Abstract
The substitution of the normalized aggregate by residual foundry sand (WFS) was studied on the physical properties of mortars by means of resistance to compression and capillary absorption tests. The aggregate was replaced by WFS in its natural state (WFS), washed residual foundry sand (WFSW) and heat treated residual foundry sand (WFST). The WFS had a percentage of bentonite, which was sought to be thermally activated. It was found that the physical behavior of the mortars containing WFS and WFSW was similar to that of the control sample. The clay recovered from the sand washing was evaluated for its pozzolanic potential, it was found that, with the thermal treatment, the montmorillonite acquires pozzolanic behavior. Mortars with WFST presented a drop in compressive strength. The pozzolanic effect achieved in the clay was not reflected in the compressive strength of the mortars with WFST.
Highlights
RESUMEN: Sustitución de áridos por arena de fundición residual: efectos sobre las propiedades físicas de morteros
The behavior of Waste Foundry Sand (WFS) and WFSW as aggregate in mortars is to fill voids causing less porosity due to physical effect, which allows them to achieve similar and even higher values of compressive strength with respect to the control sample, up to a maximum of 20% replacement
The compressive strength values found for all the samples are attributed to the coefficients obtained in the capillary suction test since, with the lower porosity and lower absorption speed, the mortar presented a greater mechanical resistance and that happens with WSF (15% and 20%) and WFSW (15 and 20%), while for WFST the coefficients yielded higher values explaining the drop in the compressive strength of these mixtures
Summary
For the preparation of mortars, local cement, Ottawa standard sand according to ASTM C-778 and residual foundry sand were used as a partial substitute for standardized sand. While for the pastes, the cement was replaced by 15%, 20% and 25% raw clay or heat-treated clay. The water / material-cementing ratio was 0.5 for all samples. The proportions of materials used for the preparation of mortars and pastes are presented in Tables 3 and 4 respectively. Aggregate water/cementitious-materials ratio (w/c) Aggregate replacement percentage. Local (Grade: 42.5 MPa) Ottawa Sand (Mortar Control) Waste Foundry Sand (WFS) Washed Waste Foundry Sand (WFSW) Heat treated Waste Foundry Sand (WFST). Three types of mortar were made with WFS, washed WFS (WFSW) and heat-treated or calcined WFS (WFST) with substitutions of 15%, 20% and 25%.
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