Abstract
The influence of NaCl salt in the hydration of the Portland cement paste class G was studied using a Non Conventional Differential Thermal Analysis (NCDTA) on the first 24 hours of cement hydration. The mass of salt used corresponds to 0, 5, 10, 15 and 20% of mass of water used in the preparation of the pastes. The water/cement ratio (w/c) remained constant, being 0.46, and the pastes final volume was 99.9mL. Applying a deconvolution method to separate overlapped NCDTA peaks it was possible to estimate the energy released during the different stages of hydration and the effect of salt in cement hydration process. The presence of up to 10% of salt accelerated the hydration process and increased the hydration of C3S and C3A, while the 20% of the salt causes a delayed hydration and decreased the hydration of C3S and C3A. Futhermore, cement pastes with the same percentages of NaCl and with different hydration times were evaluated by Thermogravimetry (TG), Derivative Thermogravimetry (DTG) and Differential Thermal Analysis (DTA). After 28 days the presence of salt caused a greater increase in the formation of hydrated products.
Highlights
IntroductionWhen there is a flow of cement slurry in the annular of the well drilled in a saline zone, dissolution of the salts present in the rock by cement paste can occur, changing its physical properties among other effects, such as an acceleration or reduction of cement hydration
Cementing is one of the most important processes in the oil well drilling
NaCl is applied on water used to prepare cement paste to mitigate dissolution in saline zone[1,2,3]
Summary
When there is a flow of cement slurry in the annular of the well drilled in a saline zone, dissolution of the salts present in the rock by cement paste can occur, changing its physical properties among other effects, such as an acceleration or reduction of cement hydration. NaCl is applied on water used to prepare cement paste to mitigate dissolution in saline zone[1,2,3]. The Friedel's salt formation in cement pastes containing NaCl is reported[1,4,12,13]. Rocha et al.[1] concluded that there was a formation of Friedel's salt in the paste with NaCl due to reaction of ion Cl- with aluminate phase in cement class G. The authors analyzed the hydrated phases by the mass loss on the thermogravimetry (TG) curves
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