**6.3 Flexural strength**

*Sandy Materials in Civil Engineering - Usage and Management*

silica content present in the used foundry sand.

Torres et al. [33] is shown in **Figure 6**.

**6.2 Split tensile strength**

regular concrete.

used foundry sand as 24.8 and 26.5 MPa, respectively, and for 25% used foundry sand, the compressive strength was below the compressive strength of control mix. In the majority of the research findings, the concrete containing used foundry sand has higher compressive strength than conventional concrete. As per Siddique et al. [54], the increase in compressive strength of the concrete made with used foundry sand may be due to the higher fineness of the used foundry sand than the regular sand, which resulted in the formulation of a denser concrete matrix along with the

In some cases, the compressive strength of used foundry sand incorporated concrete is more or less the same as that of the control mix up to a certain percentage of used foundry sand content, and after that, the compressive strength decreases significantly. Prabhu et al. [53] stated that the concrete mix containing foundry sand up to 20% replacement of fine aggregate with foundry sand, the compressive strength observed was moderately close to the strength of the control mix, but beyond 20% replacement, the concrete mix showed lower strength than control mix. Some researchers pointed out specific reasons for the reduction of compressive strength of concrete made with used foundry sand beyond certain replacement levels of fine aggregate with used foundry sand. Singh and Siddique [31, 56] and Siddique et al. [57] pointed out that the compressive strength of concrete containing used foundry sand above a particular percentage gets reduced probably due to the increase in surface area of fine particles, which lead to the reduction of water-cement gel in the concrete matrix, and hence, the binding process of the coarse and fine aggregates does not take place properly. The graph of the compressive strength of ultra-high-strength concrete made with natural sand replaced by foundry sand at 0, 10, 20, and 30% at 7, 14, and 28 days as reported by

Depending on the source of used foundry sand, the concrete incorporating used foundry sand shows inferior or at par or superior split tensile strengths than the

In some cases, the split tensile strength of concrete made with used foundry sand

increases with the percentage increase in used foundry sand in the concrete mix up to a certain level and decreases afterward. Sohail et al. [30] described that up to 40% replacement of river sand with waste foundry sand from a gray iron foundry, the split tensile strength of concrete at 28th day increases, and further, it reduces consistently up to 100% replacement. Patil et al. [58] confirmed that the split

**18**

**Figure 6.**

*Compressive strength vs. % foundry sand.*

The flexural strength of the concrete containing used foundry sand shows marginal variations with the addition of used foundry sand. The flexural strength of concrete incorporating used foundry sand usually increases marginally to that of normal concrete. In the research on the properties of concrete with used foundry

**Figure 7.** *Split tensile strength vs. % waste foundry sand.*

sand, Siddique et al. [54] observed that the flexural strength of 28.5 MPa characteristic compressive strength concrete consecutively increased with the percentage increase of used foundry sand up to 30% replacement level in which the flexural strength of control mix was 3.41 MPa and the flexural strength at 30% replacement was 4.18 MPa.

In some cases, the flexure strength seems to decrease with the increase in percentage addition of used foundry sand. Seshadri and Salim [12] reported that the high-performance concrete having 60 MPa characteristics compressive strength showed a decrease in flexure strength on the increase in replacement of fine aggregate with used foundry sand, in which the control mix has a flexural strength of 10.05 MPa, and at 40% used foundry sand content, the flexural strength decreased to 7.05 MPa. As per Torres et al. [33], at 10% replacement of fine aggregate with foundry sand, the ultra-high-strength concrete showed an increase in flexure strength, and further, it showed a consecutive decrement in flexure strength for 20 and 30% replacement of fine aggregates with foundry sand. Prabhu et al. [53] observed that the flexural strength of concrete with foundry sand content up to 20% of fine aggregates has similar results as that of the control mix; further, the flexural strength decreases after 20% replacement level. The flexural strength variation of concrete having 36.5 and 46 MPa compressive strength at 28 days made with regular sand replaced at 0, 10, 30, 50, 70, and 100% to chemically bonded foundry sand with water to cement ratio 0.55 and 0.45 as reported by Mavroulidou and Lawrence [41] is shown in **Figure 8**.

### **6.4 Modulus of elasticity**

Generally, the modulus elasticity of concrete containing used foundry sand increases up to certain percentage content of used foundry sand and then tends to decrease with further increase in the used foundry sand content. Manoharan et al. [28] observed that the modulus of elasticity of concrete increased with percentage replacement of natural river sand with used foundry sand from 0 to 20%, and further addition of used foundry sand decreased the modulus of elasticity, the modulus of elasticity of control concrete was 23.60 GPa, whereas at 20% replacement of river sand with used foundry sand, the elastic modulus increased to 25.40 GPa. As per the research findings of Prabhu et al. [53], the replacement of fine aggregate

**21**

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

with used foundry sand slightly improved the modulus of elasticity of concrete mix. Some researchers observed marginal reduction of modulus of elasticity by the addition of used foundry sand. Basar and Aksoy [34] stated that the waste foundry sand content in the ready-mixed concrete reduces the modulus of elasticity. The variation of modulus of elasticity of ultra-high-strength concrete made with foundry sand at 7, 14, and 28 days for foundry sand percentages of 0, 10, 20, and 30% as reported in

**7. Absorption and permeability characteristics of concrete made with** 

The absorption and permeability characteristics of concrete include water absorption, rapid chloride permeability, sorptivity, and carbonation. The absorption and permeability characteristics of concrete incorporating used foundry sand

The concrete made with used foundry sand is generally more permeable than the normal concrete. However, some researchers reported that the inclusion of used foundry sand has no impact on the water absorption of the concrete. The water absorption is somewhat related to the compressive strength also. As per Basar and Aksoy [34], the concrete having higher water absorption has lower strengths. The water absorption of the hardened concrete has a significant effect on the durability characteristics of concrete. Khatib et al. [26] reported that water absorption of the concrete mix containing used foundry sand, the control mix showed the least and increased for 20, 40, 60, 80, and 100% replacement of fine aggregates with foundry sand. It is further confirmed that the water absorption of 56 days cured concrete samples also followed the same trend. Ready-mixed concrete with used foundry sand also showed similar behavior on water absorption. Basar and Aksoy [34] stated that the water absorption of ready-mixed concrete containing waste foundry sand increased with the increase in percentage replacement of fine aggregate with waste foundry sand. Some researchers observed a marginal decrease in water absorption of the concrete containing used foundry sand over the normal concrete. Salokhe and Desai [59] reported that the foundry waste sand had no apparent impact on

the research findings of Torres et al. [33] is shown in **Figure 9**.

are discussed in detail in the following paragraphs.

**used foundry sand**

**Figure 9.**

**7.1 Water absorption**

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

*Elastic modulus variation of foundry sand concrete.*

**Figure 8.** *Flexural strength vs. % foundry sand.*

*A Review on the Usage of Recycled Sand in the Construction Industry DOI: http://dx.doi.org/10.5772/intechopen.92790*

**Figure 9.** *Elastic modulus variation of foundry sand concrete.*

*Sandy Materials in Civil Engineering - Usage and Management*

and Lawrence [41] is shown in **Figure 8**.

**6.4 Modulus of elasticity**

was 4.18 MPa.

sand, Siddique et al. [54] observed that the flexural strength of 28.5 MPa characteristic compressive strength concrete consecutively increased with the percentage increase of used foundry sand up to 30% replacement level in which the flexural strength of control mix was 3.41 MPa and the flexural strength at 30% replacement

In some cases, the flexure strength seems to decrease with the increase in percentage addition of used foundry sand. Seshadri and Salim [12] reported that the high-performance concrete having 60 MPa characteristics compressive strength showed a decrease in flexure strength on the increase in replacement of fine aggregate with used foundry sand, in which the control mix has a flexural strength of 10.05 MPa, and at 40% used foundry sand content, the flexural strength decreased to 7.05 MPa. As per Torres et al. [33], at 10% replacement of fine aggregate with foundry sand, the ultra-high-strength concrete showed an increase in flexure strength, and further, it showed a consecutive decrement in flexure strength for 20 and 30% replacement of fine aggregates with foundry sand. Prabhu et al. [53] observed that the flexural strength of concrete with foundry sand content up to 20% of fine aggregates has similar results as that of the control mix; further, the flexural strength decreases after 20% replacement level. The flexural strength variation of concrete having 36.5 and 46 MPa compressive strength at 28 days made with regular sand replaced at 0, 10, 30, 50, 70, and 100% to chemically bonded foundry sand with water to cement ratio 0.55 and 0.45 as reported by Mavroulidou

Generally, the modulus elasticity of concrete containing used foundry sand increases up to certain percentage content of used foundry sand and then tends to decrease with further increase in the used foundry sand content. Manoharan et al. [28] observed that the modulus of elasticity of concrete increased with percentage replacement of natural river sand with used foundry sand from 0 to 20%, and further addition of used foundry sand decreased the modulus of elasticity, the modulus of elasticity of control concrete was 23.60 GPa, whereas at 20% replacement of river sand with used foundry sand, the elastic modulus increased to 25.40 GPa. As per the research findings of Prabhu et al. [53], the replacement of fine aggregate

**20**

**Figure 8.**

*Flexural strength vs. % foundry sand.*

with used foundry sand slightly improved the modulus of elasticity of concrete mix. Some researchers observed marginal reduction of modulus of elasticity by the addition of used foundry sand. Basar and Aksoy [34] stated that the waste foundry sand content in the ready-mixed concrete reduces the modulus of elasticity. The variation of modulus of elasticity of ultra-high-strength concrete made with foundry sand at 7, 14, and 28 days for foundry sand percentages of 0, 10, 20, and 30% as reported in the research findings of Torres et al. [33] is shown in **Figure 9**.
