Influence of spatial dislocation of water on the properties of lightweight high-performance concrete

Abstract

To prepare high-performance concrete, the mixing water was normally blended with the dry constituents directly, whereas in this study part of water was pre-located in the lightweight aggregates (LWA) for producing a high-performance lightweight concrete (HPLC). With the pre-location of water in the LWA, an extremely low w/b ratio paste (ultra high-performance composite) was resulted for producing HPLC. High-performance cement mortar (HPCM) was prepared with similar volumes of natural aggregates for comparison. Based on the initial spatial dislocation of mixing water in two systems, the physical, thermal and durability properties of high-performance cementitious composites were evaluated and compared. The results showed that the HPLC experienced delayed heat evolution when compared with that of the HPCM, while the cumulative heat output and degree of cement hydration of the two systems were similar. With the use of an increasing amount of LWA, the density of HPLC decreased significantly while the water penetration and ion permeability of HPLC were comparable to those of HPCM. More importantly, the HPLC exhibited a higher structural efficiency and much lower thermal conductivity than the HPCM. In addition to the pozzolanic reactivity and internal curing provided by the water-entrained LWA, the dislocation of mixing water method also enhanced the microhardness of the paste matrix, which contributed to the excellent performance of HPLC.