Effect of delaying addition time of SMF superplasticizer on the physico-mechanical properties and durability of cement pastes

This research aimed to investigate the influence of delaying addition time of laboratory prepared sulphonate melamine formaldehyde (SMF) superplasticizer on the physico-mechanical characteristics and durability of cement pastes subjected to elevated temperature up to 800 degrees C, or immersed in 4\% MgSO4 and 4\% MgCl2. The compressive strength increases with delayed addition time at 7.5 min up to 90 days. The cement pastes containing 1.0 mass\% SMF superplasticizer, with delayed addition time at 7.5 min, has highest compressive strength, bulk density and lower total porosity. The presence of SMF superplasticizer with delaying addition time process of mixing increases the compressive strength, bulk density and decreases the total porosity. These work together to produce a compact structure, inhibiting the chloride and sulphate ions penetration, hence the total sulphate and chloride contents decrease. (C) 2012 Elsevier Ltd. All rights reserved.