养护条件对次轻混凝土强度及抗盐冻性能的影响

Influence of Curing Condition on Strength and Salt-frost Resistance of Specified Density Concrete

研究了养护条件对不同水胶比次轻混凝土强度及盐冻性能的影响,并通过对其内部相对湿度、孔结构及水化产物的测试分析探究其作用机理。结果表明,自然养护条件下,掺50%体积轻骨料次轻混凝土早期强度较低,而其在7~28 d龄期内增长率高;特别是低水胶比混凝土,其14 d龄期强度超过标准养护与水中养护条件下试件强度。对于低水胶比混凝土,水中养护和标准养护可中止或减缓混凝土内水分向外界迁移,水泥的充分水化导致水泥石结构更致密,混凝土抗盐冻性能较好。对于高水胶比混凝土,自然养护条件下混凝土28 d龄期的内部相对湿度仍有90%,其内部存在充足水分供给水泥水化,水泥石孔结构良好;当处于盐溶液中时,相比于含水率较高的水中养护与标准养护下混凝土,自然养护条件下混凝土的水饱和程度低,故其抗盐冻性能最好。

The influence of curing condition on strength and salt-frost property of specified density concrete with different water-binder ratios were investigated,and the internal relative humidity(IRH),pore structure and hydrated products were analyzed to explore the mechanism.The results show that the early strength of specified density concrete with 50%volume of lightweight aggregate under natural curing condition was lower,but its growth rate at the age of 7—28 days was high.Especially for concrete with a low water-binder ratio,its strength at the age of 14 days exceeded those under standard curing and water curing conditions.For concrete with a low water-binder ratio,water curing and standard curing could stop or slow down the migration of internal water outside,and full hydration of cement led to a denser structure of hardened cement paste,so the salt-frost resistance of concrete was better.For concrete with a high water-binder ratio,the IRH of concrete at 28 days still reached 90%under natural curing condition,and there existed sufficient water for the hydration of cement,and the pore structure of hardened cement paste was refined.When placed in salt solution,the water saturation degree of co ncrete under natural curing condition was lower,compared to concrete with a higher moisture content under water curing and standard curing conditions,so the concrete under natural curing condition had best salt-frost resistance.