A silicate cement reinforcing agent, its preparation method and application

Abstract

This invention relates to the field of cement-based admixtures, and in particular to a silicate cement reinforcing agent and its preparation method and application. It is prepared by high-temperature calcination, rapid cooling and grinding of CaO, SiO2 and CaCl2 as raw materials. The composition is Ca3SiO4Cl2, Ca2SiO4 and a small amount of SiO2. When added to cementitious materials, it can increase the hydration rate of the mineral phase of silicate cement clinker, significantly improve the compressive strength of cement-based materials, and enhance the early flexural strength of cement-based materials without impairing the later flexural strength of cement mortar.

Description

Technical Field

[0001] This invention relates to the field of cement-based admixtures, and in particular to a silicate cement reinforcing agent, its preparation method, and its application. Background Technology

[0002] Cement concrete is widely used in building construction, but its slow setting and hardening speed and long early strength development time limit its application in some special situations. Early strength agents, as admixtures, can accelerate cement hydration and promote the development of early concrete strength, thus compensating for the shortcomings of cement concrete in cold climates, emergency rescue projects, and road repairs where rapid hardening and strength development are required.

[0003] Currently, commonly used early-strength accelerators fall into two main categories: chlorine-based and non-chlorine-based. Chlorine-based accelerators include calcium chloride (CaCl2) and alkali metal chlorides, while non-chlorine-based accelerators include nitrates, nitrites, thiocyanates, formates, and alkanolamines. CaCl2 can promote the hydration rate of cement, shorten the setting time, and increase cement strength. Alkali metal chlorides can also promote cement strength, but the effect is limited, and they also increase the risk of alkali-aggregate reaction, leading to a decrease in later strength and durability. Chlorine-based accelerators are easily soluble in water, forming a large amount of free chlorine, which can damage the passivation film formed by steel bars in highly alkaline environments, thus accelerating steel corrosion. Among non-chlorine-based accelerators, nitrates have a relatively small effect on promoting cement strength, while nitrite and thiocyanate accelerators have weak toxicity and are therefore less commonly used. Alkanolamine accelerators can improve the early strength of cement, but have little effect on the later strength. Moreover, the dosage of alkanolamine accelerators is difficult to control; too little has little effect, while too much can easily cause problems with the workability of the cement.

[0004] Existing patents US4119467A and JPS534033A disclose an early-strength cement mainly composed of alite, belite, calcium aluminochloroaluminate, calcium chlorosilicate, and calcium aluminoferrite. However, this cement requires high preparation temperature and complex preparation methods. The early strength of the cement mainly comes from the hydration of chlorine-containing minerals, resulting in high chlorine content and thus making preparation difficult. In this technology, when the content of alite and belite is high, the 3d strength of the cement is less than 5 MPa. When there are many chlorine-containing minerals, the later strength of the cement is also insufficient. As the most widely used cement, silicate cement requires not only high early strength but also sufficient later strength. The early strength of silicate cement is mainly provided by two mineral phases, C3A and C3S, while the later strength is mainly provided by C2S. Therefore, this patented technology cannot be used to guide how to improve the strength performance of silicate cement, and its application scenarios are limited. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a silicate cement reinforcing agent, which is prepared by high-temperature calcination, rapid cooling, and grinding of CaO, SiO2, and CaCl2 as raw materials. The composition consists of Ca3SiO4Cl2, Ca2SiO4, and a small amount of SiO2. When added to cementitious materials, it can increase the hydration rate of the mineral phase of silicate cement clinker, significantly improve the compressive strength of cement-based materials, and enhance the early flexural strength of cement-based materials without impairing the later flexural strength of cement mortar.

[0006] Specifically, the preparation method of the silicate cement reinforcing agent of the present invention comprises the following steps:

[0007] 1) Weigh out 110-120 parts CaO, 55-65 parts SiO2, and 110-115 parts CaCl2 by weight.

[0008] 2) Mix CaO, SiO2, and CaCl2 evenly, grind, and press into a cake.

[0009] 3) Calcine the cake at 850-950℃ for 1.5-2 hours, cool it rapidly, grind it, and pass it through a 200-mesh sieve to obtain the final product.

[0010] The main components of the silicate cement reinforcing agent of this invention are Ca3SiO4Cl2, Ca2SiO4, and a small amount of SiO2. Among them, Ca3SiO4Cl2 can provide some of the calcium ions required for cement hydration through its own dissolution, and can also provide CSH gel as a nucleation site to promote cement hydration through its hydration. The research of this invention shows that the Ca3SiO4Cl2 component has little effect on the induction period in the early stage of cement hydration, but mainly increases the hydration rate and the hydration exothermic peak in the accelerated period of cement. It can also accelerate the hydration of C2S and C4AF in the later stage of cement hydration and increase the content of hydration products such as CSH gel. Therefore, Ca3SiO4Cl2 can promote the hydration rate of cement clinker phase and improve the strength performance of cement at the same age.

[0011] Furthermore, the silicate cement reinforcing agent prepared in this invention contains some chlorine dissolved from the minerals, which reacts with the aluminum phase in the cement to form F salts. On the one hand, this reduces the content of free chloride ions. In addition, the small-particle-size F salts formed can fill pores, reduce porosity, optimize pore size distribution, and increase the proportion of gel pores, which helps to improve the strength and durability of cement. Ca3SiO4Cl2 can accelerate the hydration rate of C3S and aluminum phases (C3A, C4AF) in cement in the early stage, and accelerate the hydration rate of C2S in the later stage. By reducing porosity and optimizing pore size distribution, it can improve the compressive strength of cement in 1-28 days.

[0012] Preferably, in step 1), 115 parts CaO, 60 parts SiO2, and 111 parts CaCl2 are weighed out by weight.

[0013] Preferably, step 2) grinding is performed using a planetary ball mill, and the grinding time is 12-17 minutes.

[0014] Preferably, step 2) pressing is performed using a press with a pressure of 100KN.

[0015] Preferably, in step 2), the diameter of the cake is 10cm.

[0016] Preferably, step 3) calcination is performed using a muffle furnace.

[0017] Preferably, step 3) rapid cooling uses air cooling.

[0018] This invention also relates to silicate cement reinforcing agents, specifically, those prepared by the above-described preparation method.

[0019] The present invention also relates to the application of the above-mentioned silicate cement reinforcing agent in improving cement strength, wherein preferably, the amount of silicate cement reinforcing agent added to the cementitious material is 0.1-10%. Detailed Implementation

[0020] To demonstrate the technical effect of this invention, a silicate cement reinforcing agent was prepared and added to the mortar as an admixture. The compressive strength of the mortar was determined according to GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)". The cement used was P·O42.5 cement, and the amount of silicate cement reinforcing agent added was 5% of the mass of the cementitious material.

[0021] Example 1

[0022] The silicate cement reinforcing agent is prepared by the following steps:

[0023] 1) Weigh out 115 parts CaO, 60 parts SiO2, and 111 parts CaCl2 by weight.

[0024] 2) Mix CaO, SiO2, and CaCl2 evenly, grind, and press into a cake.

[0025] 3) Calcine the cake at 850℃ for 2 hours, cool it rapidly, grind it, and pass it through a 200-mesh sieve to obtain the final product.

[0026] The mortar was tested and found to have a 3-day compressive strength of 37.3 MPa, a 7-day compressive strength of 49.6 MPa, and a 28-day compressive strength of 66.3 MPa.

[0027] Example 2

[0028] The silicate cement reinforcing agent is prepared by the following steps:

[0029] 1) Weigh out 120 parts CaO, 55 parts SiO2, and 115 parts CaCl2 by weight.

[0030] 2) Mix CaO, SiO2, and CaCl2 evenly, grind, and press into a cake.

[0031] 3) Calcine the cake at 950℃ for 1.5 hours, cool it rapidly, grind it, and pass it through a 200-mesh sieve to obtain the final product.

[0032] The mortar was tested and found to have a 3-day compressive strength of 36.5 MPa, a 7-day compressive strength of 47.9 MPa, and a 28-day compressive strength of 65.0 MPa.

[0033] Comparative Example 1

[0034] The silicate cement reinforcing agent is prepared by the following steps:

[0035] 1) Weigh out 160 parts CaO, 65 parts SiO2, and 75 parts CaCl2 by weight.

[0036] 2) Mix CaO, SiO2, and CaCl2 evenly, grind, and press into a cake.

[0037] 3) Calcine the cake at 950℃ for 1.5 hours, cool it rapidly, grind it, and pass it through a 200-mesh sieve to obtain the final product.

[0038] The mortar was tested and found to have a 3-day compressive strength of 31.3 MPa, a 7-day compressive strength of 40.5 MPa, and a 28-day compressive strength of 52.4 MPa.

[0039] Comparative Example 2

[0040] The silicate cement reinforcing agent is prepared by the following steps:

[0041] 1) Weigh out 90 parts CaO, 45 parts SiO2, and 155 parts CaCl2 by weight.

[0042] 2) Mix CaO, SiO2, and CaCl2 evenly, grind, and press into a cake.

[0043] 3) Calcine the cake at 950℃ for 1.5 hours, cool it rapidly, grind it, and pass it through a 200-mesh sieve to obtain the final product.

[0044] The mortar was tested and found to have a 3-day compressive strength of 31.7 MPa, a 7-day compressive strength of 41.4 MPa, and a 28-day compressive strength of 51.2 MPa.

[0045] Comparative Example 3

[0046] The silicate cement reinforcing agent is prepared by the following steps:

[0047] 1) Weigh out 120 parts CaO, 55 parts SiO2, and 115 parts CaCl2 by weight.

[0048] 2) Mix CaO, SiO2, and CaCl2 evenly, grind, and press into a cake.

[0049] 3) Calcine the cake at 1050℃ for 1.5 hours, cool it rapidly, grind it, and pass it through a 200-mesh sieve to obtain the final product.

[0050] The mortar was tested and found to have a 3-day compressive strength of 33.4 MPa, a 7-day compressive strength of 42.5 MPa, and a 28-day compressive strength of 56.9 MPa.

[0051] Blank example

[0052] No cement reinforcing agent was added during the preparation of the mortar specimens in the blank example.

[0053] The mortar was tested and found to have a 3-day compressive strength of 27.8 MPa, a 7-day compressive strength of 36.1 MPa, and a 28-day compressive strength of 47.6 MPa.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a silicate cement enhancing agent, characterized by, It is prepared by the following steps: 1) CaO 110-120 parts, SiO2 55-65 parts, CaCl2 110-115 parts are weighed by weight parts, 2) CaO, SiO2, CaCl2 are mixed uniformly, grinded, and pressed into material cake, 3) the material cake is calcined at 850-950℃ for 1.5-2h, rapidly cooled, grinded, and passed through 200 mesh sieve, and then obtained.

2. The method for preparing the silicate cement reinforcing agent according to claim 1, characterized in that, CaO 115 parts, SiO2 60 parts, CaCl2 111 parts are weighed by weight parts in step 1).

3. The method for preparing the silicate cement reinforcing agent according to claim 1, characterized in that, The grinding in step 2) adopts planetary ball mill, and the grinding time is 12-17min.

4. The method for preparing the silicate cement reinforcing agent according to claim 1, characterized in that, The pressing in step 2) adopts press machine, and the pressure is 100KN.

5. The method for preparing the silicate cement reinforcing agent according to claim 1, characterized in that, The diameter of the material cake in step 2) is 10cm.

6. The method of claim 1, wherein the portland cement strength enhancer is prepared by the steps of: The calcination in step 3) adopts muffle furnace.

7. The method for preparing the silicate cement reinforcing agent according to claim 1, characterized in that, The rapid cooling in step 3) adopts air cooling.

8. A silicate cement enhancing agent characterized by, It is prepared by the preparation method in any one of claims 1-7.

9. The use of the silicate cement enhancer in claim 8 in improving the strength of cement.

10. Use according to claim 9, characterized in that, The adding amount of the silicate cement enhancer in cementitious material is 0.1-10%.