钢-聚丙烯混杂纤维混凝土与变形钢筋粘结破坏试验研究

为研究混杂纤维混凝土的力学特性,以纤维体积率和长径比为关键变量,采用单端中心拉拔试验方法,进行了钢-聚丙烯混杂纤维混凝土(SPHFRC)与带肋变形钢筋粘结破坏的试验研究,建立了粘结强度计算公式。试验结果表明:SPHFRC与变形钢筋之间的粘结强度与SPHFRC的强度正相关。相比于单掺钢纤维混凝土、单掺聚丙烯纤维混凝土和普通混凝土,SPHFRC的极限粘结强度相应提高9.2%、20.8%和26.2%;混杂纤维不仅提高了钢筋周围混凝土的抗拉强度,同时提供了侧向约束,在钢筋混凝土粘结破坏的全过程路径中均发挥着有利作用。本文提出的SPHFRC与变形钢筋粘结强度计算公式明确清晰,适用性良好,为促进混杂纤维钢筋混凝土的应用提供有益的探索。具有互补性的混杂纤维,在正混杂效应下,可有效提高混凝土的综合力学性能。本研究可为相应技术规程提供理论支持与试验依据。

Experimental study on bonding failure between steel-polypropylene hybrid fiber reinforced concrete and deformed reinforcement

In order to study the mechanical performance of the hybrid fiber reinforced concrete，an experimental study on the bonding failure between the steel-polypropylene hybrid fiber reinforced concrete( SPHFRC) and the deformed ribbed-reinforcement is carried out with the method of single-ended central pull-out experiment by taking the volume fraction and length-diameter ratio of the fiber as the key variables，and then a bonding strength calculation formula is established. The experiment result shows that the bonding strength between SPHFRC and the deformed reinforcement is positively correlated to the strength of SPHFRC. Compared with the concrete mixed only with steel fiber，the concrete mixed only with polypropylene hybrid fiber and the conventional concrete，the ultimate bonding strength of SPHFRC is correspondingly increased by 9. 2% 、20. 8% and 26. 2% respectively， while the hybrid fiber not only enhances the tensile strength of the concrete around the reinforcement，but also provides the relevant lateral restraint simultaneously，thus plays an favorable role in the path of the full process of the bonding failure. The calculation formula for the bonding strength between SPHFRC and the deformed reinforcement proposed herein is clear and definite along with a better adaptability，thus provides a beneficial exploration to promote the application of the hybrid fiber reinforced concrete. Under the positive hybrid effect，the hybrid fiber with relevant complementarity can enhance the comprehensive mechanical performance of concrete. This study can provide theoretical support and experimental basis for the corresponding technical regulations concerned.