Matches in UGent Biblio for { ?s ?p Cement-superplasticizer compatibility has become a major area of interest due to the increasing use of high performance and self-compacting concrete mixtures. The interaction between superplasticizer and cement can cause significant retardation effects on the hydration and setting properties of cement. However, not much data have been published to quantify this. In this study, mortar mixtures with three cement types and two different superplasticizers were tested by calorimetric and ultrasonic measurements to investigate the effects on both hydration and setting. Also the strength of the mortar samples was tested. The types of superplasticizers used, were polycondensates of naphtalene sulphonate (PNS) and polycarboxylic ethers (PCE). Based on the ultrasonic measurements, the addition of PCE and PNS caused an initial setting retardation of approximately 1.2 and 3.4 h on the portland cement, 1.9 and 4.8 h on the portland-fly ash cement and 0.5 and 1.6 h on the blast-furnace cement mixtures. This difference decreased after 16 to 20 h when the stiffness development of the samples with PNS or PCE approached the mixtures without superplasticizers. Similar to the setting, the release of the heat of hydration was more postponed by the addition of PNS than by PCE. Contrary to PNS, PCE benefited the strength of the mortar mixtures. Generally, the effect of the superplasticizers clearly differed according to the cement type in the mixture.. }
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- aggregation abstract "Cement-superplasticizer compatibility has become a major area of interest due to the increasing use of high performance and self-compacting concrete mixtures. The interaction between superplasticizer and cement can cause significant retardation effects on the hydration and setting properties of cement. However, not much data have been published to quantify this. In this study, mortar mixtures with three cement types and two different superplasticizers were tested by calorimetric and ultrasonic measurements to investigate the effects on both hydration and setting. Also the strength of the mortar samples was tested. The types of superplasticizers used, were polycondensates of naphtalene sulphonate (PNS) and polycarboxylic ethers (PCE). Based on the ultrasonic measurements, the addition of PCE and PNS caused an initial setting retardation of approximately 1.2 and 3.4 h on the portland cement, 1.9 and 4.8 h on the portland-fly ash cement and 0.5 and 1.6 h on the blast-furnace cement mixtures. This difference decreased after 16 to 20 h when the stiffness development of the samples with PNS or PCE approached the mixtures without superplasticizers. Similar to the setting, the release of the heat of hydration was more postponed by the addition of PNS than by PCE. Contrary to PNS, PCE benefited the strength of the mortar mixtures. Generally, the effect of the superplasticizers clearly differed according to the cement type in the mixture.".