Effect of some chemical admixtures on the physico-chemical and rheological 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 was 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 90days) 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 analyses. The results showed clearly that as the dosage of admixtures increases, the water of standard consistency decreases, this leads to a decrease in the total porosity of the cement pastes, and consequently the compressive strength value increases. Also as the admixture dosage increases, adsorption of their particles on the cement particles increases, so the negative charge on cement particles increases leading to more repulsion between them which enhances the rheological properties of cement pastes. The X-ray diffraction and scanning electron microscopy analyses indicated that the main hydration products formed are nearly amorphous calcium silicate hydrates, calcium sulphoaluminate hydrates (ettrringite and monosulfate hydrates) and portlandite (CH).