International Journal of Advanced Materials Research Vol. 1, No. 2, 2015, pp. 45-52 http://www.aiscience.org/journal/ijamr * Corresponding author E-mail address: karroudj@usthb.dz (K. Arroudj), arroudjkarima@yahoo.fr (K. Arroudj) Comparative Study of Chemical Activity of Different Ultrafine Cementitious Additions Karima Arroudj 1, * , Madiha Lanez 1 , Mohamed Nadjib Oudjit 1 , Arezki Tagnit-Hamou 2 1 Built and Environment Laboratory « LBE», Faculty of Civil Engineering, University of Sciences and Technology Houari Boumediene, Algiers, Algeria 2 Cementitious Materials Laboratory, Department of Civil Engineering, University of Sherbrooke, Sherbrooke, (Québec), Canada Abstract The properties of concrete are governed by cement hydration. The latter can be modified through the incorporation of siliceous additions, which leads to the densification of the concrete’s matrix by its physical “filling” and chemical role “ pozzolanic reactivity”. This incorporation allows to product an ecological, economic and perform concrete. Thus, contribute to sustainable development in construction field. In order to better understand the pozzolanic effect of the siliceous additions in Portland cement pastes, x-ray diffraction (XRD) analysis of lime pastes containing three ultrafine additions (Silica fume “SF”, ground blast-furnace slag “S”, and finely ground quartz from dune sand “DS”) was carried out. This analysis is a simplified approach to that of cement pastes for which the principal reaction is the fixing of lime “Portlandite”, released during cement hydration, by additions and forming the second-generation of calcium silicate hydrates (C-S-H) denser and therefore more compact cement matrix. This research shows that the very finely ground DS, in spite of its crystalline nature, has a partial pozzolanic reactivity. Ground slag, with a lower fineness than that of DS and a low silica content, has a better pozzolanic reactivity than DS because it has an amorphous structure, which explains the importance of mineralogical structure on the pozzolanic reaction. The pozzolanic reactivity of a siliceous addition is related not only to its fineness and silica content, but also especially to its morphology. Keywords X-Ray Diffraction, Siliceous Addition, Pozzolanic Reactivity, C-S-H, Amorphous Structure Received: April 9, 2015 / Accepted: April 29, 2015 / Published online: May 15, 2015 @ 2015 The Authors. Published by American Institute of Science. This Open Access article is under the CC BY-NC license. http://creativecommons.org/licenses/by-nc/4.0/ 1. Introduction To achieve sustainable development in civil engineering is the aim of many studies around the world. One tone of cement produced generates an emission of about 0.9 tons of CO2. [1, 2]. One way to reduce this emission and energy consumption for the cement industry is to introduce SCMs substitution. These additions are usually industrial waste or natural deposits with a pozzolanic character. They contribute to compactness of cement paste by fixing of Portlandite released during the hydration of cement. This reaction leads to formation of second-generation calcium silicate hydrates (CSH). and thus, to sustainable economic and ecological concrete [3, 4, 5, 6]. The pozzolanic additions activity was always associated with the presence of an amorphous phase produced during grinding. Therefore, ground quartz crystal structure is generally considered chemically inert. [2, 7]. However, several studies have shown that the current ground quartz presents a pozzolanic activity called "partial". This reactivity is mainly due to the presence of fine particles adsorbed on amorphous crystalline particles. [8, 9, 10, 11]