| The history of Roller Compacted Concrete (RCC), the advantages of the technology of dam constructing using RCC and the application of RCC in northern cold areas were summarized. The importance of air-content to concrete anti-frozen durability was described, and the fact of the time-dependent air-content changing was pointed out. The influence of by cement, fly-ash, fine aggregate, coarse aggregate, admixture and water on the air-content was analyzed. The changing of air-content was observed through experiments. From different aspects such as the dehydration, the spot surface contact, the surface tension drop and the air bubble migration fusion, the mechanism of time-dependent air-content changing was analyzed. The influence of time-dependent air-content changing on RCC performance was studied by way of the comparative tests on air-content changed with the initial of 6 groups of RCC. The 6 groups of RCC included 3 groups of the second grade RCC of F300 and 3 groups of the third grade RCC of F50, each with 3 different types of aggregate. The property of fresh concrete, the physical and mechanical properties and frost-resisting durability of the initial one and that after 30 minutes were compared. The results showed that the air-content had certain loss, the physical and mechanical properties were improved, the frost-resisting durability had less change and the relative dynamic modulus of elasticity decreased fast after 30 minutes. The air void parameter was tested by three methods. The results showed that the air-content had certain loss, the average bubble radius decreased, and the air void spacing factor increased after 30 minutes. There were errors between the three methods but the changing trend was the same. The air void spacing factor would increase if the stone powder was partially or totally regarded as the cementitious material. It would be reference for the RCC design and construction in extreme cold and dry climate areas.
|
PDF Full Text Request