Monitoring the gain on consistency over time of cementitious suspensions mixed with vermiculite residue

Reference	Presenter	Authors (Institution)	Abstract
04-039	Marcel Hark Maciel	Rojas-Ramírez, R.A.(University of São Paulo); Maciel, M.H.(University of São Paulo); Romano, R.C.(University of São Paulo); Pileggi, R.G.(University of São Paulo); Vieira-Coelho, A.C.(University of São Paulo);	The consolidation of cementitious suspensions has direct relationship with the chemical reaction. However, that phenomenon is directly affected when it is used mineral additions with different physical characteristics than the cement. Materials with finer particle size distribution and higher specific surface area (SSA) can to cause effects of distinct natures: (i) chemical, due to the highest available surface to accentuate the hydrated products formation; (ii) physical, due to the intensification of agglomeration forces. One way for monitoring the consolidation process is through the evolution of gain on consistency, estimated by the evolution of yield stress over time, using an oscillatory rheometry test named strain sweep. In that test, the sample is submitted to changes on the strain, to obtain its critical deformation from which it is calculated the corresponding yield stress. This work was aimed to evaluate the influence of the addition of fine vermiculite residue on the consolidation process of cementitious suspensions by the monitoring of the yield stress during early age. The results indicate that the vermiculite addition strongly increases the yield stress in the first hours of hydration. It was clear that just evaluating the changes on the chemical reaction it is not possible to explain the quick hardening. That phenomenon is easier to understood when it is considered the higher initial SSA of the suspensions with vermiculite, that intensified the approximation between the particles in the beginning of chemical reaction. Then, to the same reactivity and hydrates formation, the approximation of particles generates intensification of surface forces between then, increasing the kinetics consolidation of the suspension.
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