PSI - Issue 70

C. Manoj Prabhu et al. / Procedia Structural Integrity 70 (2025) 207–214

209

1.1 Research significance Over the past two decades, notable research has been undertaken on geopolymer concrete (GPC) employing diverse industrial waste materials and by-products. However, very few investigations have focused on the durability of fly ash-based GPC with rice husk ash (RHA). The fundamental novelty of this study is the evaluation of the long term durability of GPC by combining the combined effects of fly ash (FA), RHA, and ground granulated blast furnace slag (GGBFS). This study intends to use waste by-products in GPC to improve mechanical and durability qualities, minimizing reliance on natural resources and providing an alternative binder material. Furthermore, building sustainable concrete reduces greenhouse gas emissions and other environmental implications. This study promotes the use of high-performance RHA-based concrete, which contributes to sustainable construction. 2. Materials used This study utilizes fly ash, rice husk ash (RHA), ground granulated blast furnace slag (GGBFS), alkaline activators, fine and coarse aggregates, and water as ingredients. Class F fly ash from a thermal power plant is used as the principal binder owing to its high silica and alumina content, which interacts with alkaline activators to produce a geopolymer matrix. RHA, an industrial byproduct rich in amorphous silica, was employed as a substitute for fly ash in proportions of 0%, 5%, 10%, 15%, 20%, and 25%. GGBFS was utilized to enhance early strength and durability by supplying additional calcium for geopolymerization. The alkaline activator solution consisted of sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) in a 1:2.5 ratio, with NaOH concentrations of 10M and 12M. In accordance with IS 383:2016 specifications, manufactured sand (M-sand) was employed as the fine aggregate, while crushed granite stone (10 mm to 20 mm) was utilized as the coarse aggregate. To ensure compliance with IS 456:2000 criteria, the alkaline solution and concrete were made with contaminant-free double-distilled water.

(c)

(a)

(b)

Fig.1.Sample of materials; (a) Fly ash; (b)GGBFS; (c) RHA

3. Methodology This study analyzes the durability of GPC incorporating RHA as a partial substitute for fly ash. GPC specimens were made and cured in ambient temperatures. Water absorption (WA), sorptivity, rapid chloride penetration (RCPT) sulphate attack resistance were all measured. Water absorption was measured using ASTM C642, which involved oven-drying 100 mm cube specimens and then immersing them in water to quantify the percentage of absorbed water. Sorptivity was tested in accordance with ASTM C1585, using 100 mm cube specimens to determine the rate of water absorption caused by capillary action. The examination of sulphate resistance was carried out in accordance with ASTM C1012, which involved immersing 100 mm cube specimens in a 5% sodium sulphate solution and monitoring weight loss and strength retention The RCPT was performed in accordance with ASTM C1202, utilizing cylindrical specimens of 100 mm in diameter and 50 mm in height to evaluate the total charge passed through the concrete and assess chloride ion ingress. Some of the durability test setups are illustrated in Fig. 2. Table 1 outlines the mixture proportions. Table.1. Mix Proportions for GPC mixes

S.No

Mix ID

Fly Ash (%)

RHA (%)

GGBFS (%)

NaOH (Molarity)

Alkaline Ratio (NaOH:Na₂SiO₃)

Water - Binder Ratio

1

10M - 0

70

0

30

1:2.5

0.35