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The replacement of natural materials by industrial by-products has given a variety of new construction materials that are economically viable and ecologically beneficial. Blast furnace slag is one of these industrial by-products. Its beneficial proprieties and characteristics have led to rapid growth of production in Algeria and worldwide. This research deals with the effect of alkaline activation of slag cement with clinker. Various agents that activate the process were used for testing, and it showed that compressive strength at 28 d, which reached 150% with respect to compressive strength obtained from slag cement at different percentages of slag (50%–80%), increased considerably. Alkaline activators accelerate hydration and stimulate the hardening process. The results also show the efficacy of steam cured treatment on the compressive strength.Key words: slag cement, activation agent, hydration, hardening, steam curing.

Sand is an inert element essential in the composition of concrete; its use ensures granular continuity between the cement and gravel for better cohesion of concrete. This paper presents the results of a study that investigated the influence of sand quality on the properties of fresh and hardened SCC (self-compacting concrete). The dune sands are very fine materials characterized by a high intergranular porosity, high surface area and low fineness modulus; on the other hand crushed (manufactured) sand has a high rate into thin and irregular shapes which influence the workability of concrete. The amount of dune sand varies from (0%, 50% to 100%) by weight of fine aggregates. The results show that the rheological properties favour the use of dune sands; however the mechanical properties support the use of crushed sand.

The alkali-activated slag (AAS) cement is an interesting building material, confronting to the new economical and ecological challenges. In order to enhance its physical properties in comparison with ordinary Portland cement (OPC), we used natural pozzolana as a mineral addition. The parameters studied are: the fineness of the addition (5350 and 5650 cm2/g), and its percentage (0 to 30%). The activator used is NaOH (5M) and the curing temperature was fixed at 20°C. The results show the possibility to obtain compound alkali-activated slag cement with better stability and a compressive strength higher than 35 MPa.