Mechanical and Civil Engineering Seminar

Over its lifetime, cement-based materials transition from behaving as a near-Newtonian fluid to a viscoelastic fluid/solid to eventually a rock-like solid. And although the first two phases are fleeting compared to the third phase, this earlier life period is intimately tied to materials processing. Therefore, the corresponding properties are critical in determining the efficiency of the placement process during construction, as well as the eventual performance of the structure in place. This requires that the rheological properties of the material be well characterized and controlled. During placement, the material undergoes a wide range of deformations – very large during processes such as pouring and pumping, but then diminishingly small after placement when it is essentially at rest. Thus, rheological protocols should be designed to simulate these conditions. This talk will cover studies that investigate the specific rheological aspect of thixotropy in cement paste and mortar systems that incorporate highly-purified attapulgite clay through static shear and dynamic rheological protocols that span wide timescales and magnitudes of deformations and rates.