Using Cement By-Pass Dust and Fine Dune Sands in Semi-Flexible Pavement Applications

In many countries around the world, grout is used to produce semi-flexible
pavement mixtures. Grout is formed by mixing cement with water. Additives such
as fine silica sand, silica fume, fly ash, and plasticizer are used in grout production
to improve the workability and mechanical properties of the grout. In Egypt, fine
dune sands and cement by-pass dust are abundantly available. This study aims at
evaluating the suitability of using fine dune sands and cement by-pass dust to
replace Portland cement in producing grout mixes suitable for semi-flexible
pavement applications. To achieve the study objective, three groups of grout mixes
were investigated; The first group is control mix using ordinary Portland cement
only. The second group composed of ordinary Portland cement with fine sand. The
last group composed of ordinary Portland cement with cement by-pass dust. The
percentage of water needed for mixing was determined using Marsh funnel.
Volumetric properties of grout mixes were then determined. Unconfined
compressive strength and indirect tensile strength tests were conducted on samples
casted from these mixes at 7 and 28 days of curing to define their mechanical
properties. It was found that Replacing 25% of the cement with fine sand dune
achieved good viscosity and high compressive and tensile strength, and offered
cost savings compared to the control mix. While using of cement by-pass dust
resulted in reducing the strength of grout mixes.