CN115124285A

CN115124285A - Environment-friendly impervious concrete

Info

Publication number: CN115124285A
Application number: CN202111498299.4A
Authority: CN
Inventors: 梁峥; 毕根有; 董福生; 高帅洋; 冯亚培; 高雅静; 刘新锋
Original assignee: Dengfeng Zhonglian Concrete Co ltd
Current assignee: Dengfeng Zhonglian Concrete Co ltd
Priority date: 2021-12-09
Filing date: 2021-12-09
Publication date: 2022-09-30

Abstract

The invention belongs to the technical field of concrete, and particularly relates to environment-friendly anti-permeability concrete which comprises the following components in parts by weight: 1 of cement weight ratio; the weight ratio of the stones is 3.67-4.92; the weight of the sand accounts for 5.14-5.85; the weight ratio of tap water is 0.63-0.67; the weight ratio of the additive to the water reducing agent is 0.04; the weight of the fly ash accounts for 0.36-0.41; the weight ratio of the mineral powder is 0.28-0.45; the weight ratio of the waste water is 0.21-0.29; the weight ratio of the swelling waterproof agent is 0.11-0.12. The environment-friendly anti-permeability concrete provided by the invention has the following beneficial effects: adding wastewater with the concentration of 5%, curing the concrete specimen for 28 days under standard conditions according to the water used for the mixture, and respectively performing impermeability tests by adopting a step-by-step pressurization method and a water seepage height method under the condition of adding 30% of the water used for the mixture, wherein three types of impervious concrete, namely C25P6, C30P6 and C35P6, are determined to reach the impermeability grade of P6 by the step-by-step pressurization method; by controlling the concentration and the mixing amount of the waste water, when the concrete is prepared, the fineness of cement slurry in the waste water is fine, the compactness of the concrete is improved, and the anti-permeability of the concrete is improved.

Description

Environment-friendly impervious concrete

Technical Field

The invention belongs to the technical field of concrete, and particularly relates to environment-friendly impermeable concrete.

Background

In order to realize high performance of concrete and full utilization of natural resources, mineral admixture and waste water of waste concrete after sand and stone separation are fully utilized, and the mineral admixture and the waste water are applied to the concrete through advanced technology and a large number of tests according to the requirements of national standards, so that the performance of the concrete is improved, the cost is saved, and good technical, economic and environmental benefits are achieved.

The concrete admixture is specifically defined in GB/T18736-2002 mineral admixture for high-strength and high-performance concrete: the addition of various fine mineral admixtures for improving the durability of concrete, also called mineral admixtures, is mainly characterized by fine mineral materials with fineness smaller than that of cement particles, and is mainly used for improving the durability and the working performance of concrete.

The self-performance of low-calcium fly ash, granulated blast furnace slag and concrete wastewater is mainly adopted and mixed into waterproof and anti-permeability concrete according to a certain proportion to achieve a good anti-permeability effect.

The waste water obtained after the existing concrete station, cleaning equipment or mud tank truck is generally directly discharged without treatment, even the waste water after precipitation treatment is discharged, and the waste water is not further utilized to manufacture concrete.

Disclosure of Invention

In view of the above, the invention provides an environment-friendly impermeable concrete, which aims to solve the problems that the waste water obtained after the existing concrete station, cleaning equipment or mud tank truck is generally directly discharged without treatment, and even the waste water after the precipitation treatment is discharged, the waste water is further utilized to prepare the concrete.

In order to achieve the purpose, the invention is realized by the following technical scheme:

the invention provides environment-friendly anti-permeability concrete which comprises the following components in parts by weight: 1 of cement weight ratio; the weight ratio of the stones is 3.67-4.92; the weight of the sand accounts for 5.14-5.85; the weight ratio of tap water is 0.63-0.67; the weight ratio of the additive to the water reducing agent is 0.04; the weight of the fly ash accounts for 0.36-0.41; the weight ratio of the mineral powder is 0.28-0.45; the weight ratio of the waste water is 0.21-0.29; the weight ratio of the swelling waterproof agent is 0.11-0.12.

In the above-described environment-friendly anti-permeability concrete, as a preferred technical scheme, the weight ratio of the components of the concrete C25P6 is cement to stones to sand to tap water to fly ash to wastewater: the expansion waterproofing agent is 1: 5.85: 4.29: 0.67: 0.04: 0.41: 0.28: 0.29: 0.11.

In the above-mentioned environment-friendly impervious concrete, as a preferred technical solution, the weight ratio of the components of the concrete C30P6 is cement, stone, sand, tap water, admixture, coal ash, mineral powder, wastewater: the expansion waterproofing agent is 1: 5.6: 4.2: 0.65: 0.04: 0.5: 0.4: 0.28: 0.12.

In the above-mentioned environment-friendly impervious concrete, as a preferred technical solution, the weight ratio of the components of the concrete C35P6 is cement, stone, sand, tap water, admixture, coal ash, mineral powder, wastewater: the expansion waterproofing agent is 1: 5.14: 3.67: 0.63: 0.04: 0.36: 0.45: 0.21: 0.12.

In the above-mentioned environment-friendly impervious concrete, as an optimized technical scheme, the waste water is produced by washing waste concrete in a concrete station or washing a tank body of a transport tank car, separating sand and stones by a sand-stone separator, and diluting waste slurry by a drainage ditch system, a multistage sedimentation tank system and an automatic injection clear water system.

In the above environment-friendly impervious concrete, as a preferred technical scheme, the total water consumption of the wastewater station is 30%, and the concentration of wastewater is 5%.

In the environment-friendly anti-permeability concrete, as a preferred technical scheme, the mineral powder and the fly ash are used for replacing part of cement, and the proportion of the mineral powder and fly ash admixture in the total mass of the mineral powder, the cement and the fly ash is 40-50%; wherein the mixing amount of the mineral powder is 25 percent.

In the above-mentioned environment-friendly impervious concrete, as a preferred technical scheme, the swelling waterproofing agent is FAE fiber crack-resistant swelling waterproofing agent.

The invention provides environment-friendly anti-permeability concrete which has the following beneficial effects:

(1) adding wastewater with the concentration of 5%, curing a concrete test piece for 28 days under standard conditions according to the water used for the mixture and the water used for the mixture of 30%, respectively carrying out impermeability tests by adopting a step-by-step pressurization method and a water seepage height method, and determining that three impermeability concretes, namely C25P6, C30P6 and C35P6, all reach the impermeability grade of P6 by the step-by-step pressurization method;

(2) by controlling the concentration and the mixing amount of the waste water, when the concrete is prepared, the fineness of cement slurry in the waste water is fine, so that concrete gaps are filled, the compactness of the concrete is improved, and the anti-permeability capability of the concrete is improved;

(3) the waste water improves the compressive strength of the concrete to a certain extent, and is beneficial to the strength development of the test piece; when the waste water is used for preparing low-grade concrete, the early strength of the concrete is low, but the later strength of the concrete is well developed. The high alkalinity of the wastewater promotes the secondary hydration of mineral admixtures, reduces the porosity, improves the compactness of concrete, and further improves the impermeability of the concrete, which is consistent with the impermeability result;

(4) the fine particles in the admixture (fly ash and mineral powder) are uniformly distributed in the cement slurry to fill capillary pores, so that the pore structure of the concrete is improved, the effect of increasing the compactness is achieved, the impermeability of the concrete is facilitated, and the mineral admixture with a high proportion is beneficial to secondary hydration in the alkaline environment of wastewater, so that the compactness of the concrete is enhanced.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the table in the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all 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.

Exemplary embodiments of the present invention are described below in conjunction with specific cases:

the first embodiment is as follows: an environment-friendly impervious concrete comprises the following components in parts by weight of kg/m 3: 1 of cement weight ratio; the weight ratio of the stones is 3.67-4.92; the weight of the sand accounts for 5.14-5.85; the weight ratio of tap water is 0.63-0.67; the weight ratio of the additive to the water reducing agent is 0.04; the weight of the fly ash accounts for 0.36-0.41; the weight ratio of the mineral powder is 0.28-0.45; the weight ratio of the waste water is 0.21-0.29; the weight ratio of the swelling waterproof agent is 0.11-0.12.

In the above-mentioned environment-friendly impervious concrete, as a preferred technical solution, the weight ratio of each component of the concrete C25P6 is cement, stone, sand, tap water, admixture, fly ash, mineral powder, wastewater: the expansion waterproofing agent is 1: 5.85: 4.29: 0.67: 0.04: 0.41: 0.28: 0.29: 0.11.

In the above-described environment-friendly impermeable concrete, as a preferred technical scheme, the weight ratio of each component of the concrete C30P6 is cement to stone to sand to tap water to admixture to fly ash to mineral powder to wastewater: expansion waterproofing agent 1: 5.6: 4.2: 0.65: 0.04: 0.5: 0.4: 0.28.12.

In the above-described environment-friendly impermeable concrete, as a preferred technical scheme, the weight ratio of each component of the concrete C35P6 is cement, gravel, sand, tap water, admixture, fly ash, mineral powder, wastewater: the expansion waterproofing agent is 1: 5.14: 3.67: 0.63: 0.04: 0.36: 0.45: 0.21: 0.12.

In the above-mentioned environment-friendly impervious concrete, as the preferred technical scheme, the waste water is the waste water produced by washing the waste concrete or washing the tank body of the transport tank car in the concrete station, after separating out sand and stone by the sand-stone separator, the waste slurry is diluted by the drainage ditch system, the multistage sedimentation tank system and the automatic clear water injection system.

In the above-mentioned environment-friendly impervious concrete, as a preferred technical scheme, the total water consumption of the wastewater station is 30%, and the concentration of wastewater is 5%.

The mineral powder mainly comprises granulated blast furnace slag

Granulated blast furnace slag is a mineral admixture with latent hydraulic properties. The material contains a large amount of CaO (35-48 percent) and contains active SiO2 and Al2O 3. The additive has no independent hydraulicity per se, but under the excitation of CaO and CaSO4, the latent hydraulicity can be excited to generate slow hydration; when excited by an alkali metal compound such as Na2O or K2O, the compound is strongly hydrated to form a hard hardened body, that is, a so-called "alkali slag cement". The material has certain volcanic ash reaction capability.

Due to the unique chemical composition and particle size of the ground slag, granulated blast furnace slag plays a very important role in concrete. The method mainly comprises the following steps: volcanic ash effect: the slag micro powder particles are spherical, the surface is smooth and compact, the main chemical components of the slag micro powder particles are SiO2, Al2O3 and CaO, the slag micro powder particles have ultrahigh activity, the slag micro powder particles are doped into cement, and during hydration, the activated SiO2 and Al2O3 react with Ca (OH)2 generated in a mixed gelling system to further form a hydrated calcium silicate product which is filled in gaps. Finer slag admixtures will increase the contact area with other admixtures, i.e., affect the effective area for reaction with Ca (OH)2, and thus affect the extent of reaction with Ca (OH)2 and the quantity and quality of the hydration product. When the slag powder is ground, more internal defects can be exposed, and the particle reaction area is increased, so that the reaction activity and the reaction opportunity are improved. (II) micro-particle effect: the slag micro powder is wrapped around the cement particles and the aggregates, the quality of the interface is increased due to the ultra-fining, and more siliceous materials and cement particles are densely arranged at the interface to generate more hydrates, so that the interface is firmly connected. The hydration product (calcium silicate hydrate gel) is filled in the gap, the compactness is increased, the large and small particles are stacked, the size of the filled gap is reduced, and the obtained fine structure and the pore structure are much finer than those of common cement stone, so that the ion diffusivity can be reduced, and good erosion resistance, durability and high strength are obtained. Meanwhile, the levigated slag has less adsorption water and additives and has a certain water reducing effect. The additive is mixed into cement to mix concrete, so that the slump of the concrete can be increased, the loss of the slump of the concrete is reduced, the effect is more effective than that of mixing additives such as retarder and the like, and the flowing property of the concrete can be obviously improved. (III) crystal nucleus effect: after a sufficient amount of active fine-grinding admixture is mixed, the fine powder can play a role of a crystal nucleus in the hydration process, so that the hydration of silicate minerals is promoted, and the compactness of a cement stone structure is improved. The active SiO2 in the admixture can gradually react with Ca (OH)2 in the set cement and high-alkaline calcium silicate hydrate for the second time to generate low-alkaline calcium silicate hydrate, and meanwhile, Ca (OH)2 also reacts with active Al2O3 in the admixture to generate calcium aluminate hydrate, or reacts with SiO2 and Al2O3 to generate calcium aluminate hydrate. Thus, the quantity of hydration products is increased, and unstable high-alkalinity hydrate is converted into low-alkalinity stable hydrate, so that the structure of the cement stone is compact and stable, and the strength and the performance of the cement stone are greatly improved.

Secondly, fly ash:

fly ash is a powdery ash particle collected from pulverized coal-fired boiler flue gas, the particle size of which is so fine that it can flow in air and be collected by special equipment. The fly ash is a clay pozzolanic material and has potential hydraulic activity. The fly ash is used as a raw material for cement production, so that the fly ash becomes a useful precious resource, the problems of environmental pollution and land occupation caused by the fly ash are solved, the environmental pollution caused by the cement concrete industry is reduced, and the fly ash is the best way for continuously developing roads in the cement concrete industry.

Fly ash is a mineral admixture with pozzolanic reactivity. The material contains little CaO, but contains a large amount of active SiO2 and Al2O3 which have no independent hydraulic property and no potential hydraulic property. The activity of the calcium silicate hydrate and the calcium silicate hydrate is shown in that the calcium silicate hydrate and the calcium silicate hydrate with gelling performance can generate secondary hydration reaction (volcanic ash reaction) with Ca (OH)2 precipitated by cement hydration at normal temperature.

Physical activity of fly ash: the physical activity is the sum of the particle effect and the micro-aggregate effect of the fly ash, is a general term of various physical effects which are not related to the properties of chemical elements of the fly ash, can promote the gelling activity of products and improve the performance (such as strength, impermeability and wear resistance) of the products, is the most valuable activity of the fly ash which can be fully utilized, and is a main source of early activity.

The high-quality fly ash particles are finer than cement, contain a large amount of spherical glass beads, and can be used as aggregates to be doped into mortar, so that the gradation of the fine aggregates tends to be more reasonable. However, it is different from the filling behavior of ordinary inert mineral powder, and the fly ash is also characterized by active filling behavior. The active filling behavior of the fly ash is the hydration reaction of the fly ash active particles, and the microstructure shows that the interface of the fly ash particles and the cement slurry is glued, so that the interface of the slurry and the aggregate has the functions of compacting and replacing air, the gas content is reduced, and the filling effect is enhanced.

But the active filling behavior of the fly ash can not be fully exerted in the later period of the mortar. In the hardening development stage and the hardening early stage, the function of the physical filling material is mainly exerted in the hardening later stage after hardening, and the function of the active filling material is also exerted. Due to the filling action of the fly ash, the internal pores of the mortar, particularly the channels of capillary pores in the slurry, can be reduced, which is very beneficial to improving the impermeability of the mortar.

Meanwhile, the fly ash glass beads play a role of ball bearings so that the fly ash also has a water reducing effect. The water demand of the concrete mortar is mainly determined by the gaps between the mixed particles in the concrete mortar, so that the gaps between the mixed particles must be reduced to reduce the water demand while maintaining a certain consistency. Important factors affecting the void fraction of the mixed particles are mainly from the aggregate.

The concrete mortar is doped with a proper amount of fly ash, namely, an aggregate with a ball effect, so that gaps among mixed particles can be filled, and the rheological property of fresh concrete can be improved.

Chemical activity of fly ash

The fly ash has volcanic ash activity and self-hardening, the reaction process is mainly a dissolution reaction controlled by diffusion, the surface of the fly ash particles at the early stage is dissolved, the reaction product is precipitated on the surface of the particles, and calcium ions at the later stage continuously diffuse to the core part through the surface layer and the precipitated hydration product layer to react with the active SiO 2. The cement particle hydration reaction is performed firstly, and the fly ash active substance is reacted later, so the reaction is called as secondary reaction, and the two hydration reactions are alternately performed in the mortar, supplement each other and mutually restrict each other.

Table 1: chemical composition of mineral admixtures and their comparison with Cement Clinkers (%)

Name (R)	CaO	SiO2	AL2O3	FeO2	MgO	C
							Cement clinker	62-67	20-24	4-7	2-6	Small amount of	-
Low calcium flyash	6.5-10	34-60	17-31	2-25	1-5	＜10
							Slag of mine	30-50	27-40	5-33	1-3	1-21	-

Thirdly, the waste water after the concrete is separated by sand and stone

The waste water used in production is mainly waste water generated by washing waste concrete and a tank body of a transport tank car, sand and stones are separated by a sand-stone separator, and the waste water is mixed with clear water for use after precipitation, dilution, stirring and metering. The concrete waste water precipitate mainly comprises unhydrated gelled materials (cement, mineral powder, fly ash and the like), hydrated calcium silicate gel, residual additives, Ca (OH)2, a small amount of mud, fine aggregate particles and other insoluble substances, has a pH value as high as 12, and is strong in alkalinity. A large number of tests prove that when the concentration of the waste water is 5 percent, the water consumption for production and mixing can be added to 30 percent for the concrete with the concentration of c30 or below, the influence on various performances of the concrete is not large, the performance is optimal, and the strength of the concrete is stable. However, according to the characteristics of waste water, the use of waste water is prohibited in the production of special concrete, high-grade concrete prestressed concrete, decorative concrete, high-strength concrete and concrete exposed to corrosive environment of C40 and above.

Fourth, the function of the admixture in concrete

The chemical composition and characteristics of the admixture determine that the admixture not only plays a good role in filling and compacting and a good role in micro-aggregate in concrete, but also has different surface adsorption effects and pozzolan activities. The functions can improve the internal pore structure of the concrete, influence the hydration process of concrete gel components, coordinate the strength development of the concrete, effectively improve the composition and structure of hydration products, optimize the structure and performance of an interface transition area in the concrete, and finally improve the comprehensive performance of the concrete.

The role of mineral admixtures in concrete can be generally divided into:

1. volcanic ash effect

Among mineral components of the cement clinker, the mineral components which greatly contribute to the strength are C3S and C2S, and hydration products generated after the hydration of the two are mainly high-alkalinity hydrated calcium silicate and calcium hydroxide. Compared with calcium silicate hydrate with high alkalinity, the calcium silicate hydrate with low alkalinity has much higher strength and higher stability. The main reason is that after the mineral admixture is added, the composition of the cementitious substance in the set cement can be improved, calcium hydroxide is reduced or eliminated, the quality of the cementitious substance of calcium silicate hydrate is improved, the quantity of the cementitious substance is greatly increased, and the interface structure of the set cement and the aggregate is also improved. The active SiO2 in the active mineral admixture can react with calcium hydroxide and high-alkalinity calcium silicate hydrate for the second time to generate low-alkalinity calcium silicate hydrate with higher strength and better stability.

2. Filling and compacting effect

The fine particles in the admixture are uniformly distributed in the cement paste, capillary pores are filled,

improving the concrete pore structure and increasing the effect of compactness; after a proper amount of mineral admixture is mixed into the concrete and is uniformly mixed, the grain composition of the powder is more reasonable, and the compactness is improved; the impermeability and Cl erosion resistance of the concrete are improved.

The average particle size of cement is usually 20 to 30 μm, and since particles smaller than 10 μm are insufficient, the filling property of cement particles is not good. The superfine mineral materials such as superfine fly ash and superfine slag with the average particle size of 3-6 microns can be filled in gaps among cement particles, so that the compactness of the set cement is improved, and the strength and the impermeability of the set cement are improved.

3. Plasticizing effect

Because the particle size of the superfine mineral admixture is far smaller than that of cement particles, the superfine mineral admixture plays a role of rolling balls among the cement particles, so that the fluidity of cement paste is increased; meanwhile, in the slurry without the mineral admixture, gaps among cement particles are not filled by solid particles, so that a large amount of mixing water is filled in the gaps, and after the mineral admixture is doped, the filling water filled in the gaps can be replaced by the superfine mineral admixture filled among the cement particles to form free water, so that a water spacer layer among the particles is thickened, and the flowability of the fresh concrete is increased.

Furthermore, mineral admixtures are generally less dense than cement and when incorporated into cement slurries, the resulting cement slurries are more bulky than previously, which is one of the reasons for improving the plasticity of the concrete.

4. Effect of improving durability

When portland cement concrete is in an environment with aggressive media, the aggressive media react with hydration products ca (oh)2 and C3AH6 or C4AH13 in the set cement to produce dissolved or expanded substances, which destroy the concrete structure.

After the mineral admixture is added, on one hand, due to the dilution effect and the volcanic ash effect, the quantity of hydration products Ca (OH)2 which are easy to cause corrosion, coarse crystallization and weak strength is reduced, low-alkalinity hydrated calcium silicate with high strength, better stability and more quantity is generated, the composition of hydrated cementitious substances is improved, the enrichment and directional arrangement of Ca (OH)2 on a transition region of a cement stone-aggregate interface are reduced, and thus, the cement stone-aggregate interface structure is optimized; on the other hand, the mineral admixture is uniformly dispersed in the concrete, and as the hydration is carried out, the structure of the set cement and the interface structure are more compact due to the exertion of the volcanic ash effect and the micro powder filling compaction effect, the porosity inside the concrete is reduced, and the pore structure is improved, so that a water seepage channel which is possibly formed is blocked, the invasion of erosion media including chloride is also blocked, and the durability of the concrete is greatly improved.

Table 2:

application of admixture in concrete engineering

1. The admixture can replace part of cement, the cost is low, and the economic benefit is remarkable; 2. the later strength of the concrete is increased. The mineral fine admixture contains active SiO2 and Al2O3, and reacts with gypsum in cement and Ca (OH)2 generated by hydration of the cement to generate C-S-H, C-A-H and hydrated calcium sulphoaluminate. The later strength of the concrete is improved; 3. the workability of the fresh concrete is improved. After the fluidity of the concrete is improved, the concrete is easy to separate and bleed, and after the mineral fine admixture is doped, the concrete has good cohesiveness. The admixture with small water requirement such as fly ash can also reduce the water-cement ratio of the concrete and improve the durability of the concrete; 4. the temperature rise of the concrete is reduced. The cement hydration generates heat, the concrete is a poor heat conductor, the internal temperature of the concrete can reach 50-70 ℃ in the large-volume concrete construction, the temperature is higher than the external temperature, temperature stress is generated, the internal volume of the concrete expands, and the external concrete shrinks along with the reduction of the air temperature. The internal expansion and external contraction create large tensile stresses in the concrete, resulting in cracks in the concrete. The addition of the admixture reduces the consumption of cement, further reduces the hydration heat of the cement and reduces the temperature rise of the concrete; 5. the alkali-aggregate reaction is inhibited. Experiments prove that when the mixing amount of the mineral admixture is large, the alkali-aggregate reaction can be effectively inhibited; 6. the durability of the concrete is improved. The durability of the concrete is closely related to Ca (OH)2 generated by cement hydration, and the mineral fine admixture and the Ca (OH)2 are subjected to chemical reaction, so that the content of Ca (OH)2 in the concrete is reduced; meanwhile, large capillary pores in the concrete are reduced, the pore structure of the concrete is optimized, the concrete structure is more compact, and the durability of the concrete, such as frost resistance, impermeability, sulfate erosion resistance and the like, is improved; 7. the super-overlapping effect is compounded by different fine mineral admixtures. The fine admixtures of different minerals have respective characteristics in the concrete, for example, the slag volcanic ash has higher activity, is beneficial to improving the strength of the concrete, but has large self-drying shrinkage; the concrete doped with the high-quality fly ash has small water demand, and has small self-drying shrinkage and drying shrinkage, and can ensure better anti-carbonization performance under low water-cement ratio.

Fifthly, carrying out impermeability comparison test on the waste water mixed concrete and the reference concrete

(I) test raw Material

1. Cement (C) GB 175-: the middle-linked P.O 42.5 cement is selected, and the main performance indexes are shown in table 3.

2. Fly ash (F) GB/T1596-2017: the Huarun class II fly ash is selected, and the main performance indexes are shown in table 4.

28d Activity (%)	Fineness (0.045mm)	Ignition loss (%)	Water demand ratio (%)
				75	28	5.0	103

3. Mineral powder (K) GB/T18046-2017: the mineral powder of grade S95 is selected and used, and the main performance indexes are shown in table 5.

4. Polycarboxylic acid admixture GB 8076-: the main properties of Luoyang Junjiang are shown in Table 6.

5. Pebble (G) GB/T14685-2011: according to the test, 5-25 mm of broken stones are adopted, the grading is good, the mud content is 0.4%, the mud block content is 0.2%, the needle-shaped particles are 6%, the apparent density is 2675kg/m3, and the bulk density is 1560kg/m 3;

6. mechanism sand (S1) GB/T14684-2011: the sand is made by a washing machine, the fineness modulus is 3.4, the gradation is good, the mud content is 1.0 percent, and the mud block content is 0 percent;

7. fine sand (S2) GB/T14684-2011, wherein the fineness modulus is 0.8, the mud content is 1.5 percent, and the mud block content is 0.2 percent;

8. tap water (W): JGJ63-2006 Water Standard for concrete;

9. and (3) recovering wastewater: JGJT328-2014 green production and management technical specification of ready-mixed concrete, using wastewater with the concentration of 5 percent;

FAE fibre anticracking expansion waterproof agent (Table 7)

(II) impermeability test after mixing waste water into concrete

The concrete test method comprises the steps of carrying out concrete test preparation by adopting 3 reference mixing ratios of different cement-based materials, wherein three marks are C25P6, C30P6 and C35P6 respectively, testing the slump and the time-lapse slump of the concrete according to GB/T50080 standard of common concrete mixture performance test method, manufacturing a concrete test piece of 150mm multiplied by 150mm, demoulding and taking out after 1d of maintenance, placing in a standard maintenance room for maintenance, and testing the compressive strength of the concrete after 3d, 7d and 28d of age.

The water permeability resistance test was carried out according to the test method specified in GB/T50082-2009, using a truncated cone-shaped test piece (top diameter 175mm, bottom diameter 185mm) with a height of 150 mm. And curing for 28 days under standard conditions, and measuring the impermeability of the waterproof concrete by adopting a step-by-step pressurization method.

1.1 Standard concrete mix proportion (Table 8)

1.2 Standard cured concrete test pieces of 3d, 7d and 28d reference concrete (Table 9).

1.3 Standard concrete impermeability test (Table 10)

2.1 according to the reference mixing proportion, selecting the wastewater with the slurry concentration of 5%, adding 30% of the total amount of the water for the mixture to replace the water for the mixture, and setting the mass ratio of the water consumption of the tap water to the wastewater as follows (Table 11):

2.2 Standard curing Strength and workability of waste concrete 3d, 7d and 28d (Table 12)

2.3 Permeability comparison tests were carried out on the concrete mixed with 5% strength waste water and the reference concrete (Table 13)

And (3) test analysis: from the test results, the permeation resistance of the mixed concrete prepared by the tap water and the mixed concrete mixed with 30 percent of wastewater has no obvious difference.

And (4) conclusion:

(1) when the wastewater with the concentration of 5% is mixed, the concrete specimen is maintained for 28 days under the standard condition according to the water for the mixture and under the condition of mixing the water for the mixture for 30%, a step-by-step pressurization method and a water seepage height method are respectively adopted for carrying out impermeability test, and three types of impervious concrete, namely C25P6, C30P6 and C35P6, are tested to reach the impermeability grade of P6 by the step-by-step pressurization method.

(2) By controlling the concentration and the mixing amount of the waste water, when the concrete is prepared, the fineness of the cement slurry in the waste water is fine, so that concrete gaps are filled, the compactness of the concrete is improved, and the anti-permeability capability of the concrete is improved.

(3) The waste water improves the compressive strength of the concrete to a certain extent, and is beneficial to the strength development of the test piece. When waste water is used for preparing low-grade concrete, the early strength is low, but the later strength is well developed. The high alkalinity of the wastewater promotes the secondary hydration of the mineral admixture, reduces the porosity, improves the compactness of concrete, and further improves the impermeability, which is consistent with the impermeability result.

Claims

1. An environment-friendly impervious concrete is characterized in that: the paint comprises the following components in parts by weight:

1 of cement weight ratio;

the weight ratio of the stones is 3.67-4.92;

the weight of the sand accounts for 5.14-5.85;

the weight ratio of tap water is 0.63-0.67

The weight ratio of the additive to the water reducing agent is 0.04;

the weight of the fly ash accounts for 0.36-0.41;

the weight ratio of the mineral powder is 0.28-0.45;

the weight ratio of the waste water is 0.21-0.29;

the weight ratio of the swelling waterproof agent is 0.11-0.12.

2. The environmentally friendly impermeable concrete according to claim 1, characterized in that: the weight ratio of each component of the concrete C25P6 is cement, carpolite, sand, tap water, admixture, coal ash, mineral powder and wastewater: swelling waterproofing agent = 1: 5.85: 4.29: 0.67: 0.04: 0.41: 0.28: 0.29: 0.11.

3. The environmentally friendly impermeable concrete according to claim 1, characterized in that: the weight ratio of the components of the concrete C30P6 is cement, stones, sand, tap water, the admixture, the coal ash, the mineral powder and the wastewater: expansion waterproofing agent = 1: 5.6: 4.2: 0.65: 0.04: 0.5: 0.4: 0.28: 0.12.

4. The environmentally friendly impermeable concrete according to claim 1, characterized in that: the weight ratio of the components of the concrete C35P6 is cement, stones, sand, tap water, the admixture, the coal ash, the mineral powder and the wastewater: swelling waterproofing agent = 1: 5.14: 3.67: 0.63: 0.04: 0.36: 0.45: 0.21: 0.12.

5. The environmentally friendly impermeable concrete according to claim 1, characterized in that: the waste water is produced by washing waste concrete in a concrete station or washing a tank body of a transport tank car, separating sand and stones through a sand-stone separator, and diluting waste slurry through a drainage ditch system, a multistage sedimentation tank system and an automatic clear water injection system.

6. The environmentally friendly, impervious concrete according to any one of claims 1-7, wherein: the total water consumption of the wastewater station is 30%, and the concentration of the wastewater is 5%.

7. The environmentally friendly impermeable concrete according to claim 1, characterized in that: the mineral powder and the fly ash are used for replacing part of cement, and the proportion of the mineral powder and fly ash admixture in the total mass of the mineral powder, the cement and the fly ash is 40-50%; wherein the mixing amount of the mineral powder is 25 percent.

8. The environmentally friendly impermeable concrete according to claim 1, characterized in that: the expansion waterproof agent is an FAE fiber anti-cracking expansion waterproof agent.