Mix design method applying to normal weight concrete are generally difficult to use with light weight aggregate concrete. The lack of accurate value of absorption, specific gravity and free moisture content in the aggregate make it difficult to apply water cement ratio accurately for mix proportion.

Lightweight concrete mix design is usually established by trial mixes. The proportion of fine to coarse aggregate and cement and water required are establish based on the previous experience with particular aggregate various degree of water absorption by different light weight aggregate is one of the serious difficulty in the design of mix proportion. A reliable information of saturated surface dry bulk specific gravity become difficult.

Mixing procedure

Mixing procedure for light weight concrete may vary with different type of aggregate . The general practice for structural light weight concrete is to mix the aggregate and about 2/3 of the mixing water for a period upon one minute prior to the addition of cement and the balance mixing water.mixing is done continuously as required for homogeneity . Usually 2 or more minute are required to get uniform mixing. In case of some insulating concrete the aggregate is added at the end of mixing to minimize degradation.

Mix design data have been prepared for several. Propitiatory lightweight aggregate available in the United Kingdom.