含气量对混凝土流动性、强度和氯离子渗透性的影响

摘要

Defoamer and air - entraining agent was used to adjust the air content of fresh grade 30 MPa concrete from 1%to 9.8%.The effects of air content of fresh concrete on the liquidity,the compressive strengths at 3 d,7 d and 28 d ages respectively and the resistance to chloride ion permeability were investigated.The results show that the liquidity of concrete increase gradually by the air content in-creased from 1%to 5%,but continue to increase the air content hardly improve the liquidity more.Namely,through the addition of air -entraining to improve the effect of liquidity is limited. The compressive strengths of concrete at 3 d and 7 d ages showed a poor relation-ship with the air content,except that at 28 d age,which appeared close to completely linear relationship with the air content;generally, as the air content of concrete increases from 1.6% to 9.8% the chloride permeability of concrete rise,but characterized by periodic chan-ges.It indicated that in the practical engineering air - entraining agent can be used to increase the air content of concrete and to improve the resistance to forest,meanwhile affect little of resistance to the chloride permeability of concrete.%采用消泡剂和引气剂调整 C30新拌混凝土的含气量从1％~9．8％之间变化，研究了含气量与新拌混凝土的流动性及其3、7、28 d 抗压强度、抗氯离子渗透性的关系，结果表明：含气量从1％逐渐增加到5％，混凝土的流动性逐渐提高，但继续增加含气量对流动性的改善作用不再增加，即通过引气作用提高混凝土流动性的作用有限；混凝土3 d 和7 d 的早期强度与含气量的相关性较低，而28 d 的后期强度与含气量呈现接近完全线性关系；随着混凝土的含气量从1．6％增加到9．8％，混凝土的氯离子渗透性总体呈上升趋势，但表现为阶段性变化；说明在实际工程中通过引气剂适当增加混凝土的含气量可在不影响其抗氯离子渗透性前提下增加混凝土的抗冻性。