Compared with normal-weight concrete, lightweight aggregate concrete (LWAC) has a lower compressive strength. However, its plus points, including preferable fire resistance, appropriate durability, and dead-load decline lead to the LWAC’s application in the construction industry. A practical method to overcome its drawback could be adding nano-silica (NS) to the mixes. For this purpose, the current experimental work aimed at researching to explore the compressive response of LWAC containing different dosages of nano-silica. Therefore, cylindrical specimens of size 150 × 300 mm improved by nano-silica were subjected to compressive cyclic and monotonic loading; six dosages of NS, including 0, 1, 2, 3, 4, and 5 weight percent of cement were added to mixes as cement replacement. Experimental stress-strain curves were investigated to determine the stress-strain relationships. The results show that the addition of up to 3 wt % nano-silica improves the properties of LWAC, as it was found to enhance compressive strength and modulus of elasticity during monotonic loading, shift up the common point coordinate, and reduce the stiffness degradation of the reloading paths in cyclic loading. However, larger dosages of nano-silica (4% and 5%) were found to have diminishing returns, considering the improved properties of LWAC. Furthermore, stress-strain models for the nano-silica-incorporated LWAC were proposed in compression. The experimental findings were also compared with the proposed model. There was an acceptable concurrence between the proposed model data and experimental findings.
