Effect of using Metakaolin on chloride ion penetration in high performance steel fiber reinforced concrete

Abstract EN

This paper attempts to reduce the penetrability of high performance steel fiber reinforced concrete to chloride ions originating from external sources, by using High Reactivity Metakaolin (HRM) as a highly active pozzolanic material, in order to prolong the time to initiation of the steel fibers corrosion and to minimize concrete damage that may occur due to the exposure to chloride ion penetration.

According to pozzolanic activity index (P.A.I.), 8% content of HRM was used as a partial replacement by weight of cement with 2% steel fibers by volume of concrete.

During the exposure period of 300 days in 4.5% of NaCl solution, the total and free chloride contents (Cltotal, Clfree) with the chloride profiles at the ages of 28 and 300 days were investigated.

Also the rapid chloride penetrability test (RCPT), compressive and flexural strengths tests were conducted at the ages of 28, 90, 180 and 300 days.

Results showed that the incorporation of 8% HRM caused a reduction in the (Clfree/Cltota) ratio, the chloride penetration depth and the electrical conductivity with percentages of 21%, 40% and 43% respectively after 300 days exposure to chloride solution in comparing with the mix of 0% HRM.

Results also indicated that the losses in compressive and flexural strengths after exposure of 300 days to chloride solution for the mix incorporating 8% HRM were by 5% and 5.8% respectively while they reached 9.5% and 11% respectively for the mix without HRM in relation to the correspondent test specimens cured in tap water.