Feasibility of structural retrofit concrete pipelines using limestone calcined clay cement Engineered Cementitious Composites (LC3 ECC)

Abstract

Advances in pipeline rehabilitation technology are urgently needed to address aging concrete pipelines operating in aggressive conditions. Current repair methods have limitations on enhancing pipe structurally. In this research, ductile ECC was employed as a durable retrofitting material for concrete pipe. Firstly, two strength grades of ECC were developed. Tensile strain capacity ranging from 5.4 to 9.3 % was obtained. Owing to the tailored crack width (average 61.6 μm at 8% strain) and self-healing capacity, the 2% pre-tensioned ECC retained 10-10 m/s of the coefficient of permeability after 14 d of testing. The cracked concrete pipe was repaired by ECC/mortar, then examined by three-edge loading and flexural tests. Although ECC had lower strength than the referenced mortar, ECC-repaired pipe attained higher load and deformation capacity than the mortar-repaired pipe. ECC distributed the macro crack into multiple tiny cracks, leading to the pipe being an oval shape with residual load capacity after crushing, compared to the brittle failure of the mortar-repaired pipe. The cracked ECC pipe retained its structural integrity and enabled the intrinsic leak-proof function of the cracked ECC pipe. Finally, ECC demonstrated the ability to structurally and functionally (leak-proof) retrofit the concrete pipe, suggesting a durable promising repair material for concrete pipe.