Repair concrete structures with high-early-strength engineered cementitious composites (HES-ECC): Material design and interfacial behavior

Aimed at realizing the effective strengthening and durable repair of concrete structures, particu-larly in emergencies like traffic interruption triggered by broken roads and damaged bridges, nine groups of specimens were designed and tested in this paper to develop the high-early-strength Engineered Cementitious Composites (HES-ECC) featured as both high early-strength and superior long-term-deformability. The high-early-strength effect of sulphoaluminate cement, silica fume, and Portland cement on HES-ECC was compared, as well as their influence on the de-formation ability of HES-ECC. Moreover, the interfacial behaviors between HES-ECC and existing concrete structure were clarified, considering the effects of interfacial agents, interfacial treat-ment methods, and interfacial roughness. The results indicate that HES-ECC with 6% silica fume mixed could obtain both the high early-strength and superior long-term-deformability. The flex-ural strength at 3 h could reach 66.67% of that at 28d. The compressive strength could reach up to 28.7 MPa at 3 h, and the ultimate tensile strain could remain 4.21% at 28d. Cement paste in-terfacial agent could enhance the chemical adhesive bonding between HES-ECC and existing con-crete while polymer modified interfacial agent was incompatible. The increased roughness of chiseled interface was beneficial to both the bearing capacity and the deformation ability. Inter-facial shear performance of the grooved interface was scarcely deteriorated even if the roughness decreased by 54.18% compared with the chiseled interface. The recommended interfacial treat-ment is chiseled interface combined with grooved interface, as well as a thickness of 1-2 mm ce-ment paste interfacial agent. This study provides valuable and credible experimental data for pro-moting the application of HES-ECC in repairing existing concrete structures in practice.

Automated summary

In this paper, nine groups of specimens were tested to develop high-early-strength Engineered Cementitious Composites (HES-ECC) for the effective strengthening and repair of concrete structures. The high-early-strength effect of different cement types was compared, along with their impact on the deformation ability of HES-ECC. The interfacial behaviors between HES-ECC and existing concrete were also clarified, considering the effects of interfacial agents, treatment methods, and roughness. The results show that HES-ECC mixed with 6% silica fume can achieve both high early-strength and superior long-term-deformability. The study provides valuable experimental data for promoting the application of HES-ECC in repairing existing concrete structures.