Combined effect of powdered dune sand and steam-curing using solar energy on concrete characteristics
Résumé
This paper explored an economic, environmental and technological alternative, namely steam-curing using solar energy, which harnesses solar radiation to accelerate cement hydration and increase the pozzolanic activity of powdered dune sand (PDS) by activating the less reactive silica; thus allowing the concrete to acquire high initial strengths. In addition, using PDS, as cement addition, reduces the use of clinker. Combined effect of PDS and steam-curing on concrete characteristics is worth studying. The effect of different PDS rates on both workability and mechanical strengths at various ages of water-curing was investigated. Thereafter, the effects of curing procedures on mechanical strengths of specimens incorporating PDS were examined. Three curing methods were used: water-curing and steam-curing at 42 degrees C, at 26 degrees C. Indeed, it was essential to determine the optimum PDS rate and appropriate steam-curing cycle. Finally, the effect of subsequent water-curing after steam-curing at 42 degrees C (SC42) was also studied. The results reveal that PDS plays a beneficial role on the workability up to the rate of about 15%. It should be noted that there exists an optimal rate of around 10% PDS for which higher mechanical strengths are obtained at 28-day and 60-day. SC42 is more useful than at 26 degrees C because the pozzolanic activity of PDS begins to be significant from the third day. After 3 days of SC42, the highest compressive strength (Cs) at 28 days was achieved at 10% PDS. Flexural strengths were in great accordance with the Cs regardless of the PDS rate and the steam-curing cycle. SC42 and up to 20% PDS, not only improves mechanical strengths, but also reduces production costs in addition to significant environmental impact. It is essential to use the technique of subsequent water-curing (of 3-day) because it has a significant effect on the compressive strengths of concretes containing PDS after 3-day of SC42. Results confirmed that PDS can be used as an addition to cement in the production of precast concrete using eco-friendly and economical technique. This finding has significant implications for the economics of concrete construction in the southern regions of the country where the dune sand is very abundant.