Experimental research was conducted to clarify fundamental characters of high-strength concrete plasticized by air-entraining and high-range water-reducing admixture. Plasticized high-strength concrete was water cement ratio of 28 to 48%, and target slump-flow was fluidized to 50cm using air-entraining and high-range water-reducing admixture.
Investigated items are adsorption characteristics of air-entraining and high-range water-reducing admixture and influence of the difference of various conditions of water cement ratio, unit water amount, slump before plasticization, environmental temperature, fluidization time on properties of plasticized high-strength concrete.
As a result, air-entraining and high-range water-reducing admixture showed different adsorption characteristics during mixing and plasticization, and at plasticization, fluidity could be increased with less use than at mixing. Considering the adsorption characteristics of air-entraining and high-range water-reducing admixture, the agglomeration characteristics of cement is thought to change markedly within 180 minutes from 120 minutes after mixing. The decrease in slump-flow amount after plasticization of plasticized high-strength concrete is larger than that of standard high-strength concrete. Also, slower the plasticization time, larger the decrease in slump-flow amount. The setting time of plasticized high-strength concrete tends to be faster than standard high-strength concrete, and the difference increases as environmental temperature to colder. Among properties of hardened concrete, effect of plasticizing by air-entraining and high-range water-reducing admixture on compressive strength, Young's modulus and drying shrinkage ratio was small.
From the above results, high-strength concrete plasticized by air-entraining and high-range water-reducing admixture has same points to be noted as conventional plasticized concrete, such as decrease in slump-flow amount after plasticization is larger and setting time faster. However, it is possible to obtain hardened concrete comparable to standard high-strength concrete while reliably obtaining necessary slump-flow.
