ANHYDRITE IN CLINKER

There are contradicting opinions about the behaviour of concrete made of cement produced of clinker containing anhydrite. Some authors claim that this concrete will expand with or even without heat treatment after long water curing. On the other hand, many researches have shown that anhydrite in clinker is quickly dissolved and reacts with aluminates during early hydration and can not be a source of expansion. In this paper, results of the examination of cements prepared of clinkers rich in sulphates are presented. Some clinkers contained anhydrite as a separate phase, and in others anhydrite formed numerous inclusions in belite. These inclusions were the product of decomposition of sulphate spurrite. Heat treated mortar made of cement from clinker containing anhydrite inclusions in belite presented expansion after water curing during 400 days. However cement made of clinker containing anhydrite as a separate phase did not expand under the same conditions. Also mortar of cement made of clinker of similar mineralogical composition, but low in sulphate and with interground gypsum, did expand only when the SO3 content was equal to 4.0%. The results of these experiments allow the final conclusion that clinker containing anhydrite forming inclusions in belite gives mortars which expand after heat treatment during long water curing.

• INTRODUCTION

• MATERIALS

• METHODS

• RESULTS AND DISCUSSION

• CONCLUSIONS

• REFERENCES