**9. Long-term strength characteristics of concrete made with used foundry sand**

Many research findings are available on the long-term strength characteristics of concrete made with used foundry sand. Siddique et al. [54] studied the long-term strength characteristics of concrete incorporating used foundry sand and reported that the compressive strength, split tensile strength, flexural strength, and modulus of elasticity were improved much at 365 days over the strength at the 28th day for the concrete incorporating used foundry sand. It is to be noted that no detrimental effects were noticed in the strength parameters on aging due to the incorporation of used foundry sand in the concrete mix. Generally, the long-term strength characteristics increase up to certain percentage content of the foundry sand, and the further increase of foundry sand content, the strength decreases. Siddique et al. [63] stated that at 365 days, the compressive strength of concrete increases with percentage replacement of 10, 20, and 30% fine aggregates with foundry sand and decreased for 40, 50, and 60% foundry sand content.

**25**

*A Review on the Usage of Recycled Sand in the Construction Industry*

**10. Leaching in concrete and mortars made with used foundry sand**

The used foundry sand is a nonhazardous material. However, the chemicals present in the used foundry sand can leach into the groundwater and may affect the groundwater quality. As per Siddique et al. [7], the liquid drains or leaches from a landfill are called leachate. The leachate test is essential to assess the suitability of the used foundry sand for certain applications. Very few research observations are available on the leachate analysis of the concrete/mortars made with used foundry sand. Monosi et al. [64] conducted dynamic leaching tests on mortar samples as per Italian standards. They reported that the mortars made from used foundry sand do not release leachate higher than the values specified by Italian standards, and the pH of the leachate was found to be alkaline during the entire testing period. Fero et al. [65] observed that the concentrations of organic compounds in groundwater leached from an iron foundry landfill were below their

In some cases, the used foundry sand may contain heavy metals. Navarro-Blasco et al. [45] reported that in mortars with used foundry sand, the used foundry sand appeared to be contaminated with heavy metals. In another research conducted by Kaur et al. [66] performed a metal analysis of the leachate obtained from concrete made with untreated and fungal treated waste foundry sand and indicated that waste foundry sand is the contributor of the concentration of leachable metals in concrete containing waste foundry sand. Results from the above research further showed that metal concentration in leachate obtained from fungal treated waste foundry sand incorporated concrete is less than the leachate of untreated waste

The foundry industries all over the world generate an enormous quantity of waste sand every year. Many investigations conducted on the reuse of waste foundry sand over the years suggested that the sand discarded from the foundry industries as waste material can be recycled and utilized for beneficial applications in road embankment formation, structural fill, pipe bedding, asphalt concrete, mortars, and different types of concretes. But horizons are still open for the researchers for further innovations in the application of used foundry sand mainly related to the needs in the construction industry where better strength and durability properties are of the paramount concern. In most of the research findings, it suggested that 10–30% fine aggregates can be replaced with used foundry sand for the manufacture of concrete and mortars with sufficient strength parameters with reduced cost. Some researchers estimated that the cost reduction is much significant if the waste foundry sand can be employed in making concrete or concrete products near the foundry industries itself. Due to fine particles present in the used foundry sand, the workability of used foundry sand admixed concrete is profoundly much less than the workability of regular concrete having the same water to binder ratio. However, the researchers suggested that this deficiency can be overcome by adding superplasticizers to the mix. Some researchers pointed out that by performing some inexpensive treatments to the used foundry sand, the strength parameters of used foundry sand incorporated concretes and mortars can be enhanced further. Most of the researchers are in the view that the used foundry sand is a nonhazardous material. However, some researchers suggested that it is better to conduct leachate analysis in advance to avoid the chances of corrosion of the reinforcement if the used foundry sand is proposed to be utilized in the production of concrete for RCC

*DOI: http://dx.doi.org/10.5772/intechopen.92790*

respective detection limits.

foundry sand concrete.

**11. Conclusion**
