Effect of admixtures on the behaviour of lightweight concretes

This paper presents an experimental investigation of the combined effect of a superplasticiser admixture and metakaolin material on the mechanical behaviour of expanded clay lightweight concrete containing recycled glass aggregate. The optimum dosage of the superplasticiser admixture (type SNF) was adjusted and used by weight of cement. The short- and long-term mechanical properties of concrete mixes were measured in accordance with the relevant British/EN standards. The results obtained were compared with the results of control concrete mixes (without superplasticiser). They showed that the superplasticiser admixture exhibited a 20% reduction in mixing water content. All measured values of unit weight, compressive and splitting tensile strengths increased when the superplasticiser admixture and metakaolin material were used. The concrete mix containing 30% recycled glass revealed an increase in the mechanical strength compared with the mix of 15% recycled glass. However, the workability of the superplasticiser concrete mixes was degraded, reaching 44% reduction in slump value.