The role of carbonation in the occurrence of MgSO4 crystallization distress on concrete

Abstract

Based on the definition of physical salt attack, the Guide to Durable Concrete (ACI 201.2R) suggests that MgSO4 cannot lead to crystallization distress on concrete. In this paper, concretes consisting of 30% fly ash (FA), 20% limestone powder (LP), 50% slag (SG) and pure Portland cement (PC) were acceleratingly carbonated for 20d before being partially immersed in a 10% MgSO4 solution. After 150d of partial exposure, MgSO4 crystallization was attributed to the damage of the outer layer of carbonated FA, SG, LP concrete specimens in the evaporation zone. The outer layer of FA and LP concretes used as reference had also become carbonated and detached due to MgSO4 crystallization. The test results supported the idea that MgSO4 crystallization distress can occur in concrete through carbonation, and that concrete carbonation should be considered when analyzing physical salt attack on concrete.