On Freeze-Thaw Damage of Concrete Due to Combined Effect of Chloride Penetration and Carbonation

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(1) Combined action of freeze-thaw and chloride penetration(1)Chlorides existing in the mortar moved toward inner parts and partially concentrated due to freeze-thaw action and the tendencies were pronounced when a freezing temperature was lower and freeze-thaw cycles increased.(2) The effects of chlorides were serious on the scaling damage and the degree of damages were different in different chloride type, curing condition, water cement ratio and air content.(2) Combined action of freeze-thaw and carbonation(1) Carbonation after freeze-thaw action was accelerated and the degree of carbonation was different in different air content.(2) Weight change due to freeze-thaw action after carbonation increased a little, however, the change of relative dynamic modulus of elasticity was not pronounced.(3) Combined action of freeze-thaw, chroride penetration and carbonation(1) Freeze-thaw action in the presence of chloride affected the rate of carbonation.(2) Scaling damage due to freeze-thaw action in the presence of chloride after carbonation increased, then the mechanism of deterioration was complicated and must be clear in the future.(3) It will be possible to make a synthetic diagnosis of damaged concrete due to combined action of freeze-thaw, chloride penetration and carbonation, through the analyzes concerning the pull-off strength, rebound number or pulse velocity from a side view of strength, and recovering speed or coefficient of water absorption in the rapid test from a side view of tightness.