Influence of temperature on rheological properties of self-compacting mortars and concretes in rest state

The rheological properties of fresh mortars and self-compacting concretes (SCC) at rest – the static yield value gs and the thixotropy factor A_T – at temperatures from 10 to 30^◦C were investigated. The static yield value g_s and the thixotropy factor A_T of SCC depends on the temperature and the w/c ratio. Immediately after casting, the static yield value g_s of the SCC is the higher the higher the temperature and/or w/c ratio are. Thixotropy factor A_T of fresh SCC depends mainly on w/c ratio – the higher w/c ratio the lower A_T is. The increase in temperature of SCC reduces thixotropy factor A_T, but the effect is insignificant. During the 40 minutes that the SCC remain at rest, the static yield value g_s increases and this increase is faster for mixes with a higher w/c ratio. Thixotropy factor A_T of SCC left in rest first increases over time, but then, after just 20 to 40 minutes, begins to decrease. Temperature does not affect static yield value g_s and thixotropy factor A_T changes in time. The nature of the effect of temperature on the rheological properties of mortars and SCC is analogous. It was proven that model mortars can be used to predict the effect of temperature on the rheological properties of SCC both in the flow phase and at rest and to predict changes in these parameters over time. The implications of the temperature effect on the rheological properties of SCC in terms of formwork pressure were also discussed.