不同水胶比及养护条件对内养护混凝土吸水性能的影响

Influences of water-to-cement ratio and curing condition on water absorption of internal curing concrete

为了研究预湿轻骨料的内养护效率受混凝土自身水胶比和外界养护条件的影响,采用改进的ASTM 1585试验方法,开展了不同水胶比、不同养护条件(饱和石灰水养护、喷雾养护、密封养护、干燥养护)下普通混凝土及内养护混凝土毛细吸水试验。从混凝土的水化程度、混凝土孔隙率等角度,解释了水胶比、养护条件以及内养护材料对混凝土中水分传输的影响。结果表明:水胶比、养护条件以及内养护材料的掺入对混凝土中水泥的水化和混凝土材料的孔隙率有较大影响。高水胶比试件比低水胶比试件具有更大的累积吸水量及二次吸水率,水胶比为0.5的试件的累积吸水量及二次吸水率分别为水胶比为0.3的试件的1.4～2.1倍和3～4倍;预湿轻骨料的掺入对高水胶比试件的累积吸水量、初始吸水率和二次吸水率的改善作用并不明显,但可以显著降低低水胶比试件的吸水能力,对于水胶比为0.3的试件,其累积吸水量和二次吸水量的降低幅度分别为7.7%～18.6%和20.4%～27.4%;随着外界养护环境湿度的降低,低水胶比试件的初始吸水率变化较小,累积吸水量和二次吸水率有轻微的上升;预湿轻骨料在低水胶比、密封养护条件下内养护效率较高。

In order to study the influences of water-to-cement ratio and curing condition on internal curing efficiency of pre-wet lightweight aggregates, the capillary water absorption tests of ordinary concrete and internal curing concrete with different water-to-cement ratios under different curing conditions(i.e. saturated lime water curing, moist curing, sealed curing and drying) were carried out by using the improved ASTM 1585 test method. Besides, the influences of water-to-cement ratio, curing condition and internal curing material on moisture transport in concrete were explained by taking the degree of hydration and porosity of concrete into consideration. The results show that the water-to-cement ratio, curing condition and the internal curing material have great influence on the hydration and porosity of concrete. Concrete with a high water-to-cement ratio has greater cumulative absorbed water and secondary sorptivity than that with a low water-to-cement ratio. The cumulative absorbed water and secondary sorptivity of the concrete with a water-to-cement ratio of 0.5 are 1.4-2.1 times and 3-4 times of those with a water-to-cement ratio of 0.3, respectively. Although the use of pre-wet lightweight aggregates has little internal curing effect on the cumulative absorbed water, initial sorptivity and secondary sorptivity of concrete with a high water-to-cement ratio, it can significantly reduce the absorptivity of concrete with a low water-to-cement ratio. For the concrete with a water-to-cement ratio of 0.3, the decrease of cumulative absorbed water and secondary sorptivity range from 7.7%-18.6% and 20.4%-27.4%, respectively. With the decrease of external environmental humidity, the change of the initial sorptivity of concrete with a low water-to-cement ratio is small, but the cumulative absorbed water and secondary sorptivity increase slightly. The curing efficiency of the pre-wet lightweight aggregates is higher when used with a low water-to-cement ratio and under the sealed curing condition.