Effects of seawater and supplementary cementitious materials on the durability and microstructure of lightweight aggregate concrete

This study is investigated the mechanical properties and durability of lightweight aggregate concrete (LAC) incorporating of metakaolin (MK) and ground granulated blast furnace slag (GGBFS) mixed with artificial seawater. The compressive strength, chloride penetration, drying shrinkage and hydration products of LAC are analyzed. In addition, the micro-hardness of interface transition zone (ITZ) and microstructure development of LAC are characterized by different analytical techniques. The results indicate that the compressive strength of LAC containing 10 wt% GGBFS and 10 wt% MK with seawater mixing exceeds 50 MPa at 28 days. The resistance to chloride ion penetration and drying shrinkage of LAC are improved significantly by the addition of MK and GGBFS, and seawater mixing cannot deteriorate its chloride permeability due to the formation of Friedel's salt (Fs). The combinations of pozzolanic reaction of MK and GGBFS, internal curing of lightweight aggregate and accelerated cement hydration by seawater result in denser hydration products and reduction of Ca/Si ratio in ITZ, which have a great beneficial impact on the durability properties of LAC. (C) 2018 Elsevier Ltd. All rights reserved.