Properties of Mortar andConcrete Using Red Mud and Finely Ground Silica


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Title: Properties of Mortar andConcrete Using Red Mud and Finely Ground Silica

Author(s): K. Kohono

Publication: Special Publication

Volume: 153


Appears on pages(s): 1103-1120

Keywords: air entrainment; chlorides; concretes; drying shrinkage; fineness; mortars (material); silica; steam curing; strength; sulfate resistance; Materials Research

Date: 6/1/1995

The properties of mortar and concrete using the mineral admixture consisting of red mud and finely ground silica were investigated in order to use effectively an industrial byproduct from a chemical factory. This paper reports on the effects of five mixing ratios of red mud to finely ground silica on flow value and air content of fresh mortar, compressive strength, resistance to chloride penetration, and sulfate resistance of hardened mortar compared with those of plain mortar. Secondly, the compressive strength and the drying shrinkage of concrete specimens cured at 20 C in water and a steam chamber at the maximum temperature of 65 C were investigated on the concrete using the admixture consisting of five percent red mud and five percent finely ground silica and 10 percent finely ground silica only. The substitution was 10 percent of cement. The flow value of mortars tends to decrease with an increasing rate of red mud content, when the substitution of the mineral admixture for cement is 50 percent. The air content of fresh mortar becomes maximum when the mixing ratio of red mud and finely ground silica is equal. The compressive strengths of mortars containing red mud are lower than that of plain mortar at each age. The mortars containing finely ground silica exhibit higher strength from seven to 28 days. The resistance to chloride penetration and the sulfate resistance of the mortars are clearly improved by the use of this mineral admixture. The compressive strength of concrete at each age using red mud as a single admixture increases slightly when compared to concrete using the admixture consisting of red mud and finely ground silica. The drying shrinkage of the concrete using this admixture is higher than that of plain concrete, and the shrinkage is slightly reduced by the adoption of steam curing.