Particle packing and rheology of cement pastes at different replacement levels of cement by α-Al2O3 submicron particles

• Published in: Construction & building materials 2017-05, Vol.139, p.256-266
• Main Authors: Štefančič, Mateja, Mladenovič, Ana, Bellotto, Maurizio, Jereb, Vesna, Završnik, Lina
• Format: Article
• Language: English
• Subjects: Cement paste; Particle packing; Rheology; Submicron particles; α-Al2O3
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2017.02.079

•Cement pastes containing α-Al2O3 submicron particles and a PCE superplasticizer.•Microstructure of the fresh pastes is controlled by the Specific Surface Area.•Widening particle size distribution has a minor role on packing and porosity.•Progressive initial hydration retardation on increasing α-Al2O3 particle content.•Slightly enhanced microstructure of hardened pastes at replacement levels of 2 and 4wt%. The aim of this study was to clarify the micro-scale processes which control the fresh and hardened properties of hydrating cement pastes containing up to 10wt% of α-Al2O3 submicron particles and a polycarboxylate-type superplasticizer. The main factor controlling the changes in the microstructure and properties of the fresh pastes with increasing α-Al2O3 cement replacement levels was found to be the increase in the total specific surface area, whereas particle packing played only a minor role. However, in the case of the hardened pastes much more complex and somewhat counteracting effects were observed. Depending on the cement replacement level of the pastes, the sum of these effects was either a hardly noticeable improvement in their mechanical properties, compared to those of the reference paste, or even a reduction in them. These differences decreased with increasing curing time.