Abstract:
The fresh and hardened concrete properties are affected by water-cement ratio and the extensive
way of water addition in the concrete is from aggregates. Aggregates contain some moisture
based on the porosity of the particles and the moisture condition of the storage area. Fine
aggregate can contain up to 10% of surface moisture content which causes significant variation
in the mixing water content. Therefore the main objective of the study was to study the influence
of river sand moisture content on fresh and hardened concrete properties.
In the research work, river sand quarried from Gambella and brought Jimma for selling was
preferred as it is the commonly used sand in Jimma. Before using the sand in concrete, the
physical property tests were conducted to identify as the sand meets the requirements of the
standards. The concrete was then mixed varying the moisture contents of the sand from 1% to
10% in steps of 1%. The properties of concrete including workability, unit weight, compressive
strength, and split tensile strength were conducted and compared with control and the standard
specifications.
The results of the Gambella river sand sample material properties test showed a meeting of
Ethiopian and ASTM standard specifications. The workability of the concrete showed reduction
as the moisture contents of the sand increased. However, the slumps of sand up to 3% moisture
contents resulted within 25-50mm. The unit weight of the concrete showed a slight reduction as
the sand moisture content increased. But, all the densities of the concrete mix exceeded the
1850kg/m3 which is the maximum density required for lightweight aggregate concrete.
Compressive and tensile strengths decreased as the moisture contents of river sand moisture
content increased. However, the influence of the moisture contents of river sand was not
significant on tensile strength compared to the compressive strength. Meanwhile, the river sand
having moisture content up of 9%, 6% and 4% satisfied ACI 209 criteria at 7th, 14th and 28th
curing days respectively. Therefore, the moisture contents of the river sand should be considered
during mixing the concrete on site and kept constant
