Interfacial Behavior of Glass Fiber-Reinforced Polymer Bars Embedded in Concrete with Internal Curing Agents

This paper presents an experimental investigation into the interfacial behavior of glass fiber-reinforced polymer (GFRP) bars embedded in concrete mixed with internal curing agents. Such an innovative concept to achieve high-performance concrete (HPC) structures has a number of advantages-for example, improved early-age cracking resistance and long-term sustainability. Of interest is the interaction between the noncorrosive GFRP and the internally cured concrete when mechanically loaded. Three types of presaturated internal curing agents-namely, microporous lightweight aggregate (LWA), crushed returned concrete aggregate (CCA), and superabsorbent polymer (SAP)-are employed to supply necessary moisture inside the concrete so that autogenous shrinkage is controlled, along with minimizing self-desiccation and expediting cement hydration. The effect of various replacement or addition ratios of the curing agents is examined in terms of concrete strength, surface friction, and interfacial stresses. A refined bondslip relationship is established in accordance with test observations and probability-based simulation. Simplified design equations are proposed to estimate the embedment length of GFRP bars for the application of internally cured concrete.