"Effetto di un nuovo accelerante (Me-S-H) sulla microstruttura e sulle cinetiche di idratazione del silicato tricalcico del cemento Portland: studio numerico e sperimentale"

Abstract

Nowadays, the details of the kinetics of cement hydration and microstructural development, as well as the influence of various additives on such processes, are still under investigation. In this thesis, the effects of the newly developed copper/calcium silicate hydrate accelerating admixture Mapefast Ultra (hereafter Me-S-H, standing for metal-silicate hydrate) on the permeability and mechanical properties of concrete are investigated. In this study, different tricalcium silicate and mortar specimens, with and without Me-S-H, are analysed at different times of hydration by means of numerical and experimental techniques. X-ray powder diffraction (XRPD) and HydratiCA, a new computer model of reaction-diffusion processes on cementitious systems, have provided a qualitative and quantitative analysis and monitoring of kinetics of C3S hydration; X-ray computed micro-tomography (X-μCT) and scanning electron microscopy (SEM) have allowed the monitoring of the microstructure development of cement pastes during hydration and the detailed examination of the interfacial transition zones, respectively. The data show that the new accelerating admixture promotes a faster hydration and nucleation and growth of C-S-H in the pore solution, inducing a decrease of the capillary porosity and permeability due to the increase of the geometrical tortuosity and fraction of disconnected pores.