盐湖环境对碱激发混凝土强度和孔结构的影响

Effect of bittern environment on strength and pore structure of alkali-activated concrete

为阐明碱激发混凝土在盐湖环境下的强度发展规律,对比研究了在清水和模拟盐湖环境中,NaOH和KOH激发矿渣水泥混凝土强度发展和微观结构的变化。试验结果表明:养护于清水和盐湖溶液中的碱激发矿渣混凝土强度分别在NaOH和KOH掺量为5%和8%时具有最高的抗压强度。盐湖养护细化了混凝土中小于100 nm的孔结构,且对KOH激发混凝土孔结构细化效果更为明显。混凝土中的孔含量随着龄期逐渐降低,养护于盐湖溶液中的混凝土孔含量随着龄期下降幅度更大。养护于盐湖溶液中的NaOH激发矿渣混凝土中出现了NaCl晶体,NaCl晶体是盐湖溶液中Cl^-和NaOH溶解出的Na^+离子结合的产物,并随着水化进行不断长大。养护在清水中NaOH激发混凝土和养护在清水和盐湖中的KOH激发混凝土均出现了方解石晶体相。养护于盐湖溶液的混凝土界面过渡区的裂纹比清水养护的试样裂纹宽度更细。

For exploring the strength evolution of alkali- activated slag（AAS） concrete in salt lake environment,a comparative study of strength and microstructures of NaOH and KOH activated slag concrete immersed in fresh and artificial bittern solution was conducted.The experimental results show that the AAS concrete is activated by 5%NaOH and 8%KOH exhibits excellent compressive strength in fresh water and bittern solution.Pore smaller than 100 nm is refined by bittern solution,and the refinement effect on KOH activated slag concrete is more remarkable than on NaOH activated slag concrete.Pore content of concretes decreases with the age,and the scope of the decrease for concrete cured in bittern solution is greater than cured in fresh water.NaCl crystal can be observed in NaOH activated concrete cured in bittern solution,and this is results of crystallization of Cl-- from bittern solution and Na-＋ originated from activator.The size of NaCl crystal particles gradually increase with the hydration.Some of calcite crystals have also been detected in KOH activated concrete cured in bittern solution or in fresh water,but only in NaOH activated concrete cured in fresh water.All concrete display microcracks in interfacial aggregate-paste zone.However,the crack width in concrete cured in bittern solution smaller than that in concrete cured in fresh water.