface does not sink, and the phenomenon of segregation caused by over-vibration is avoided;

Example 3

A construction process of fair-faced concrete comprises the following steps:

1) 395 parts of cement, 715 parts of sand, 1010 parts of stones, 170 parts of water, 100 parts of fly ash and 12 parts of water reducing agent are taken for stirring for later use;

3) firstly pouring a layer of stone-removed cement mortar with the thickness of 50mm to the bottom in the template, pouring concrete after compaction, and vibrating by using a vibrating rod, wherein the vibration time of each vibration point is 20-30 seconds generally until no air bubbles escape and the concrete surface does not sink, so that the phenomenon of segregation caused by over-vibration is avoided;

The preparation method of the water reducing agent comprises the following steps:

mixing 25-35 parts of methyl allyl polyoxyethylene ether, 3-4 parts of acrylic acid, 0.5-2 parts of sodium polyaspartate, 5-7 parts of coconut oil and 0.5-1 part of ammonium persulfate, and stirring at 60-70 ℃ for 1-2 hours to obtain the water reducer.

Comparative example

The water reducing agent containing the chlorine salt component is adopted, the rest is the same as that in the embodiment 1, and CN201310704531.4 in the prior art is selected as the water reducing agent.

The prepared concrete is evaluated according to the following quality standards, specifically as follows:

1. the appearance quality is generally specified in Table 2

TABLE 2

2. Deviation of dimension

And (4) master control items:

the cast-in-place structure should not have dimensional deviations that affect structural performance and service functions.

For the parts which exceed the allowable deviation of the size and influence the structural performance, installation and use functions, a technical processing scheme is proposed by a construction unit and is approved by a supervision (construction) unit for processing. The treated part should be rechecked and accepted. Checking quantity: and (6) checking the total number. The checking method comprises the following steps: and measuring and checking the technical processing scheme.

General items:

the dimensional deviation of the cast-in-place structure bare concrete should meet the specifications of table 3 below. Checking quantity: and dividing the inspection batches according to the structural joints or construction sections. In the same inspection batch, 10% of the number of the components of the beam and the column should be checked, and the number of the components is not less than 3.

TABLE 3 tolerance of fresh water concrete structure

The quality of the main control project is all qualified through sampling inspection.

The quality of the general project is qualified through sampling inspection; when the counting inspection is adopted, except for special requirements, the qualified point rate of a general project is 80% or more, the deviation of the unqualified point is not more than 1.5 times of the allowable deviation, and serious defects are not required.

According to the standards, the concrete products prepared in the embodiments 1 to 3 all meet the related requirements of the appearance quality and the size deviation, the qualified point rate reaches more than 98 percent, and the success rate of one-step forming of the fair-faced concrete is effectively improved; the concrete product prepared by the comparative example showed the phenomenon of frost or moisture regain.

The performance test of the water reducing agent of each example is carried out according to the standard GB/T8077-2012:

TABLE 4 measurement results of fluidity of cement paste

The water reducing agents of examples 1 to 3 exhibited excellent dispersing ability and slump retaining ability.

The following method can be adopted for repairing and protecting the fair-faced concrete in the later period:

1. concrete finished product repairing and surface spraying construction

1) The method is characterized in that the defect part of the engineering concrete finished product is repaired by adopting cement paste (or mortar) prepared from common cement and white common cement of the same variety used in the engineering, and a test is firstly carried out on a sample plate to determine the repairing method and the material ratio.

2) The concrete product has no obvious repairing mark in the repaired part after the cement slurry (or mortar) in the repaired part is hardened and polished with fine sand paper and washed with water.

3) The outer surface of the bare concrete project can be sprayed with a transparent protective agent or a colored transparent protective agent for protective treatment, and the sprayed layer is uniform and transparent.

4) The selected protective agent has good cohesiveness to the surface of concrete, good aging resistance in the open air environment and no corrosiveness to the concrete.

5) Before spraying construction, the whole surface is cleaned, and after drying, spraying construction can be carried out.

6) The transparent paint is preferably fluorocarbon resin paint, polyurethane paint or acrylic resin paint, and the construction method is carried out according to the requirement of the product specification

2. Finished product protection

1) The subsequent construction process of the fair-faced concrete can not damage or pollute the finished product of the fair-faced concrete finished by the previous process; when the outer hanging frame is used after the form is removed, a rubber plate is padded at the contact point of the outer hanging frame and the concrete wall surface, so that the scratch is avoided.

2) Before engineering, plastic film is used for protection to prevent the surface of concrete from being polluted.

3) The consciousness of protecting the concrete finished product by the conscious of field personnel is improved through publicity.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The fair-faced concrete is characterized by comprising the following components in parts by weight:

2. The fair-faced concrete of claim 1, which is prepared from the following components in parts by weight:

389 parts of cement, 709 parts of sand, 1005 parts of stone, 160 parts of water, 97 parts of fly ash and 11.2 parts of additive.

3. The bare concrete according to claim 1, wherein: the cement is selected from portland cement, ordinary portland cement, portland slag cement, pozzolanic portland cement, portland fly ash cement, and composite portland cement.

4. The bare concrete according to claim 3, wherein: the cement is selected from P.O42.5 ordinary portland cement.

5. The bare concrete according to claim 1, wherein: the sand is selected from sand having one or more of the following specification characteristics:

1) medium sand with fineness modulus more than 2.6;

2) the mud content is less than 3.0 percent;

3) the content of mud lumps is less than 1.5 percent.

6. The bare concrete according to claim 1, wherein: the stones are selected from the group having one or more of the following specification characteristics:

1) the grain diameter is 5-25 mm;

2) the mud content is less than 1 percent;

3) the content of mud blocks is less than 0.5 percent;

4) the stone contains needle-shaped particles no more than 15%.

7. The bare concrete according to claim 1, wherein: the water reducing agent is prepared from the following components in parts by weight: 25-35 parts of methyl allyl polyoxyethylene ether, 3-4 parts of acrylic acid, 0.5-2 parts of sodium polyaspartate, 5-7 parts of coconut oil and 0.5-1 part of ammonium persulfate.

8. The construction process of the fair-faced concrete is characterized by comprising the following steps of:

1) stirring the concrete for later use;

2) selecting a template type and installing;

4) and (5) removing the mold and maintaining.

9. The bare concrete construction process according to claim 8, wherein: in the step 1), the prepared spare concrete after stirring meets the requirements that the pressure bleeding rate is less than 22 percent and the slump loss is less than 30 percent after 90 min.

10. The bare concrete construction process according to claim 8, wherein: in the step 4), the formwork stripping time of the bare concrete of the vertical surface structure is 1-2 times longer than that of the common concrete; the concrete curing time is generally not less than 14 days.