多尺度聚丙烯纤维混凝土孔结构及抗冻性

选用2种尺寸聚丙烯细纤维与1种聚丙烯粗纤维,进行单掺及混掺,对9组不同纤维掺量试件进行快速冻融循环试验、抗压、劈裂试验及压汞试验,研究不同冻融次数下混凝土质量、动弹性模量变化以及冻融循环前后混凝土拉、压强度变化;研究多尺寸聚丙烯纤维对混凝土孔结构的改善情况;研究多尺寸聚丙烯纤维混凝土孔结构与抗冻性的关系,并对孔结构对混凝土抗冻性能的影响加以分析。试验结果表明:将聚丙烯纤维掺入素混凝土后,混凝土的微观孔结构和抗冻性能得到明显改善;在相同掺量条件下,聚丙烯粗纤维和多尺寸聚丙烯纤维对混凝土抗冻性有较大改善,且多尺寸聚丙烯纤维对混凝土的抗冻性改善效果最好:相比于素混凝土冻融后抗拉、压强度,单掺聚丙烯细纤维混凝土强度损失分别降低了9.95%～11.94%和4.29%～7.62%,单掺聚丙烯粗纤维混凝土强度损失分别降低了27.36%和16.67%,混掺多尺寸聚丙烯纤维混凝土强度损失分别降低了46.77%～53.23%和41.90%～50%。

Study on pore structure and frost resistance of multi-scale polypropylene fiber reinforced concrete

To study the frost resistance mechanism of multi-scale polypropylene fiber reinforced concrete(MPFC), crude polypropylene fibers in one size and fine polypropylene fibers in two sizes were selected to single-dope and mix-dope with concrete. The mass loss rate, the relative dynamic elastic modulus variation, and the tensile and compressive strength of the polypropylene fiber reinforced concrete before and after freeze-thaw cycle were analyzed based on the fast freeze-thaw cycle test and compression and splitting test. Mercury intrusion porosimetry(MIP) was carried out to study the relationship between frost durability degradation of cement concrete and pore structure. Besides, the influence of pore structure on the anti-frost performance is analyzed. The research indicates that adding polypropylene fiber into plain concrete can improve both the microstructure and the frost resistance of concrete. Under the condition of the same total fiber addition, crude polypropylene fiber and multi-scale polypropylene fiber can bring great improvement on frost resistance of concrete, and the effect of multi-scale polypropylene fiber on frost resistance of concrete is the best. Compared with the common concrete after freeze-thaw cycle, the compression and tensile strength loss of single-dope of fine fiber are reduceded by 9.95% to 11.94% and 4.29% to 7.62% respectively while the strength loss of single-dope crude fiber is reduced by 27.36% and 16.67% respectively, and that of MPFC decreases by 46.77% to 53.23% and 41.90% to 50% respectively.