**11. Conclusion**

*Sandy Materials in Civil Engineering - Usage and Management*

**8. Ultrasonic pulse velocity (UPV) tests on used foundry sand concrete**

The ultrasonic pulse velocity (UPV) test is one of the nondestructive tests (NDTs) to check the quality of the concrete. In this test, the quality and strength of concrete are evaluated by noting down the velocity of an ultrasonic pulse passing through a concrete body. A very few research results are only published on the UPV tests on concrete containing waste foundry sand. Khatib et al. [26] reported that the concrete specimens cured for 28 days showed a consistent decrease in ultrasonic pulse velocity values when the fine aggregates in the concrete mix were replaced with foundry sand in the range of 0, 20, 40, 60, 80, and 100%. The same trend was observed for the specimens cured for 56 days also. Prabhu et al. [15] also stated that the increasing amount of waste foundry sand in the concrete systematically decreases the ultrasonic pulse velocity of concrete made with natural sand replaced

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

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

with 0, 30, 60, and 100% of waste foundry sand.

for 40, 50, and 60% foundry sand content.

**foundry sand**

**Figure 12.**

*Carbonation depth vs. % used foundry sand.*

**24**

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

structures. From the analysis of the research works done so far, it can be established that the use of waste foundry sand in the construction industry can not only eliminate the problems of waste management and environmental impacts but also substantially boost up the sustainable developmental activities by way of reducing the consumption of natural resources. However, the feasibility of employing used foundry sand in civil engineering applications in the construction industry will invariably depend on the local cost and the availability of the used foundry sand in the required quantities where the construction work is to be executed. Amidst many research findings and suggestions, the beneficial use of used foundry sand in civil engineering applications is only a bare minimum at present. A collective effort from the researcher community, academicians, and industrialists is highly needed for the full utilization of the recycled used foundry sand from the industrial wastes in the construction industry soon.
