平板法试验研究高强与高性能混凝土抗裂性能

Flat Tests on Crack-resistant Property of High Strength and Performance Concrete

高强与高性能混凝土胶结料用量较多,砂率较大,粗骨料用量相对较少,而且水胶比较低,常掺有其它掺合料,因此若处理不妥易出现混凝土早期开裂现象.本文在圆环法试验的基础上通过平板法试验,研究分析不同水胶比和不同粉煤灰掺量对高强与高性能混凝土开裂性的影响.研究结果表明,高强与高性能混凝土的裂缝主要发生在早期,因此在早期就应该及时采取控制裂缝的措施;在低水胶比的情况下,水胶比对高强与高性能混凝土抗裂性能的影响较为明显,水胶比越小,开裂越严重;掺入粉煤灰对混凝土抗裂有所改善,但是其掺量对抗裂的影响并不是呈定向规律,而是存在着最优掺量.

This paper is aimed at introducing the flat tests on high strength and performance concrete to assess its crack-resistant property. Nowadays, high strength and performance concrete has been used extensively due to its unique advantages. However, there are still some issues needed to be addressed. The occurrence of severe cracks is one of the prominent problems. A series of experiments have been done by the authors through ring tests. In this paper we further investigate the influence factors through flat tests for different water to bond（w/b） ratios and for different dosages of flown ash as a partial replacement of cement. The experimental results show that the appearance of cracks is mainly at early age （within 1 day）. Therefore,it is necessary to control the cracks at the early age. In addition,if the surface is plastered again after 2 hours of casting, the crack-resistant property can be greatly improved. Our results also demonstrate that the crack-resistant property can also be improved if the flown ash is added, and the optimum dosage of flown ash is at 15-30% of total bond, At the same time,w/b seems to be more influential than normal at low level,which indicates that more severe cracks occur as w/b drops.