Some factors affecting the compressive strength of concrete

Abstract

Summary Abrams's law of compressive strength versus water/cement ratio is well known and many investigators have studied the possible effects of other factors, such as cement content and sand concentration, upon concrete strength. In particular, the British and American literature is often at variance concerning these secondary effects so that a primary aim of the present paper is to reconcile these conflicting views. Any considerations of secondary effects require a very clear definition of what is meant by ‘compressive strength’ and ‘water/cement ratio’. Furthermore, different aggregates can give significantly different results. These considerations are illustrated by presenting data for curves relating compressive strength and water/cement ratio for three distinct criteria for compressive strength and two types of coarse aggregate. The paper then re-examines the effects of varying both the cement content and the sand concentration, for a given water/cement ratio, upon the compressive strength. It is shown that the effects of these secondary factors are in general fairly small and that rational explanations can be given for the often conflicting conclusions obtained by earlier investigators.