Effects of Curing Time on the Mechanical Property and Microstructure Characteristics of Metakaolin-Based Geopolymer Cement-Stabilized Silty Clay

Metakaolin (MK), which has a fine particle size and higher activity in high alkaline environments, has been widely used in the fields of soil treatment engineering to stabilize soils. MK is used to replace part of ordinary Portland cement (OPC) with 0 : 15, 2 :13, 4 : 11 and 6 : 9 mass ratios of MK to OPC in this study. The mechanical property (e.g. stress-strain relationship, strength, and deformation performance) and microstructure characteristics of MK-based geopolymer cemented silty clay are investigated using unconfined compressive strength (UCS), nuclear magnetic resonance (NMR), and scanning electronic microscopy (SEM) tests. In addition, strength increase coefficient (ζs) and elasticity modulus increase coefficient (ζe) are defined to evaluate the effects of curing time on the mechanical property of MK-based geopolymer cemented silty clay. Moreover, the relationships among porosity, UCS, and E50 of MK-cemented silty clay are studied. By incorporating 2% MK, the UCS and E50 of MK-cemented silty clay at 28 d are 1.32 and 1.30 times compared with MK0 group, respectively. The increase rate of UCS and E50 from 1 d to 7 d is faster compared with that from 7 d to 28 d. Furthermore, the microstructure of the sample modified by 2% MK is most homogeneous and dense. Finally, the optimistic mass ratio between MK and cement is 2 : 13 for silty clay in this test condition.