Stabilization and Recycling of Sand in Pedestrian Walkways

Abstract: The production of construction and demolition waste (CDW) in urban areas is growing
rapidly. While the storage and disposal of CDW waste is costly, its recovery can help to conserve
natural resources. This study investigates the characteristics of recycled sand obtained from the
processing of CDW waste and the possibility of its reuse for pedestrian pathways. Physico-chemical
and mineralogical characteristics of the recycled sand were investigated for its reuse. The percentage
of fine particles in sand (below 0.63 μm) is 2.8%. The grain size of sand fulfills the particle size
requirement of French standards. The methylene blue value of sand is 0.05 g/100 g. The GTR
classification of recycled sand is D2 which is insensitive to water and suitable for road applications.
A mineralogical analysis of soil shows that quartz, albite and microcline are important minerals
in recycled sand. XRF analysis shows that CaO and SiO2 are major oxides in the recycled sand.
The characterization of sand was followed by a manufacturing of cylindrical specimens of sand to
observe the compressive strength. Samples were compacted with dynamic compaction by applying
the Proctor normal energy of 600 kN·m/m3. The compressive strength testing of specimens shows
that non-stabilized sand samples have compressive strength around 0.1 MPa which is considerably
lower for its reuse in pedestrian pathways and road applications. Due to the low bearing capacity
of sand, recycled sand was stabilized with the addition of binders such as Rolac (hydraulic binder),
ground-granulated blast furnace slag (GGBS) and ECOSOIL® (slag mixes) with different percentages
of the binder ranging from 0 to 7% for the optimization of the binder and for economic efficiency.
The compressive strength of sand samples increases with the increasing percentage of the binder.
The increase in strength is more important with a higher percentage of binders (5%, 6% and 7%). At
a 7% binder addition, specimens with Rolac, GGBS and ECOSOIL binders show the compressive
strength of 1.2 MPa, 0.5 MPa and 0.5 MPa. At a 7% Rolac addition, specimens have a compressive
strength higher than 1 MPa and meet the strength requirement for soil reuse in the foundation and
subbase layers of roads with low traffic. The experimental work shows that recycled sand can replace
conventional quarry sand for road applications and pathways with the addition of a local binder,
which is an eco-friendly and economical practice.