矿物掺合料对高性能混凝土收缩分布的影响

The influence of mineral admixtures on the distribution of shrinkage in high performance concrete

为了探索掺不同矿物掺合料高性能混凝土的非均匀收缩特征,采用固定多组位移传感器的方法测试了单面干燥条件下不同深度处混凝土的收缩变形,同时采用湿度传感器监测了各混凝土中相对湿度变化.结果表明:单面干燥条件下,表层混凝土的相对湿度降低和收缩增长速率明显大于内层混凝土,距离干燥表面100 mm处的收缩值比10 mm处低15%～33%.掺硅灰使混凝土内外层收缩梯度明显减小,掺粉煤灰和矿渣粉均使混凝土内外层收缩梯度增大.各矿物掺合料混凝土试件表层和内部的收缩与其相对湿度之间均存在较好的线性关系.

High performance concrete may contain different mineral admixtures which cause differential shrinkage characteristics.In order to study the phenomenon,several pairs of fixed displacement sensors at various depths from the exposed surface were used to measure shrinkage strain in concrete samples.Only one surface of each concrete specimen was exposed to dry conditions during the experiment.Relative humidity in the concrete at various depths was also studied using embedded humidity sensors.The results showed that the surface of the concrete had less relative humidity and more shrinkage than the interior of the concrete.And concrete at a depth of 100 mm from the drying surface had shrinkage of 15% to 33% less than concrete at a depth of 10 mm.Such shrinkage differences relative to distance from the drying surface were decreased significantly by the addition of silica fume.On the other hand,shrinkage increased with the addition of fly ash or granulated blast furnace slag powder.There was a good linear relationship between shrinkage and relative humidity at different depths from the exposed surface for every type of concrete.