CN107391790B - Green self-compacting concrete and preparation method thereof - Google Patents

Abstract

The invention discloses a green self-compacting concrete and a preparation method thereof, wherein the preparation method comprises: calculating the packing density of a cementitious material system, an aggregate system and a mixture system according to a solid particle accumulation mode and a compressible accumulation model; Preselected cementitious material combination, preferred sand ratio, and preselected volume ratio of cementitious material system and aggregate system; water and cementitious material system are determined according to the compressive strength requirements of green self-compacting concrete and the bulk density of the cementitious material system Calculate the specific dosage of cementitious material system, aggregate system and water; determine the dosage of water reducer according to the specific dosage of the cementitious material system; stir and mix evenly to obtain green self-compacting concrete. From the perspective of solid particle accumulation and considering the properties of the raw materials actually selected, the invention optimizes the bulk compactness in combination with the compressible accumulation model, and significantly reduces the amount of cementitious materials.

Description

Green self-compacting concrete and preparation method thereof

technical field

The invention relates to the field of concrete, in particular to green self-compacting concrete and a preparation method thereof.

Background technique

Self-compacting concrete relies on its own weight without additional manual or mechanical vibration. It has excellent working properties such as high fluidity, homogeneity and segregation resistance in pouring construction, and has good mechanical and durability after hardening. High performance concrete. However, the proportion design of self-compacting concrete usually contains a large amount of cementitious material, which leads to high hydration heat, large shrinkage and creep after hardening, and the large amount of CO ₂ emissions generated in the concrete production process will aggravate environmental pollution, and CO ₂ The main source of emissions is cement, which accounts for about 74%-81% of the total _CO2 emissions from concrete, followed by coarse aggregate, which accounts for about 13%-20%. Therefore, the development of green self-compacting concrete with low cementitious material consumption that is more in line with engineering economic and environmental requirements will be an important direction in the future.

At present, there are many mix proportion design methods for self-compacting concrete based on different theories and control parameters at home and abroad, because to meet the stricter performance requirements of the mixture, there are many mix ratio parameters, and the methods to obtain these parameters are also different. For example, the fixed sand and gravel volume content method in European regulations and the advanced method proposed by Japan require a large amount of cementitious materials. These powder-rich self-compacting concrete not only have high cost, but also have large carbon emissions.

Therefore, the existing technology still needs to be improved.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a preparation method of green self-compacting concrete, which aims to solve the technical problems of high cost and heavy pollution caused by the large amount of cementing material in the existing concrete.

The present invention proposes a preparation method of green self-compacting concrete, comprising:

Determine the compaction index of the green self-compacting concrete according to the solid particle accumulation method and the compressible accumulation model, and calculate the bulk compactness of the cementitious material system, aggregate system and mixture system respectively according to the compaction index;

According to the bulk density of the cementitious material system, a preselected combination of cementitious materials is obtained; according to the bulk density of the aggregate system, the preferred sand ratio is obtained; according to the bulk density of the mixture system, the preselected combination of cementitious materials and The preferred sand ratio determines the volume ratio of the preselected cementitious material system to the aggregate system;

According to the compressive strength requirements of green self-compacting concrete and the bulk compactness of the cementitious material system, the mass ratio of water to cementitious material system is determined, and the specific dosage of cementitious material system, aggregate system and water is calculated. The specific dosage range of the cementitious material system is 340kg/m ³ to 380kg/m ³ ;

Determine the dosage of superplasticizer according to the specific dosage of the cementitious material system;

The cementitious material system, the aggregate system, the water and the water reducing agent with determined specific dosages are stirred and mixed uniformly to obtain green self-compacting concrete.

Preferably, the compaction index of the green self-compacting concrete is determined according to the solid particle accumulation mode and the compressible accumulation model, and the bulk density of the cementitious material system, the aggregate system, and the mixture system are calculated respectively according to the compaction index. Before the step of the method, it includes: collecting the performance parameters of preselected cementitious materials and preselected aggregates; the preselected aggregates include: coarse aggregates and fine aggregates; the performance parameters include: density, particle size distribution and particle size distribution. grade volume fraction.

Preferably, the preselected cementitious material combination ratio is obtained according to the bulk density of the cementitious material system; the preferred sand ratio is obtained according to the bulk density of the aggregate system; according to the bulk density of the mixture system, the Preselecting the combination of cementitious materials and the preferred sand ratio, and determining the volume ratio of the preselected cementitious material system to the aggregate system, includes:

According to the different volume ratio combinations of the preselected cementitious materials in the cementitious material system, the bulk density of the cementitious material system with different volume ratio combinations is calculated to determine the combination ratio of the preselected cementitious materials to the cementitious material system;

Calculate the bulk density of the aggregate system under different sand ratios to determine the optimal sand ratio;

Calculate the bulk density of the mixture system composed of different volume ratios of the aggregate system and the cementitious material system, and determine the volume ratio of the cementitious material system to the aggregate system.

Preferably, after calculating the bulk compactness of the aggregate system under different sand ratios and determining the sand ratio, the steps include: according to the sand ratio, using a specified amount of ultra-fine sand powder to replace the original medium sand content; the specified amount range It is 0-20% of the volume content of medium sand.

Preferably, the cementitious material system includes: fly ash and cement; the volume content of the fly ash in the cementitious material system ranges from 20% to 40%.

Preferably, the volume ratio of the cementitious material system to the aggregate system is in the range of 1:5.5 to 1:6.5.

Preferably, the water reducing agent includes: one or more of lignosulfonates, naphthalenes, melamines, sulfamates, aliphatics and polycarboxylic acids; The dosage of the water agent is 2%-4% of the mass of the cementitious material system.

Preferably, before the step of obtaining the green self-compacting concrete by stirring and mixing the cementitious material system, the aggregate system, the water and the water reducing agent with specific dosages, the steps include:

The cementitious material system, the aggregate system, the water and the water reducing agent with the determined specific dosages are formed into a mixture, and the work performance test of the mixture is carried out, and the compressive strength of the mixture is verified;

According to the test results of the work performance of the mixture and the compressive strength of the mixture, the specific dosages of the cementitious material system, the aggregate system, the water and the water reducing agent are adjusted to meet the needs.

Preferably, the cementitious material system, the aggregate system, the water and the water reducing agent will be determined in specific dosages to form a mixture, and the work performance test of the mixture is carried out, and the compression resistance of the mixture is verified. Strength; according to the work performance test results of the mixture and the compressive strength of the mixture, adjust the specific dosage of the cementitious material system, aggregate system, water and water reducing agent to meet the needs, including:

According to the specific dosage, the specific dosage of cementitious material system, aggregate system, water and water reducing agent was taken to form a mixture, and the working performance of the mixture was tested. By adjusting the dosage of the water reducing agent, the mixture was The compound meets the performance requirements;

Under the condition that the working performance is met, verify whether the mixture meets the compressive strength requirements;

If not satisfied, adjust the composition ratio of the cementitious material system or the mass ratio of the water to the cementitious material system to balance the workability of the mixture with the compressive strength.

The present invention also provides a green self-compacting concrete prepared by the above-mentioned preparation method of the green self-compacting concrete.

Beneficial technical effects of the present invention: The present invention starts from the perspective of solid particle accumulation and fully considers the properties of the raw materials actually selected, and carries out calculation and analysis in combination with the compressible accumulation model. Optimized, on the premise of ensuring the performance of green self-compacting concrete, the amount of cementitious materials was significantly reduced. Using theoretical analysis to calculate the optimal proportioning parameters of each component, and combining with experiments to test and verify, on the one hand, the number of trial mixing experiments of the proportioning parameters is greatly reduced, and on the other hand, it can fully reduce the cost of concrete production and CO ₂ emissions. , to meet the performance requirements of self-compacting concrete. The cementitious material system of the green self-compacting concrete of the invention includes a certain amount of fly ash, which reduces the amount of cement and achieves the effect of green environmental protection; a certain amount of ultra-fine sand powder is used in the aggregate of the green self-compacting concrete. The amount of medium sand is replaced to improve the compactness of the mixture. The green self-compacting concrete of the present invention satisfies both requirements of target working performance and mechanical performance, is green and environmentally friendly, and has low cost.

Description of drawings

1 is a schematic flowchart of a method for preparing green self-compacting concrete in an embodiment of the present invention;

Fig. 2 in one embodiment of the present invention, the wet bulk density of slurry changes trend diagram with the volume content of fly ash;

Fig. 3 changes trend diagram of bulk compactness of aggregate system with sand ratio S/A in an embodiment of the present invention;

Fig. 4 is a trend diagram of the variation trend of the bulk compactness of the mixture system with V _a /V _b in an embodiment of the present invention.

The realization, functional characteristics and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments.

Detailed ways

It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

1, an embodiment of the present invention proposes a method for preparing green self-compacting concrete, comprising:

S1: Determine the compaction index of the green self-compacting concrete according to the solid particle accumulation method and the compressible accumulation model, and calculate the bulk density of the cementitious material system, aggregate system, and mixture system respectively according to the compaction index;

S2: obtain a preselected cementitious material combination according to the bulk density of the cementitious material system; obtain a preferred sand ratio according to the bulk density of the aggregate system; Combination and the preferred sand ratio, determine the volume ratio of the preselected cementitious material system and the aggregate system;

S3: Determine the mass ratio of water to the cementitious material system according to the compressive strength requirements of the green self-compacting concrete and the bulk compactness of the cementitious material system, and calculate the specific dosage of the cementitious material system, the aggregate system and the water, The specific dosage of the cementitious material system ranges from 340kg/m ³ to 380kg/m ³ ;

S4: Determine the dosage of superplasticizer according to the specific dosage of the above-mentioned cementitious material system;

S5: The cementitious material system, the aggregate system, the water and the water-reducing agent with the determined specific dosages are stirred and mixed uniformly to obtain green self-compacting concrete.

The embodiment of the present invention starts from the perspective of solid particle accumulation and fully considers the properties of the actual selected raw materials, and combines the compressible accumulation model for calculation and analysis to optimize the bulk compactness of the green self-compacting concrete mixture from the nature of particle accumulation. The optimal ratio parameters of each component are calculated by theoretical analysis, and are tested and verified in combination with experiments. On the one hand, the number of trial mixing experiments of the ratio parameters is greatly reduced, and on the other hand, the amount of cementitious materials used in concrete can be fully reduced. , the specific dosage range of the cementitious material system in the embodiment of the present invention is 340kg/ ^{m 3} to 380kg/m ³ . In the embodiment of the invention, the specific dosage of the cementitious material system is obviously reduced, which meets the performance requirements of green self-compacting concrete and the requirements of green environmental protection.

Further, before the step of determining the compaction index of the green self-compacting concrete according to the solid particle accumulation mode and the compressible accumulation model, the steps include: collecting the performance parameters of the preselected cementitious material and the preselected aggregate; the above-mentioned preselected aggregate includes: Coarse and fine aggregates; the above performance parameters, including: density, particle size distribution and size volume fraction.

In the embodiment of the present invention, the cementitious material system is composed of preselected different cementitious materials, the aggregate system is composed of preselected different aggregates, and then the cementitious material system and the aggregate system form a mixture system according to a certain ratio , the cementitious material system, the aggregate system and the water are mixed to form a mixture. The performance parameters of the preselected cementitious materials and preselected aggregates are collected to calculate the bulk density of the cementitious material system, the aggregate system and the mixture system, and then determine the specific content of the cementitious material system, the aggregate system and the water. The target working performance and compressive strength are selected according to the design requirements, existing specifications and engineering experience.

Determine the density ρ _b of the cementitious material, measure the particle size distribution of the cementitious material and the volume fraction _yi of the particle size by a laser particle size analyzer; measure the coarse and fine aggregate densities ρ _g , ρ _s , and the aggregate particle size respectively distribution and the volume fraction y _i of each grade; measure the bulk density of the aggregate grade, and then calculate the remaining bulk density β _i of each grade of the particle by the compressible packing model.

The calculation of the remaining bulk density and the actual bulk density involved in the calculation of the bulk density is calculated through the compressible accumulation model. The calculation process is as follows:

First, the volume fraction _yi of each particle size of the cementitious material particles is measured by a laser particle size analyzer, and the volume fraction _yi of each particle grade of the sand particles is measured by a standard vibrating screen machine, and the characteristic particle size d _t of each particle size is calculated according to each particle size interval. ,Calculated as follows:

log ₁₀ (d _t )=[log ₁₀ (d _max )+log ₁₀ (d _min )]/2, where d _max and d _min are the maximum and minimum particle diameters in the particle size interval, respectively.

Then two kinds of interactions between particles of each size are considered: loosening effect and wall effect. The calculation formula is as follows:

b _ij =1-(1-d _i /d _j ) ^1.50 j=(1, 2, 3..., i-1); in the formula, a _ij and b _ij are particle j to particle i respectively The resulting loosening effect coefficient sum is the Coanda effect coefficient produced by particle j to particle i, and d _i and d _j are the particle sizes of particle size i and particle size j, respectively. Furthermore, in the multi-component mixture, when the particles are dominated by the i-th grade, according to the basic parameters determined above, the virtual bulk density γ _i of the multi-particle system of the i-th grade particles can be calculated, and the formula is as follows:

式中，β_i和β_j分别为第i、j级颗粒粒级的剩余堆积密实度。

In the formula, β _i and β _j are the residual bulk compactness of the i-th and j-th grades, respectively.

After obtaining the virtual packing density γ _i of the multi-particle particles, different compaction indices K are selected according to different particle packing methods. In the embodiment of the present invention, it is the green self-compacting concrete under the condition of wet packing and adding superplasticizer, and K is selected. =7. Finally, according to the K value and the virtual bulk density γ _i , the actual bulk density α _t is inversely calculated, and the formula is as follows:

Determination of β _i for cementitious materials: After measuring the volume fraction _yi and characteristic particle size d _t of each material, it is assumed that each particle size β _i is equal, that is, β ₁ =β ₂ =...=β _n =β _i , then the actual bulk density α _t of each material is determined by the minimum water demand method, and then the β _i of the cementitious material is inversely calculated by the above formula.

Determination of β _i for sand and gravel materials: after the sand and gravel are sieved, the density ρ and bulk density ρ ₀ can be tested for each particle size, and then the actual bulk density can be calculated by the formula α _t = ρ ₀ /ρ. degree, and then determine the β _i of the sand and gravel material.

和复合粒级剩余堆积密实度

由以下计算公式算得：When the particle interval of each cementitious material overlaps, the particle volume fraction after compounding

and residual bulk compactness of composite fractions

It is calculated by the following formula:

式中：y_i ^*为复合后第i粒级的颗粒体积分数；y_ij为第j种材料的第i粒级颗粒在该材料中的体积分数；r_j为第j种材料在复合材料所占的体积比；β_i ^*为复合后第i粒级的剩余堆积密实度；β_ij为第j种材料在i粒级的颗粒剩余堆积密实度。

In the formula: y _i ^* is the particle volume fraction of the i-th grade after compounding; y _ij is the volume fraction of the i-th grade particles of the j-th material in the material; r _j is the j-th material in the composite material. β _i ^* is the residual bulk density of the i-th grade after compounding; β _ij is the remaining bulk density of the j-th material in the i-th grade.

In the embodiment of the present invention, the cementitious material system includes cement and fly ash, so as to reduce the amount of cement and achieve the effect of environmental protection; the preselected aggregate includes coarse aggregate crushed stone, and the fine aggregate includes ultrafine sand powder and medium sand. The thickness of sand is divided into four grades: coarse, medium, fine and ultra-fine according to the sand's fineness modulus, of which the fineness modulus of ultra-fine sand is between 0.2 and 0.3.

In the embodiment of the present invention, the particle size distribution of cement, fly ash and ultra-fine sand powder is determined by a laser particle size distribution analyzer; the particle size distribution of sand and gravel aggregate is determined by sieving with a standard vibrating screen machine; the particle size distribution results are shown in the table 1 to Table 3. The apparent density of each raw material was measured by the pycnometer drainage method, and the results are shown in Table 4. The actual bulk density of cement, fly ash and ultrafine sand powder was measured by the minimum water demand method, and the remaining bulk density was calculated. The results are shown in Table 5. The bulk density of medium sand and crushed stone is calculated from the density and bulk density, and then the remaining bulk density β _i can be calculated. The results are shown in Table 6.

Table 1 Cement and fly ash particle size distribution

Table 2 Ultrafine sand particle size distribution

Grain size distribution of sand and gravel in Table 3

Table 4 Density of each raw material

Table 5 Actual bulk density α _t and residual bulk density β _i of cement, fly ash and ultra-fine sand

In Table 6, the actual bulk density α _t and the remaining bulk density β _i of each grade of sand and gravel

Further, the above-mentioned preselected cementitious material combination ratio is obtained according to the above-mentioned bulk compactness of the cementitious material system; the preferred sand ratio is obtained according to the above-mentioned aggregate system bulk compaction; And the above-mentioned preferred sand ratio, in the step of determining the volume ratio of the preselected cementitious material system and the aggregate system, including:

According to the different volume ratio combinations of the preselected cementitious materials in the cementitious material system, the bulk density of the cementitious material system with different volume ratio combinations is calculated to determine the combination ratio of the preselected cementitious materials to the cementitious material system;

Calculate the bulk density of the aggregate system under different sand ratios to determine the optimal sand ratio;

Calculate the bulk density of the mixture system composed of different volume ratios of the above-mentioned aggregate system and the cementitious material system, and determine the volume ratio of the above-mentioned cementitious material system to the aggregate system.

According to different volume ratio combinations of preselected cementitious materials in the cementitious material system, the bulk density α _t of the different combinations is calculated, and the optimal cementitious material system combination is selected accordingly.

Calculate the optimal bulk density α _t of the aggregate system under the conditions of different sand ratios S/A, and determine the optimal sand ratio δ, which is expressed by the following formula:

式中：m_s、V_s、ρ_s分别为中砂的质量、体积、密度；m_a为总骨料体系质量；V_g、ρ_g分别为粗骨料体积、密度。

where m _s , V _s and ρ _s are the mass, volume and density of the medium sand, respectively; _{ma is the mass of the total aggregate system; V g and ρ g are the} volume and density of the coarse aggregate, respectively.

Calculate the bulk density of the mixture system with different volume ratios of aggregate system and cementitious material system V _a /V _b , and determine the optimal volume ratio of aggregate system and cementitious material system ω corresponding to the optimal bulk density α′ _t ,Calculated as follows:

According to the target compressive strength f _c to determine the water-binder mass ratio θ, and combining the optimal sand rate δ and the volume ratio of the aggregate system to the cementitious material system ω, the volumetric content V _b of the cementitious material system can be calculated. The formula is as follows:

V _w +V _b +V _g +V _s =1;

上述计算式中，m_w、V_w、ρ_w为用水量的质量、体积、密度。

In the above calculation formula, m _w , V _w , and ρ _w are the mass, volume and density of water consumption.

After calculating V _b according to the above formula, the dosage of each proportioning material can be obtained. The calculation formula is as follows:

m _b =V _b ·ρ _b ;

m _w =m _b ·θ;

m _a =V _a ·ρ _a =V _b ·ω ·ρ _a ;

m _g =m _a ·δ;

m _s =m _a -m _g ; in the formula, m _b is the mass of the cementitious material system.

Further, after the above-mentioned calculation of the bulk compactness of the aggregate system under different sand ratios, and after the step of determining the sand ratio, it includes:

Sand ratio is the percentage of the mass of sand in the concrete to the total mass of sand and stone. According to the sand rate, a specified amount of ultra-fine sand powder is used to replace the original medium sand content; the specified amount is in the range of 0-20% of the volume content of the medium sand.

After calculating the optimal sand rate δ, the superfine sand powder is used to replace the original medium sand content. When the sand ratio is δ=0.45, the optimum is reached, at this time α _t =0.7264, and then the medium sand is replaced by 15% ultra-fine sand powder volume to improve the compactness of the mixture.

Further, the above cementitious material system includes: fly ash and cement; the volume content of the fly ash in the cementitious material system ranges from 20% to 40%.

According to the change trend diagram of wet bulk density of slurry with fly ash volume content in Figure 2, the increase trend of bulk density after fly ash and cement are compounded, the embodiment of the present invention comprehensively considers the working performance and mechanical properties of the mixture, The volume content of fly ash is selected to be 30%. , try to reduce the amount of cement to achieve the effect of green environmental protection and low cost.

Further, the volume ratio of the above-mentioned cementitious material system to the aggregate system is in the range of 1:5.5 to 1:6.5.

According to the relationship between the bulk density of the mixture and the volume ratio V _a /V _b of the aggregate and the cementitious material in Fig. 4, under the condition of different sand ratios, the bulk density of the mixture used is between 5.5<V _a /V _b <6.5 They are all at large values. In this scheme, three groups of schemes are selected at equal intervals, and V _a /V _b are 5.7, 6.0, and 6.3, respectively.

Further, the above water reducing agent includes: one or more of lignosulfonate, naphthalene, melamine, sulfamate, aliphatic and polycarboxylic acid series; the water reducing agent The dosage of the agent is 2%-4% of the mass of the cementitious material.

的关系，本方案取θ＝0.45，减水剂采用西卡聚羧酸减水剂，且使用量胶凝材料质量的3.5％。结合最佳砂率δ及V_a/V_b，即可算出三组m_b分别为373kg/m³、359kg/m³、347kg/m³。本发明实施例的绿色自密实混凝土在平衡其工作性能及力学性能的前提下，相比于常规设计中400-550kg/m³胶凝材料使用量，本发明实施例将胶凝材料用量大幅降低至347kg/m³，混凝土生产成本及碳排放量明显降低。According to the ratio of target compressive strength f _c to water glue mass

In this scheme, θ=0.45, Sika polycarboxylate water-reducing agent is used as the water-reducing agent, and the usage amount is 3.5% of the mass of the gelling material. Combining the optimum sand rate δ and V _a /V _b , the m _b of the three groups can be calculated to be 373 kg/m ³ , 359 kg/m ³ and 347 kg/m ³ , respectively. On the premise of balancing its working performance and mechanical properties, the green self-compacting concrete of the embodiment of the present invention greatly reduces the amount of cementitious material used in the embodiment of the present invention, compared with the use amount of 400-550kg/m ³ cementitious material in the conventional design. To 347kg/m ³ , concrete production costs and carbon emissions are significantly reduced.

Further, the above-mentioned cementitious material system, aggregate system, water and water reducing agent with specific dosages will be uniformly stirred and mixed, before the step of obtaining the green self-compacting concrete, including:

The cementitious material system, the aggregate system, the water and the water reducing agent with the determined specific dosages are formed into a mixture, and the work performance test of the mixture is carried out, and the compressive strength of the mixture is verified;

According to the test results of the work performance of the mixture and the compressive strength of the mixture, the specific dosages of the cementitious material system, the aggregate system, the water and the water reducing agent are adjusted to meet the needs.

Further, the above-mentioned cementitious material system, aggregate system, water and water reducing agent with specific dosages will be determined to form a mixture, and the work performance test of the mixture will be carried out, and the compressive strength of the above-mentioned mixture will be verified; according to According to the test results of the work performance of the mixture and the compressive strength of the mixture, the steps to adjust the specific dosage of the above-mentioned cementitious material system, aggregate system, water and water reducing agent to meet the needs include:

According to the specific dosage, the specific dosage of cementitious material system, aggregate system, water and water reducing agent was taken to form a mixture, and the working performance of the mixture was tested. By adjusting the dosage of the water reducing agent, the mixture was The compound meets the performance requirements;

Under the condition that the working performance is met, verify whether the mixture meets the compressive strength requirements;

If not satisfied, adjust the composition ratio of the cementitious material system or the mass ratio of the water to the cementitious material system to balance the workability of the mixture with the compressive strength.

In the embodiment of the present invention, according to the mixing ratio shown in Table 7, with reference to the specifications of ASTM C1610, ASTM C1611, and ASTM C1621, tests such as green self-compacting concrete slump expansion SF, expansion time T500, visual stability index VSI, etc. were carried out; 7 days after hardening and 28-day compressive strength were measured with reference to the ACI 318 specification, and the results are shown in Table 8. From the test results in Table 8, it can be seen that the configured green self-compacting concrete has good working performance, SF≥650mm, 2s<T500<8s, the mixture is relatively uniform, and no segregation occurs, that is, VSI≤1. In terms of mechanical properties, the compressive strength of the configured green self-compacting concrete after hardening for 28 days is f _c >35MPa. Therefore, the configured green self-compacting concrete meets the requirements of both the target working performance and mechanical properties, which verifies the practicability and feasibility of the green self-compacting concrete mix proportion design method with low cementitious material consumption proposed by the present invention.

Table 7 Green self-compacting concrete mix ratio (kg/m ³ )

Table 8 Test results of working performance and mechanical properties of green self-compacting concrete

The embodiment of the present invention also provides a green self-compacting concrete, which is prepared by the above-mentioned preparation method of the green self-compacting concrete.

In the embodiment of the present invention, the cementitious material system of the green self-compacting concrete is 70% by volume of cement and 30% by volume of fly ash, which reduces the amount of cement and achieves the effect of green environmental protection; the aggregate of the green self-compacting concrete includes coarse aggregate crushed The fine aggregates include superfine sand powder and medium sand, and the medium sand is replaced with a volume content of 15% superfine sand powder to improve the compactness of the mixture. The green self-compacting concrete of the embodiment of the present invention starts from the perspective of solid particle accumulation and fully considers the properties of the raw materials actually selected, carries out calculation and analysis in combination with the compressible accumulation model, and optimizes the accumulation density of the mixture from the essence of particle accumulation. The green self-compacting concrete slump expansion SF≥650mm, 2s<T500<8s, VSI≤1, the compressive strength reaches C30 or more, and meets the requirements of both the target working performance and mechanical performance, and is environmentally friendly and low cost price. In the embodiment of the present invention, the amount of cementitious material for the green self-compacting concrete is as low as 347kg/m ³ , wherein the amount of cement is only 243kg/m ³ , which is the lowest cementitious amount compared to JGJ/T 283-2012 "Technical Specifications for the Application of Green Self-compacting Concrete" The material consumption is reduced by 57kg/m ³ , which is 14.25% lower than that, and the production cost is reduced by at least 22.5 yuan/m ³ .

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the description and drawings of the present invention, or directly or indirectly applied to other related All technical fields are similarly included in the scope of patent protection of the present invention.

Claims (9)

1. A preparation method of green self-compacting concrete is characterized by comprising the following steps:

determining the compaction index of the green self-compacting concrete according to the solid particle stacking mode and the compressible stacking model, and respectively calculating the stacking compactness of a cementing material system, an aggregate system and a mixture system according to the compaction index;

obtaining a preselected cementing material combination according to the stacking compactness of the cementing material system; obtaining the optimal sand rate according to the stacking compactness of the aggregate system; determining the volume ratio of a preselected cementing material system to an aggregate system according to the stacking compactness of the mixture system, the preselected cementing material combination and the preferred sand rate;

determining the mass ratio of water to the cementing material system according to the compression strength requirement of the green self-compacting concrete and the stacking compactness of the cementing material system, and calculating the specific mixing amount of the cementing material system, the aggregate system and the water, wherein the specific mixing amount of the cementing material system is 340kg/m³To 380kg/m³；

Determining the mixing amount of the water reducing agent according to the specific mixing amount of the cementing material system;

uniformly stirring and mixing the determined concrete mixing amount of the cementing material system, the determined aggregate system, water and the water reducing agent to obtain green self-compacting concrete;

the cementing material system comprises 30% of fly ash and 70% of cement by volume;

the volume ratio range of the cementing material system to the aggregate system is 1: 5.5 to 1: 6.5.

2. the method for preparing green self-compacting concrete according to claim 1, wherein the step of determining the compaction index of green self-compacting concrete according to the solid particle stacking mode and the compressible stacking model, and calculating the stacking compactness of the cementing material system, the aggregate system and the mixture system according to the compaction index comprises the following steps:

collecting performance parameters of a pre-selected cementing material and a pre-selected aggregate; the preselected aggregate comprising: coarse aggregate and fine aggregate; the performance parameters comprise: density, particle size fraction distribution and size fraction volume fraction.

3. The method for preparing green self-compacting concrete according to claim 1, wherein the pre-selected binding material combination ratio is obtained according to the packing compactness of the binding material system; obtaining the optimal sand rate according to the stacking compactness of the aggregate system; the step of determining the volume ratio of the preselected cementitious material system to the aggregate system according to the bulk density of the mix system, the preselected cementitious material combination and the preferred sand rate comprises:

according to the combination of different volume ratios of the preselected cementing materials in the cementing material system, calculating the stacking compactness of the cementing material system combined by different volume ratios so as to determine the combination proportion of the preselected cementing materials to form the cementing material system;

calculating the stacking compactness of the bone material system under different sand rates, and determining the preferred sand rate;

and calculating the stacking compactness of the mixture system consisting of the aggregate system and the cementing material system in different volume ratios, and determining the volume ratio of the cementing material system to the aggregate system.

4. The method for preparing green self-compacting concrete according to claim 3, wherein the step of calculating the aggregate system packing compactness at different sand rates and determining the sand rate comprises the following steps:

according to the sand rate, replacing the original sand mixing amount with the specified amount of superfine sand powder; the specified amount range is 0-20% of the volume mixing amount of the medium sand.

5. The method for preparing green self-compacting concrete according to claim 1, wherein the cementitious material system comprises: fly ash and cement; the volume mixing amount of the fly ash in the cementing material system is 20-40%.

6. The method for preparing green self-compacting concrete according to claim 1, wherein the water reducing agent comprises:

one or more of lignosulfonate, naphthalene, melamine, sulfamate, aliphatic or polycarboxylic acid; the amount of the water reducing agent is 2-4% of the mass of the cementing material system.

7. The preparation method of the green self-compacting concrete according to claim 1, wherein the step of uniformly mixing the determined specific mixing amount of the cementing material system, the aggregate system, the water and the water reducing agent comprises the following steps:

forming a mixture by the determined concrete mixing amount of the cementing material system, the aggregate system, water and the water reducing agent, testing the working performance of the mixture, and verifying the compressive strength of the mixture;

and adjusting the specific mixing amounts of the cementing material system, the aggregate system, the water and the water reducing agent according to the working performance test result of the mixture and the compressive strength of the mixture to meet the requirements.

8. The preparation method of the green self-compacting concrete according to claim 7, wherein the concrete mixture is prepared from the cementing material system, the aggregate system, water and the water reducing agent with specific mixing amounts, the working performance of the mixture is tested, and the compressive strength of the mixture is verified; according to the testing result of the working performance of the mixture and the compressive strength of the mixture, the concrete mixing amounts of the cementing material system, the aggregate system, the water and the water reducing agent are adjusted to meet the requirements, and the method comprises the following steps:

respectively taking a cementing material system, an aggregate system, water and a water reducing agent with specific mixing amounts according to the specific mixing amounts to form a mixture, testing the working performance of the mixture, and adjusting the mixing amounts of the water reducing agent to enable the mixture to meet the working performance requirement;

verifying whether the mixture meets the requirement of compressive strength under the condition of meeting the working performance;

if not, adjusting the composition proportion of the cementing material system or the mass ratio of the water to the cementing material system to balance the working performance and the compressive strength of the mixture.

9. A green self-compacting concrete, characterized in that it is prepared by the method of any one of claims 1-8.

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