A lightweight structural concrete formulation comprises a wet mix of about 460 kg/m3 of cementitious material such as ordinary Portland cement of which about 50 percent has been replaced by ground granulated basic furnace slag (GGBFS) and 7 percent by silica fume (SF) in other words the mix introduces between about 178 and 228 kg/m3 therefore the combination is good to produce secondary reaction products when the cement hydrates which produces secondary calcium silicate hydrate (C—S—H) which makes the structure dense and thereby increases its mechanical durability characteristics of the concrete product. Possible ratios of GGBFS and SF are 30-70 percent and 5-10 percent, respectively. By making the structures dense increases the mechanical and durability characteristics of the concrete product. Other ratios have been made including GGBFS of 30-70 percent and silica fume 5-10 percent, respectively. It can be noted that the silica fume was added to the mixture as a supplementary cementitious material (SCM) not as an aggregate. It should also be noted that the particle sizes of GGBFS ranges between about 20-40 mm and that of silica fume is less than 20 mm.