香港粉煤灰的特征与沿岸混凝土工程耐久性

Characteristics of Fly Ash in Hong Kong and the Durability of Concrete for Coastal and Offshore Engineering

采用综合测试手段，对香港粉煤灰的理化特性、粒度分布、表面结构进行了较为系统的研究．结果表明：该粉煤灰以铝硅玻璃体（高铝）为主，其晶相为莫来石和少量石英，含碳量较低，平均粒度为１１．６μｍ，明显小于香港水泥颗粒的平均粒度１９．６μｍ．Ｎ２吸附比表面积测定表明：香港粉煤灰具有较大的比表面积，约为水泥的２．３倍．表面结构以球形为主且大部分球体具有明显的气孔与内部空腔相连，从而导致了较强的离子吸附效应．１ａ的对比实验表明：在混凝土中掺入质量分数为２５％的粉煤灰不但能显著降低Ｃｌ－渗透系数，而且也减少了ＳＯ２－４引起的破坏，因而可大幅度延长沿岸混凝土工程的使用寿命．

The physical and chemical properties, particle distribution and surface texture of fly ash in Hong Kong were systematically investigated by means of different test methods. The results indicate that fly ash in Hong Kong is mainly composed of aluminum silicate glassy phases with high content of aluminum. The crystal phase of fly ash is mullite and contains small amount of quartz and lower content of carbon. The average diameter of fly ash in Hong Kong (11.6 μm) is much smaller than that of cement (19.6 μm). The test by using nitrogen absorption meter demonstrates that fly ash in Hong Kong has fairly large specific surface which is about 2.3 times as high as that of cement. The surface testure exists mainly in form of spherial particle, most of these spherial particles have obvious pores which are connected with the inner hollow cores. It results in effective absorption capability. The comparison test in one year shows that concrete with 25 percent fly ash addition by mass of cement remarkably reduces the permeability coefficient of chloride ion and expansion deterioration caused by SO 2- 4 ion. This means that the service life of the concrete in coastal and offshore structures can be greatly prolonged.