• Grout rheological properties for preplaced aggregate concrete production

      Ganaw, Abdelhamed I.; Hughes, David C.; Ashour, Ashraf F. (2014-12)
      This paper investigates the effect of cement based grout rheology on the injection process through coarse aggregate for producing preplaced aggregate concrete. Four different sands were used in the grout production at different water-cement ratios and cement-sand ratios. Superplasticiers and pulverised fuel ash were also employed in the grout production. Coarse aggregate of known weight was compacted into 150 mm cubic forms, and then the grout was injected through a plastic pipe under self weight into the stone ‘skeleton’. It has been found that there are threshold values of the rheological parameters beyond which full injection is not possible. In particular, all grout mixes with and without additives and admixtures exhibited the same yield stress threshold value for full injection, whereas the threshold values for other rheological properties including the grout plastic viscosity, flow time and speed were different according to the materials added to the mix.
    • Rheological properties of mortars prepared with different sands

      Ganaw, Abdelhamed I.; Ashour, Ashraf F. (2014-09)
      The principal aim of this paper is to investigate the effect of sand grading, surface morphology, and content on the rheological properties—that is, yield stress and plastic viscosity—of fresh mortar. Mortars were produced from four different types of sand at two volumetric cement-sand ratios of 1/0.9 and 1/0.6. Each blend was prepared with five water-cement ratios of 0.60, 0.55, 0.50, 0.45, and 0.40. The rheometer was used to determine yield stress and plastic viscosity parameters of each cement paste and mortar. Test results show that the relative yield stress and plastic viscosity of mortar to cement paste is inversely proportional to the excess paste thickness up to low values, below which the surface texture of sand particles becomes significant.