矿物掺合料对自密实混凝土抗氯离子渗透性的影响

Influence of Mineral Admixtures on the Resistance to Penetration of Chloride Ion in Self-compacting Concrete

耐久性是自密实混凝土(SCC)的重要性质。本文应用电通量法研究了掺粉煤灰、矿渣的SCC抗氯离子渗透性能,通过对单掺和复掺时SCC电通大小的分析发现:粉煤灰和矿渣都能改善SCC的抗氯离子渗透性能,矿渣提高SCC的抗氯离子渗透性能要优于粉煤灰,二者复掺对SCC抗氯离子渗透的复合叠加效应并不明显。其机理是粉煤灰和矿渣提高水泥石密实性,强化混凝土界面过渡区,粉煤灰、矿渣物理化学吸附作用能固结Cl-,降低Cl-渗透性。SCC中掺入掺合料能减少离析、避免泌水,达到自密实效果,粉煤灰对混凝土流动增大的作用效果要优于磨细矿渣的效果。掺合料复掺对自密实混凝土强度具有复合叠加效应,混凝土28 d强度等级可提高1～2级。

Durability is an important property for self-compacting concrete（SCC）.This paper studied the resistance to chloride ion penetration performance of SCC with addition of fly ash and slag based on concrete coulomb electric flux test.Both fly ash and slag can improve the resistance to chloride ion permeability in SCC and slag shows better effect than fly ash.The addition of both fly ash and slag show little effect on the resistance to chloride ion permeability in SCC.The mechanism is that the addition of fly ash or slag can improve the density of cement paste and reinforce the interfacial transition zone between cement paste and aggregate.Both physical and chemical adsorption of Cl-on the mineral admixtures contributes to the consolidation of Cl-and the reduction of Cl-permeability.The mineral admixtures can decrease the risk of segregation and bleeding in SCC.Fly ash is more effective than the slag powder for improving SCC fluidity.The addition of both slag and fly ash shows an enhanced effect on the SCC strength gain and SCC strength grade at 28d can be increased from 5 MPa to 10 MPa.