Effect of metakaolin on the microstructure of cement-based artificial marble slabs incorporating natural marble offcuts under vacuum vibration compaction method

Abstract

Large number of natural marble resources consumption and waste caused by the increasing demand and mining technology of natural marble have severe impact on the surrounding land and ecological environment, while cement-based artificial marble is a good place for these natural marble offcuts to go. The natural marble offcuts pretreated to different particle sizes in this study were mixed with white Portland cement coupled with a certain amount of acrylic emulsion and polypropylene fiber to fabricate cement-based artificial marble slabs (CAMS) via vacuum vibration compaction (VVC) moulding method. Among which metakaolin (MK) was incorporated to explore its effect on the properties and microstructure of CAMS. The results denoted that the properties of CAMS were susceptible to the contents of MK. At the optimal MK content of 4 wt%, the optimal flexural strength, bulk density and water absorption of the specimens at 28 d were 19.0 MPa, 2506 kg/m3 and 0.32 %, respectively. Meanwhile, results obtained by hydration heat, SEM, MIP and 29Si NMR tests show that the addition of MK reduced the total porosity of CAMS specimens and the degree of polymerization of silicon-oxygen tetrahedra in CSH gel, and effectively enhanced the toughness of the specimens. The evident reduction of early hydration heat with the incorporation of MK is of great significance to moulding and early curing process of large volume cement-based artificial marble blocks in actual production.