This thesis presents the results of an investigation on the suitability of pumice and scoriarnaggregates in ribbed-slab construction. The aggregates were assessed for their utilization inrntopping and web construction of ribbed-slab. The suitability of using scoria as both fine andrncoarse aggregate; and pumice as fine aggregate in all-lightweight concrete production isrnassessed. The properties of scoria-scoria concrete (ScScC) and scoria-pumice concrete (ScPC)rnare evaluated by conducting comprehensive series of tests on workability, density and strength.rnExperimental and theoretical investigations were conducted to study the strength andrndeformation characteristics of ribbed-slab with 60 mm topping.rnPart of the experimental program was dedicated to the study of mix design for the production ofrnall-lightweight structural concrete. The second part of the experimental program was concernedrnwith full size slab testing. Theoretical investigations were conducted parallel to the experimentalrninvestigations.rnDeveloped ScScC mixtures have attained required strength and density to be accepted asrnstructural lightweight concrete; however, ScPC cannot be used as structural concrete.rnComparison of test results showed that ribbed-slabs can be constructed using scoria aggregatesrnwith 47% fine content, 1.6 A/C ratio and 0.4 W/C in range of normal cement content.rnKeywords: Scoria, Pumice, Lightweight aggregates, Lightweight concrete, Ribbed-Slab, mixrndesign, Density, Strength.