Lightweight concrete can be produced by replacing the normal aggregate with lightweight aggregate either partially or fully, depending upon the requirements of density and strength. The present study covers the influence of different aggregate curing conditions and admixtures on the strength of lightweight expanded clay aggregate concrete under normal curing and vacuum curing with and without addition of silica fume. The grade of the concrete is M40. The lightweight aggregate used is LECA, an expanded clay aggregate. Investigations were carried out up to a replacement of 50% of coarse aggregate. The workability and strength at different ages are presented.