An Experimental Approach to Lightweight Aggregate Concrete Material Modeling Parameters Under Cyclic and Biaxial Loadings

Abstract This study examines the mechanical behavior of structural lightweight aggregate concrete (LWAC) through uniaxial, cyclic, and biaxial compressive testing on cubic specimens at the macro level. The research focuses on mapping the biaxial failure stress envelope in the compression–compression domain and calibrating the Kupfer and Gerstle biaxial failure criterion specifically for LWAC, enabling its application in numerical simulations. A quadratic failure model is also proposed to predict LWAC's biaxial failure stress envelope. In addition, uniaxial cyclic compression tests were performed, allowing the determination of the cyclic stress–strain relationship and the calculation of the elastic damage index for LWAC under repeated loading. Tests on cylindrical and prismatic specimens further explored how increased uniaxial compressive strength influences key mechanical properties, such as the elastic modulus, splitting tensile strength, modulus of rupture, and axial stress–strain response. The biaxial tests revealed that LWAC has a biaxial compressive strength that is, on average, 21% greater than its unconfined uniaxial compressive strength at a stress ratio of 0.51 ( $$\alpha = 0.51$$ α = 0.51 ). The uniaxial cyclic tests show that LWAC experiences less post-peak damage compared to normal-weight aggregate concrete (NWAC), with the residual strength-to-peak stress ratio ( $${\sigma }_{res}/{\sigma }_{peak}$$ σ res / σ peak ) being 1.85 times greater in LWAC than in NWAC.