Experimental investigation of effect of admmixture on concrete strength and frost-resistance

摘要

The influence of admixture on concrete strength and frost-resistance was analyzed by using the mercury intrusion method and the rapid frozen-thaw method under the condition of the same water/binder ratio in this paper. The results showed that the intensity of the concrete with single doped compound mineral admixture is slightly lower than the normal concrete's in concrete 28-days strength experiment when the fixed water/binder ratio is 0.38, but the extent of the concrete strength growth is bigger, and maybe exceed the normal concrete's at the late period of the whole session. It also could be found that the concrete strength added single air entraining agent is lower, particularly the strength of the concrete double mixed with compound mineral admixture and air-entraining agent is lowest. In term of the pore structure, the porosity rate of concrete can be lower and the harmful hole is decreased as well as the less-harmful hole and no-harmful hole are increased when the compound mineral admixture is mixed. The porosity rate will increase, closed pore and less-harmful hole will enhance by a wide margin if the admixture of air entraining agent is added. Moreover, the pore size distribution of concrete becomes reasonable if these two substances are admixed at the same time. From the aspect of frost-resistance, the concrete with co-doped compound mineral admixture and air-entraining agent is best, the concrete with uni-doped air-entraining agent is better secondarily and the concrete with compound mineral admixture alone is just slightly better.