Classification of Concrete hardening agent and cement quick-setting agent
What is a concrete hardening agent?
Concrete hardening agent is one of the substantial admixture varieties used earlier in the development history of admixtures for concrete. So far, the industry has successfully developed a variety of concrete hardening agents, including chloride and sulfate. On this basis, research has obtained a variety of composite concrete admixtures, such as early-strength water reducing agent, early-strength type Antifreeze and early strength pumping agent, etc. According to its chemical composition, first strength agents can be divided into inorganic early strength agents, organic early strength agents and composite admixtures.
What is the cement quick-setting agent?
Cement quick-setting agent is a concrete admixture that makes cement concrete set and hardens quickly. The cement quick-setting agent only accounts for 2% to 3% of the amount of cement in the concrete. Still, it can make the concrete initially set within 5 minutes. The accelerator sets within 12 minutes to achieve the purpose of emergency repair or the rapid setting of concrete in the shaft. Cement quick-setting agent is mainly used in sprayed concrete and sprayed mortar engineering. It is widely used in underground engineering, tunnel engineering, dyke slope reinforcement, water plugging engineering, slip form construction, road repair, spray anchor support, etc. Fast hardening technology. Cement quick-setting agent can be divided into powder cement quick-setting agent and liquid cement quick-setting agent according to the status; according to its alkali metal ion content, it can be divided into alkaline cement quick-setting agent and low alkali cement quick-setting agent and alkali-free cement quick-setting agent three categories; according to the main chemical substances, it can be divided into aluminum oxide clinker plus carbonate system, sulfoaluminate system, water glass system and low Alkali or alkali-free cement quick-setting agent, etc. Besides, there are reports that organic-inorganic composite cement quick-setting agents are used to develop organic-inorganic blended cement quick-setting agents. Its compressive strength proliferates and can significantly reduce the amount of dust and rebound during construction. However, organic cement The introduction of a quick-setting agent often affects the quick-setting effect of the cement slurry.
The mechanism of concrete hardening agent and cement quick-setting agent
Whether it is a concrete hardening agent or a cement quick-setting agent, the types are different, and the mechanism of action is also other, and the early strengthening or coagulation effect of a concrete hardening agent or cement quick-setting agent often needs to be carried out through multiple action mechanisms.
How does concrete hardening agent work?
The mechanism of action of concrete hardening agent and cement quick-setting agent is similar, both of which achieve early strength or quick-setting effect by promoting the hydration of tricalcium aluminate and tricalcium silicate in Portland cement. The difference is that the early-strength effect of the early-strength agent is often reflected in many aspects. It will not only promote the hydration of tricalcium aluminate but also promote the hydration of tricalcium silicate so that the concrete hardening agent can be used in the early stage of hydration. Continue to play the role of initial strength to not affect the later power of concrete too much.
How does cement quick-setting agent work?
The coagulation acceleration of cement quick-setting agent is often highly targeted. A series of chemical reactions destroy the retarding effect of gypsum in cement and rapidly and massively form calcium aluminate hydrate, and calcium sulfoaluminate hydrate Such as insoluble matter shortens the induction period of cement and promotes the rapid setting of cement paste, but at the same time, it will inevitably lead to problems such as insufficient strength of cement mortar (or sprayed concrete) in the later stage.
The purpose of concrete hardening agent and cement quick-setting agent
There are significant differences between concrete hardening agent and cement quick-setting agent in type, performance, effect and mechanism, and their applications are also quite different.
In the concrete process, adding a concrete hardening agent can significantly increase the early strength of concrete without affecting its later strength, and can dramatically shorten the curing time. Therefore, first strength agents are mostly used in winter construction and concrete component production. In winter construction, the concrete with early strength requirements generally needs to add an early strength agent to shorten the demoulding and curing time, speed up the construction progress, and effectively avoid freezing damage, thereby effectively improving construction efficiency and saving concrete construction costs. In the production of concrete components, the application of concrete hardening agents is even more common to stretch steel bars as soon as possible, speed up formwork turnover and pedestal utilization.
Because the setting time of the cement quick-setting agent is short, it is not possible to ensure that the concrete is well mixed and poured within a short period before the initial setting. It is not suitable for the general formwork method of pouring concrete. Therefore, accelerators should not be used in general engineering. Cement quick-setting agent is mostly used for sprayed concrete construction or as a quick plugging material.
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