Measuring Improvement in Fly Ash Based Concrete Impregnated with Glass Fiber

Abstract

In cement and concrete, fly ash has been utilized as a mineral additive. Utilizing it offers a number of benefits, including enhanced workability and strength characteristics as well as environmental advantages linked to waste disposal and lower carbon dioxide emissions. Constantly 1.5%, 2.5%, and 3.5% of the cement\'s weight is reinforced with alkali-resistant glass Fibers. Glass Fibers improved split and flexural strength without increasing compressive strength and served as an effective crack arrester. For this study, concrete of M30 grade is utilized. Studying fly ash\'s viability as a mineral additive to replace cement and provide extra glass fibre reinforcement in concrete is the primary goal of this project. Concrete\'s several structural qualities, such as its compressive, split, and flexural strength, are satisfied by the use of glass Fibers as extra reinforcement and fly ash as a partial substitute for cement. The complete investigation came to the conclusion that the best combination of all the mixes was 10% FA + 3.5% GF, which gave the most tensile strength; 10% FA + 3.5% GF showed greater flexure strength; and 10% FA showed good compressive strength at 28 days compared to standard concrete. After seven days, fly ash blends no longer exhibit improved compressive strength or split tensile strength.

Introduction

Background

Recent advancements in construction materials have led to increased interest in sustainable alternatives to conventional Portland cement. One such solution is geopolymer concrete, especially when glass fibers and fly ash are incorporated. These materials aim to improve concrete's mechanical properties, durability, and environmental performance.

• Glass fibers improve tensile strength, ductility, and reduce cracking and bleeding.

• Fly ash, a byproduct of coal combustion, serves as a partial cement replacement, lowering CO? emissions and improving workability.

Objectives

1. Design M35 grade concrete mixes with varying dosages of glass fiber and fly ash.

2. Assess workability (slump test) of fresh concrete mixes.

3. Evaluate compressive, flexural, and split tensile strengths.

4. Compare modified mixes to a control (standard mix without additives).

Literature Review Insights

• Glass fibers increase strength, reduce bleeding, and enhance concrete durability.

• Fly ash improves workability and can replace up to 20% of cement without significant strength loss.

• Combined use of both materials improves mechanical performance but affects workability and may require superplasticizers.

• Several studies confirm improved compressive, tensile, and flexural strength at optimal levels of glass fiber (~0.1–0.3%) and fly ash (~10–30%).

Key Inferences

• Partial cement replacement cuts costs and environmental impact.

• Optimal strength and flexibility depend on dosage, particle size, and fiber distribution.

• Curing conditions and chemical interactions also influence performance.

• Long-term durability studies (e.g., shrinkage, creep) are essential for practical application.

Materials Used

• Cement: OPC 43 grade

• Fly Ash: Specific gravity 2.2

• Glass Fiber: AR type, 24 mm length, specific gravity 2.68

• Aggregates: 10 mm and 20 mm nominal size

• Water: Potable water

• Superplasticizer: Conplast SP430g8

Concrete Mix Design

• Base mix: 1:1.46:2.79 (cement:fine agg.:coarse agg.), w/c ratio 0.4, 1% SP.

• Fly ash replacement levels: 0%, 10%, 20%, 30%

• Glass fiber content: 0%, 1.5%, 2.5%, 3.5%

• Total 10 different mix combinations (M–M9) were created and tested.

Testing Methodology

• Compressive Strength: 150mm cubes

• Split Tensile Strength: 150x300mm cylinders

• Flexural Strength: 100x100x500mm beams

• Tests conducted at 7 and 28 days.

Results & Discussion

• Slump Test: No linear trend; best workability at 30% fly ash + 1.5% glass fiber.

• Slump decreased significantly in higher glass fiber mixes without enough SP, indicating reduced workability.

• Strength tests showed improvement at optimal glass fiber and fly ash levels but declined when dosages exceeded effective thresholds.

Conclusion

The conclusions drawn from various tests conducted on grade M35 are listed below: 1) When glass fibres and fly ash are substituted for the control mix, the compressive strength, split tensile strength, and flexural strength all exhibit a similar trend of strength variation. There is a dip in values that progressively rises to 10% fly ash before beginning to decline from 20% to 30% fly ash, with the biggest decline occurring from 30% fly ash and 3.5% glass fibres. 2) The aforementioned fluctuations in slump values, which are respectively, suggest that these values do not exhibit a consistent pattern but rather a fluctuating one that peaks at the 10% flash and 1.5% glass fibres replacement level. In comparison to the reference value of the control mix, the slump values of grade M35 show percentage changes of -6.67%, -20%, -33.33%, +0%, -13.33%, -26.67%, +6.67%, -6.67%, and -20%. 3) The percentage change in the specimen\'s compressive strength values corresponding to the RL of replaced fly ash and glass fibres compared to the control mix after 28 days of appropriate curing and quality control is +0.27%, +5.88%, +8.29%, -3.74%, +0.54%, +4.28%, -8.02%, +3.21%, and +0%, respectively. 4) The trend of the fluctuations in the split tensile strength value is similar to that of the compressive strength. This suggests that the substituted component is affecting the various concrete strength characteristics in a comparable way. The percentage change from the level of the control mix as recorded during the test is +6.45%, +16.13%, +25.8%, +3.23%, +9.68%, +16.13%, -3.23%, +6.45%, +9.68%, respectively, after 28 days of appropriate curing and quality control. 5) The percentage change in the flexural strength values of the specimen corresponding to the RL of replaced fly ash and glass fibres as compared to the control mix after 28 days of appropriate curing and quality control is +1.81%, +5.45%, +9.09%, -1.81%, +1.81%, +5.45%, -5.45%, -3.64%, and +1.81%, respectively.

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Copyright

Copyright © 2025 Er. Ajay Kumar Chaudhary, Dr. Hemant Sood, Er. Jasvir Singh Rattan. 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.