Valorization of Local Mineral Admixtures in Concretes

This study is an extension of previous researches on mortars with mineral admixtures and super-plasticizers. In this way, the same methodology was applied to concretes and the use of mineral admixture was limited to low cost materials available in Algeria as limestone, pozzolan and blast furnace slag, with current cement and super-plasticizer. The experimental methodology used was based on the volume substitution of the cement by admixtures in mixtures with the absolute volume of the solid phases and workability preserved constant. The main results achieved showed that the super-plasticizer demand of concretes depends on the nature and the quantity of the incorporated admixture. The combined use of admixtures and super-plasticizer has generally a favourable effect on compressive strengths at 07 and 28 days at low rates of cement substitution, which vary significantly with the nature, fineness and quantity of the used admixtures. At 07 days, limestone admixtures give better improvements and reach more than 20 % of gain to the compressive strength of the reference concrete with no admixtures or super-plasticizer, at 10 % of the cement substitution and still better until 30 %. At 28 days, blast furnace slag admixtures give better improvements at 28 days and reach more than 20 % of gain to the compressive strength of the reference concrete at 20 % of the cement substitution and still better until 30 %. This contribution to the compressive strength is explained on the one hand by the reduction of the quantity of water in the mixtures at the same consistency, by the use of the super-plasticizer and on another hand by the activity of Limestone admixtures at early ages and to the latent hydraulic properties of blast furnace slag at 28 days