Centrifugally sprayed Engineered Cementitious Composites: Rheology, mechanics, and structural retrofit for concrete pipes

Current trenchless rehabilitation techniques for deteriorated concrete pipelines have limitations in field operation, pipeline geometry and size, durability, and structural retrofit. In this research, an innovative technology utilizing centrifugally sprayed ECC (CS ECC) to retrofit cracked concrete pipes is established. Rheology is engineered by hydroxypropyl methylcellulose for viscosity enhancement, citric acid for rheology evolution retardation, and hybrid synthetic fibers for flowability control. CS ECC is demonstrated capable of building up to 50 mm thickness on both vertical and horizontal concrete pipes, with reachable diameters over 300-900 mm. A 25 mm CS ECC (5.7 MPa-tensile strength and 5.3%-ductility) lining enhances the cracked concrete pipe by 2.2 times in load capacity and by 1.5 times in deformation capacity. Combining the advantages of mechanical and leak-proof performance, low cost, fast construction, self-healing ability, and expansive coupling with host pipe, the developed CS ECC holds promises in rehabilitating concrete pipelines, tunnels, and culverts.