No abstract

Since antiquity, man used to stock up materials and products existing in his close surroundings to build his house, which provides him shelter and comfort. Within the present work, mixtures of plaster and dune sand have been studied with the aim of valorization of locally abundant materials. The tests showed that with the addition of dune sand and the compaction, an optimal mixture (67% plaster and 33% dune sand) can be used as a carrier element for construction of up to three levels; since significant increase of the mechanical strength has been observed. The element obtained offers an acceptable thermal insulation with a decrease in the thickness of the outer wall construction. The use of this gypsum’s mortar block as a carrier element in a structure not exceeding three levels, also enables a considerable savings especially in areas where sand and plaster are abundant and relatively inexpensive

This paper deals with the development of expressions relating structural seismic response parameters to the epicentral distances of an earthquake and the natural period of several reinforced concrete buildings (6, 9 and 12 storey), with three floor plans: symmetric, monosymmetric, and unsymmetric. These structures are subjected to seismic spectrum of accelerations collected during the Boumerdes earthquake (Algeria, May 21 st , 2003, Mw=6.8) at different epicentral distances. The objective of this study is to develop relations between structural responses namely: base shear, storey displacements, interstory drifts and epicentral distance and fundamental period for a given earthquake. The seismic response of the buildings is carried out in both longitudinal transverse and directions by the response spectrum method (modal spectral approach).

Much of the current research on concrete engineering has been focused on including siliceous additions as supplementary cementitious materials (SCMs). Silica reacts with Calcium hydroxide release during cement hydration, and produces more C-S-H. The latter contributes to increase compactness, mechanical strengths and sustainability of concrete. This paper explores the hydration characteristics of cement paste based on various natural mineral additions, that are very abundant in Algeria and present a high silica content (ground natural pozzolana “PZ” and ground dune sand “DS”). For this purpose, several analyses were carried out on modified cement pastes and mortars. TheseSCMswere introduced by replacement levels of 15, 20 and 25 by weight of cement. We first, studied the effect of these SCMs on the heat of hydration and mechanical strength of mortars at different ages. The evolution of hydration of modified paste was studied, by using Thermal analysis (TG/TDA) at different ages, to analyze the Calcium Hydroxide (CH) content of the modified pastes. It is shown that the CH content of the mixes including SCMs is lower than that of the plain cement paste, indicating that silica reacts with the cement paste through a pozzolanic reaction. Increased pozzolanic activity results in higher amounts of Calcium Silicate Hydrate in the paste, which in turn results in higher compressive strength for modified cement mortars. Due to its crystalline morphology, the ground DS particles present a partial pozzolanic effect, compared to PZ which is semi-crystalline. Modified mortars by 20% DS can be the optimal composition. It presents satisfactory results: good mechanical strength and low heat of hydration. It can lead to an economic and sustainable concrete. Ground DS is very abounded in Africa and free of any impurities and can be a good alternativeSCMsin cement industry.