Effect of Some Chemical Additives on the Physico-Chemical Properties of Oil Well Cement Pastes

Abstract

In this work the effect of the prepared melamine formaldehyde sulfanilate (MFS) and cyclohexanone formaldehyde sulfonate (CFS) on the physico-chemical properties of oil well cement were investigated. The chemically combined water content, compressive strength, gel/space ratio and degree of hydration for each paste at different time intervals (1, 3, 7, 28 and 90 days) were determined. The rheological properties were determined using mini slump test. The morphology of cement pastes and the phase composition of the hydrated products were investigated using scanning electron microscope and x-ray diffraction analysis. The results showed clearly that as the dosage of admixtures increases, the water of consistency decreases, this lead to decrease the total porosity of the cement pastes, and consequently the compressive strength value increased. Also as the admixture dosage increases, its adsorption on the cement particles increases, so the negative charge on it increases leading to more repulsion between them which enhances the rheological properties of cement pastes. The X-ray diffraction analysis indicated that the main hydration products formed are nearly amorphous calcium silicate hydrates, calcium sulphoaluminate hydrates (ettrringite and monosulphate hydrates) and portlandite (CH).