CONICET | Buscador de Institutos y Recursos Humanos

The construction of buildings by incompetent craftsmen and the use oflow quality building materials, including low quality concrete havebeen identified in the literature as two of the major reasons for theincessant collapse of building in Nigeria. The roadsidecraftsmen/artisans usually/generally construct buildings using 1:2:4cement-fine aggregate-large aggregate mix ratio irrespective of thecement strength class. In this paper, the investigation conducted todetermine the appropriate concrete mix ratios required to produceClass 20/25 and Class 25/30 concretes commonly used for design ofbuilding structural members using the Portland-limestone cementgrades 32.5 and 42.5 that are available in the Nigerian open marketis presented. Investigation revealed that the cube compressivestrength of 1:2:4 concrete produced with Portland-limestone cementgrade 32.5 is less than the minimum 25MPa required for concrete Class20/25 and a richer 1:1.5:3 concrete produced with Portland-limestonecement grade 32.5 may be needed to produce concrete Class 20/25.Investigation also revealed that Portland-limestone cement grade 32.5may not be suitable for the production of concrete class 25/30 withcube compressive strength of 30MPa as the cube compressive strengthof 1:1:2 concrete produced with Portland-limestone cement grade 32.5may not attain 30MPa. Concrete strength classes 20/25 and class 25/30can be produced with Portland-limestone cement grade 42.5 using 1:2:4and 1:1.5:3 mix ratios respectively. To produce concrete withstrength class C20/25 which is the minimum concrete strength classrecommended for the construction of the load-bearing buildingstructural members using the 1:2:4 mix ratio, Portland-limestonecement grade 42.5 is required