BFRP bars reinforced geopolymer-based coral aggregate concrete beams with sustainable and high seawater erosion resistance: Flexural durability, economic, and ecological analysis

Abstract

Cement-based coral aggregate concrete (CAC) and its structures suffer from high carbon emissions, poor resistance to permeation, and inadequate durability under hygrothermal marine environments. To overcome these drawbacks, this study employed slag-fly ash-based geopolymers as alternatives to ordinary Portland cement (OPC) and basalt fiber-reinforced polymer (BFRP) bars as reinforcements for developing innovative BFRP bars reinforced geopolymer-based CAC (GPCAC) beams. Through the accelerated aging method in laboratory, the flexural durability and deterioration mechanism of cement-based CAC beams and GPCAC beams under seawater wet-dry cycling conditions were comparatively analyzed. The results revealed that the number of cracks in GPCAC and CAC beams at the time of damage decreased, while the crack spacing and width increased after exposure to seawater corrosive environments. Additionally, an increase in the initial flexural stiffness of both GPCAC and CAC beams was observed after exposure to seawater wet-dry cyclic environments, but this increased stiffness did not translate into an enhanced ultimate loading capacity. Conversely, both GPCAC and CAC beams showed varying degrees of degradation in ultimate loading capacity and deflection values with increasing exposure time and temperatures. Moreover, GPCAC beams featured outstanding resistance to seawater attacks than CAC beams. After 12 months of seawater wetting-drying cycles at 60 °C, the flexural capacity of CAC beams deteriorated by approximately 25 %, whereas that of GPCAC beams only diminished by approximately 16 %. Furthermore, GPCAC beams boasted a lower carbon footprint and energy emission than CAC beams. In comparison to cement-based CAC beams, the energy consumptions and CO₂ emissions of GPCAC beams were reduced by 21.9 % and 35.0 %, respectively.