CN120878004A - Machine-made sand concrete containing stone powder and corresponding mix proportion design method - Google Patents
Machine-made sand concrete containing stone powder and corresponding mix proportion design methodInfo
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- CN120878004A CN120878004A CN202511386744.6A CN202511386744A CN120878004A CN 120878004 A CN120878004 A CN 120878004A CN 202511386744 A CN202511386744 A CN 202511386744A CN 120878004 A CN120878004 A CN 120878004A
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- G—PHYSICS
- G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
- G16C—COMPUTATIONAL CHEMISTRY; CHEMOINFORMATICS; COMPUTATIONAL MATERIALS SCIENCE
- G16C60/00—Computational materials science, i.e. ICT specially adapted for investigating the physical or chemical properties of materials or phenomena associated with their design, synthesis, processing, characterisation or utilisation
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B18/04—Waste materials; Refuse
- C04B18/12—Waste materials; Refuse from quarries, mining or the like
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/04—Portland cements
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- G16C20/60—In silico combinatorial chemistry
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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Abstract
本申请涉及混凝土设计领域，具体公开了一种含石粉机制砂混凝土以及相应的配合比设计方法。该方法包括：计算混凝土的粗、细骨料及胶凝材料用量，将细骨料含石粉机制砂采用快速筛分方式，测定其石粉含量并全部计入胶凝材料，并替代部分水泥以及粉煤灰、矿粉，形成胶凝体系，其中水泥用量的10%‑20%替代水泥，剩余部分替代粉煤灰、矿粉；采用公式γLf=‑3.16x²‑0.048x+1计算石粉具体替代水泥比例下的强度影响系数，并据此计算胶凝体系的胶砂强度；调整确定满足配制强度要求的用水量，最终确定混凝土各组分用量。本发明将含粉机制砂中的石粉作为胶凝组分，实现了高石粉含量机制砂的高效资源化利用，降低了水泥及粉煤灰用量，解决了混凝土长期不低碳的问题。
This application relates to the field of concrete design, specifically disclosing a method for designing concrete with manufactured sand containing stone powder and the corresponding mix proportion. The method includes: calculating the amounts of coarse and fine aggregates and cementitious materials in the concrete; rapidly sieving the stone powder content of the fine aggregate, manufactured sand containing stone powder, and including it entirely in the cementitious materials, replacing a portion of cement, fly ash, and mineral powder to form a cementitious system, wherein 10%-20% of the cement content is replaced, and the remaining portion replaces fly ash and mineral powder; calculating the strength influence coefficient under the specific cement replacement ratio using the formula γLf = -3.16x² - 0.048x + 1, and calculating the mortar strength of the cementitious system accordingly; adjusting and determining the water content to meet the strength requirements, and finally determining the amounts of each component in the concrete. This invention uses stone powder from manufactured sand containing stone powder as a cementitious component, achieving efficient resource utilization of high-stone-powder-content manufactured sand, reducing the amount of cement and fly ash used, and solving the long-term problem of non-low-carbon concrete.
Description
Technical Field
The application relates to the field of concrete, in particular to stone powder-containing machine-made sand concrete and a corresponding mix proportion design method.
Background
In recent years, machine-made sand is taken as a main sand source of concrete, a certain amount of stone powder is brought in the production process of the machine-made sand, when a traditional mixing proportion method is adopted, the stone powder in the machine-made sand is taken as a part of fine aggregate, so that calculated sand rate is larger than actual sand rate, the grading of each component of the concrete is unreasonable, in order to meet the working requirements of the concrete, the concrete is generally improved by adopting a method for increasing the total amount of cement or cementing material, thereby bringing about larger cement consumption or cementing material of the concrete, being unfavorable for low carbon and environmental protection, being unfavorable for the stability of the concrete body, and causing the problem of cracks to remain serious.
The machine-made sand is used as an important building aggregate, is made by mechanically crushing, screening, shaping and other processes on parent rock, rock particles with the particle size of less than 4.75mm are produced, and a large amount of stone powder (usually particles with the particle size of less than 75 mu m) is inevitably produced in the production process, and particularly under the dry production process, the stone powder content in the machine-made sand is often more than 10% and even can be more than 20%, the existing standard (sand for common concrete, stone quality and inspection method standard (JGJ 52) strictly stipulates that the stone powder content is not more than 10% when the machine-made sand is used for the artificial sand of the concrete with the strength grade of C25 and below, and the stone powder content is not more than 7% when the machine-made sand is used for the concrete with the strength grade of C30-C55. How to solve the contradiction between the prior regulation and the machine-made sand with high stone powder content and the regulation, and to scientifically design and produce the mix proportion of the concrete according to the prior art regulation, and to realize the reasonable utilization of the machine-made sand containing powder is the technical background of the patent.
At present, the general treatment mode of stone powder in machine-made sand in the industry has fundamental defects, and the method is mainly characterized in the following two aspects:
Firstly, the stone powder is classified as an inert mineral admixture, and according to the standards of limestone powder application technical regulations (JGJ/T318) and the like in concrete, the stone powder with the standard activity index is often regarded as the inert mineral admixture. This approach ignores the potential chemical gelling activity of the stone powder and does not calculate its contribution in the cementitious material system. The stone powder which is taken as the cementing material system is counted into other components, so that the calculated sand rate is larger than the actual sand rate, the grading of each component of the concrete is unreasonable, the calculated water-gel ratio is also larger than the actual water-gel ratio, and the workability of the concrete is reduced. In order to meet the working requirements on the premise of ensuring the strength, the water consumption (actually slurry with a certain water-cement ratio) is increased, so that the cement consumption or the cementing material consumption is increased, the concrete is not low carbon, the slurry-bone ratio is increased, the volume stability of the concrete is poor, and the durability is seriously insufficient due to easy cracking.
Secondly, the stone powder is regarded as waste material to be forcedly washed out, namely, more conservative and common practice is to wash out machine-made sand by adding extra cost, water and energy source in order to meet the upper limit requirement on the stone powder content in the current standard, and discharge precious stone powder as waste mud. This not only results in significant waste of resources, but also brings about serious environmental burdens (such as sludge accumulation, water pollution) and economic costs (treatment costs and sand loss).
Therefore, developing a set of method which can scientifically quantify the gelation performance of stone powder and guide the accurate design and production of machine-made sand concrete with higher stone powder content has become an urgent need for promoting industry recycling and waste utilization and technical development.
Disclosure of Invention
In order to solve the problems, the application provides the stone powder-containing machine-made sand concrete and a corresponding mix proportion design method.
The method comprises the steps of calculating the consumption of coarse aggregate and fine aggregate of concrete and cementing materials, measuring the stone powder content of fine aggregate stone powder-containing machine-made sand in a rapid screening mode, completely counting the cementing materials, replacing part of cement, fly ash and mineral powder to form a novel cementing system, wherein 10% -20% of the consumption of cement replaces the cement, the rest replaces the fly ash and mineral powder, calculating the strength influence coefficient of stone powder under the concrete replacement proportion by adopting a formula gamma Lf = -3.16x2-0.048x+1, calculating the strength of the cement sand of the cementing system according to the strength influence coefficient, adjusting and determining the water consumption meeting the preparation strength requirement, and finally determining the consumption of each component of the concrete.
The application adopts the following technical scheme:
in a first aspect, the application provides a method for designing a mix proportion of stone powder-containing machine-made sand concrete, which comprises the following steps:
(1) According to the specification of JGJ55 of the common concrete mix proportion design rule, calculating and determining the total mass of coarse aggregate and fine aggregate of the standard concrete and the consumption of the cementing material by adopting an absolute volume method, and respectively determining the consumption of cement, fly ash and mineral powder in the cementing material;
(2) The method comprises the steps of taking machine-made sand containing stone powder as fine aggregate, determining the stone powder content in the fine aggregate through screening, and using stone powder to replace part of cement and/or fly ash and mineral powder in the calculation of a mixing ratio to form a cementing system formed by compounding cement, fly ash, mineral powder and stone powder according to a specific proportion;
the stone powder substitution principle is as follows:
stone powder in the machine-made sand is used for replacing 10% -20% of the cement consumption;
if the stone powder is left, the remaining part of the stone powder is used for replacing the fly ash and the mineral powder;
(3) According to the strength influence coefficients of the component materials, calculating the mortar strength of the novel cementing system, wherein the strength influence coefficient gamma Lf of the stone powder of the substitute cement is calculated according to the following formula:
Gamma Lf = -3.16x2 -0.048x+1 formula (I)
Wherein x is mass percent (%) of stone powder to replace cement;
(4) Calculating the required water-cement ratio according to the concrete preparation strength, namely determining corresponding water consumption if the water-cement ratio meets the strength requirement, and if the water-cement ratio does not meet the strength requirement, readjusting the consumption of the cementing material, and performing iterative calculation until the water-cement ratio meets the strength requirement;
(5) And finally determining the dosage of each component of the concrete in unit volume.
Further, the stone powder-containing machine-made sand is derived from common diabase, basalt, dolomite and limestone.
Further, in the step (2), when the stone powder is used for replacing cement in different proportions, the ratio of the strength of the obtained concrete to the strength of the reference concrete accords with the following rule:
When the proportion of stone powder to cement is 10% of the theoretical cement consumption, the ratio of the strength of the obtained concrete to the strength of the reference concrete is 89.0% -98.0%;
When the proportion of stone powder to cement is 15% of the theoretical cement consumption, the ratio of the strength of the obtained concrete to the strength of the reference concrete is 84.5% -96.4%;
when the proportion of stone powder to cement is 20% of the theoretical cement consumption, the strength of the obtained concrete is 80.88-89.82% of the standard concrete strength.
Further, in the step (3), in order to further incorporate the influence of the particle size and chemical components of the stone powder on the strength of the concrete into the calculation system, a value range of the strength influence coefficient corresponding to the 95% confidence interval of the stone powder substitution ratio is introduced on the basis of calculating the strength influence coefficient gamma Lf according to the formula.
Further, in the step (3):
when the stone powder substitution proportion is 10% of the theoretical cement consumption, the 95% confidence interval of the strength influence coefficient gamma Lf is 0.912-0.979;
When the stone powder substitution proportion is 15% of the theoretical cement consumption, the 95% confidence interval of the strength influence coefficient gamma Lf is 0.848-0.964;
When the stone powder substitution proportion is 20% of the theoretical cement consumption, the 95% confidence interval of the strength influence coefficient gamma Lf is 0.805-0.866.
Further, when determining the specific value of the intensity influence coefficient γ Lf, the method further includes the following steps:
carrying out a negative pressure screening method on the stone powder, and determining the screen residue mass ratio of particles with the particle diameter of more than 45 mu m;
If the screen residue mass ratio is smaller than 10%, taking the upper limit value of the corresponding confidence interval as gamma Lf;
If the screen residue mass ratio is 10% -20%, the calculated value according to the formula (I) is used as gamma Lf;
If the screen residue mass ratio is more than 20%, the lower limit value of the corresponding confidence interval is taken as gamma Lf.
Further, in the step (2), the stone powder used for replacing the fly ash and the mineral powder in an equivalent manner is adopted, the strength influence coefficient adopts the strength influence coefficient corresponding to the replaced fly ash and mineral powder, and the value of the strength influence coefficient is determined according to the rule of JGJ 55 in the common concrete mix proportion design rule.
In a second aspect, the application provides stone powder-containing machine-made sand concrete prepared according to the above mix proportion design method, which comprises the following components:
Cement, fly ash, mineral powder and water;
Coarse aggregate and fine aggregate of machine-made sand containing stone powder;
The stone powder in the machine-made sand is used as a part of cementing materials, and forms a composite cementing system together with cement, fly ash and mineral powder.
Further, the stone powder is derived from powder with particle size smaller than 75 μm generated in the production process of common diabase, basalt, dolomite or limestone machine-made sand.
Further, the 28-day compressive strength of the concrete is not lower than 80% of the standard concrete strength without stone powder under the same conditions.
In summary, the application has the following beneficial effects:
the application is proved by the material analysis (laser particle analyzer, XRD, sand gel test and mercury intrusion analysis) of the system for the first time, and the sand powder with different rock mass mechanisms is not an 'inert material', but has definite cementing material properties. Based on this, the present application breaks through the traditional recognition that the current standard simply classifies it as "inert admixture" or "waste" and creates a new theory and new method of incorporating stone dust as an independent cementitious component into the mix design.
According to the invention, stone powder in the machine-made sand containing the powder is used as a cementing component, and a mixing proportion calculation process and control parameters are provided, so that scientificalness and precision of mixing proportion design are realized:
a clear stone powder substitution rule (10% -20% of cement is preferentially replaced, the rest part replaces fly ash and/or mineral powder) is established, the influence coefficient of excessive stone powder is creatively hooked with the replaced materials (cement, fly ash and mineral powder), and the core technical problem that the machine-made sand with high stone powder content cannot be used for preparing high-performance concrete is solved;
-providing a quantitative design method based on an intensity influence coefficient, wherein the contribution of stone powder to the intensity of the concrete can be accurately quantized through a formula gamma Lf = -3.16x2-0.048x+1 and a corresponding 95% confidence interval;
the strength influence coefficient value principle based on the stone powder particle size (45 mu m screen allowance) is introduced, so that the design result is more reliable and more practical.
The application realizes the high-efficiency recycling of the machine-made sand with high stone powder content, reduces the consumption of cement and fly ash, and solves the problem that the concrete is not low carbon for a long time. The workability, the strength and the durability of the prepared concrete can be effectively controlled and ensured through precise design, the compressive strength in 28 days can reach more than 80% of the standard concrete, and the performance is stable and reliable. The limit of the existing standard on the stone powder content is broken, so that the machine-made sand with the large stone powder content can be safely applied to concrete engineering with the strength grade of C30 and above, and the resource range and application scene of the machine-made sand with high quality are greatly expanded.
Drawings
FIG. 1 is a concrete shrinkage test site diagram in test example one.
FIG. 2 is a diagram of a concrete slab cracking test site in test example one.
FIG. 3 is a graph showing the cracking test of a concrete slab in test example one.
FIG. 4 is a graph showing the shrinkage of concrete at 7d in test example one.
FIG. 5 is an analysis chart of particle sizes of different rock masses in a second test example, wherein A is a differential distribution curve, and B is an integral distribution curve.
FIG. 6 shows XRD analysis of different rock powder mineral components in test example II, wherein A is XRD pattern of CA (diabase), HC-S1 (dolomite), HC-S2 (limestone) and QH (limestone), and B is XRD pattern of LT-S1 (basalt), LT-S2 (dolomite), LT-S3 (limestone) and SY (limestone).
FIG. 7 is a graph showing the analysis of the sand strength of 8 kinds of stone powder in different proportions in test example III, wherein A is the sand strength of 3d, B is the sand strength of 7d, and C is the sand strength of 28 d.
FIG. 8 is a graph showing pore size distribution curves of 8 kinds of stone powder in the third test example at different substitution ratios, wherein A is 10% cement substitution ratio, B is 20% cement substitution ratio, and C is 30% cement substitution ratio.
FIG. 9 shows the porosity of the cement-based material at various alternative ratios in test example III.
FIG. 10 is a normal distribution diagram of the fourth test example at different stone powder substitution ratios, wherein A is 10% cement substitution ratio, B is 15% cement substitution ratio, and C is 20% cement substitution ratio.
FIG. 11 is a graph showing the influence coefficient of the concrete strength in test example four.
FIG. 12 is a plot of the concrete strength impact coefficient (95% confidence interval) for test example four.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the following examples, which are to be construed as merely illustrative and not limitative of the scope of the invention, but are not intended to limit the scope of the invention to the specific conditions set forth in the examples, either as conventional or manufacturer-suggested, nor are reagents or apparatus employed to identify manufacturers as conventional products available for commercial purchase.
The following describes specific embodiments of the present invention in detail. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
Examples
The embodiment provides a method for designing a mixing proportion of stone powder-containing machine-made sand concrete, which aims to prepare C50 concrete, and comprises the following steps:
(1) According to the rule of JGJ55 of the common concrete mix proportion design rule, the total mass of coarse aggregate and fine aggregate of the standard concrete and the consumption of the cementing material are calculated and determined by adopting an absolute volume method, and the consumption of the cement, the consumption of the fly ash and the consumption of the mineral powder in the cementing material are respectively determined, wherein the concrete is shown in the following table 1:
TABLE 1 theoretical calculated amount of each component of C50 concrete (unit kg/m 3)
(2) The method comprises the steps of selecting stone powder-containing machine-made sand (from diabase) as fine aggregate, rapidly screening, determining the stone powder content in the fine aggregate (710 kg/m 3) to be 60.9kg/m 3, screening the stone powder by a negative pressure screening method, wherein the mass ratio of the screen residue of particles with the particle size of more than 45 μm is 11.3%.
(3) Stone powder was used as a part of the gel material to replace cement, fly ash and mineral powder by 10%, 20% and 11%, respectively, while fine adjustment was performed on the total amount of fine aggregate, and the results are shown in table 2:
TABLE 2 usage of C50 concrete after replacement (unit kg/m 3)
Calculating the sand strength of the gel system according to the strength influence coefficient of each component material, wherein:
-the intensity influence coefficient gamma Lf of the stone powder of the replacement cement is calculated as follows:
γLf = -3.16x2 - 0.048x + 1 = 0.9636
In order to reduce the influence of the particle size and chemical components of the stone powder on the strength of the concrete, when the stone powder substitution proportion is 10% of the theoretical cement consumption, the 95% confidence interval of the strength influence coefficient gamma Lf is 0.912-0.979, and the calculated value 0.9636 is taken as the final gamma Lf because the screen surplus mass ratio of the particles with more than 45 mu m is 11.3% after the stone powder is subjected to the negative pressure screening method;
-the intensity influence coefficient of the stone powder replacing the fly ash, the value of which is determined according to the specification of JGJ 55 of the ordinary concrete mix design rule;
-the intensity influence coefficient of stone powder replacing mineral powder, the value of which is determined according to the rules of the common concrete mix design rules JGJ 55.
(5) The water-gel ratio was calculated from the concrete formulation strength, the corresponding water usage was determined, and finally the amounts of the components per unit volume of concrete were determined as shown in table 3. The concrete prepared according to the mixing ratio is numbered YH-C50.
TABLE 3 design of the proportions of the components of C50 concrete (unit kg/m 3)
This comparative example provides a C50 concrete prepared according to the mix design route of the conventional method, taking into consideration the stone powder in the stone powder machine-made sand as a part of the fine aggregate, specifically with the number JZ-C50 as shown in Table 4.
Test example 1
Performance testing of C50 concrete provided in examples and comparative examples
1. Component comparison analysis:
TABLE 4 comparative analysis of C50 concrete mix design (unit kg/m 3)
According to the method of the embodiment 1, the stone powder is calculated by the water-cement ratio, the cement consumption in single concrete is reduced by 30kg, the total amount of the cementing material is reduced by 60kg, and the bone cement ratio is reduced from original 0.58 to 0.49.
2. The experimental method comprises the following steps:
-performing an early self-shrinkage test of the concrete using a NELD-ES731 series non-contact concrete shrinkage deformation tester, as shown in figure 1;
the concrete slab constraint cracking test was performed according to the standard of the test method for ordinary concrete long-term performance and durability (GB/T50082), as shown in FIG. 2.
3. Experimental results
(1) The compressive strength values at different ages are shown in table 5.
TABLE 5 compressive strength values (MPa) for C50 concrete mix designs
The 3d age plate surface cracking condition tracking observation is carried out on the JZ-C50 concrete and the YH-C50 concrete, the result is shown in figure 3, 2 cracks appear on the JZ group plate surface, the widest part of the cracks can reach 0.2mm, and no macroscopic cracks are found on the YH group surface.
(2) The concrete shrinkage test results are shown in fig. 4.
As can be seen from FIG. 4, the shrinkage curves of JZ-C50 and YH-C50 both show a trend of slightly expanding and then shrinking, and the shrinkage value increases faster in the first 40 hours and then gradually tends to slowly increase, and when the test time is 40 hours, the shrinkage value of YH-C50 accounts for about 73% of the shrinkage value of JZ-C50, and the volume stability of YH-C50 concrete is obviously better than that of JZ-C50 concrete designed by adopting the conventional technical route.
Test example two
This test example examined the gel properties of stone dust in powder-containing machine-made sand from different rocks
1. The test method comprises the following steps:
(1) Testing raw materials:
The stone powder is from 8 groups of powder-containing machine-made sand which is common in engineering, and the numbers of the powder-containing machine-made sand are CA (diabase), LT-S1 (basalt), LT-S2 (dolomite), LT-S3 (limestone), SY (limestone), QH (limestone) and HC-S1 (dolomite) HC-S2 (limestone) respectively. The machine-made sand is screened according to the specification of the national standard 'sand for building' (GB/T14684-2022), and the sand with the size of less than 0.075mm is taken as stone powder for research. The cement adopts P.O 42.542.5 ordinary Portland cement, the fly ash adopts II-grade fly ash produced by a large Tang Chenglong power plant, the mineral powder adopts S95-grade mineral powder produced by Lilin company, and the sand adopts standard sand for ISO test.
(2) Test design
The stone powder is used as a cementing material to influence the strength of concrete, and the experiment design is carried out by referring to the method for testing the strength of cement mortar (ISO method) (GB/T17671-2021) and carrying out the experiment of replacing the fly ash with the same proportion as the comparison. In order to eliminate the influence of other factors outside the stone powder on the pore structure of the cement-based material, the mercury-pressing test block is manufactured by selecting cement paste with the same water-cement ratio as that of the cement sand. According to the glue sand strength test result and mercury-pressing porosity analysis, a reasonable stone powder substitution proportion range is obtained, and concrete strength tests of different stone powder and different mixing amounts under the common water-glue ratio of 0.3 and 0.5 are carried out in combination with national standard 'test method Standard of physical and mechanical properties of concrete' (GB/T50081-2019).
In order to eliminate the influence of other factors on the strength, the test raw materials are selected from different batches of cement, and stones, fly ash, mineral powder and the like, and uniform technical parameter materials are selected.
(3) Mixing ratio of rubber sand and concrete
The mortar test and concrete mix are detailed in tables 6 and 7.
TABLE 6 test mixing ratio of rubber sand
TABLE 7 design of concrete mix ratio
2. Results and analysis
2.1 Particle size analysis
Particle size analysis was performed on 8 groups of representative stone dust by a laser particle sizer, the particle size curve being shown in figure 5.
Based on the above test results, the evaluation values D (n) of different particle sizes and the cumulative ratio of different particle sizes of stone powder and other cementing material particles are established, and are shown in tables 8 and 9.
TABLE 8 evaluation values of different particle sizes (μm) of powder particles
TABLE 9 cumulative ratio of different particle sizes (%)
In combination with the analysis, the particle size distribution of the sandstone powder with different mechanisms is different from each other due to different production processes, but the particle size distribution of the different rock stone powder is between the mineral powder and the fly ash, which shows that the stone powder has the property of replacing part of cement, the fly ash and the mineral powder in terms of the particle size distribution.
According to the 'centrality hypothesis' model, stone powder can be used as secondary centrality with the second-level particle size not less than 10 mu m, and cement paste is secondary medium. The cumulative distribution value of all stone powder 45 μm is smaller than the cumulative value of cement 45 μm, and the defect of particle size between 0.075mm and 0.045mm caused by the fact that the current cement is too fine is just supplemented, especially stone powder with relatively coarse particles such as LT-S1, LT-S2 and the like. Therefore, the properties of the cementing material are met from the dimension effect of different stone powder, the defect of the particle size grading of the filler of a system below 0.075mm in the concrete component can be effectively filled, and the particle size grading of the cementing material is better perfected, so that the filling effect is optimized. Therefore, a proper amount of stone powder is mutually combined with cement, fly ash and mineral powder, so that the overall grain size grading of the formed stone powder-cement-mineral powder-fly ash combined cementing material system is better, and the concrete performance is better.
2.2 Chemical composition of different stone powders
According to XRD analysis results (figure 6) of different stone powders, the different stone powders are mainly CaCO 3, and the chemical compositions of the different stone powders are shown in table 10:
TABLE 10 mineral composition of different stone powders
Therefore, the common rock powder is mainly CaCO 3, the contents of Ca (Mg) CO 3, siO 2 and the like have certain variation range, but the main chemical composition CaCO 3、Ca(Mg)CO3、SiO2 has potential hydration activity, and can generate a certain capability of hydrated calcium silicate C-S-H under the conditions that the specific surface area is more than 350m 2/kg and alkali or sulfate exists.
2.3 Specific surface area
The specific surface area test method and procedure of the stone powder are shown in Table 11 with reference to Specification of Cement specific surface area test Fabry-Perot method (GB/T8074-2008).
TABLE 11 specific surface area values for different stone powders (m 2/kg)
According to the fineness detection result, the specific surface area of the sand powder of a common mechanism is approximately 350m 2/kg, so that the stone powder has certain active excitation physical conditions.
In conclusion, through the particle size distribution, chemical components and fineness analysis of the stone powder, the common stone powder has similar properties of the cementing material compared with other cementing materials, and can be used as the cementing material to replace part of cement.
Test example three
The test example examines the sand strength and mercury-pressing test of different stone powder under the substitution of different proportions
The test method of this test example is described in test example two.
3.1 Mortar strength
The 3d, 7d, 28d gum sand block strengths of the different stone powders at 0%, 10%, 20%, 30%, 40% substitution ratios are shown in fig. 7.
As can be seen from the 3d intensity measurement (FIG. 7A), the average value of the intensity intervals of the 10% substitution ratio is improved by about 10% -15% compared with the standard intensity value without stone powder in the same age, the average value of the intensity intervals of the test block of the 20% substitution ratio is slightly reduced by about 5% compared with the standard intensity without stone powder, the average value of the intensity intervals of the test block of the 30% substitution ratio and the 40% substitution ratio is reduced by about 0% -30% compared with the standard intensity value without stone powder, and the intensity of the test block of the stone powder 3d in each different mixing amount interval is different according to the type of stone powder. The strength value of the stone powder rubber sand test block with the same substitution ratio with the fly ash in the 3d age period is reduced more, which indicates that the strength contribution value of the stone powder to the concrete in the 3d period is much larger than that of the fly ash.
As shown in the 7d strength measurement (figure 7B), the average strength of the 10% substitution ratio is improved by about 10% compared with the standard strength value without stone powder in the same period, the average strength of the 20% substitution ratio is further reduced by about 15% -25%, the average strength of the 30% substitution ratio and the 40% substitution ratio is reduced by about 25% -45% more than the standard strength value without stone powder, and the strength of the test block of the stone powder 7d in each different doping amount interval is different according to the type of stone powder. The strength value of the test block of the fly ash corresponding to the same substitution proportion of 7d is close to the lower limit value of the mortar strength interval doped with the stone powder in the same age, which indicates that the strength contribution value of the stone powder to the concrete is larger than that of the fly ash in 7 d.
As can be seen from the 28d strength measurement (FIG. 7C), the 10% substitution ratio strength average value is slightly reduced by about 5% compared with the standard strength value without stone powder in the same age, the 20% substitution ratio strength average value is further reduced by about 10% -15% compared with the standard strength value without stone powder, the 30% substitution ratio strength average value and the 40% substitution ratio strength average value are more greatly reduced by about 30% -45% compared with the standard strength value without stone powder, and the test block strength of the stone powder 28d in each different doping amount interval is different according to the type of stone powder. The intensity value of the mortar with the corresponding same substitution ratio of the fly ash to 28d is close to the average value of mortar intensity of each section of the same-age stone powder, which indicates that the average value of the intensity contribution of different stone powder to concrete at 28d is consistent with the fly ash.
As can be seen from the foregoing fig. 5, the particle size of the stone dust is an important factor affecting the upper and lower limits of each interval, the stone dust particle size is relatively small with respect to cement or fly ash, the intensities of 3d and 7d are substantially in the upper limit region of each section at 10% and 20% substitution ratios, but the intensities of 3d and 7d are not significantly affected by the particle size fineness at 30% and 40% substitution ratios, and the particle size distribution fineness has a large influence on the test piece intensity of 28d at 10% and 20% substitution ratios, but the intensity of 28d is not significantly affected by the particle size fineness at 30% and 40% substitution ratios. Secondly, for stone powders meeting a certain fineness similarity, the chemical composition is also another important factor affecting the upper and lower limits of each interval.
3.2 Mercury intrusion test analysis
The pore size distribution and the porosity of the 28d slurry test block under cement are replaced by 0%, 10%, 20% and 30% of the coal ash, mineral powder and sand powder with different rock mechanisms in engineering according to the same proportion, and the result is shown in figure 8.
Under the condition that the replacement proportion of different stone powder is 10%, 20% and 30%, the pore diameter differential distribution curve of the slurry test block is higher than that of the standard test block without stone powder like the fly ash and mineral powder, which shows that the pores in the cement-based slurry material containing stone powder are greatly increased, and the strength of the concrete is reduced. Therefore, the upper limit of the mixing amount of the stone powder exists for ensuring the quality of the concrete.
As can be seen from fig. 9, the average values of the porosities of all the stone dust-containing cement slurries of the interval sections at the substitution ratios of 10%, 20% and 30% were 19.86%, 19.89% and 21.73% in order. From this, compared with the average value of the porosities in the ratio of 10% -20% of stone powder substitution, the average value of the porosities in the ratio of 20% -30% of stone powder substitution is larger, and the porosity of each stone powder in the interval of 30% substitution is larger. Considering that the strength and the porosity of the concrete have a strong correlation, when the stone powder substitution ratio is more than 20%, the development of the strength is unfavorable, and the method accords with the rule that the strength of the rubber sand test block is reduced by a larger extent than the standard strength under the substitution ratio of 30% and 40% of stone powder.
The common sand usage amount in the mixing ratio of the concrete is 800kg/m 3~1000kg/m3, the national standard "sand for building" (GB/T14684-2022) prescribes that the stone powder content in the machine-made sand is not more than 15%, the maximum content of single concrete stone powder is about 120kg/m 3~150kg/m3, the stone powder is taken as a cementing material, and the optimal replacement proportion of the stone powder in the machine-made sand for simultaneously meeting the strength and the workability is about 8% -22% of the cement mass.
And combining the strength and mechanism analysis of the rubber sand with different substitution ratios, wherein stone powder in the common different rock mechanism sand in the engineering can be used as a cementing material. Therefore, the stone powder content in the machine-made sand is considered in the design of the concrete mixing proportion, the cement dosage is deducted from the cement with the optimal replacement proportion, the cement is replaced by the proportion range of 10% -20%, the performances of the concrete such as strength, workability and the like can be met, and if the stone powder content in the machine-made sand exceeds the range, the part of the stone powder content in the machine-made sand can be considered to replace part of the fly ash or mineral powder.
Test example four
The test example examines the influence coefficient of different stone powder to the concrete strength under the substitution of different proportions
4.1 Parameter analysis
According to the common 9 groups of stone powder, each group replaces cement according to the replacement proportion of 10%, 15% and 20%, and the obtained concrete strength value is obtained.
Combining 10%, 15%, 20% mortar test intensity data and concrete intensity data, 24 data in total for each group at 10%, 20% substitution ratio was used as random samples, 16 data in total for each group at 15% substitution ratio was used as random samples, and respective probability density profiles (fig. 10) were obtained according to different stone powder substitution ratios.
The normal distribution of different stone powder substitution ratios has two parameters of average value and standard deviation, the meaning of the average value parameter is the average level of the concrete strength under the same stone powder substitution ratio, the meaning of the standard deviation parameter is the uniformity of the concrete strength under the same stone powder substitution ratio, the better the uniformity is, the smaller the standard deviation is, the curve is in 'thin and high' distribution, namely, all the values are concentrated near the average value, and the degree of dispersion is smaller. As can be seen from fig. 10, the ratio of the test intensity to the reference intensity of the stone powder at each alternative ratio has a better fitting degree between the histogram distribution and the probability distribution curve, and the ratio distribution of the test intensity to the reference intensity of the stone powder at each alternative ratio can be considered to be in accordance with the normal distribution curve.
4.2 Normal distribution model analysis
The cement is replaced according to the proportion of 10%, 15% and 20% of stone powder, the concrete strength under different replacement proportions is obtained, normal model verification is carried out, and relevant parameters such as corresponding average value, standard deviation, quantiles at 95% probability and the like are obtained according to the data, as shown in table 12.
TABLE 12 Normal distribution model parameter values
Experimental data analysis shows that when the stone powder substitution ratio is 10%, the strength ratio of the concrete strength to the reference value is 89.0% -98.0%, when the stone powder substitution ratio is 15%, the strength ratio of the concrete strength to the reference value is 84.5% -96.4%, and when the stone powder substitution ratio is 20%, the strength ratio of the concrete strength to the reference value is 80.88% -89.82%.
4.3 Coefficient of intensity influence
The strength influence coefficient of the stone powder is obtained by normalizing the strength test results of the concrete with different strength grades under different substitution ratios (figure 11), the compressive strength of the concrete is wholly in a decreasing trend along with the increase of the stone powder substitution ratios, and regression analysis is carried out on the data to obtain the strength influence coefficient expression (I) under different stone powder substitution ratios:
Gamma Lf = -3.16x2 -0.048x+1 formula (I)
Wherein x is mass percent (%) of stone powder to replace cement;
The formula can provide quantitative reference for the influence of different replacement proportions of stone powder on the strength of concrete. The intensity influence coefficients of the stone powder at the substitution ratios of 10%, 15% and 20% were obtained according to the intensity influence coefficient expression (I), and the results are shown in Table 13.
TABLE 13 influence coefficient of the strength of stone powder at different doping amounts
Taking the particle size of the stone powder and the influence of chemical components on the strength into consideration, the 95% confidence interval strength influence coefficient values corresponding to the stone powder doping amounts of 10%, 15% and 20% are calculated and an envelope graph is made (figure 12), and the calculated results of the strength influence coefficient confidence intervals are shown in table 14.
TABLE 14 confidence intervals of the intensity influence coefficients of stone powder at different doping amounts
4.4 Upper and lower Limit determination and Effect
From the results of table 14, the intensity influence coefficient value intervals at the stone powder substitution ratios of 10%, 15% and 20% were formed as shown in table 15.
TABLE 15 influence coefficient of the strength of stone powder at different doping amounts
Since the stone powder has specific surface area up to 350m 2/kg or more and alkali or sulfate is present for the activation of stone powder activity, the capability of generating hydrated calcium silicate C-S-H is provided, so that according to the result of a mortar test, on the premise of a certain substitution ratio, the strength influence of stone powder on cement-based materials mainly depends on the particle size or fineness of stone powder, therefore, whether calcium stone powder or siliceous stone powder is used, the upper and lower limits of 28d strength influence coefficients are determined, and according to the particle size of stone powder, the fineness analysis of different stone powder can refer to the negative pressure screening method in the Specification of cement fineness test method screening method (GB/T1345-2005), and stone powder screen residue data are shown in Table 16.
Table 16.45 μm or more in terms of mass fraction (%)
The size of the ratio of the screen residual mass of particles with the particle size of more than 45 mu m can be used for determining upper and lower limit values, when the value is less than 10%, the upper limit value of the stone powder influence coefficient interval can be calculated according to the intensity influence coefficient formula, when the value is between 10 and 20%, the calculated value of the formula (I) can be directly taken as the stone powder influence coefficient, and when the value is more than 20%, the lower limit value of the stone powder influence coefficient interval can be taken according to the formula.
4.5 Intensity influence coefficient expression validation
5 Kinds of stone powder with different rock quality and different batches of stone powder from the same manufacturer are randomly selected, two common C30 and C50 mixing ratios are randomly selected, the consistency of materials with the selected mixing ratios is maintained, the strength test of the concrete 28d is randomly carried out according to the replacement proportions of 10%, 15% and 20%, the calculated value and the experimental value of the formula (I) are compared and analyzed, and the result is shown in Table 17 in detail.
TABLE 17 evaluation analysis of influence coefficients
As can be seen from the table, the ratio of the calculated value to the test value fluctuates around 1.0, the calculated result is well matched with the test result, the average value and standard deviation of the calculated value to the test value ratio are respectively 1.03 and 0.12, the strength influence coefficient expression obtained based on regression analysis and the test value have good prediction precision and applicability, and the method can be used for calculating the influence of the 10% -20% stone powder doping amount on the strength of the concrete.
The present embodiment is only for explanation of the present application and is not to be construed as limiting the present application, and modifications to the present embodiment, which may not creatively contribute to the present application as required by those skilled in the art after reading the present specification, are all protected by patent laws within the scope of claims of the present application.
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