lightweight concrete LECA 1 algorithm 1 complex additive 1 compressive cylinder strength 1 compressive strain 1 compressive strengthdesign 1 dispersed reinforcement 1 expanded clay concrete 1 hollow microsphere 1 machine learning 1 model 1 nano-SiO2 1 nanomodifier 1 nanoparticle 1 optimization 1 polypropylene fiber 1 post fire 1 prediction 1 quality metric 1 steel fiber 1 stress-strain diagram 1 sustainable materials 1