Influence of supplementary cementitious materials on factors controlling the fresh state of hydraulic binders

Abstract

It is obvious that SCMs (supplementary cementitious materials) have diverse effects on the physical and chemical properties that can contribute in the development of the mechanical performance of cementitious materials. Moreover, the key factor to better use SCMs in blended cements is to control their fresh state properties. However, limited literature is available on the influence of SCMs on the rheological behavior of fresh pastes. In light of the increasing interest concerning the fresh state properties of hydraulic binders based SCMs, this contribution reports the rheological behavior of various hydraulic binders based GGBS (ground granulated blast-furnace slag), FA (fly ash), limestone or calcined clays, and explore the factors influencing the particle interactions during the structural build-up/breakdown process when stress is applied to the system.Yield stress and elastic modulus are considered to be the main indicators to quantify the structural changes of sheared fresh pastes. By introducing functionalized (–COO-) nanocellulose fibrils, the ability of water retention due to the hydrophilic character has reduced the mixing water in the fresh GGBS paste leading to the increase in the yield stress and viscosity. The use of limestone has increased the yield stress and elastic modulus of the cement paste. The angular shape of limestone particles and the filler effect can increase the friction and compact the cement suspensions leading to the loss of workability. However, the combination of limestone and FA can promote the fluidity of the paste due to the spherical shape of FA particles. On the other hand, when it is combined with calcined clays, limestone has a dilution effect leading to the reduction of the yield stress and elastic modulus of calcined clays blended cement at an early age while, the chemical equilibrium of limestone and calcined clays can provide strong structure network of the system and an increase in the yield stress and elastic modulus of the paste with time. However, calcined clays can reduce the mixing water in the slurry that can prevent the workability for extended durations.