326 Journal of the Tunisian Chemical Society, 2017, 19, 326-334 * Corresponding author, e-mail address: hatemmajdoub.fsm@gmail.com Effect of a partial replacement of Portland cement by date seeds on the mechanical and chemical behavior of the mortar Chiraz Elazizi a , Halim Hammi a , Wiem Marzouk b , Hatem Majdoub b* and Adel M’nif a a Useful Materials Valorization Laboratory, National Centre of Research in Materials Science, Technologic Park of Borj Cedria, B.P. 73, 8027 Soliman, Tunisia b University of Monastir, Laboratoiry of Interfaces and Advanced Materials (LIMA), Faculty of Sciences of Monastir, Bd. de l’environnement, 5019 Monastir, Tunisie (Received: 02 Juillet 2017, accepted: 01 November 2017) Abstract: The aim of this experimental study is a comparative analysis of the behavior of cementitious mortars developed from a mixture of CEM II / A-L 32.5N and different proportions of the dates seeds (DS) from Phoenix Dactylifera L. and therefore highlight the influence of DS on the strength and durability of the mortars and try to bring a better understanding about the chemical reactions responsible for the increase of sustainability. Techniques such as X-ray diffraction and Scanning Electron Microscopy were used to determine the structure of the new formulation. After curing specimens at 28 days in water, they are immersed in the same concentration acid solutions of 5% (HCl, CH 3 COOH). Mass measurement tests are performed at different ages. The results are used to demonstrate the beneficial effect on the compressive strength and the durability of such DS addition, while having a natural setting retarder or accelerator according to the addition rate. Keywords: Sustainability, Mortar Biomass (Dates Seeds), compressive strength, acid attack, setting time. INTRODUCTION In the cement industry, looking for a less expensive binder incorporating industrial waste and natural resources has become a major concern for the deficit level in the manufacture of Portland cement and its climate issues. Different types of additions such as natural pozzolan, fly ash, silica fume, blast furnace slag and calcareous filler among others are usually included. The incorporation of these active and inert mineral additives in the binder can improve their characteristics as has been highlighted in several studies [1-4]. Among these resources the biomass could exert an important role, since it is renewable, CO 2 neutral energy resource and its by-products are increasingly used worldwide. Utilization of agricultural by-products substitutes for natural resources provides an alternative for natural minerals [5,6]. Most of the papers are focused on the feasibility of using biomass fly ash as a partial cement replacement material [7,8]. While, only a few papers deal with the valorization of the agriculture by-products in cement based materials [9]. For these reasons, the addition of Date Seeds (DS) in mortar due to its wide availability in Tunisia and high polysaccharides content and consequent potential as organic additive [10-13]. This study investigates the effect of the partial substitution of a quantity of Portland cement by Date Seeds (DS) powder on the mechanical strength, setting time and durability towards acid environment elaborate mortars. Moreover, we will compare the behavior of prepared mortars with only cement (CEM II 32.5 N) and the mortars containing different dosages of DS. Crystalline phases were performed by XRD analysis with a Philips PW 3050/60 2q goniometer and a PW 3373/00 copper cathode, at a scanning speed of 2°/min (Fig. 1), and the results of DRX (Fig. 7) are fitted using X’pert High score software.