Glass fiber-reinforced polymer (GFRP) reinforcement has been considered as a replacement for the traditional steel reinforcement, mainly due to its corrosion resistance. In this paper, a total of 13 concrete columns and beams (length/diameter = 5.3) fully reinforced with GFRP longitudinal bars and spirals were experimentally studied. An additional two reference columns were also constructed with steel rebars and GFRP spirals to quantify the effect of the long bars. Factors such as the number of longitudinal bars, the pitch of the spirals, and load eccentricities were examined. It was found that the load capacities of the specimens with GFRP reinforcement were up to 12.3% lower than those with steel reinforcement; however, with sufficient transverse reinforcement, the GFRP-reinforced specimens were up to 15% more ductile. Reducing the pitch of the GFRP spirals and increasing the number of longitudinal reinforcing bars both resulted in an increase in the ductility and load capacity, demonstrating the contribution of transverse and longitudinal reinforcement. Strains well beyond the ultimate strain capacity of the concrete were measured in the longitudinal GFRP bars, illustrating the significant confinement provided by the spirals. The experimental results were favorably underpredicted by the recommended simplified method derived in this paper. In order to simplify the design process of circular members, a factor β_c was introduced to the current design rules in the international design standards and validated by the experimental results.

Glass fiber-reinforced polymer (GFRP) bars in construction are increasing in popularity due to their excellent corrosion resistance, high tensile strength to weight ratio, and low maintenance. Geopolymer is a modern cementitious material that is known for its corrosion resistance and low carbon footprint. Combining the two could produce a green yet durable composite material that can be applied to aggressive environments such as Australia’s coastal zones. This paper experimentally investigates the load-moment interaction of GFRP-reinforced air-cured geopolymer concrete columns. The behavior of reinforced geopolymer concrete under combined loading were studied with 11 half-scale specimens. Three different stirrup spacings (75, 150, and 250 mm) were examined. Effective confinement was achieved by reducing the stirrup spacing such that high strains were measured in the concentric columns with closely spaced (75 mm) stirrups. A comparison between the experimental data and international design codes showed that such codes were conservative when ignoring the compressive strengths of the longitudinal GFRP bars. The experimental results were better represented when the compressive strengths of the bars were included; on average, the GFRP-reinforced geopolymer concrete columns exhibited 10.8% increase in strength with respect to unreinforced concrete sections.

This study compared the effect of seven common curing conditions on the compressive strength, pore alkalinity, efflorescence, and shrinkage of five alkali-activated fly ash and slag (AAFS) mortars and one cement mix. The fly ash to slag ratio and the activator content were altered in the AAFS mortars, which were then placed in the fog room, the carbonation chamber, the outside environment, bottom contact with water, and surface contact with 0%, 3.5%, and 10% sodium chloride solutions. It was found that the shrinkage was primarily a function of the dryness of the environment. The submerged curing conditions increased the extent of leaching but reduced shrinkage. For mixes with a high activator content, the effect of leaching was small. Therefore the compressive strength improved as a result of the reduced shrinkage, with the highest achieving 129.5 MPa at 56 days. The alkalinity of the curing solutions decreased as their salinity increased after 56 days of submergence. The rate of diffusion decreased as the concentration difference of the sodium cations decreased; therefore, the extent of leaching was lowered. This could incentivize the use of AAFS instead of cement, especially in highly saline underground environments.