Multiple impact dynamic compression properties of lightweight engineered geopolymer composites containing ceramsite under different initial impact damages

Engineered geopolymer composites (EGC) has become a popular building material with excellent tensile properties, impact resistance and low carbon emissions. In practical engineering, building structures often suffer multiple impacts damage during their service life. In this study, an active "sacrifice" method was proposed to prepare lightweight EGC (LW-EGC) by breaking ceramsite with low elastic modulus first to absorb the impact energy. The dynamic compression performance of LW-EGC under multiple impacts loads was studied using a split Hopkinson pressure bar (SHPB), and the effects of initial damage, steel fiber content and ceramsite types were considered. The stress-strain curve, dynamic peak stress and strain evolution, energy absorption, damage evolution and failure patterns of LW-EGC under multiple impacts were analyzed. The results indicated that the higher the initial damage level, the faster the dynamic peak stress decayed of the material under multiple impacts. The addition of steel fibers can significantly improve the impact resistance of LW-EGC. Specifically, LWEGC with a steel fiber content of 0.5 % by volume exhibited the highest number of impact resistance times (15 times) and energy absorption capacity (5.321 MJ/m3). Furthermore, LW-EGC-M, which was mixed with fly ash ceramsite, demonstrated the best resistance to multiple impacts. The cumulative damage of LW-EGC showed a significant exponential increase as the number of impacts increased.