TEN YEAR STUDY INTO THE EFFECTIVENESS OF GGBS AT PREVENTING ASR

The expansions of several hundred concrete prisms containing reactive natural aggregate were monitored for ten years to investigate the relationship between the alkali content of concrete and the expansion caused by Alkali Silica Reaction. The prisms were moist-stored at 20°C and at 38°C. The concretes had concrete alkali contents between 4.5 and 11 kg/m³ and contained between 0 and 70% ground granulated blastfurnace slag. The alkali content of the ground granulated blastfurnace slags ranged from 0.58 to 0.83% and that of the Portland cements from 0.54 to 1.15%. Storage at the higher temperature accelerated the rate of expansion, and slightly increased the ultimate expansion. The correlation between the two temperatures was very good in terms of classifying mixes as either ‘expanding’ or ‘nonexpanding’ and it is concluded that storage at 38°C is an accelerated test that can be used to reliably predict what would happen at normal temperature. Mixes containing GGBS tolerated high alkali contents in the concrete, without expansion and this effect increased with the proportion of GGBS. The results of the programme are discussed in relation to various rules that have been proposed to take advantage of the effectiveness of GGBS in preventing ASR.

• INTRODUCTION

• METHOD OF TEST

• RESULTS

• CONCLUSIONS

• REFERENCES