Evaluation method of cracking resistance of lightweight aggregate concrete

JI Tao(季韬), ZHANG Bin-bin(张彬彬), CHEN Yong-bo(陈永波), ZHUANG Yi-zhou(庄一舟)

(College of Civil Engineering, Fuzhou University, Fuzhou 350116, China)

Abstract:The cracking behavior of lightweight aggregate concrete (LWAC) was investigated by mechanical analysis, SEM and cracking-resistant test where a shrinkage-restrained ring with a clapboard was used. The relationship between the ceramsite type and the cracking resistance of LWAC was built up and compared with that of normal-weight coarse aggregate concrete (NWAC). A new method was proposed to evaluate the cracking resistance of concrete, where the concepts of cracking coefficient ζ_t(t) and the evaluation index A_cr(t) were proposed, and the development of micro-cracks and damage accumulation were recognized. For the concrete with an ascending cracking coefficient curve, the larger A_cr(t) is, the lower cracking resistance of concrete is. For the concrete with a descending cracking coefficient curve, the larger A_cr(t) is, the stronger the cracking resistance of concrete is. The evaluation results show that in the case of that all the three types of coarse aggregates in concrete are pre-soaked for 24 h, NWAC has the lowest cracking resistance, followed by the LWAC with lower water absorption capacity ceramsite and the LWAC with higher water absorption capacity ceramsite has the strongest cracking resistance. The proposed method has obvious advantages over the cracking age method, because it can evaluate the cracking behavior of concrete even if the concrete has not an observable crack.

Key words:ceramsite type; cracking resistance; lightweight aggregate concrete; evaluation index; evaluation method