Creep and shrinkage performance of kenaf bio fibrous concrete composites

Abstract

Fibrous Concrete Composite (FCC) is a high performance concrete that possesses an improved tensile strength and ductility with restraint to shrinkage and creep under sustained load compared to Plain Concrete (PC). As a result of global quest for sustainable, renewable and green materials to achieve a bio based economy and low carbon foot print environment, the use of fibre to produce fibrous concrete composite has continuously received significant research attention. While several researches have been conducted on metallic and synthetic fibrous concretes, they exhibit several unavoidable drawbacks and bio fibrous concrete has been proved to be a better alternative. This research investigates the creep and shrinkage performance of concrete reinforced with Kenaf bio fibre. After material characterization, concrete reinforced with fibre optimum volume fraction of 0.5% and length of 50 mm was used for the study. The fresh and hardened properties of the concrete were studied under short term quasi static loading. Thereafter, the compressive creep test, uniaxial tensile creep test and flexural creep test at 25% and 35% stress levels at creep loading ages of 7 and 28-day hydration period were conducted. The long term deformation behaviour of the Kenaf Bio Fibrous Concrete Composite (KBFCC) was observed and monitored. Results show that the compressive creep strains of KBFCC is 60.88% greater than the PC, but the deformation behaviour of the specimens shows 33.78% improvement in ductility. Also, uniaxial tensile creep response of fibrous concrete deforms at the rate of 0.00283 mm/day and 0.00702 mm/day at 25% and 35% stress level respectively, but the deformation rate becomes insignificant after 90 days due to the presence of fibre. In addition, the flexural creep test reveals that 0.064 mm/day and 0.073 mm/day deformation rate at 25% stress level of the KBFCC becomes less significant after 40 days of loading. The outcome of the morphology image analysis on the concrete composite shows that Kenaf fibres act as bridges across the cracks, which enhances the load-transfer capacity of the matrix, thus influencing the long term performance of KBFCC. Accordingly, statistical analysis shows that the CEB-FIP creep model is the best fit model for predicting compressive and tensile creep of KBFCC, while EC2 creep and shrinkage models are for predicting flexural creep and shrinkage strain of KBFCC, respectively. A creep and shrinkage prediction model is proposed based on the experimental data for better prediction of KBFCC. Conclusively, KBFCC exhibits appreciable shrinkage, tensile and flexural strength under static short term and long term sustained loads compared to PC.