Abstract: A light-weight concrete comprising cement, highly porous coarse and/or fine aggregates, such as furnace bottom-ash from thermal power stations or other porous natural or artificial materials, with a porosity of about 20-50% and an additive, preferably fly-ash from thermal power stations and other natural or artificial finely ground materials passing a 100 .mu.m screen, and water. According to the invention the additive is used for (i) closing (bridging) air-voids in the cement paste and pores in the light-weight aggregates which increases the concrete density and strength, although using the highly porous aggregates and low to medium cement content; (ii) increasing the durability of the concrete by closing the air-voids and pores in the hardened mortar; (iii) reducing the segregation of concrete mix constituents arising due to the difference in density of the porous aggregate and the surrounding cement paste and (iv) lowering the consumption of cement.