Lightweight aggregate concrete is a relatively new type of concrete that can be manufactured using solid waste or recycled by-products. This method has significant merits in mitigating the negative impact of the production of Portland cement on the environment and reducing the consumption of natural resources.

The mechanical properties of lightweight aggregate concrete are significantly influenced by the particle shape, surface texture, and chemical composition of the waste. It is also a matter of the proportion of coarse and fine aggregates in concrete mixtures. The compressive strength levels required by the construction industry for design strengths of cast-in-place, precast, and prestressed concrete can be easily obtained with lightweight aggregate concrete.

This is because the specific gravity of lightweight aggregate concrete is lower than that of normal concrete. This can be achieved by increasing porosity, or by introducing air voids in the concrete.

Porous aggregates are often used to produce lightweight concrete, including pumice, thermally treated shale, diatomite, scoria, volcanic cinder, etc. The porous nature of these materials enables them to achieve lower specific gravity, and this can result in stronger concretes.

Some of these lightweight aggregates have a high number of micro pores, which are responsible for their low specific density. However, other lightweight aggregates have fewer micro pores and thus have a higher specific density.

The effect of water absorption on the strength of lightweight concrete is marginal. For example, a sample P2 with B700 having 17% water absorption produced a lower strength than that of N1 and S6 which both contained the same amount of B700.