Early age monitoring and hardened properties of SCC with limestone filler and active mineral additions

摘要

An experimental program on SCC with limestone filler and three active mineral additions (AMA), microsilica (MS),udnanosilica (NS) and Metakaolin (MC), was carried out to evaluate their influence during early ages and in theudhardened state. The aim was to characterize SCC further than the usual workability and mechanical parameters, inudthe understanding that the main microstructural changes in the material occur during the first hours and that earlyudage cracking, porosity, pore size and permeability can compromise SCC durability.udIn-situ temperature, ultrasonic pulse velocity, mass loss and free drying shrinkage of samples subjected to a windudflow were simultaneously monitored for 24 hours. Profiles of the reaction process, the microstructural evolution andudthe physical effects of water evaporation were obtained. The early age measured parameters were related to audreaction index (Ir,24), defined as the fraction of heat produced (accumulated plus released) with regard to the totaludheat at 24 hours. The simultaneous monitoring of those parameters allowed a better understanding of theudmechanisms involved during early ages. These parameters were compared to the early age cracking due to dryingudshrinkage.udIn the hardened state, a mechanical characterization was conducted and porosity and vapor permeability wereudmeasured on paste samples (without aggregates) under two environmental conditions during setting process:udsubjected to 3 m/s air flow and covered with a plastic film. The use of AMA increased mechanical strength.udAlthough, the early age cracking risks also increased, especially in the case of AMA with smaller particle size (NSudand MC). The external conditions applying on the samples during early ages also modify porosity, pore size andudpermeability of the hardened SCC.