Post Date:10,Apr,2023

(1) Influence on concrete mixture

Early strength agent can generally shorten the setting time of concrete, but when the content of tricalcium aluminate in cement is low or lower than gypsum, sulfate will delay the setting time of cement. Generally, the air content in concrete will not be increased by early-strength admixture, and the air content of early-strength water-reducing admixture is determined by the air content of water-reducing admixture. For example, the gas content will not increase when compounded with calcium sugar water reducer, but will increase significantly when compounded with calcium wood water reducer.

(2) Impact on concrete

Early strength agent can improve its early strength; The improvement degree of the same early strength agent depends on the amount of early strength agent, ambient temperature, curing conditions, water cement ratio and cement type. The impact on the long-term strength of concrete is inconsistent, with high and low. Early strength agent has a good effect in a reasonable range of dosage, but when the dosage is large, it will have a negative impact on the later strength and durability of concrete. Early strength water-reducing agent also has good early strength effect, and its performance is better than that of early strength agent, which can control the change of late strength. Triethanolamine can stimulate the early strength of cement. It can accelerate the hydration of tricalcium aluminate, but delay the hydration of tricalcium silicate and dicalcium silicate. If the content is too high, the strength of concrete will be reduced.

Durable sulfate early strength agent has no effect on reinforcement corrosion, while chloride early strength agent contains a large amount of chloride ions, which will promote reinforcement corrosion. When the dosage is large, the chemical corrosion resistance, wear resistance and frost resistance will also be reduced. For concrete, reducing the flexural strength of concrete and increasing the early shrinkage of concrete have little impact on the later stage of concrete. At present, the use of chloride-containing additives has been prohibited in the new national standard. In order to prevent the effect of chloride salt on reinforcement corrosion, rust inhibitor and chloride salt are often used together.

When using sulfate early strength agent, it will increase the alkalinity of concrete liquid phase, so it should be noted that when the aggregate contains active silica, it will promote the reaction between alkali and aggregate, and cause the concrete to be damaged due to alkali expansion.