Natural hydraulic lime versus lime-metakaolin modified silt in earthen heritages

The paper analyses the potential of lime-metakaolin (L-MK) to substitute natural hydraulic lime (NHL) modified silt in earthen heritages, since the availability of NHL is reduced in many countries, unlike traditional lime and metakaolin. Unconfined compressive strength (UCS) and splitting tensile strength (STS) of the specimens were discussed according to curing time, mix proportion, and attributes of hydration products. The results show that UCS and STS of L-MK modified silt containing 4-12% MK are approximately 2.60-8.49 times of that of materials without MK, that is MK can effectively improve the quality of lime silt. With the same lime and NHL content, the strength of L-MK modified silt approximately equals to or slightly higher than that of NHL for the addition of MK. The microstructure reveals that the hydraulicity of L-MK modified silt is significantly enhanced for the hydraulic cementitious substances (CSH, C(4)AH(13), et al.) generated by the hydration reaction for L-MK modified silt, similar to NHL. Therefore, it can be concluded that L-MK may replace NHL as a cheaper and equally effective solution for earthen site protection.