Abstract
Lightweight aggregate concrete consisting of glazed hollow bead (GHB) as lightweight aggregate is studied for the influence of nanosilica (NS) content, prewetting time for GHB, water-cement ratio, and curing humidity, on the interface structure between GHB and cement paste. This research analyzed the influences of various factors on the interface zone structure by measuring microhardness (HV) and hydration degree of cement paste (HD) nearby the interface zone (1 mm) between GHB and cement paste at different periods of aging. Due to the sampling limitation, the interface zone in this test is within 1 mm away from the surface of lightweight aggregate. The HD of cement paste was determined through chemically combined water (CCW) test. The results were expected to reflect the influence of various factors on the interface zone structure. Results showed that the rational control of the four factors studied could fully mobilize the water absorption and desorption properties of GHB to improve the characteristics of the interfacial transition zone.
Highlights
The research on microstructure mainly focused on aggregate, cement, and interfacial transition zone between them
Many pores leading to the directional alignment of Ca(OH)2 often become the weakest link in the normal concrete
The HV can be calculated by Formula (2): Table 1: Physical properties of glazed hollow bead (GHB)
Summary
The interfacial transition zones (ITZs) exist between cement paste and aggregate, which have essentially the same components as in cement paste but have largely different structure and properties from the cement paste. This is attributed mostly to the film of water that forms around the aggregate particles. The strength of interface zone between GHB and cement paste has important influence on the macroscopic properties of the lightweight aggregate concrete. In the lightweight aggregate concrete, the composition and structural characteristics of lightweight aggregate determine the interaction mechanism of light aggregate and cement paste, making it different from that of normal concrete. This is in favor of the cement hydration because it hardens and densifies the interface structure
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