泵送纤维混凝土工作性与自由收缩性能试验研究

Experimental Investigation on the Workability and Free Shrinkage of Pumping Fiber Reinforced Concrete

本文通过测定不同配合比新拌混凝土及0.5 h和1.0 h后的坍落度,研究了砂的含泥量以及聚丙烯纤维对泵送混凝土工作性能的影响;参照德国工业标准(DIN)测定不同配合比混凝土的自由收缩量,研究了聚丙烯纤维对混凝土自由收缩性能的影响。试验结果表明,低掺量聚丙烯纤维对混凝土的坍落度影响不大,而砂的含泥量却对混凝土坍落度及其经时损失影响较大,砂的含泥量应控制在4.2%以内;掺加0.9 kg/m^3聚丙烯纤维可明显降低混凝土自由收缩应变,降低达15.3%,明显改善混凝土的抗裂性能。最后,将本文实测混凝土自由收缩应变与ACI 209建议模型及王铁梦模型计算结果进行对比,发现ACI 209更适用于预测纤维混凝土的收缩应变。

Based on the measurement of the slump for fresh concrete and that after 0.5h and 1.0h of different concrete mix,the effect of clay content and polypropylene fibers on the workability of pumping concrete was investigated.In addition,according to the german guideline（ DIN）,the free shrinkage of different concrete mix was measured to investigate the effect of polypropylene fibers on the free shrinkage of concrete. The results showed that polypropylene fibers with low dosage had little effect on the concrete slump.However,the clay content affected the slump and the slump loss of concrete greatly. A clay content lower than 4. 2% is suggested.With the addition of 0.9 kg / m3 polypropylene fibers,the free shrinkage at early age decreases by 15.3%,which demonstrates that polypropylene fibers can improve the crack resistance of concrete at early age significantly.Finally,comparisons between experimental data and ACI 209 and Wang＇s model were performed and ACI 209 model was found to be suitable for evaluating the free shrinkage strain of fiber reinforced concrete.