Compression-casting produces a densified concrete structure that lends itself to precast components operating in aggressive environments. In particular, compression-cast concrete (CC) reinforced with noncorrosive fiber-reinforced polymer (FRP) bars is an attractive combination for structures operating in marine environments. However, in such scenarios, FRP bars are susceptible to damage due to impingement of the coarse aggregate during compaction. This damage may affect durability. This paper presents the first experimental investigation on the effect of compression casting on the durability of glass FRP (GFRP) and basalt FRP (BFRP) bars embedded in concrete and exposed to seawater. Concrete prisms with embedded FRP bars were submerged for up to 360 days in substitute ocean water at a temperature of 40°C. In addition, standalone GFRP and BFRP bars were conditioned in the same manner to study the influence of the concrete cover. The test matrix includes different CC and normal-cast concrete (NC) mixes. The objective was to study the influence of casting method, compressive strength, alkalinity, and use of seawater and sea sand in lieu of fresh water and conventional sand. The residual tensile strength of the FRP bars after conditioning served as a quantitative measure of degradation. Several test methods were employed to characterize pre-exposure surface damage from compression casting and to gain insight into the degradation mechanisms. For a given FRP material, the durability of bars embedded in CC was negligibly affected by surface damage. In fact, strength loss was comparable to that of companion FRP bars, either embedded in NC or standalone. Under all exposure conditions and durations, the BFRP bars underperformed the GFRP bars. Dissolution of the vinyl ester resin due to ester hydrolysis was preliminarily identified as the governing degradation mechanism for all FRP bars, both standalone and embedded in NC and CC, irrespective of mix design and exposure duration.
Wang et al. (Mon,) studied this question.