Stress-strain relationship for plain and fibre-reinforced lightweight aggregate concrete

Lightweight aggregate concrete (LWAC) shows good performance in structural applications owing to its expected lower contribution to the deadweight of a structure, it nonetheless exhibits significant reduction in certain mechanical properties compared with the normal weight aggregate concrete. The inclusion of fibres could provide some positive changes to its mechanical properties and stress–strain behaviour. This study experimentally investigated the mechanical properties and full stress–strain curve of LWAC reinforced with steel and carbon fibres, involving specimens of strength classes ranging from LC40 to LC60 and fibre volume fractions from 0% to 0.9%. The test results showed that steel fibres could significantly improve the flexural strength and splitting tensile strength. Both the steel and carbon fibres strengthened the crack resistance of LWAC, while the compressive strength was not obviously enhanced. A general stress–strain model adapted to both plain LWAC and fibre-reinforced LWAC was proposed by comparing and modifying the existing models, and a statistically stochastic damage constitutive model was derived. The validity of the proposed models was examined by experimental results and test data from other studies.