CORROSION RESISTANCE OF CEMENT MORTARS WITH METAKAOLINITE

In this paper the effect of metakaolin addition on the corrosion resistance of cement mortar is studied. Metakaolin, produced by controlled thermal treatment of kaolin, can be used as concrete constituent, since it has pozzolanic properties. A poor Greek kaolin (kaolinite: 52% w/w) has been thermally treated at 650°C for 3h and the produced metakaolin (MK) had been ground to the appropriate fineness (20% residue at 13.6 micron). In addition, a commercial metakaolin (MKC) of high purity has been used. Several mixture proportions were used to produce mortar specimens, where metakaolin replaced an amount either of sand or of cement. Mortar specimens where then exposed to the corrosive environment of either partial or total immersion in 3.5% w/w NaCl solution. For the evaluation of the performance of metakaolin, the following methods were used: measurement of compressive strength, corrosion potential, carbonation depth, mass loss and finally electrochemical measurements of the corrosion rate by the Linear Polarization method. As a result it seems that when metakaolin is added as a percentage of up to 20% w/w, either as sand or as cement replacement, there is a protective effect leading to increased compressive strength and to reduced corrosion rate, whereas when metakaolin is added in greater percentages there is no positive effect.

• INTRODUCTION

• EXPERIMENTAL

• RESULTS AND DISCUSSION

• CONCLUSIONS

• REFERENCES