EFFECT OF DELAY IN PLACEMENT OF CONCRETE WITH AND WITHOUT AIR ENTRAINMENT

Abstract

"We shall never }mow every thing about the properties of concrete but it is important that information of practical importance is disseminated as it becomes available". (Structural Concrete ,Sept .1965) The delay in placement of concrete is a major factor which- effects the workability and strength of concrete. The contract specifications stipulate wastage of concrete if not poured in a reasonable_ time. This entails loss of useful effort, money and time. If this concrete can be economically regained and used, much money can be saved. Efforts to study the effect of delay on concrete and remedial measures to restore the workability -and strength, will help in salvaging waste concrete and indirectly help engineers in planning cheaper indigineous process for concrete placement. Work, though heterogenous and of varying degrees of control, done by. different questers is reviewed and their findings charted. Laboratory work was done for different types of mixes for three conditions of _tests viz 1tunagitated", "agitated" and "agitated and slurried". The results obtained are discussed, plotted and basic relations involving delay period and various other properties,,, parameters of concrete are statistically derived'. Recommendations for additional cement for restoring strength of different types of mixes have been made.