Extrudability of cement-based materials

The extrudability of cementitious materials with the use of penetration resistance (PR) test is investigated. The extrusion of cementitious pastes requires controlling the rheology to obtain good-quality products. PR is used to measure the setting time of concrete in the ASTM Standard C 403 and PR has been related to the rheological parameters of a cementitious paste. A Type I Portland cement was used and methyl hydroxyethyl cellulose was used to produce extrudable pastes. The test was performed at room temperature and was consolidated into a rectangular container. A series of needles was used to penetrate the paste and a smaller needle was used as the PR increased. The vertical force was applied and the force was recorded at each penetration against hydration time. It was observed that the upper limit for PR corresponding to current extrusion setup was above 2000 kPa and the paste was to dry to be extruded. After mixing with water paste was extrudable and in the range of 10-2000 kPa.