Microstructure characteristics in the cement paste containing micronized sand filler

In recent decades, the cement industry became aware, more and more, of the economic and environmental problems of concrete associated with the use of ordinary Portland cement (OPC). Attempts have been made to partially replace the cement by active or inert components, such as limestone filler, fly ash and finer sands. Whether the blend material is feasible and guarantees the long term properties in comparison with OPC is still an open research area. In this study, cement pastes with an without micronized sand have been investigated by means of mercury intrustion porosimetry (MIP) and electronic scanning electron microscope (ESEM). The proportion of replacement was 20% by weight. From the results, paste with micronized sand (CM6) can increase the rate of hydration compared with OPC paste when the water to binder ratio is kept constant (w/b = 0.4). When the water to cement ratio is kept constant w/c = 0.4), paste with micronized sand has lower porosity and finer pore structure compared with OPC paste. Seen from the interfacial transition area, big pores and mainly located around sand particles. Sand particles can give some contribution to compensate the increasing of porosity in CM6.