Author ORCID Identifier

https://orcid.org/0009-0002-1263-8637

Author Linked-In Account

https://www.linkedin.com/in/selescadevi/

Date of Award

16-7-2025

Document Type

Thesis

School

School of Civil Engineering

Programme

Ph.D.-Doctoral of Philosophy

First Advisor

Dr.S.S.Vivek

Keywords

Self-Compacting Concrete, Mono Fiber, Hybrid Fiber, Kaolin Limestone Blend, Hybrid Slag Blend

Abstract

This study examined the consequences of mono and hybrid natural fibers on the mechanical and fresh properties of self-compacting concrete (SCC), in response to the growing demand for environmentally friendly building materials. In mono fiber, Abaca fiber (AF) at 0.25% and 0.5% dosage, basalt fiber (BF) from 0.25% to 2% at 0.25% increments, and sisal fiber (SiF) from 0.25% to 1.5% at 0.25% increments were evaluated through slump flow diameter, T500, compressive and tensile strength. AF at 0.25% ensured good flow with 6.6% and 4.16% higher compressive and tensile strength over 0.5% AF. SiF up to 1% improved strength but reduced flow due to high hemicellulose content. BF peaked at 1.25% dosage but still underperformed over the control SCC.

From hybrid fiber mixes, M_A0.25_B0.25 mix met EFNARC guidelines and showed the peak compressive strength of 45.4 MPa, whereas M_A0.25_B1.75 improved its tensile strength by 21.42% over control SCC. AF-BF mixes improved the strength but reduced flow at higher dosages due to fiber interlocking. AF-SiF hybrid mixes showed poor flow (330-375 mm) due to the clustering effect. However, M_A0.25_S0.5 improved compressive and tensile strength by 22.22% and 26.08% over the control SCC, respectively.

Hybrid fibers improved the hardened characteristics; however, the key fresh characteristics of SCC were not met under constant HRWR. To address economic and workability limitations, a non-fibered SCC with two tailor-made SCMs was developed. A hybrid slag blend (HSB-ultrafine slag and GGBS in a 2:1 ratio with 1.5% gypsum) and kaolin limestone blend (KLB-calcined kaolin and limestone powder in a 2:1 ratio along with 1% gypsum) for the cement substitution from 10% to 50%. HSB at 40% (HSB.4) enhanced flow with reduced HRWR, while KLB mixes demand 0.6% to 2% HRWR.

HSB.4 and KLB.5 mixes improved strength, impact resistance, and durability, though increased brittleness at higher dosages. Microstructural analysis, such as SEM, XRD, and FTIR, confirmed stable carbo aluminate formation in KLB with reduced porosity and negligible chloride penetration. Hence, the KLB.5 mix is a viable approach for producing high-strength, high-performance SCC with a better economy index and enhanced sustainability.

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