Optimization of the SO3 content of an Algerian Portland cement: Study on the effect of various amounts of gypsum on cement properties
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Date
2017-12-18
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Université de M'sila
Abstract
Portland cement CEM I is obtained from (95–97%) of clinker and (3–5%) of gypsum, according to EN 197-1
(2011) standard. Sulfur trioxide SO3 is the main component of gypsum (Calcium Sulfate Dihydrate
CaSO4 2H2O), it may also originate from clinker, the previous standard has limited its content in cement
at 4%. It is known that the gypsum acts as a cement setting regulator, however, an appropriate gypsum
quantity (optimum) may improve other properties such as: mechanical response, dimensional variations
and hydration process. This optimum gypsum content is related to several parameters, namely: SO3 %,
cement SSB (specific surface Blaine), C3A % and alkali %. The aim of this work is to find, through an experimental
protocol, the optimum gypsum content of an Algerian Portland cement CEM I. 10 variants containing
various % of gypsum were formulated, where properties of anhydrous cements, cement pastes
and normalized cement mortars were studied. Results show that when gypsum is added below or above
the optimum, water demand for normal consistency, setting times, compressive strength, heat of hydration,
swelling, drying shrinkage and hydration degree were adversely affected. It has been experimentally
demonstrated that this optimum gypsum content is 5.5% by weight.
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Keywords
Cement, Gypsum content, SO3 , Optimum, Hydration