再生粗骨料的形态及缺陷对再生混凝土干燥收缩和力学性能的影响

Influence of Shapes and Defects in Recycled Aggregate on Drying Shrinkage and Mechanical Properties of Recycled Aggregate Concrete

本工作分析了三种不同工艺制备的再生粗骨料的形态、附着砂浆及界面区显微硬度,研究了骨料形态和缺陷对其干燥收缩和力学性能的影响,最后结合骨料的释水效应、显微硬度和断裂形态,探讨了不同工艺制备的再生骨料引起的缺陷差异及其对再生混凝土干燥收缩和力学性能的影响机理。结果表明:相对颚式破碎,反击式破碎制备的骨料的粒形较好,针片状较少,骨料表面附着的水泥浆体显著减少,采用圆盘整形工艺则可以进一步提高颗粒的粒形,减少骨料表面附着的砂浆。再生骨料中含有的砂浆导致其吸水率较高,具有一定的内养护作用,能够降低其早期收缩,但后期水分的蒸发仍会导致再生混凝土的干缩增大。反击式破碎制备的再生骨料(RA-C1)界面显微硬度高于颚式破碎制备的再生骨料(RA-E),且以其制备的混凝土的强度也大于RA-E组;反击式破碎+整形制备的再生骨料(RA-C2)虽然界面性能最好,但由于骨料强度不高导致其力学性能相对较低。

The shapes,attached mortar and the microhardness of interface transition zone of recycled coarse aggregate prepared by three different processes were analyzed.And the effects of aggregate shapes and defects on drying shrinkage and mechanical properties were studied.Combining with the drainage characteristics,microhardness and failure patterns of aggregate,the difference of defects caused by different processes on recycled aggregate and its influence mechanism on drying shrinkage and mechanical properties of recycled concrete were discussed.The results show that comparing with jaw crusher,the aggregate prepared by impact crusher has better shape,less needle shape,and the content of attached mortar is obviously reduced.And the disc reshaping technology can further improve the aggregate shape and reduce the content of attached mortar on the aggregate surface.The mortar contained in recycled aggregate leads to high water absorption,which has a certain internal curing effect and reduce its early shrinkage,but the evaporation of water in the later period would lead to the increase of dry shrinkage of recycled concrete.The interfacial microhardness of recycled aggregate RA-C1 prepared by impact crusher is higher than that of RA-E prepared by Jaw crusher,and the strength of concrete prepared by impact crusher is higher than that of RA-E,while RA-C2 prepared by impact crusher and reshaping has the best interfacial properties,its mechanical properties are relatively low due to the low strength of aggregate.