Analysis of properties for Lime-metakaolin (L-MK) restoration mortar

摘要

There are various factors affecting drying shrinkage of cement-based material, including use quantity of cement and auxiliary cementitious material, water cement ratio, maintenance system and drying condition, and in addition, total quantity of coarse and fine aggregate, matching and category also affect drying shrinkage of cement-based material. But seen from composition and structure of mortar, shrinkage distortion is mainly caused by shrinkage of multi-pore binder phase, i.e. C-S-H gel phase. Evaporation and migration of evaporable water in pore are main source of drying shrinkage power. On the other hand, drying shrinkage performance of mortar is closely concerned with composition and structure of mortar (maturity of mortar) when drying starts. Pozzolanic reaction of auxiliary cementitious material in mortar occurs after certain age of mortar hydration to maintain mortar of different ages (i.e. mortar of different maturity), and essential difference shall exist in its drying shrinkage distortion mechanism. To clearly describe drying shrinkage mechanism where MK affects cement-based material, this paper researches drying shrinkage and weightlessness behavior of cement mortar of different maturity and with different MK content under 55±5%R.H. condition, and researches composition and pore structure of mortar of different maturity by adopting thermal synthetic analysis (TG/DSC) and mercury intrusion method (MIP).