不同配合比再生混凝土高温后的残余抗压强度

Residual compressive strength of recycled aggregate concrete with the different mixture ratio after high temperature

浇筑15种配合比的100mm×100mm×100mm混凝土立方体试件,将不同水胶比(0.34、0.4和0.5)、不同粉煤灰掺量(0%、30%和50%)的普通混凝土和再生混凝土试件经200~800℃高温处理后进行静压试验,并测得其抗压强度.结果表明:经400℃高温作用后,不同于普通混凝土,水胶比为0.34时的再生混凝土强度低于水胶比为0.4时的强度;对于不同配合比混凝土试件,高温时的强度损失率,低水胶比时较高水胶比时大;粉煤灰的微集料效应可以弥补低水胶比下水泥浆与再生骨料结合面不良的缺陷;粉煤灰的二次水化作用可以有效弥补再生混凝土因高温作用引起的强度损失.

The concrete cube specimens （100 mmX 100 mmX 100 ram） with 15 kinds of mixture ratios were cast.And the compressive strengths of ordinary and recycled aggregate concrete with different water-binder ratios（0. 34, 0.4, and 0. 5） and fly-ash dosage （0%, 30%, and 50%） were tested after exposure to high temperature（200-800℃）. The results show that after exposure to 400 ℃, the compressive strength of recycled aggregateconcrete at low water-binder ratio （0.34） is lower than at high water-binder ratio （0.4）, which is different fromthe ordinary concrete. In addition, the compressive strength loss rate of the specimens with lower water-binderratio is larger than the higher one. The micro-aggregate effect of fly-ash can remedy the poor surface combinationbetween cement and recycled aggregates, especially at low water-binder ratio. And the secondary hydration of fly-ash can compensate for the strength loss of recycled aggregate concrete because of high temperature.