Shrinkage behavior enhancement of infra-lightweight concrete through FRP grid reinforcement and development of their shrinkage prediction models

Abstract

Infra-lightweight concrete (ILC) is an efficient alternative of normal concrete (NC) for structural applications with low strength but high thermal performance requirements. Three types of ILCs with dry densities 600, 700 and 800 kg/m3 have been manufactured by using high water to cement ratio (w/c) and expanded clay lightweight aggregates (ECLAs). Experimental studies showed that shrinkage strains in ILCs can be up-to 1.51 mm/m as compared to 0.2–0.8 mm/m for NCs, which affects the structural durability of ILCs. To control shrinkage strains of ILCs, ILCs have been then reinforced with two types of fiber reinforced polymers (FRPs): carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP). For each type of FRP, two different grid arrangements of size 21 × 21 mm and 25 × 25 mm have been used. Although all FRP grid reinforcements are effective as they reduced the shrinkage strains significantly and close to the shrinkage strains of NCs, CFRP reinforcement with 25 × 25 mm grid is most effective as it reduced the shrinkage strains up-to the maximum level. Also, experimental shrinkage strains have been compared with five commonly used prediction models and it has been found that each model failed to accurately predict the shrinkage strains. Therefore, a new prediction model has been developed by modifying one of the existing model i.e. B3 model for shrinkage prediction of ILC which considers the effect of water content, compressive strength and dry density. Another prediction model for FRP reinforced ILCs has also been developed to incorporate the influence of any type of reinforcement in ILC. A comparison of modified prediction models with experimental results has shown that the models can predict shrinkage accurately and can be utilized for normal ILCs as well as reinforced ILCs.