Valorization of the Use of Calcareous Tuff and Dune Sand in Saharan Road Design

Abstract

This research objective is to propose a co-valorization of powdered tuff, containing a slight amount of clay and dune sand, by mixing the two substances at different rates such as 0%, 5%, 15%, 25% and 35% of sand. The adapted criteria formulas are those recommended by the technical Saharan road. The results of the proposed study showed that "tuff-sand" mixtures are denser with a lower optimum water content modified proctor, the fine rate decreases together with the plasticity index, whereas the bearing index (CBR: California bearing ratio test) increases. The intrinsic characteristics, cohesion and sensitivity of mixtures with respect to compactness are almost identical to those of tuff without addition. The optimal adapted sand incorporation rate is estimated at 25% at 96% of compactness. Under these conditions, the amount of fines decreases from 40% to an acceptable level of 25% and the plasticity index from 16.2 to 12. The compaction water content decreases by 36% and the CBR (bearing index) increases by 30% and the compressive strength and sensitivity, according to compactness, of the elaborated material are almost identical to those of tuff without addition.

Contribution to the characterization and valuation of a mixture of clay and dune sand for road construction

“…The importance of this phenomenon depends essentially on the quantity of swelling minerals. Its study is based on several aspects, namely: geological, climatological and geotechnical [7].Swelling potential classi cation was performed using indirect methods [8,9].The known stabilization products being dune sand, the solution obtained from the husk of the would reduce the swelling of clay soils [10].The stabilization of clay soils, and to extract from scienti c work the correlations established between the various geotechnical, physical, chemical, and mechanical parameters, determined from direct and indirect characterization tests [11][12][13].Geotechnical road tests are regulated by several standards which are essentially based on mechanical parameters to assess the compliance of the use of a material [14].In the particular case of ne clay soils,different identi cation parameters sometimes give results that do not ultimately allow an unequivocal decision to be made on the swelling nature of the soils [15].Improving soil properties, also called soil treatment or stabilization, is a technique introduced many years ago with the main purpose of making soils capable of satisfying clay soils [16].This treatment is often carried out to increase the strength, reduce or increase the permeability as well as to decrease the compressibility and minimize the sensitivity of the ne soil to variations in water content [17].For this purpose, it is necessary to use the other exterior material to improve the geotechnical performance of the site. Several studies have been carried out on the phenomena related to this type of soil [18].…”