Effect of polypropylene fibres on the shrinkage cracking behaviour of lightweight concrete

A study has been carried out to understand the effect of polypropylene fibres on the shrinkage cracking behaviour of lightweight concrete using a restrained ring test. Polypropylene fibres of 0 to 1.0% by volume in lightweight aggregate concrete and 0 to 2% by volume in foamed concrete were used. Steel and alkali-resistant glass fibres of 0.5% by volume were also used in the lightweight aggregate concrete for comparison. The effect of fibres on compressive and tensile strength, modulus of elasticity, flexural toughness and free shrinkage properties are also studied. The results indicate that the polypropylene fibres have less influence on the compressive strength, modulus of elasticity and free shrinkage of lightweight aggregate concrete and foamed concrete. However, the addition of fibres resulted in an increase in the tensile strength in both the concretes. Polypropylene fibres have shown comparable performance in improving toughness in both lightweight aggregate concrete and foamed concrete, while a significant effect in enhancing the flexural toughness and controlling shrinkage cracking behaviour was observed with an increase in the fibre content. At comparable polypropylene fibre percent, flexural toughness and shrinkage cracking resistance of lightweight concrete were found to be lower than that of normal weight concrete. Among the different fibres used in lightweight aggregate concrete, steel and glass fibres have exhibited better and poorer performance than polypropylene fibre, respectively in terms of flexural toughness and shrinkage cracking behaviour.