Superfine Mineral Powder And Polymer Modified Cement-based High-performance Materials

In this thesis, The hydration products of hardened cement pastes containing polymer and ultra-fine powder, and of C3S> C3A pastes with carbonates, were identified by XRD. Effects of ultra-fine powder on microstructure of hardened cement pastes(HCP), and on interfacial transition zone(ITZ) between aggregate and cement pastes were studied by XRD and SEM. And the compressive strength of hardened cement pastes(HCP) was also tested.The results indicate that both silica fume and nano-Si02 were amorphous substances, the pozzolanic activity of nano-SiO2 was very greater than that of silica fume. Silica fume itself could act as "crystal nucleus" during Ca(OH)2 crystallizing while nano-SiO, couldn't did so. Silica fume diminished crystal orientation and average particle size of Ca(OH)2 as a result of it's "crystal nucleus" and pozzolanic reaction with Ca(OH)2, but nano-SiO2 just have pozzolanic reaction with Ca(OH)2 to decrease crystal orientation and average particle size of Ca(OH)2. Both silica fume and nano-SiO2 can fill in interspace of the particles of cement. But nano-SiO2 can more effectively uptake Ca(OH)2 and diminish crystal orientation and average particle size of Ca(OH)2 during forepart hydration of cement, and improved the interfacial transition zone(ITZ) between aggregate and cement, the microstructure of hardened cement pastes(HCP) , as well as compressive strength of hardened cement pastes(HCP). PVA retard the hydration at all ages, and SAE just prevent cement hydration at early age. Both PVA and SAE impair influence of silica fume and nano-SiO2 on crystallization of Ca(OH)2. At age of 28d, Ca(OH), on the interfacial transition zone(ITZ) between aggregate and cement which contains SAE and mineral powder, converts to calcite-like carbonates.Results also show that with nano-CaCO3 added to C3S , the average grain size of Ca(OH)2 increase. As for C3S paste with limestone, crystal orientation of Ca(OH)2 is very strong while the average grain size of Ca(OH)2 increase. The hydration products of C3A pastes containing 52.6% or 27% nano-CaCO3 is just monocarboaluminate.