Application of key technology of waste stone chips in medium-low strength grade concrete

Abstract

The invention discloses an application of a key technology of waste stone chips in medium and low strength grade concrete, and relates to the technical field of building materials, which comprises cement, waste stone chips, machine-made sand, broken stone, secondary fly ash, S95 mineral powder, and a polycarboxylic acid high performance water reducer. The water reducing rate of the polycarboxylic acid high-performance water reducing agent is 22%, and the solid content is 8.5%; the breaking strength of the cement in 28 days is 8.7 MPa, and the compressive strength of the cement in 28 days is 52.13 MPa; the apparent density of the machine-made sand is 2.68 g / cm < 3 >, the silt content is 2.2%, and the fineness modulus is 2.8, and the broken stones are configured in a continuous particle size of 5mm-25mm. The method has the beneficial effects that the pollution of the waste stone chips to the environment and the occupation of land resources are reduced; and as the price of the waste stone chips is far lower than that of the machine-made sand, the cost of raw materials can be remarkably reduced by partially replacing the machine-made sand with the waste stone chips.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, in particular to a key technology application of waste stone chips in medium and low strength grade concrete. Background Art

[0002] With the rapid development of the construction industry, the demand for concrete is increasing, and the resources of machine-made sand and gravel, one of the main raw materials for concrete, are becoming increasingly scarce. At the same time, a large amount of waste stone chips are generated during the mining and processing of stone materials. The accumulation of these waste stone chips not only occupies land resources, but also causes serious environmental pollution. Therefore, how to reasonably apply waste stone chips to concrete and realize the recycling of resources is of great practical significance.

[0003] At present, there have been some studies on the application of waste stone chips in concrete, but there are still some problems in practical applications, such as the working performance, mechanical properties and durability of concrete are difficult to meet engineering requirements. Therefore, we proposed a key technology application of waste stone chips in medium and low strength grade concrete. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a key technology for the application of waste stone chips in medium and low strength grade concrete, which solves the problems raised in the above-mentioned background technology: by pretreating the waste stone chips and optimizing the mix ratio, the problems existing in the application of waste stone chips in concrete are solved, the performance of concrete is improved, and the resource utilization of waste stone chips is realized.

[0005] To achieve the above purpose, the present invention is implemented by the following technical scheme: an application of key technology of waste stone chips in medium and low strength grade concrete, including cement, waste stone chips, machine-made sand, crushed stone, secondary fly ash, S95 mineral powder, and polycarboxylic acid high-performance water reducer;

[0006] The polycarboxylic acid high-performance water-reducing agent has a water-reducing rate of 22% and a solid content of 8.5%; the cement has a 28-day flexural strength of 8.7 MPa and a 28-day compressive strength of 52.13 MPa; the machine-made sand has an apparent density of 2.68 g / cm 3 The mud content is 2.2%, the fineness modulus is 2.8, and the crushed stone is a continuous particle size configuration of 5mm-25mm.

[0007] Preferably, the waste stone chips are sieved with a 4.75mm square hole sieve and a 0.075mm square hole sieve to remove the residues on the upper and bottom layers to obtain stone chips with a particle size in the range of 0.15-4.75mm, and the waste stone chips have a methylene blue MB value of 1.8, a stone powder content of 22%, and a fineness modulus of 3.0.

[0008] Preferably, the waste stone chips replace the machine-made sand by 10%, and the fineness modulus is 2.8%, the methylene blue MB value is 1.0%, the stone powder content is 10%, and the bulk density is 1.4 g / cm 3 Apparent density 2.61 g / cm 3 . Mixed sand with a void ratio of 46%.

[0009] Preferably, the waste stone chips replace the machine-made sand by 20%, and the fineness modulus is 2.8%, the MB value of methylene blue is 1.1%, the stone powder content is 11%, and the bulk density is 1.41 g / cm 3 Apparent density 2.61 g / cm 3 . Mixed sand with a void ratio of 45%.

[0010] Preferably, the waste stone chips replace the machine-made sand by 30%, and the fineness modulus is 2.9%, the MB value of methylene blue is 1.1%, the stone powder content is 12%, and the bulk density is 1.41 g / cm 3 Apparent density 2.62g / cm 3 . Mixed sand with a void ratio of 44%.

[0011] Preferably, the waste stone chips replace the machine-made sand by 40%, and the fineness modulus is 2.9%, the MB value of methylene blue is 1.2%, the stone powder content is 13%, and the bulk density is 1.42 g / cm 3 Apparent density 2.62g / cm 3 . Mixed sand with a void ratio of 43%.

[0012] Preferably, the waste stone chips replace the machine-made sand by 50%, and the fineness modulus is 3.0%, the MB value of methylene blue is 1.3%, the stone powder content is 15%, and the bulk density is 1.42 g / cm 3 Apparent density 2.63g / cm 3 . Mixed sand with a void ratio of 42%.

[0013] A method for using waste stone chips in medium and low strength grade concrete comprises the following steps:

[0014] S1. Screening the waste stone chips to remove particles with too large and too small particle sizes, and obtaining stone chips with a particle size in the range of 0.15-4.75 mm;

[0015] S2, washing the sieved stone chips with water to remove dirt and impurities on the surface, and then drying them for later use;

[0016] S3, partially replace the machine-made sand with the pre-treated waste stone chips, the replacement rate is 10%-50%; the water-cement ratio is controlled within the range of 0.4-0.6; the water reducer is 0.5%-2.0% of the mass of the cementitious material; standby;

[0017] S4. Put cement, fly ash, mineral powder and other cementitious materials and pre-treated waste stone chips into a mixer and dry mix for 1-2 minutes, then add water and water reducing agent and stir for 2-3 minutes to make them evenly mixed;

[0018] S5. Pour the mixed concrete into the mold, remove it from the mold after curing at room temperature for 24 hours, and then place it in a standard curing room for curing to the specified age.

[0019] Preferably, the source of the waste stone chips is waste generated during stone mining and processing.

[0020] Preferably, the strength grade of the concrete is C15-C40.

[0021] The present invention provides an application of key technology of waste stone chips in medium and low strength grade concrete, which has the following beneficial effects:

[0022] 1. Realize the resource utilization of waste stone chips, reduce the pollution of waste stone chips to the environment and the occupation of land resources;

[0023] 2. Reduce the production cost of concrete. Since the price of waste stone chips is much lower than that of machine-made sand, using waste stone chips to partially replace machine-made sand can significantly reduce the cost of raw materials;

[0024] 3. The performance of concrete is improved. Through the pretreatment of waste stone chips and optimization of mix ratio, the prepared medium and low strength concrete can meet the engineering requirements in terms of working performance, mechanical properties and durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the relationship between the amount of stone chips replaced and the slump of the concrete mixture of the present invention;

[0026] Figure 2 Schematic diagram of the relationship between the amount of stone chip replacement and concrete strength of the present invention. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0028] Example 1

[0029] 1.Raw materials

[0030] Cement: P·O42.5 ordinary Portland cement, its performance index meets the requirements of "General Portland Cement" (GB175-2007);

[0031] Fly ash: Class II fly ash, its performance indicators meet the requirements of "Fly ash used in cement and concrete" (GB / T1596-2017);

[0032] Artificial sand: medium sand with a fineness modulus of 2.8, whose performance indicators meet the requirements of "Construction Sand" (GB / T14684-2022);

[0033] Waste stone chips: from a stone processing plant, after screening and water washing pretreatment, the particle size is in the range of 0.15-4.75mm;

[0034] Stone: Continuously graded crushed stone with a particle size of 5-25 mm, and its performance indicators meet the requirements of "Pebbles and Crushed Stones for Construction" (GB / T14685-2022);

[0035] Water: tap water;

[0036] Water reducing agent: Polycarboxylic acid high performance water reducing agent, water reducing rate is 25%.

[0037] 2. Concrete mix ratio

[0038] Cement: 280kg / m 3 ; Fly ash: 70kg / m 3 ; Artificial sand: 450kg / m 3 ; Waste stone chips: 250kg / m 3 ; Stone: 1100kg / m 3 ; Water: 170kg / m 3 ; Water reducing agent: 6.0kg / m 3 .

[0039] 3. Concrete preparation and performance testing

[0040] According to the above mix ratio, first put cement, fly ash and waste stone chips into a mixer and dry mix for 1 minute, then add water and water reducing agent and mix for 2 minutes, and finally add gravel and mix for 1 minute to make it evenly mixed;

[0041] The mixed concrete was poured into a 100mm×100mm×100mm cubic test mold and a 150mm×150mm×300mm prism test mold, and after curing at room temperature for 24 hours, the concrete was demoulded and then placed in a standard curing room for curing to the age of 7 days and 28 days;

[0042] The compressive strength, flexural strength, slump, expansion and impermeability of concrete are tested in accordance with the "Standard Test Methods for Mechanical Properties of Ordinary Concrete" (GB / T50081-2019) and the "Standard Test Methods for Long-term Properties and Durability of Ordinary Concrete" (GB / T50082-2009).

[0043] The test results show that the slump of the concrete is 180mm, the expansion is 450mm, the 7d compressive strength is 30.2MPa, the 28d compressive strength is 39.1MPa, the 28d flexural strength is 4.8MPa, and the water-resistance grade is P8. All performance indicators meet the design requirements.

[0044] Example 2

[0045] 1.Raw materials

[0046] Cement: P·O42.5 ordinary Portland cement;

[0047] Mineral powder: S95 grade mineral powder, its performance indicators meet the requirements of "Granulated blast furnace slag powder for cement, mortar and concrete" (GB / T18046-2017);

[0048] Artificial sand: medium sand with fineness modulus of 2.8;

[0049] Waste stone chips: waste stone chips after pretreatment;

[0050] Stone: Continuously graded crushed stone with a particle size of 5-25mm;

[0051] Water: tap water;

[0052] Water reducing agent: Polycarboxylic acid high performance water reducing agent, water reducing rate is 28%.

[0053] 2. Concrete mix ratio

[0054] Cement: 240kg / m 3 ; Mineral powder: 80kg / m 3 ; Artificial sand: 500kg / m 3 ; Waste stone chips: 200kg / m 3 ; Stone: 1050kg / m 3 ; Water: 160kg / m 3 ; Water reducing agent: 5.6kg / m 3 .

[0055] 3. Concrete preparation and performance testing

[0056] According to the above mix ratio, first put cement, mineral powder and waste stone chips into a mixer and dry mix for 2 minutes, then add water and water reducer and mix for 3 minutes, and finally add gravel and mix for 1 minute to make it evenly mixed;

[0057] Pour the mixed concrete into the test mold, remove it from the mold after curing at room temperature for 24 hours, and then put it into the standard curing room for curing to the age of 7 days and 28 days;

[0058] The performance of concrete is tested according to relevant standards.

[0059] The test results show that the slump of the concrete is 190mm, the expansion is 480mm, the 7d compressive strength is 29.8MPa, the 28d compressive strength is 40.2MPa, the 28d flexural strength is 4.5MPa, and the water-resistance grade is P8. All performance indicators meet the design requirements.

[0060] Table 1:

[0061]

[0062] In the present invention, waste stone chips are added to C30 concrete. As the proportion of waste stone chips replacing fine aggregate increases, the fluidity of the concrete mixture decreases sharply and the cohesiveness is very high.

[0063] The surface of waste stone chips is smooth, which can give full play to its own ball effect, increase the fluidity of cement paste, and play a role in reducing water. Different ways of adding waste stone chips can better fill and optimize the pore structure of hardened concrete and improve the uniformity of fresh concrete.

[0064] Through the research of the present invention, it is found that by utilizing the characteristics of waste stone chips and adding waste stone chips in different proportions to replace machine-made sand, construction waste can be more fully utilized to achieve environmental benefits, and more costs can be reduced to achieve better economic benefits for enterprises. The addition of waste stone chips can better improve the particle grading between sands, improve the density of concrete by optimizing the particle size distribution, and increase the strength of concrete.

[0065] In terms of improving the workability of concrete, an appropriate amount of waste stone chips can significantly improve the segregation and bleeding of concrete mixture without affecting the fluidity of concrete, and has a certain thickening, viscosity increasing and slurry raising effect.

[0066] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. Application of key technology of waste stone chips in medium and low strength grade concrete, characterized by: Including cement, waste stone chips, machine-made sand, crushed stone, secondary fly ash, S95 mineral powder, polycarboxylic acid high-performance water reducer; The polycarboxylic acid high-performance water-reducing agent has a water-reducing rate of 22% and a solid content of 8.5%; the cement has a 28-day flexural strength of 8.7 MPa and a 28-day compressive strength of 52.13 MPa; the machine-made sand has an apparent density of 2.68 g / cm 3 The mud content is 2.2%, the fineness modulus is 2.8, and the crushed stone is a continuous particle size configuration of 5mm-25mm.

2. The key technology application of waste stone chips in medium and low strength grade concrete according to claim 1 is characterized by: The waste stone chips are sieved with a 4.75mm square hole sieve and a 0.075mm square hole sieve to remove the residues on the upper and bottom layers, thereby obtaining stone chips with a particle size ranging from 0.15 to 4.75mm. The waste stone chips have a methylene blue MB value of 1.8, a stone powder content of 22%, and a fineness modulus of 3.

0.

3. The key technology application of waste stone chips in medium and low strength grade concrete according to claim 1 is characterized by: The waste stone chips 10% replace the machine-made sand to obtain a fineness modulus of 2.8%, a methylene blue MB value of 1.0%, a stone powder content of 10%, and a bulk density of 1.4 g / cm 3 Apparent density 2.61 g / cm 3 . Mixed sand with a void ratio of 46%.

4. The key technology application of waste stone chips in medium and low strength grade concrete according to claim 1 is characterized by: The waste stone chips 20% replace the machine-made sand to obtain a fineness modulus of 2.8%, a methylene blue MB value of 1.1%, a stone powder content of 11%, and a bulk density of 1.41 g / cm 3 Apparent density 2.61 g / cm 3 . Mixed sand with a void ratio of 45%.

5. The use of waste stone chips in medium and low strength grade concrete according to claim 1, characterized in that: The waste stone chips 30% replace the machine-made sand to obtain a fineness modulus of 2.9%, a methylene blue MB value of 1.1%, a stone powder content of 12%, and a bulk density of 1.41 g / cm 3 Apparent density 2.62g / cm 3 . Mixed sand with a void ratio of 44%.

6. The use of waste stone chips in medium and low strength grade concrete according to claim 1, characterized in that: The waste stone chips 40% replace the machine-made sand to obtain a fineness modulus of 2.9%, a methylene blue MB value of 1.2%, a stone powder content of 13%, and a bulk density of 1.42 g / cm 3 Apparent density 2.62g / cm 3 . Mixed sand with a void ratio of 43%.

7. The use of waste stone chips in medium and low strength grade concrete according to claim 1, characterized in that: The waste stone chips can replace the machine-made sand by 50%, and the fineness modulus is 3.0%, the MB value of methylene blue is 1.3%, the stone powder content is 15%, and the bulk density is 1.42 g / cm 3 Apparent density 2.63g / cm 3 . Mixed sand with a void ratio of 42%.

8. The method for using waste stone chips in medium and low strength grade concrete according to claim 1, characterized in that: The following steps are involved: S1. Screening the waste stone chips to remove particles with too large and too small particle sizes, and obtaining stone chips with a particle size in the range of 0.15-4.75 mm; S2, washing the sieved stone chips with water to remove dirt and impurities on the surface, and then drying them for later use; S3, partially replace the machine-made sand with the pre-treated waste stone chips, with a replacement rate of 10%-50%; The water-cement ratio is controlled within the range of 0.4-0.6; the water reducing agent is 0.5%-2.0% of the mass of the cementitious material; it is reserved; S4. Put cement, fly ash, mineral powder and other cementitious materials and pre-treated waste stone chips into a mixer and dry mix for 1-2 minutes, then add water and water reducing agent and stir for 2-3 minutes to make them evenly mixed; S5. Pour the mixed concrete into the mold, remove it from the mold after curing at room temperature for 24 hours, and then place it in a standard curing room for curing to the specified age.

9. The method for using waste stone chips in medium and low strength grade concrete according to claim 8, characterized in that: The source of the waste stone chips is the waste generated during stone mining and processing.

10. The method for using waste stone chips in medium and low strength grade concrete according to claim 8, characterized in that: The strength grade of the concrete is C15-C40.

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