聚丙烯纤维和机制砂中石粉对水泥砂浆抗裂性能的影响

Effects of Polypropylene Fiber and Stone Powder of Machine-made Sand on Resistance of Cement Mortar to Cracking

通过试验研究了聚丙烯纤维掺量和长度、机制砂中石粉等量替代水泥比对水泥砂浆抗裂性能的影响,考虑了长度8mm的聚丙烯纤维在0.4—1.2kg/m3范围内的6个掺量、长度19mm的聚丙烯纤维在0.8—1.2kg/m3范围内的3个掺量以及在2.5%—15%范围内的5个石粉等量替代水泥比,采用现行标准试验方法测定了15种新拌水泥砂浆的稠度和分层度以及30个水泥砂浆试件的裂缝宽度和长度,采用开裂指数和抗裂性能比评价水泥砂浆的抗裂性能.结果表明:新拌砂浆均具有良好的工作性能,稠度和分层度均在合理范围内;适当掺量的聚丙烯纤维或采用适量的石粉等量替代水泥,均可有效改善水泥砂浆的抗裂性能,短纤维比长纤维具有更好的改善效果;在一定范围内,随着聚丙烯纤维掺量或石粉等量替代水泥比的增加,水泥砂浆的抗裂性能比增大而开裂指数降低;当聚丙烯纤维掺量为1.0kg/m3或石粉等量替代水泥比为10%时,水泥砂浆的抗裂性能最佳.

Experiments were carried out to study the resistance of cement mortar to cracking affected by the mass content and length of polypropylene fiber and the replacing ratio in mass of cement by stone powder of machine-made sand. Six mass content from 0.4 kg/m3 to 1.2 kg/m3 of polypropylene fiber in 8 mm long, three mass content from 0.8 kg/m3 to 1.2 kg/m3 of polypropylene fiber in 19 mm long and five replacing ratio from 2.5% to 15% were considered. In accordance with the current test standard, the consistency and layreing of fifteen fresh cement mortars and the width and length of cracks on thirty specimens were measured, the resistances of cement mortar to cracking were evaluated by the cracking index and the cracking resistance ratio. The results showed that all of the fresh cement mortars were in good workability with reasonable values of the consistency and layreing, the resistances of cement mortar to cracking were effectively improved by proper admixing polypropylene fiber or replacing cement by stone powder, the better improvement shall be given by polypropylene fiber with shorter length. In certain ranges, the cracking resistance ratio increased while the cracking index decreased in general with the increase of mass content of polypropylene fiber and replacing ratio of cement by stone powder. The resistance of cement mortar to cracking reached the best with 1.0 kg/m3 polypropylene fiber or 10% replacing ratio in mass of cement by stone powder.