Experimental Investigation of Strength and Durability Performance on Geopolymer Concrete using Industrial Waste Material

Abstract

Concrete is one of the most used construction materials nowadays. Portland cement is the major ingredient in concrete. The main factor that does not require Portland cement or emit greenhouse gases is geopolymer. The geopolymer technique described by Davidovits (1978) as an alternative to Portland cement in concrete shows promise. He suggested polymerising alkaline liquids with silicon and aluminium in geological sources or byproducts like fly ash, slag, and rice husk ash to make binders. He called these binders geopolymers. Geopolymers are most likely to come from fly ash and slag. So, this study looks at the mechanical, long-term, and microstructural properties of geopolymer concrete made from fly ash and ground granulated blast furnace slag. This project investigates how different amounts of class F Fly Ash (FA) and Ground Granulated Blast Furnace Slag (GGBS) change the mechanical and long-lasting properties of geopolymer concrete (GPC). Alkaline activators include Na?SiO? and NaOH. This study examined the compressive, split tensile, bond, and flexural strengths. We also explored water absorption, rapid chloride permeability, and sulphate attack tests using low-calcium fly ash and ground granulated blast furnace slag-based geopolymer concrete. These parameters were measured at ambient room temperatures after 7, 28, 56, and 90 days of cure. This research looked at the short-term mechanical, long-term durability, and microstructural properties of GPC mixtures made from FA and GGBS. This study also evaluated short-term mechanical, durability, and micro-level GPC to M45 grade ordinary concrete. Fibre-reinforced geopolymer concrete has been studied. Different geopolymer concrete mixtures have been tested for mechanical and durability. Fibres were added to concrete at 0.25%, 0.5%, 0.75%, and 1.0% by volume. We tested the compressive, split tensile, and flexural strength of fibre-containing mixtures after 28 days. Similar mixtures\' RCPT, water absorption, and acid attack have been tested.

Introduction

• Geopolymer technology, introduced by Davidovits (1978), presents a sustainable alternative to Portland cement by significantly reducing CO? emissions (up to 80%).

• Fly ash (FA) and Ground Granulated Blast Furnace Slag (GGBS) are key industrial by-products used as binders in GPC.

• Unlike traditional concrete, GPC does not require hydration but undergoes polymerization using alkaline activators (e.g., sodium hydroxide and sodium silicate).

2. Motivation for GPC

• The cement industry is the third-largest coal consumer in India and is highly energy-intensive.

• Thermal power plants generate large amounts of fly ash, posing disposal challenges.

• Using FA and GGBS in concrete helps reduce environmental impact and enhance technical performance.

3. Materials and Methods

A. Source Materials

• Class F fly ash (low-calcium)

• GGBS

• Aggregates (75–80% of total mass)

• Steel fibers (used in varying dosages: 0.25%, 0.5%, 0.75%, 1.0% by volume)

B. Mix Design

• Activator/fly ash + GGBS ratio: 0.35

• NaOH to Na?SiO? ratio: 1:2.5 (10M NaOH used)

• Comparative analysis with M45-grade OPC concrete

• Ambient curing (no external heat applied)

4. Objectives

• Evaluate mechanical properties:

  • Compressive strength

  • Split tensile strength

  • Flexural and bond strength

• Assess durability using:

  • RCPT (Rapid Chloride Permeability Test)

  • Water absorption

  • Acid resistance

• Analyze the effect of FA:GGBS ratios and fiber content

5. Key Findings

A. Compressive Strength (MPa)

• Best-performing mix: FA0-GGBS100

• GPC with 100% GGBS consistently outperformed M45-grade OPC concrete at all ages.

• Compressive strength decreases with increasing FA content.

• Strength increases with curing time for all mixes.

B. Split Tensile Strength

• Tested after 90 days of curing.

• Highest values were recorded for mixes with higher GGBS content.

• Fibers enhanced tensile strength, especially at 0.5–0.75% dosage.

Conclusion

In geopolymer concrete, the compressive and split tensile strengths decrease as the FA content increases. This deterioration is dependent on the length of time that the concrete is allowed to cure. With increasing age, both the split tensile strength and the compressive strength of the material rise for a certain mix %. The mix proportions of FA: GGBS: 0:100 enable the geopolymer concrete to achieve the greatest compressive and split tensile strengths, regardless of the length of time it takes for the concrete to cure. After a period of seven days of curing, the compressive and split tensile strengths of geopolymer concrete begin to increase at a rapid pace; however, this rate begins to decrease as the concrete approaches maturity. A significant difference may be seen in the binding strength of geopolymer concrete when compared to that of conventional concrete that is constructed utilising conventional components. The bond strength of the geopolymer concrete accounts for about one-third of the compressive strength of the material. If the quantity of FA in the mix is increased, the binding strength of geopolymer concrete will decrease regardless of the amount of time it takes for the concrete to cure. When geopolymer concrete is allowed to mature, the binding strength of the material increases. The percentage of water absorption goes down when more GGBS is added to the geopolymer concrete mix, but this decrease depends on how long the concrete is left to cure. does not matter how much GGBS is included in the mixture; the proportion of water that is absorbed continues to decrease as the curing period in increases. According to the RCPT, preparing a geopolymer concrete mixture with a ratio of FA: GGGBS:0:100 leads to the production of thick concrete with a less porous structure. GPC (FA39-GGBS61) has a beginning material cost that is about 32 percent more than that of CC (M45) when the compressive strength measurement is taken after 28 days. A few different geopolymer concrete mixtures were subjected to research, in which the impact of steel fibres was investigated. number of different percentages of fibres were added to the mixture, including 0.25%, 0.5%, 0.75%, and 1.0% by volume of construction material. e compressive strength, split tensile strength, and flexural strength of several different mixtures that included fibres were examined after 28 days. The study also examined the flexural strength as a mechanical parameter. In a similar manner, researchers investigated the durability characteristics of the comparable mixtures, such as RCPT, water absorption, and acid attack. The primary observation from the examinations was that the mechanical and durability properties of the mixtures were comparable. As As the amount of steel fibres added to fibre forced geopolymer concrete mixes increased, the mixes\' properties got better.

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Copyright © 2025 Biru Charan , R. Vijay . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.