PSI - Issue 70

Hariharan kannan et al. / Procedia Structural Integrity 70 (2025) 658–665

660

2.5. Waste foundry sand With 85 – 99% silica content, foundry sand is a premium silica sand. The iron-based and non-iron metal casting factories produce it as a byproduct. When the sand ended its life in the foundry, it is detached and disposed of in landfills, which degrades the environment and contributes to pollution by Manoharan et al (2018). Foundries efficiently recycle and reuse the sand for casting metals multiple times. This sand is known as waste foundry sand (WFS). The properties of WFS are mentioned in Table 3 and Table 4. 2.6. Fly ash Fly ash is produced in electricity generation while burning pulverized coal. It can easily dissolve and react with cement paste as it was small in size, glassy texture and its chemical characteristics. As per AASHTO M 295/ASTM C 618 classification fly ash is categorised to Class C or Class F. Higher lime concentration (CaO) in Class C fly ash make it more sensitive at early ages compared to Class F. However the concrete attains early strength due to higher CaO concentration, it produces negative effect on alkali silica reaction by Elchalakani et al (2017). The properties are

mentioned in Table 5 and 6. Table 1 Characteristics of aggregates Attributes

FA

CA

Fineness Modulus

4.2

6.5

Specific Gravity of material

2.79

2.54

Table 2 Properties of Na 2 SiO 3 Attributes

Na 2 SiO 3

Ratio of overall solid to liquid by mass

2.8

Density Colour

1.6g/cc

Pale

Table 3 Chemical configuration of waste foundry sand Constituent

Attributes

SiO 2 Fe 2 O 3 Al 2 O 3 MgO CaO SO 3 Lol

85.6 4.33 5.22 1.85 0.5 0.055 2.12

3. Mix proportion The mix of 50 MPa specified strength of the geopolymer concrete was prepared using different percentages of blended binders. The design for mixing process employed in this research was influenced by earlier studies on fly ash based GPC by Pavithra et al (2016). Potassium hydroxide (KOH), sodium silicate (Na₂SiO₃), sodium hydroxide (NaOH), and combinations of these were the most widely utilized activators by Mahmood (2021). The typical molarity range used in geopolymer concrete is 8M to 16M.For higher strength, a molarity between 10M to 14M is often considered optimal. Table 5 displays the specifics of the calculated mix proportions.