矿物掺合料对高强混凝土抗裂性能的影响

Effect of mineral admixtures on crack resistance of high strength concrete

抗裂性是高强混凝土最重要的指标之一。以脆性系数和特征长度为高强混凝土抗裂性评价指标,研究矿物掺合料(粉煤灰、硅粉和磨细矿渣)对高强混凝土抗裂性的影响。结果表明,矿物掺合料能有效地降低高强混凝土的脆性系数和特征长度,提高其抗裂性。同时得到抗裂性能最佳的配合比。机理分析表明,掺入细小的高活性磨细矿渣、硅粉和粉煤灰时能极大地改善过渡区的微结构,降低混凝土的Ca(OH2)、钙矾石和孔隙率,提高C—S—H胶体含量,并极大地降低过渡区的原生裂纹,从而提高高强混凝土的抗裂性。

Crack resistance is one of the most important indexes of High Strength Concrete （HSC）. Taking brittleness coefficient and characteristic length as indexes for evaluation of crack resistance of HSC, the effect of mineral admixtures including fly ash,silica fume and ground slag on crack resistance of HSC is studied. The results show that mineral admixtures can decrease brittleness coefficient and characteristic length of HSC effectively, and improve its crack resistance.At the same time,the optimum mix proportion of crack resistance is obtained. Mechanism analysis also shows that mixing fine and high activity ground slag,silica fume and fly ash into concrete can greatly improve the microstructure in the transition zone, decrease Ca（OH）2, ettringite and porosity in concrete,increase content of C-S-H gel and greatly reduce the original microcracks in the transition zone, and therefore improve crack resistance of HSC.