Novel pervious concrete material based on LC3 cement and preparation method of novel pervious concrete material

Abstract

The invention discloses a novel pervious concrete material based on LC3 cement and a preparation method thereof, the novel pervious concrete material comprises the following raw materials by mass: 59-73 parts of gravel, 5-6 parts of Portland cement, 2-3 parts of metakaolin, 1-1.5 parts of limestone, 0.5 part of gypsum powder, 0.2 part of silica fume, 2.4 parts of water, and 0.04-0.06 part of a water reducer; the preparation method comprises the following steps: mixing all the raw materials, molding, demolding and curing to obtain the novel pervious concrete material. According to the invention, through scientific design of the mix proportion, the synergistic effect of the metakaolin, the limestone powder, the silica fume and the gypsum powder is brought into full play, so that the pervious concrete has excellent compressive strength, abrasion resistance and high durability while maintaining high porosity.

Description

Technical Field

[0001] The present invention relates to a concrete material, in particular to a concrete material based on LC 3 A new type of permeable concrete material based on cement and a preparation method thereof. Background Art

[0002] As a new type of building material, permeable concrete has good water permeability due to its high porosity. It is widely used in urban drainage systems, landscape construction, parking lots, sidewalks and other fields. However, while maintaining a high porosity, the current permeable concrete materials have problems such as poor mechanical properties, weak impact resistance and poor durability. Although high porosity helps rainwater infiltration and discharge, it also leads to low compressive strength, susceptibility to external impact, and fragile structural characteristics; in addition, due to the presence of pores, the material easily absorbs water, and long-term exposure to harsh environments will cause cracks, peeling and other problems, reducing its durability. Although the existing technical solutions have been improved by using different cements or additives, it is still difficult to effectively improve the compressive strength, impact resistance and durability while ensuring high porosity, resulting in difficulty in meeting higher performance requirements in some projects.

[0003] In addition, with the increasing severity of environmental pollution and resource shortages, the burden of traditional cement production on the environment has become more prominent. The large amount of carbon dioxide emissions during cement production has had a profound impact on global climate change. Therefore, the development of a more environmentally friendly and low-carbon cement material has become a hot topic in current research. Summary of the invention

[0004] Purpose of the invention: The first purpose of the present invention is to provide a new type of permeable concrete material with excellent compressive strength, abrasion resistance and high durability while maintaining high porosity; the second purpose of the present invention is to provide the LC-based 3 The invention discloses a preparation method of a new type of permeable concrete material based on cement.

[0005] Technical solution: The present invention is based on LC 3 The new type of permeable concrete material of cement includes, by weight, 59-73 parts of gravel, 5-6 parts of silicate cement, 2-3 parts of metakaolin, 1-1.5 parts of limestone, 0.5 parts of gypsum powder, 0.2 parts of silica fume, 2.4 parts of water, and 0.04-0.06 parts of water reducing agent.

[0006] Portland cement, limestone, metakaolin and gypsum powder are mixed and stirred in the above proportions to obtain LC 3 cement.

[0007] Preferably, the Blaine specific surface area of ​​the silicate cement is 450 m 2 / kg or more.

[0008] Preferably, the strength grade of the silicate cement is 42.5 or above.

[0009] Preferably, the specific surface area of ​​the metakaolin is 200 to 300 m 2 / g.

[0010] Preferably, the particle size of the limestone powder is greater than 325 mesh.

[0011] Preferably, the gypsum powder contains CaSO 4· 2H2O content is greater than 97%.

[0012] Preferably, the SiO2 content in the silica fume powder is greater than 95%.

[0013] Preferably, the apparent density of the gravel is 2700-2800 kg / m 3 , bulk density is 1550~1650kg / m 3 The crushing index is not more than 15%, and the aggregate particle size is 10-20mm.

[0014] Preferably, the water reducer is a polycarboxylate water reducer.

[0015] The LC-based 3 The preparation method of the novel permeable concrete material of cement comprises the following steps:

[0016] Step 1: Weighing

[0017] Weigh silicate cement, metakaolin, limestone powder, gypsum powder, silica fume, gravel, water and water reducing agent;

[0018] Step 2: Mixing

[0019] The silicate cement, metakaolin, limestone powder, gypsum powder and silica fume weighed in step 1 are added to the mixer in sequence, and then the water reducer is mixed with water and added to the mixer, and stirring is started until a mixture with a coagulated appearance begins to form. Finally, gravel is added to the mixer and stirring is continued. When the slurry is evenly covered on the surface of the gravel, it means that the mixture has been evenly stirred and the material is discharged;

[0020] Finally, the novel permeable concrete material is obtained by molding, demoulding and curing.

[0021] The forming step is as follows: pouring the material discharged from step 2 into a mold and spreading the material to form the mold.

[0022] The demoulding process is as follows: after the test block is left to stand at a temperature of 25° C. for 1 day, the concrete is separated from the mold.

[0023] Curing: Put the concrete into the curing room for curing for 28 days. The temperature of the curing room is controlled at 20±2℃ and the relative humidity is greater than 95%. The distance between adjacent concrete prefabricated blocks is required to be controlled at 100-500mm. After the concrete blocks are cured in the curing room for 28 days, they are removed from the curing room and are finished products.

[0024] Invention mechanism:

[0025] The present invention proposes a method based on LC 3 The new permeable concrete material of cement optimizes the performance of permeable concrete by utilizing the synergistic effect of alternative materials such as metakaolin, limestone powder, silica fume and gypsum powder. Metakaolin reacts with calcium hydroxide to form CSH gel, which refines the pore structure and enhances the strength of concrete; limestone powder generates calcium carbon aluminate through filling effect and reaction, further improving the density and durability of concrete. The appropriate amount of gypsum powder can alleviate the effect of aluminate on the setting time, and promote the formation of calcium sulfonate through the introduction of sulfate, enhance the early strength, inhibit the decomposition of calcium sulfonate, and improve the durability of the material. The introduction of silica fume is to adjust the fluidity of cement paste and improve the cementing ability of cement, thereby avoiding cement deposition caused by excessive fluidity of cement paste due to the increase in the demand for water reducer caused by metakaolin, and the fine particles of silica fume improve the structural density of cement paste through filling effect.

[0026] The present invention maximizes the synergistic effect of metakaolin, limestone powder, silica fume and gypsum powder by scientifically designing the mix ratio, so that the permeable concrete has excellent compressive strength, abrasion resistance and high durability while maintaining high porosity. 3 The low-carbon and environmentally friendly characteristics of cement provide a new solution for the application of permeable concrete in urban drainage, river management and other fields, and provide potential for sustainable development.

[0027] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0028] (1) Excellent mechanical properties: By optimizing the ratio of cementitious materials and the amount of minerals added, the density and compressive strength of concrete are significantly improved. While maintaining a high porosity, the compressive strength can reach more than 23MPa, exceeding the design strength of ordinary concrete. At the same time, it has good abrasion resistance and durability.

[0029] (2) High water permeability: The effect of increasing the viscosity of the slurry by kaolin and silica fume is very obvious, that is, the improvement of fluidity and bonding properties. Even under vibration, the cement-bonded stone is very compact and will not flow and settle to cause pore blockage. The pore distribution is optimized, which not only facilitates the infiltration of water from the concrete, but also significantly improves the hydrophobic function of concrete in urban environments and reduces the green island effect.

[0030] (3) High durability: Through the synergistic effect of kaolin, limestone and gypsum, kaolin and silica fume are both volcanic ash materials. Their reaction with calcium hydroxide can continuously generate more fine C-(A)-SH. This volcanic ash effect will continue. At the same time, limestone can also react with aluminate to generate calcium carbon aluminate. In addition, gypsum powder provides additional sulfate ions. These effects can inhibit the decomposition of calcium sulfoxide in the late stage of cement and contribute to the long-term strength maintenance, and make LC 3 The life of cement body is much longer than that of ordinary concrete;

[0031] (4) Low carbon and environmental protection: By significantly reducing the amount of traditional silicate cement clinker and introducing low-energy consumption, high-reserve mineral materials such as kaolin and limestone powder, the energy consumption and carbon dioxide emissions in the cement production process are effectively reduced. Compared with traditional silicate cement, the carbon footprint of the material of the present invention is reduced by about 30% to 40%, which meets the requirements of ecological engineering for low carbon and environmental protection;

[0032] (5) Economical applicability: LC 3 The raw materials of cement, such as kaolin and limestone powder, are widely available and low in cost. The present invention not only reduces the production cost, but also greatly reduces the carbon emission and energy consumption of concrete, making it more economical and valuable for promotion. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below in conjunction with embodiments.

[0034] Examples 1 to 3

[0035] The LC-based 3 The new type of permeable concrete material of cement has a designed porosity of 20%. The raw materials, calculated by weight, include the following components:

[0036] Example 1: 59 parts of gravel, 6 parts of silicate cement, 2 parts of metakaolin, 1.5 parts of limestone, 0.5 parts of gypsum powder, 0.2 parts of silica fume, 2.4 parts of water, and 0.04 parts of water reducing agent.

[0037] The gravel has an apparent density of 2700-2800 kg / m 3 , bulk density is 1550~1650kg / m 3 , the crushing index is not more than 15%, and the aggregate particle size is 10-20mm;

[0038] The silicate cement: Blaine specific surface area is 450m 2 / kg or more, strength grade 42.5 and above;

[0039] The specific surface area of ​​the metakaolin is 200 to 300 m 2 / g, whiteness greater than 91%, average particle size about 2μm;

[0040] The particle size of the limestone powder is about 325 mesh;

[0041] The CaSO of the gypsum powder 4· 2H2O content greater than 99%;

[0042] The SiO2 content in the silica fume powder is greater than 95%;

[0043] The water reducing agent is a high-performance polycarboxylic acid water reducing agent of mud technology, and the water reducing rate is above 27%.

[0044] The raw material properties of the following examples are the same as those of Example 1.

[0045] Example 2: 59 parts of gravel, 5.5 parts of silicate cement, 3 parts of metakaolin, 1 part of limestone, 0.5 parts of gypsum powder, 0.2 parts of silica fume, 2.4 parts of water, and 0.06 parts of water reducing agent.

[0046] Example 3: 59 parts of gravel, 5 parts of silicate cement, 3 parts of metakaolin, 1.5 parts of limestone, 0.5 parts of gypsum powder, 0.2 parts of silica fume, 2.4 parts of water, and 0.06 parts of water reducing agent.

[0047] The preparation method is as follows:

[0048] Step 1: Weigh the ingredients according to the above formula;

[0049] Step 2: Mixing: Add the silicate cement, metakaolin, limestone, gypsum and silica fume weighed in step 1 into the mixer in sequence and mix them evenly; add water mixed with a water reducer into the mixer and continue to mix until a cohesive mixture is formed, and finally add gravel into the mixer and continue to mix until the cement is evenly covered on the stone before discharging the material;

[0050] Step 3: Forming: pour the mixture evenly mixed in step 2 into a mold and spread it to form;

[0051] Step 4: Demolding: After the test block is left to stand at 25°C for 1 day, the permeable concrete is removed from the mold.

[0052] Step 5, curing: put the concrete into the curing room for curing for 28 days. The temperature of the curing room is controlled at 20±2℃ and the relative humidity is greater than 95%. The distance between adjacent permeable concrete prefabricated blocks is required to be controlled at 100-500mm when stacking in the curing room.

[0053] Step 6: Quality inspection: Conduct quality inspection on the finished products and move the qualified finished products to the yard and stack them neatly.

[0054] Embodiments 4 to 6

[0055] The LC-based 3 The new type of permeable concrete material of cement has a designed porosity of 24%. The raw materials, calculated by weight, include the following components:

[0056] Example 4: 73 parts of gravel, 6 parts of Portland cement, 2 parts of metakaolin, 1.5 parts of limestone, 0.5 parts of gypsum powder, 0.2 parts of silica fume, 2.4 parts of water, and 0.04 parts of water reducing agent.

[0057] Example 5: 73 parts of gravel, 5.5 parts of silicate cement, 3 parts of metakaolin, 1 part of limestone, 0.5 parts of gypsum powder, 0.2 parts of silica fume, 2.4 parts of water, and 0.06 parts of water reducing agent.

[0058] Example 6: 73 parts of gravel, 5 parts of silicate cement, 3 parts of metakaolin, 1.5 parts of limestone, 0.5 parts of gypsum powder, 0.2 parts of silica fume, 2.4 parts of water, and 0.06 parts of water reducing agent.

[0059] The preparation method is the same as Example 1.

[0060] Comparative Example 1

[0061] The designed porosity is the same as that of Examples 1 to 3, except that no kaolin, limestone or gypsum is added. The set formula is weighed: 58 parts of gravel, 10 parts of cement, 0.2 parts of silica fume, 2.4 parts of water, and 0.001 parts of water reducing agent. The preparation method is the same as that of Example 1.

[0062] Comparative Example 2

[0063] The designed porosity is the same as that of Examples 4 to 6, except that no kaolin, limestone or gypsum is added. The set formula is weighed: 72 parts of gravel, 10 parts of cement, 0.2 parts of silica fume, 2.4 parts of water, and 0.001 parts of water reducing agent. The preparation method is the same as that of Example 1.

[0064] The physical and mechanical properties of the concrete treated with Examples 1 to 6 and Comparative Examples 1 to 2 were compared. The same test methods and evaluation indicators were used in the tests, and the test methods and evaluation indicators all adopted JC / T 2558-2020 "Permeable Concrete".

[0065] 1. Porosity test

[0066] Porosity tests were conducted on Examples 1 to 6 and Comparative Examples 1 to 2, and the results are shown in Table 1.

[0067] Table 1 Porosity test results

[0068] sample Actual porosity Example 1 20.5 Example 2 20.9 Example 3 20.7 Example 4 24.1 Example 5 24.3 Example 6 25.3 Comparative Example 1 20.3 Comparative Example 2 24.7

[0069] From Table 1, we can see that LC3 The porosity of cement permeable concrete meets the requirements of JC / T 2558-2020 "Permeable Concrete", and the fluctuation is not much compared with the control example. Examples 1-3 have a slight increase, which may be caused by pore formation and material shrinkage during the preparation process. Although the actual porosity has increased slightly, the hydrophobic function has been greatly enhanced. And it shows that to a certain extent, the LC with low porosity design 3 The porosity of permeable concrete may have better hydrophobic properties in practical applications.

[0070] 2. Compressive strength test

[0071] Compressive strength tests were performed on Examples 1 to 6 and Comparative Examples 1 to 2, and the results are shown in Table 2.

[0072] Table 2 Compressive strength test results

[0073]

[0074]

[0075] As shown in Table 2, compared with Comparative Examples 1 to 2, the compressive strength of Examples 1 to 6 is improved to varying degrees, which indicates that LC 3 Cement has an enhancing effect on the compressive strength of permeable concrete. 3 Cement introduces kaolin, limestone, gypsum and silica fume, and utilizes the volcanic ash activity of kaolin and silica fume, the micro-filling and active effect of limestone, and the formation of calcium sulfide with the participation of gypsum powder. These reactions promote more beneficial hydration products, improve the density of the slurry, and enhance the mechanical properties of the material. These factors work together to make LC 3 In some cases, cement has a higher strength than ordinary Portland cement. The compressive strength of Examples 1 to 3 is greater than that of Examples 4 to 6, and all meet the requirements of JC / T 2558-2020 "Pervious Concrete", indicating that LC 3 Cement has a more obvious effect on improving the compressive strength of permeable concrete.

[0076] Permeability

[0077] The water permeability coefficient test was carried out on Examples 1 to 6 and Comparative Examples 1 to 2, and the results are shown in Table 3.

[0078] Table 3 Test results of water permeability coefficient

[0079] sample Water permeability cm / s Example 1 1.8 Example 2 1.8 Example 3 1.8 Example 4 3.2 Example 5 3.2 Example 6 3.5 Comparative Example 1 1.2 Comparative Example 2 2.9

[0080] As shown in Table 3, all Examples 1 to 6 meet the water permeability requirements of JC / T 2558-2020 "Permeable Concrete". Compared with Examples 4 to 6, the water permeability increase of Examples 1 to 3 is the largest. These increases indicate that the prepared LC 3 The permeability of permeable concrete will increase more significantly as the designed porosity decreases. This is mainly because the clay mineral kaolin will introduce additional pores and channels during the cement hydration process, enhancing the permeability. Moreover, because the volume of kaolin is large, the design of the group with small pores will lead to the addition of more kaolin, resulting in an increase in the degree of volume shrinkage. 3 After cement hydration, it generates less calcium hydroxide Ca(OH)2, so the alkalinity of cement paste is lower. The low alkalinity environment may cause the coagulation and hardening process of cement paste to be slower, and the macroscopic structure of cement may not be dense enough, thus forming more pores. These pores affect the permeability of water, increasing the water permeability coefficient.

[0081] The following conclusions can be drawn from the above experiments:

[0082] (1)LC 3 Cement can improve the compressive strength of permeable concrete, and Examples 1 to 6 basically meet the requirements of JC / T2558-2020 "Permeable Concrete". Although it will increase the actual porosity of permeable concrete, it will not significantly reduce the strength of permeable concrete.

[0083] (2)LC 3 The permeability of permeable concrete can fully meet the actual application requirements of the project.

Claims

1. A LC-based 3 A new type of permeable concrete material made of cement, characterized in that: Calculated by mass, the raw materials include: 59-73 parts of gravel, 5-6 parts of silicate cement, 2-3 parts of metakaolin, 1-1.5 parts of limestone, 0.5 parts of gypsum powder, 0.2 parts of silica fume, 2.4 parts of water, and 0.04-0.06 parts of water reducing agent.

2. The LC-based method according to claim 1 3 A new type of permeable concrete material made of cement, characterized in that: The Blaine specific surface area of ​​the silicate cement is 450m 2 / kg or more.

3. The LC-based method according to claim 1 3 A new type of permeable concrete material made of cement, characterized in that: The general silicate cement has a strength grade of 42.5 or above.

4. The LC-based method according to claim 1 3 A new type of permeable concrete material made of cement, characterized in that: The specific surface area of ​​the metakaolin is 200 to 300 m 2 / g.

5. The LC-based method according to claim 1 3 A new type of permeable concrete material made of cement, characterized in that: The particle size of the limestone powder is above 325 meshes.

6. The LC-based method according to claim 1 3 A new type of permeable concrete material made of cement, characterized in that: The CaSO in the gypsum powder 4· 2H2O content is greater than 97%.

7. The LC-based method according to claim 1. 3 A new type of permeable concrete material made of cement, characterized in that: The SiO2 content in the silica fume powder is greater than 95%.

8. The LC-based method according to claim 1 3 A new type of permeable concrete material made of cement, characterized in that: The apparent density of the gravel is 2700-2800 kg / m 3 , bulk density is 1550~1650kg / m 3 The crushing index is not more than 15%, and the aggregate particle size is 10-20mm.

9. The LC-based method according to claim 1 3 A new type of permeable concrete material made of cement, characterized in that: The water reducer is a polycarboxylate water reducer.

10. A LC-based method according to any one of claims 1 to 9 3 The preparation method of a new type of cement permeable concrete material is characterized in that: The following steps are involved: Step 1: Weighing Weigh silicate cement, metakaolin, limestone powder, gypsum powder, silica fume, gravel, water and water reducing agent; Step 2: Mixing The silicate cement, metakaolin, limestone powder, gypsum powder and silica fume weighed in step 1 are added to the mixer in sequence, and then the water reducer is mixed with water and added to the mixer, and stirring is started until a mixture with a coagulated appearance begins to form. Finally, gravel is added to the mixer and stirring is continued. When the slurry is evenly covered on the surface of the gravel, it means that the mixture has been evenly stirred and the material is discharged; Finally, the novel permeable concrete material is obtained by molding, demoulding and curing.

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