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Mechanism of action of early strength agent

Release time:

2022-05-19

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Concreteearly strength agentIt is one of the five varieties used earlier in the development of admixture. Its main function is to speed up the hydration rate of cement and promote the development of early strength of concrete. At present, the commonly used early strength agents in China mainly include chloride, sulfate, carbonate and composite early strength agents. As an additive to accelerate the development of concrete early strength, concrete early strength agent is in great demand in engineering, especially in winter construction or repair engineering. At the same time, the performance of early strength agent and its standard use are directly related to the safety and life of the whole project.

mechanism of action

differentearly strength agentOr the same kind of early strength agent mixed with different types of cement concrete, the effect is not exactly the same. Here only a few early strength agent as a representative, analysis of its principle of action.

Chlorine-based early strength agent: The mechanism is mainly the action of chloride in cement and C3A to generate water-insoluble hydrated chloroaluminate, which can accelerate the hydration of C3A in cement. The calcium hydroxide formed by the hydration of chloride and cement generates insoluble calcium chlorate, which reduces the concentration of calcium hydroxide in the liquid phase and accelerates the hydration rate of C3A. Moreover, the generated double salt increases the volume of the solid phase in the cement slurry and forms an internal skeleton system, which is conducive to the formation of the cement paste structure. At the same time, because the chloride is mostly soluble salt, with the role of salt, it can accelerate the dissolution rate and hydration reaction process of Portland cement clinker minerals, thereby accelerating the hardening rate of concrete mixture and improving the early strength of concrete.

Sulphateearly strength agentFor example, anhydrous sodium sulfate, soluble in water, reacts with calcium hydroxide produced by cement hydration to generate calcium oxide and calcium sulfate. The newly formed calcium sulfate particles are extremely fine, and their activity is much higher than that of doped calcium sulfate, so the rate of reaction with C3A to form hydrated calcium sulphoaluminate is much faster. Sodium hydroxide is an active agent that can increase the solubility of C3A and gypsum, accelerate the amount of calcium sulfoaluminate in cement, and lead to cement setting and hardening and early strength improvement. However, the early strength agent of sulfate has a certain corrosive effect on the steel bars in concrete, including chloride early strength agent, and attenuates the strength of cement mortar in the later stage, so chloride and sulfateearly strength agentThe amount is gradually reduced.

Key words:

Early strength agent

Effect of early strength agent

The difference between early strength agent and accelerator

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