ABSTRACT

 The X-ray diffraction (XRD) technique has been widely used in order to investigate anhydrous and hydrated cement phases. X-ray diffraction (XRD) technique has been used in several works to characterize cementitious materials. XRD pattern allows the study of cement hydration products at different curing ages and with different materials additions by analyzing peak positions and relative pattern intensities.. In this study, XRD was used in order to analyze the cementitious paste containing Nickel II Sulphate Hexahydrate chemical activator. The difffactograms obtained Were compared with literature data in order to identify the phases of analyzed materials. Rietveld refinement of XRD pattern of paste containing 3% of Nickel II Sulphate Hexahydrate chemical activator addition was also carried out, in order to analyze calcium hydroxide, calcium silicate hydrate gel, silica and ettringite structures that contribute to matrix filling. XRD pattern of cement paste withoutNickel II Sulphate Hexahydrate showed a lower concentration of silica and ettringite than the cement paste with Nickel II Sulphate Hexahydrate. In addition, the compressive strength of mortar produced 32.0MPa and 34.0MPa for mortar without activator and mortar with activator respectively. This shows that the activator is very; effective in improving the properties of concrete. This indicates that the paste with Nickel II Sulphate Hexahydrate activator will produce hydration .product that will have higher strength, low permeability and higher durability than cement paste without activator. The Nickel II Sulphate Hexahydrate addition in the cementitious matrix changed the hydrate cement products, as it induced the formation of compound phases, such as caicium silicate, which is a stable phase, contributed better to the filler effect, as its particles have higher volume than calcium hydroxide. Keywords: Chemical activator, Nickel II Sulphate Plexahydrate, cementitious hardened paste waste, XRD qualitative analysis, Rietveld refinement.