Title: Compressive Strength of Concrete Cylinders by Sulphur, Rubber Capping and Grinding Methods

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Publication: CIA

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Date: 2/28/2011

Abstract:
It is known that no matter how carefully a cylinder is finished, its end surface probably exhibits some irregularities. As required by AS 1012.9, the finished end of concrete cylinders must be capped or ground before being crushed for compressive strength. Sulphur and rubber capping are widely accepted methods. As an alternative, the ends of concrete cylinders can be ground using a grinding machine to achieve an appropriate surface profile. Data presented in this paper compares the effects of four types of cylinder end preparation methods on compressive strength, including sulphur capping, rubber capping, single end grinding and double end grinding. A total of 152 concrete cylinders measuring 100 x 200mm were used to obtain sufficient data for the statistical analysis. These concrete cylinders were crushed as per AS 1012.9 with compressive strengths ranging between 45MPa and 110MPa. It was found that concrete cylinders gave the highest and more consistent compressive strength results when double end grinding method was used. Also, it was demonstrated once more that sulphur and rubber capping methods achieved reasonable results for concrete up to 60MPa compressive strength. For concrete above 80MPa compressive strength, rubber capping method cannot be recommended while sulphur capping method can be used but the sulphur capping compound must have high compressive strength and the capping thickness must be 1-2mm.