INFLUENCE OF METAKAOLIN ON THE CHLORIDE PENETRATION PERFORMANCE OF CONCRETE Rui M. Ferreira 1 , João P. Castro-Gomes 2 , Pedro Costa 1 and Raphaele Malheiro 1 1 C-TAC – University of Minho, Guimarães, Portugal 2 C-MADE – University of Beira Interior, Covilhã, Portugal ABSTRACT Extensive research and practical experience have shown that partial replacement of cement by metakaolin improves concrete durability as a result of the refinement of the pore structure. While literature confirms much research on the performance of concrete with metakaolin, it is scarce concerning the performance with regards to chloride penetration, and the effect on the service life of reinforced concrete structures. In this study, several concrete mixes were cast with varying cement type and content and were evaluated for their chloride penetration performance. Reference mixes where made with CEM I 42,5R and CEM IV/A 42,5 type cements. Two cement contents levels where defined: 330 kg/m 3 and 440 kg/m 3 based on mix designs currently used in the ready-mix industry for C20/25 and C30/37 concretes. Cement was replaced with metakaolin with levels varying from 10 - 20%. All concretes where tested for fresh properties, compressive strength, electrical resistivity and chloride diffusion characteristics (migration and ponding), and mercury intrusion porosimetry. The results demonstrate the improved resistance to chloride penetration of concretes with metakaolin additions. A beneficial effect on strength and durability properties of metakaolin was also observed. In addition, service life design calculations of reinforced concrete structures in marine environment based on the performance indicators obtained show a significant increase in the time to fulfil the serviceability limit state of corrosion initiation. Key-words: Durability, metakaolin, chloride, electrical resistivity, service life, additions. INTRODUCTION The benefits of cementitious materials and natural pozzolans as partial replacement of Portland cement are well established for durability of concrete. Metakaolin can be used as a concrete addition, replacing partially cement due to its pozzolanic properties. Metakaolin is produced from calcining kaolin clay at a specific temperature range (500-900 ºC) to make it reactive, with the general form Al 2 O 3 -SiO 2 [1-3]. Extensive research and practical 0DQXVFULSW &OLFN KHUH WR GRZQORDG 0DQXVFULSW 50)B3DSHU,&'&BY)B5HYLHZHGGRF