掺有成孔碎渣的再生骨料混凝土的抗压及抗氯盐侵蚀性能

Compressive and Chloride Resistance Properties of Recycled Aggregate Concrete Mixed with Hole Slag

公路桥梁冲孔灌注桩施工会产生大量成孔碎渣,将其就近应用于公路桥梁的混凝土构件不失为一种有效对策。结合再生粗骨料的循环利用,同时考虑到沿海地区混凝土结构受氯盐侵蚀影响较大,文中采用成孔碎渣和再生粗骨料分别取代天然砂和天然粗骨料,制备了掺有成孔碎渣的再生骨料混凝土,开展了该类混凝土共计96个试件的抗压和抗氯盐侵蚀试验(48个抗压试件采用Φ150、高300 mm圆柱体,48个抗氯盐侵蚀试件采用Φ100、高50 mm圆柱体),以及成孔碎渣、河砂和砂浆各自的压汞测试,研究了成孔碎渣取代率(0、50%、70%、100%)和再生粗骨料取代率(0、50%、70%、100%)对该类混凝土抗压性能和抗氯盐侵蚀性能的影响。试验结果表明:该类混凝土的抗压强度总体上随着成孔碎渣取代率和再生粗骨料取代率的增加逐渐降低,且二者所引发的降幅大体相当;与再生粗骨料相比,成孔碎渣对该类混凝土弹性模量和峰值应变的影响相对有限;该类混凝土的氯离子迁移系数随成孔碎渣取代率和再生粗骨料取代率的增加总体上都逐渐增大,但成孔碎渣的影响明显低于再生粗骨料;随着成孔碎渣取代率的增加,该类混凝土的孔隙率总体呈现出先快后慢逐渐增大的趋势。实际工程中同时采用成孔碎渣和再生粗骨料时,建议二者的最大取代率都以50%为限。

Large amount of hole slag will be produced in the construction of punched cast-in-place piles for highway bridges.It is an effective countermeasure to apply the hole slag to concrete components of highway bridges nearby.Based on the recycling use of recycled coarse aggregates(RCAs)and considering that concrete structures in coastal areas are greatly affected by chloride corrosion,this paper prepared the recycled aggregate concrete mixed with the hole slag by replacing natural sand and natural coarse aggregates with the hole slag and RCAs,respectively.To investigate the effects of the hole slag replacement ratio(0,50%,70%,100%)and RCAs replacement ratio(0,50%,70%,100%)on the compressive and chloride resistance properties of such concrete,this paper carried out compression and chloride resistance tests of 96 specimens(48 cylinders withΦ150×300 mm for compression test,and 48 cylinders withΦ100×50 mm for chloride resistance test)made of such concrete,and mercury intrusion tests of the hole slag,river sand,and corresponding mortar.The test results show that:the compressive strength of such concrete decreases gradually with the increase of the replacement ratios of the hole slag and RCAs,and the reductions caused by the two are roughly the same;compared with RCAs,the influence of the hole slag on the elastic modulus and peak strain of such concrete is relatively limited;the chloride ion migration coefficient of such concrete increases gradually with the increase of the replacement ratios of the hole slag and RCAs on the whole,but the influence of the hole slag is obviously lower than that of RCAs;with the increase of the replacement ratio of the hole slag,the porosity of such concrete generally shows a trend of increasing gradually from fast to slow.When the hole slag and RCAs are used simultaneously in practical projects,it is suggested that the maximum replacement ratios of both should be limited to 50%.