Organic compounds as modifiers in Portland cement hydration

Abstract

The object of the present investigation are to study the effect of organic admixtures on the improvement of the physico-chemical and mechanical characteristics of the hardened cement pastes, when hydrated for various time intervals and their reflection on the mechanical properties of concrete construction. Admixtures for concrete are defined as materials other than cement, water, or aggregates that are added immediately before or during mixing. These admixtures have a distinct ability not only to give much workability to concrete but also to effect larger water reductions than is possible with nonnal plasticizing admixtures. The dispersing action, caused by addition of admixtures, increases the workability but with an extremely high strength owing to the marked reduction in the water/cement ratio of the concrete. In this investigation, five organic additives were prepared these are: polystyrene-maleic anhydride- polyethylene glycol condensate, PS-MA• PEG, polystyrene-succinic anhydride- polyethylene glycol condensate, PS• SA-PEG, , abietic acid- polyethylene glycol condensate ,AA-PEG, dodecyl benzene sodium sulfate , DBSS and alkyl diglycol ether sulfate, ADES.Various Portland cement pastes were made with and without additives using water/cement ratios of 0.20 and 0.25 and the admixture contents of 0.25, 0.5, and 1.0% by weight of the cement. Both of the neat cement and admixed cement pastes were hydrated for various time intervals of 0.02, 0.08, 0.25, 1, 3, 7, 28 and 90 days. At the end of any hydration time, several physicochemical studies were carried out on each cement paste.