Nano-suspension concrete early strength accelerator and preparation method thereof

Abstract

The invention provides a nano-suspension concrete early strength accelerator which can be stably dispersed in an aqueous solution and is prepared from a thixotropic solution and a nano-calcium silicate suspension according to mass ratio of 1:4-9. The thixotropic solution is prepared from the following ingredients, by weight, 15-25% of soluble fluosilicate, 20-35% of soluble aluminium salt and the balance being water. The nano-calcium silicate suspension is prepared from the following ingredients, by weight, 5-20% of soluble silicate, 8-18% of soluble calcium salt, 3-10% of a high-molecular polymer dispersant and the balance being water. The invention also provides a preparation method of the early strength accelerator. On one hand, the early strength accelerator contains no chlorine salt and has no corrosion effect on steel bars in concrete. On the other hand, the early strength accelerator is a stable suspension system, is convenient to add and is easy to uniformly disperse during the preparation process of concrete; and the early strength accelerator can remarkably raise early strength of concrete, has an obvious early strength effect especially on concrete obtained by the use of high volume of mineral admixtures and is especially suitable for production of precast concrete components.

Description

technical field [0001] The invention relates to an early-strength concrete admixture, in particular to a nanotechnology-based concrete early-strength admixture and a preparation method thereof, belonging to the technical field of concrete admixtures. Background technique [0002] Concrete is currently the most used building material in the world, and its main advantages are low price, strong bearing capacity and high durability. However, due to the slow hydration reaction process of Portland cement and the influence of ambient temperature, the strength of concrete develops slowly. Generally, it takes more than 24 hours to reach the strength of the demolition formwork, and the strength can only reach 40-50% of the design strength in 3 days. It takes more than 28 days to reach the design strength. At the same time, with the development of concrete technology, industrial wastes are used as basic raw materials in concrete more and more widely. In order to reduce the early hydra...

AI Technical Summary

Problems solved by technology

(1) Add early strength agent: chlorine salt early strength agent is the earliest application of inorganic salt early strength agent, which can improve the early strength of concrete, but seriously affects the later strength of concrete, and because it contains Cl - , easy to cause corrosion of steel bars, and is restricted in application

Sulfate early strength agents are likely to lead to poor performance in the later stage, and "white frost" is easy to precipitate on the concrete surface, affecting the appearance

(2) The method of reducing the water-binder ratio, increasing the amount of cement, or using ultra-fine cement: the problem brought about by this method is that the autogenous shrinkage of the concrete increases significantly, and the risk of cracking increases, and the low water-binder ratio not only deteriorates the concrete's flexibility. Sexuality makes the production operation difficult, and the amount of admixture increases significantly, which greatly increases the production cost

(3) Use high-temperature steam curing: Under the condition of high-temperature steam curing, the crystal size of cement hydration is coarse, the brittleness increases, and the durability decreases

[0004] According to the classical theory of cement chemistry, cement hydration reaction is a chemical reaction controlled by nucleation and crystal growth rate. One of the main reasons for the low early hydration reaction rate is that the hydration products lack crystal nuclei and the hydration induction period is too long.

Chinese patent CN201110159382.9 discloses a method for preparing seed crystals and accelerating the hydration of cement and improving the early strength of concrete. In this method, the cement stone mixed with 3% inorganic salts is first cured to a certain age, and then ground Until the specific surface area reaches 8000-15000kg / m 2 However, the main defect of this method is that the preparation of cement stone requires a long age (more than 30 days), and a large amount of inorganic salts such as calcium chloride and sodium sulfate are used, so it is easy to cause the durability of concrete to decline

Chinese patent CN201010128318.X discloses a method for preparing seed crystals and accelerating the hydration of cement to improve the early strength of concrete. The main method is to intensify the calcination of waste ceramic powder, pre-grinded carbide slag powder and modified additives by microwave. However, the main disadvantages of this method are that the stability of the source of waste ceramic powder is difficult to control, and the microwave intensified calcination process is complicated and difficult to form large-scale production

Extensive use of sulfate increases the risk of secondary ettringite expansion and failure of concrete, and ultra-fine mineral admixtures will aggravate the self-shrinkage of concrete and increase the risk of cracking

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