Understanding the role of rheology in the plastic settlement and shrinkage cracking of early age concrete

Abstract

Understanding the plastic (settlement/shrinkage) cracking phenomena of early-age concrete is important in-order to establish a holistic approach to minimise its occurrence. One of the factors associated with early-age concrete is the rheo-related behaviour which occur simultaneously within the timeframe known for plastic cracking. It is therefore useful to establish their links to broaden the knowledge of plastic cracking. This study is a novel evaluation of the influence of rheo-physical and rheo-viscoelastic behaviour on the plastic cracking behaviour by systematically altering these behaviours of formulated concrete mixes and extensively characterising them. The theory and frameworks for linking the behaviours were presented and established via statistical and analytical approaches. Significant rheo-related parameters found to influence plastic cracking phenomena include yield stress, structuration, creep and stress relaxation. The rheo-mechanics modelling suggests that the plastic cracking initiation tends to be a ductile failure that is pressure insensitive and sufficiently represented by von Mises criteria. This study opens up a consciousness to start evaluating mitigation strategies directed towards the materials optimisation of concrete mixtures to minimise the occurrence of plastic cracking in early-age concrete.

Prediction of Plastic Shrinkage Cracking of Supplementary Cementitious Material-Modified Shotcrete Using Rheological and Mechanical Indicators

“…However, coupled with the multiple regression Model IV, it is demonstrated that an inverse relationship exists between yield stress and plastic cracking. It may be that, as Kalovole highlighted, high-yield stress causes the capillary pressure and shrinkage to increase, and therefore, for a mixture with fly ash, a high G value is a factor of a decrease in cracking resistance [39]. This argument is consistent with the study [60], which states that the addition of small particle-size fillers increases capillary pressure.…”

“…In addition, an increase in the early tensile strength of the SF mixture at high capillary pressure was asserted [59]. Therefore, it is possible to conclude, according to Kalovole [39], that the high-yield stress of silica fume mixtures increases the capillary pressure, and hence, the risk of plastic cracking is increased by the high flow resistance. However, the acceleration of the hydration effect by silica fume [63,64] and the addition of a water reducer stopped the plastic cracking development.…”

“…Furthermore, nano-silica particles have been found to reduce the fluidity of mixtures. Kolawole pointed out a correlation between the yield stress and thixotropy index with the occurrence of plastic shrinkage and capillary pressure development in his study [39]. Thus, based on the brief review above, a relationship between the characteristics of plastic cracking and rheological parameters can be concluded.…”