Influence of Temperature on the Effect of Plastification in Concrete Mixtures / Temperaturos Poveikis Betono Mišinio Plastifikavimo Efekto Trukmei

Demand for plasticisers used in concrete industry is growing in Lithuania and other countries. The paper examines a plasticising admixture based on carboxylate and the influence of temperature on the properties of concrete mixtures. Two types of Portland cement – limestone CEM II/A – LL 42.5R and slag CEM II/A – S 42.5N – have been investigated. To determine the effect of plasticising admixtures on the rheological properties of a concrete mixture, the slump, spread and density of the mixture, along with the depth of cone penetration, were examined. Then, with reference to the obtained data, yield stress was calculated. The research results illustrate the effects specific to certain combinations of plasticising admixtures with different types of cement. A plasticised concrete mixture with limestone Portland cement retains its slump better and remains almost unchanged for 90 min. The slump of the plasticised concrete mixture with slug Portland cement, however, is decreasing gradually for the full period of two hours, from the moment the mixture is ready. At higher temperatures, plastification effect manifests itself in a less intensive manner. Concrete mixtures with slug Portland cement have a higher slump, spread and the depth of cone penetration. A 5 °C increase in temperature (from +15 °C to +20 °C) makes the slump decrease by 32–33% both in concrete mixtures with limestone Portland cement and in concrete mixtures with slug Portland cement.