Pumping lightweight aggregate concrete into high-rise buildings

Abstract

Lightweight aggregate concrete (LWAC), characterized with low density and high crushing strength to apparent density ratio, is a potential construction material for modern concrete structures. However, experiences in pumping LWAC to high-rise buildings are insufficient and the pumping pressure of fresh concrete may differ from normal weight concrete (NWC). Herein, three groups of shale lightweight aggregate (SLWA) were prepared to evaluate the workability of LWAC before and after pumping up to 102-m construction site. Water content and pressure loss are analyzed to understand the mechanism in slump variation of LWAC. A pumping pressure model is proposed based on friction assumption for horizontal and vertical pumping. The relationship between water content and ambient pressure is simulated. Pressure drop in pumping LWAC is found more than 4 times that in NWC at the same slump level. The main reason for large slump loss and pumping difficulty for LWAC lies in the water transportation process from mixture into porous aggregates.