超宽箱梁抗裂混凝土配合比试验研究

为防止九江长江公路大桥主桥超宽箱梁混凝土的早期开裂,进行专门的抗裂混凝土配合比优化设计试验。通过水化热、绝热温升、平板法塑性收缩开裂、温度～应力试验机开裂等试验方法,研究了胶凝材料组成对混凝土早期抗裂性的影响,配制出抗裂性能良好的C55混凝土。该混凝土采用42.5级P.Ⅱ水泥掺入25%的Ⅰ级粉煤灰、缓凝型聚羧酸盐高性能减水剂配制,绝热温升55.8℃,塑性收缩抗裂等级Ⅱ级,开裂温度8.7℃,应力储备37.3%,实际应用效果良好。

Experimental Study of Mix Proportioning of Cracking Resistance Concrete for Very Wide Box Girder

To prevent the concrete for the very wide box girder of the main bridge of Jiujiang Changjiang River Highway Bridge from early stage cracking,the optimal design and experiment for the mix proportioning of cracking resistance concrete for the box girder was specially carried out.By way of the hydration heat testing,adiabatic temperature rise testing,flat slab testing of plastic shrinkage cracking and cracking testing of temperature～stress testing machine,the influence of the cementitious material compositions on the early stage cracking resistance of the concrete was studied and the C55 concrete having good cracking resistance was accordingly prepared.The concrete is used with the Grade 42.5 P·II cement added with 25% of the Grade I flyash and high-range water reducer of retarding-type polycarboxylate.The adiabatic temperature rise of the concrete is 55.8 ℃,the level of the plastic shrinkage cracking resistance is grade II,the cracking temperature is 8.7 ℃ and the stress reserve is 37.3%.The practical application of the concrete proves that the effect of the concrete is sound.