Crystal nucleus type hydration accelerator cement cementing material in low-temperature environment and preparation method thereof

Abstract

The invention discloses a crystal nucleus type hydration accelerator cement cementing material in a low-temperature environment and a preparation method of the crystal nucleus type hydration accelerator cement cementing material. The cement cementing material is prepared by taking ordinary Portland cement and a C-S-H crystal nucleus type hydration accelerator as raw materials and designing according to a reasonable mixing ratio, and the requirement of rapid strength development of the cement cementing material in a low-temperature environment is met. In addition, the method has the advantages of reducing resource consumption and extra cost and the like, and has remarkable economic, environment-friendly and social benefits. Reliability, economical efficiency and limitation of building construction in winter can be improved, and an engineering structure is promoted to develop towards the direction of high efficiency, durability and ecology.

Description

Technical Field

[0001] The present invention belongs to the technical field of green and low-carbon building materials, and specifically relates to the influence of a crystal nucleus type hydration accelerator on the working performance and mechanical properties of cementitious materials under a low temperature environment (-3°C to 5°C). The crystal nucleus type hydration accelerator and silicate cement are used as materials to prepare cementitious materials and optimize the proportion. Background Art

[0002] In low temperature environments, the hydration reaction rate of traditional cement-based materials slows down significantly, resulting in the hindrance of their strength development, which seriously affects the progress and quality of construction projects. Especially in winter construction and projects in cold areas, the slow coagulation and hardening of cement not only prolongs the construction period, but also increases the risk of structural damage caused by strength reduction. Therefore, how to effectively promote the early strength development of cement-based materials under low temperature conditions has become a technical problem that needs to be solved urgently.

[0003] Nucleus hydration accelerator is a micro-nanoscale CSH (calcium silicate hydrate) gel nucleus material. This accelerator provides a large number of active nuclei during cement hydration, reduces the cement nucleation barrier, effectively shortens the induction period of hydration reaction, and significantly accelerates the formation of CSH gel. By promoting the early stage of hydration reaction, this accelerator can significantly improve the early strength and final strength of cement-based materials under low temperature conditions.

[0004] At present, my country has achieved innovation in construction materials and equipment, but there is still a considerable gap with actual operational requirements, and the technical reserves are still insufficient when faced with overly complex environmental conditions. Summary of the invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a crystal nucleus type hydration accelerator cement cementitious material in a low temperature environment and a preparation method thereof. This patent adopts a method for preparing a CSH crystal nucleus type hydration accelerator cement cementitious material, which helps to achieve the national goal of energy conservation and emission reduction, and the method has the characteristics of reducing resource consumption and additional costs, and has significant economic, environmental and social benefits. It can improve the reliability, economy and limitations of winter construction and promote the development of engineering structures in the direction of "high efficiency, durability and ecology".

[0006] The purpose of the present invention is to provide an optimal proportion and preparation method of a cementitious material added with a crystal nucleus type hydration accelerator in a low temperature environment in view of the slow growth of strength of traditional concrete during winter construction and the failure to meet the standard in early strength. The cementitious material is prepared by using ordinary silicate cement and CSH crystal nucleus type hydration accelerator as raw materials through reasonable proportion design, so as to meet the requirement of rapid strength development of the cementitious material in a low temperature environment.

[0007] The technical solution of the present invention is as follows:

[0008] On the one hand, the present invention provides a crystal nucleus type hydration accelerator cementitious material in a low temperature environment, which achieves the early strength of concrete according to the requirements of "General Portland Cement" (GB175-2007), so that the 7-day compressive strength of the CSH crystal nucleus type hydration accelerator cementitious material under the curing conditions of -3, 0, and 5°C reaches 17.1MPa, 18.6MPa, and 32.6MPa respectively, and the design ratio is as follows:

[0009] CSH crystal nucleus type hydration accelerator is an auxiliary material that accelerates the formation of early CSH gel and improves the early strength of concrete. The weight proportions are: 3-4 parts of hydration accelerator, 100 parts of cement, 36 parts of water, 3%-5% of CSH crystal nucleus type hydration accelerator, 0.36 water-cement ratio, curing temperatures of -3°C, 0°C, and 5°C, and humidity greater than 95%.

[0010] Furthermore, the CSH crystal nucleus type hydration accelerator is prepared by a precipitation method, which is to prepare a CSH suspension by dropping a certain concentration of calcium nitrate solution and sodium silicate solution under alkaline conditions of Ph value = 8 into a dispersant and stirring at high speed for 3 hours.

[0011] Furthermore, the dispersant is a polycarboxylic acid comb copolymer having an ultra-long side chain molecular structure.

[0012] Furthermore, the cement is early strength ordinary Portland cement (PO 52.5R), the main components of which are clinker, gypsum, limestone and slag, and meets the requirements of "General Portland Cement" (GB175-2020).

[0013] Furthermore, the main chemical components of cement clinker are: SiO2 is 22.35%, Al2O3 is 4.61%, Fe2O3 is 3.62%, CaO is 65.74%, MgO is 2.08%, SO3 is 0.32%, Na2Oeq is 0.512%, and f-CaO is 0.94%.

[0014] Furthermore, the main mineral compositions of cement clinker are: C3S is 56.93%, C2S is 21.15%, C3A is 6.10%, and C4AF is 11.00%.

[0015] Another aspect of the present invention provides a method for preparing a crystal nucleus type hydration accelerator cementitious material in a low temperature environment, comprising the following steps:

[0016] 1) First, pour cement, water and CSH hydration accelerator into the planetary cement mortar mixer in proportion, and set the motor stirring mode to low speed for 30s, high speed for 30s, stop for 90s and high speed for 60s;

[0017] 2) After the mixing is completed, the molding is carried out immediately. A 40×40×160mm mold is fixed on a vibration table, and the cementitious material is loaded into the mold twice; the mold is compacted on a cement mortar vibration table, the surface is scraped flat, and the surface is covered with plastic wrap to prevent water evaporation;

[0018] 3) Place it in a standard curing room and let it stand for 24 hours, then demould it and place it in a corresponding low-temperature environment curing room (temperature (5, 0, -3) °C, humidity > 95%).

[0019] The key to the high strength of the invented crystal nucleus type hydration accelerator cementitious material lies in the design of the hydration accelerator dosage ratio. The sample of 5.0% hydration accelerator cementitious material contains more hydration products Ca(OH)2 and AFt, and less residual hydration reactants C3S and C2S than the cement cementitious material without hydration accelerator. Therefore, at the ultra-early age of cement hydration, the addition of crystal nucleus type hydration accelerator accelerates the reaction consumption of the main reactants C3S and C2S, and then generates more hydration products Ca(OH)2 and AFt, which will inevitably promote the early construction of the internal structure of the cement paste, which is manifested in the macroscopic aspect as a shortening of the setting time and an increase in the early strength. Hydration accelerator cementitious materials in low temperature environments can be used in buildings in northern low temperature environments in the future to improve the strength of ordinary silicate concrete in engineering applications.

[0020] Beneficial effects of the present invention:

[0021] 1) Strong designability

[0022] Hydration accelerator cement gel material under low temperature environment (-3℃~5℃) can make full use of CSH crystal nucleus activity to achieve the working performance and mechanical properties of cementitious materials under different low temperature conditions, taking into account the material cost, adjusting the dosage of hydration accelerator, and achieving the optimal ratio. Different dosages of crystal nucleus type hydration accelerator control the CSH gel generation rate under different low temperature conditions, improve the early strength of cementitious materials, and solve the problem of slow setting rate of ordinary Portland cement under low temperature environment.

[0023] 2) Performance optimization

[0024] The present invention obtains the ratio of CSH crystal nucleus type hydration accelerator cementitious material under the optimal low temperature environment. When the hydration accelerator dosage is 3%, the 7d flexural strength is 3.8MPa at a low temperature of -3°C. When the hydration accelerator dosage is 4%, the fluidity under different low temperature conditions is greater than 210mm, and the setting time is 103min, 186min, and 210min at 5°C, 0°C, and -3°C, respectively. The strength increases faster and is more conducive to engineering construction. When the hydration accelerator dosage is 5%, the compressive strength is 19.8MPa and 33.4MPa at low temperatures of 0°C and 5°C, respectively. It meets the requirements of "General Portland Cement" (GB175-2007) and achieves the effect of greatly shortening the setting time and achieving low-temperature early strength.

[0025] 3) Energy saving and environmental protection

[0026] Under low temperature conditions, adding CSH hydration accelerator cement gel material can shorten the maintenance period and maintenance cost, thereby reducing greenhouse gas emissions, reducing negative impacts on the environment, and improving construction efficiency. Overall, the use of cement gel materials with hydration accelerators in low temperature environments helps to achieve a more sustainable construction method and has a positive protective effect on the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the working performance diagram of the fluidity of the crystal nucleus type hydration accelerator cementitious material under low temperature environment;

[0028] Figure 2 It is a working performance diagram of the setting time of the crystal nucleus type hydration accelerator cement gel material under low temperature environment;

[0029] Figure 3 It is the mechanical properties diagram of the 7-day compressive strength of the crystal nucleus type hydration accelerator cement gel material under low temperature environment;

[0030] Figure 4 This is a mechanical property diagram of the 7-day flexural strength of the crystal nucleus type hydration accelerator cement gel material under low temperature environment. DETAILED DESCRIPTION

[0031] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0032] Example 1: In the crystal nucleus type hydration accelerator cementitious material, the weight ratio of the hydration accelerator is 3%, and the water-cement ratio is 0.36.

[0033] Under the low temperature curing condition of -3℃, the best flexural strength of cement binder material with hydration accelerator of 3% CSH at 7 days is 3.8MPa, which is 152% higher than that of the blank sample.

[0034] Example 2: In the crystal nucleus type hydration accelerator cementitious material, the weight ratio of the hydration accelerator is 4%, and the water-cement ratio is 0.36.

[0035] Under the low temperature curing conditions of -3, 0, 5℃, the initial setting time of the cementitious material with hydration accelerator of 4% CSH was 209min, 186min, 167min respectively, which was shortened by 42%, 56.7%, 26.7% respectively compared with the blank sample; the final setting time was 238min, 223min, 220min respectively; the final setting time was shortened by 44.7%, 33.3%, 24.9% respectively compared with the blank sample; the fluidity was 224mm, 220mm, 217mm respectively. Compared with the blank sample, the fluidity was increased by 31.8%, 31.7%, 33.9% respectively.

[0036] Example 3: In the crystal nucleus type hydration accelerator cementitious material, the weight ratio of the hydration accelerator is 5%, and the water-cement ratio is 0.36.

[0037] Under the low temperature curing conditions of 0 and 5℃, the 7-day optimal compressive strength of cement binder material with hydration accelerator of 5% CSH was 19.81MPa and 33.4MPa respectively, which was increased by 65% ​​and 32.5% respectively compared with the blank sample.

[0038] The key to the high strength of the invented crystal nucleus type hydration accelerator cementitious material lies in the design of the hydration accelerator dosage ratio. The sample of 5.0% hydration accelerator cementitious material contains more hydration products Ca(OH)2 and AFt, and less residual hydration reactants C3S and C2S than the cement cementitious material without hydration accelerator. Therefore, at the ultra-early age of cement hydration, the addition of crystal nucleus type hydration accelerator accelerates the reaction consumption of the main reactants C3S and C2S, and then generates more hydration products Ca(OH)2 and AFt, which will inevitably promote the early construction of the internal structure of the cement paste, which is manifested in the macroscopic aspect as a shortening of the setting time and an increase in the early strength. Hydration accelerator cementitious materials in low temperature environments can be used in buildings in northern low temperature environments in the future to improve the strength of ordinary silicate concrete in engineering applications.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A crystal nucleus type hydration accelerator cementitious material in a low temperature environment, characterized in that: The design ratio is as follows: CSH crystal nucleus type hydration accelerator is an auxiliary material that accelerates the formation of early CSH gel and improves the early strength of concrete. The weight proportions are: 3-4 parts of hydration accelerator, 100 parts of cement, 36 parts of water, 3%-5% of CSH crystal nucleus type hydration accelerator, 0.36 water-cement ratio, curing temperatures of -3°C, 0°C, and 5°C, and humidity greater than 95%.

2. The crystal nucleus type hydration accelerator cementitious material in a low temperature environment according to claim 1, characterized in that: The CSH crystal nucleus type hydration accelerator is prepared by a precipitation method, wherein a certain concentration of calcium nitrate solution and sodium silicate solution are added dropwise under an alkaline condition of Ph value = 8, and a dispersant is stirred at high speed for 3 hours to prepare a CSH suspension.

3. The crystal nucleus type hydration accelerator cementitious material in a low temperature environment according to claim 2, characterized in that: The dispersant is a polycarboxylic acid comb copolymer with an ultra-long side chain molecular structure.

4. The crystal nucleus type hydration accelerator cementitious material in a low temperature environment according to claim 1, characterized in that: The cement is early strength ordinary Portland cement (PO 52.5R), the main components of which are clinker, gypsum, limestone and slag.

5. The crystal nucleus type hydration accelerator cementitious material in a low temperature environment according to claim 4, characterized in that: The main chemical components of cement clinker are: SiO2 is 22.35%, Al2O3 is 4.61%, Fe2O3 is 3.62%, CaO is 65.74%, MgO is 2.08%, SO3 is 0.32%, Na2Oeq is 0.512%, and f-CaO is 0.94%.

6. The crystal nucleus type hydration accelerator cementitious material in a low temperature environment according to claim 4, characterized in that: The main mineral compositions of cement clinker are: C3S is 56.93%, C2S is 21.15%, C3A is 6.10%, and C4AF is 11.00%.

7. The method for preparing a cementitious material with a crystal nucleus type hydration accelerator in a low temperature environment according to any one of claims 1 to 6, comprising the following steps: 1) First, pour cement, water and CSH hydration accelerator into the cement mortar mixer in proportion, and set the motor stirring mode to low speed for 30s, high speed for 30s, stop for 90s and high speed for 60s; 2) After the mixing is completed, the molding is carried out immediately. A 40×40×160mm mold is fixed on a vibration table, and the cementitious material is loaded into the mold twice; the mold is compacted on a cement mortar vibration table, the surface is scraped flat, and the surface is covered with plastic wrap to prevent water evaporation; 3) Place it in a standard curing room and let it stand for 24 hours, then demould it and place it in a corresponding low-temperature environment curing room with temperatures of 5°C, 0°C, -3°C and humidity > 95%.

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