MICRO-SCALE INVESTIGATIONS OF CEMENT-BASED MATERIALS WITH INCREASED RESISTANCE TO ALTERED THERMAL CONDITIONS

This paper reports on an extensive ongoing investigation into the behaviour of microstructural characteristics of cement-based mortars exposed to freezing and thawing cycles. Six different mixes of cement-based composite with varying dosage of air-entraining admixture were designed to ensure variations in the microstructure described by porosity, pore size distribution and consequently strength. The macro- and micro-scale investigation was performed on mortar exposed to alternated climate conditions concurrently with laboratory-cured material. The bulk properties determined in this study included compressive and flexural strength. On micro-scale, the pore system characteristics were established with Mercury Intrusion Porosimetry (MIP) and Scanning Electron Microscopy. Their appraisal has been regularly spaced, throughout an 18 months period. The results presented in this paper refer to material up to 6 months of age, which is the equivalent of 732 freezing and thawing cycles. The obtained data enabled establishment of relationships between micro and macro properties of the mortar. As a result, the micro-characteristics responsible for improved performance under severe conditions were identified. The application of multicriteria optimization yielded an “optimal” structural composition of a mortar of increased durability. As it appears, higher volumes of pores with their diameters smaller than 200 nm promote higher performance and durability.

• INTRODUCTION

• EXPERIMENTAL INVESTIGATION

• RESULTS AND DISCUSSION

• OPTIMIZATION

• FINAL RESULTS AND CONCLUSIONS

• REFERENCES