(a) due to the negative effect of admixture, measures can be taken in the construction process to reduce or even avoid the use of admixture can also achieve similar results. If you can use high temperature period of construction without mixing early strength agent, or improve the fineness of cement or the use of R type of high grade cement, can also achieve rapid reaction and early strength effect.
(2) Comprehensive analysis and test comparison of admixture, to ensure the positive effect, as little as possible negative effect, sometimes ignored; Would rather not use the kind of negative effect of very large admixture, will affect the quality of concrete.
(3) the reasonable amount of admixture is not fixed, is with the variety and fineness of cement, mixed material variety and amount of admixture, hardening temperature, admixture time and other factors change, therefore, obtain reasonable amount of admixture only through the corresponding engineering, specific process and specific test to determine.
(four) different admixture methods are different, such as water reducing agent method by the first admixture method, the same admixture method, stagnant water method and after the admixture method, different admixture methods appear different use effect; In addition, the different kinds of water reducing agent, the action mechanism is also different, need different mixing methods to achieve the corresponding effect.
(5) The need for correct mixing and transportation process: mixing time of concrete with admixture needs to be longer than that of ordinary concrete, in order to ensure that other materials such as admixture and cement are fully mixed. In the same way, the homogeneity of commercial concrete should be maintained in the process of transportation to avoid adverse consequences caused by local accumulation, so that it can not play a full role. Less delay insufficient and cause false coagulation and cracks, mixing too much easy to crack.
