Construction loading before the age of 28 d can have the most significant effects on the slabs,especially for multi-story structures.The changing properties of the young concrete complicate the prediction of serviceability design requirements also.An experimental investigation is performed on four simply supported Light-Weight Concrete (LWC) one-way slabs subjected to immediate loading at 14 d.Effects of aggregate type,loading levels and cracking moment together with the influences of ultimate moment capacity and service moment on the instantaneous deflection of slabs are studied.Comparison of the obtained results with predictions of existing models in the literature shows considerable differences between the recorded and estimated instantaneous deflection of LWC slabs.Based on sensitivity analysis of the effective parameters,a new equation is proposed and verified to predict the instantaneous deflection of LWC slabs subjected to loading at the age of 14 d.