Effect of Replacement of Cement by Silica Fume

Effect of Replacement of Cement by Silica Fume on the Strength Properties of SIFCON Produced From Waste Coiled Steel Fibres

A. K. Gurav, Lecturer, Department of Civil Engineering, D. Y. Patil College of Engineering and Technology, Kolhapur, Maharashtra. Dr. K. B. Prakash, Professor Department of Civil Engineering, K.L.E. Society's College of Engineering and Technology Belgaum

Slurry infiltrated fibre reinforced concrete (SIFCON), is a relatively new and advanced material of construction. It is fibre reinforced concrete (FRC) containing high percentage of fibres in which coarse aggregates are absent. SIFCON is a fabrication method in which steel fibres are preplaced in the form or in the mould to its full capacity, rather than being mixed and then cast or sprayed along with concrete. After placement of fibres, fine-grained cement based slurry is poured or pumped into the fibre network, infiltrating the air space between the fibres while conforming to the shape of the form or mould. External vibrations can also be used to aid infiltration of the slurry. SIFCON utilizes the fibres in the range of 6-20% by volume fraction as against usual range of 1-3% for fibre reinforced concrete. Due to such a high percentage of fibres tremendous improvement in strength properties can be expected. In this paper, effect of replacement of cement by silica fume on the properties of SIFCON is reported. SIFCON is made from waste coiled steel fibres obtained from lathe machine shop. The percentage of fibres used is 8%. In this study, fibres having aspect ratios like 80, 90, 100, 110, and 120 are used. Specimens are cast by replacing cement by silica fume at varying percentages like 5%, 10%, 15%, 20%, 25%, and 30% by weight of cement. The strength characteristics like compressive strength, tensile strength, and flexural strength and impact strength are evaluated.

Introduction

High performance concrete usually contains Portland cement. However, partial cement replacement by mineral admixtures can be economically advantageous. These minerals act as filler due to their small particle size that enables their penetration between cement grains. This results in reduction in the water cement ratio to achieve a given workability.1

Silica fume is most used mineral admixture in high strength high performance concrete. As defined by ACI 116R, it is very fine non-crystalline silica, produced in electric arc furnaces as a byproduct of the production of silicon or alloy containing silicon. Silica fume is mainly amorphous silica with high SiO2 content. It has extremely small particle size and large surface area. It is not precipitated silica or gel silica or colloidal silica or silica flour.2

In the discussion of high performance concrete role played by fibre reinforced concrete (FRC) is vital. Fibre reinforced concrete (FRC) is defined as a composite material which consists of conventional concrete reinforced by randomly dispersed short length fibres of specific geometry, made up of steel, synthetic material or natural fibres3. The fibres are distributed evenly throughout mix without balling or clustering4. The randomly oriented fibres help to bridge and arrest the cracks. As such, crack widening is gradual as compared to plain concrete5. This leads to better performance of concrete. Fibres have reported to be superior than wire mesh, for shortcrete. Also they overcome a difficultly in placing the mesh, especially on irregular surfaces6.

The concept of steel fibre reinforcement is very old. Steel fibres have been used since early 1900s7. Presently, steel fibres are considered as structural fibres as they enhance strength of the structure to a great extent3. The addition of steel fibres into concrete mass can dramatically increase the strength properties like compressive strength, tensile strength, and flexural strength and impact strength of concrete8. The strength properties of FRC can be increased by increasing the percentage of fibres in the concrete. But as the percentage of fibres increases, there are certain practical problems which have to be faced. The higher percentage i.e. higher volume content of fibres may cause balling effect in which the fibres cling together to form balls. Thus uniform distribution of fibres cannot be guaranteed, if percentage of fibres is more. Also longer fibres interfere with the aggregates during compaction thus hindering the proper orientation of fibres9.This fact limits the fibre content form 1 to 3 percent by volume.

The limitations of FRC and continuous ongoing demand for high performance material has led to the invention of 'Slurry infiltrated fibre reinforced concrete' (SIFCON) by Lankard in 1979. The 'Slurry infiltrated fibre reinforced concrete' is high strength, high performance material containing relatively high volume percentage of fibres as compared to FRC. SIFCON is also sometimes termed as 'High volume fibrous concrete.' In conventional FRC, the fibre content usually varies from 1 to 3 percent, while in SIFCON it varies from 6 to 20 percent by volume depending on the geometry of fibres and type of application.8 The material SIFCON has no coarse aggregates but has a high cementious content.

Research Significance

SIFCON which is considered as a high performance concrete, can also be produced by using waste coiled steel fibres obtained from the lathe machine shops. Since these fibres are available locally, they can be easily used in the production of SIFCON. Due to their coiled nature they may offer more resistance to loads. The study of effect of replacement of cement by silica fume on SIFCON produced from such waste coiled fibres may result in an economic building material.

Experimental Programme

The main aim of this experimental programme is to find out the effect of replacement of cement by silica fume on the strength properties of SIFCON produced from waste coiled steel fibres. Ordinary Portland cement of 53-grade and locally available sand with a specific gravity 2.65 and fineness modulus of 2.92 was used in the experimentation. To impart additional workability, superplastisizer (1% by weight of cement) was used. The waste coiled steel fibres were procured from local lathe machine shops. The fibres were of chrome steel having density 6.8 gm/cm3. The percentage of fibres used in the experimentation was 8%. The average thickness was 0.5 mm, with average coil diameter of 3 mm. The different aspect ratios adopted in the experimentation were 80, 90, 100, 110 and 120 giving fibre lengths 40mm, 45mm, 50mm, 55mm and 60mm respectively. The average thickness of fibres was taken into consideration in fixing the aspect ratios.

Effect of Replacement of Cement by Silica Fume on the Strength Properties of SIFCON Produced From Waste Coiled Steel Fibres
The cement mortar slurry was prepared with 1:1 proportion using w/c ratio 0.42. A superplastisizer (1% by weight of cement) was added to this slurry which increased infiltration capacity of the slurry. To study the effect of replacement of cement by silica fume on SIFCON, slurry was prepared by replacing cement by silica fume at varying percentages like 5%, 10%, 15%, 20%, 25% and 30% by weight of cement. In this experimentation Elkem microsilica grade 920-D was used. Physical and chemical properties of this silica fume are given in Tables 1 and 2 respectively.

The moulds were filled with 8% fibres, and slurry was poured into the moulds. Vibration was given to the moulds using table vibrator. The slurry was poured until no more bubbles were seen. This ensured a thorough infiltration of slurry into the fibres. The top surface of the specimen was leveled and finished. After 24 hours, the specimens were demoulded and were transferred to curing tank where they were allowed to cure for 28 days.

The effect of replacement of cement by silica fume on SIFCON was studied on compressive strength, tensile strength, flexural strength and impact strength. The cube specimens of dimension 150x150x150mm were cast, from which the compressive strength was calculated. The specimens of dimension 150mm diameter and 300mm length were cast for split tensile strength. The specimens of dimension 100x100x500mm were cast for flexural strength test. Two point loading10 was adopted on these specimens with an effective span of 400mm. The impact strength specimens consisted of plates of dimension 250x250x35 mm. For impact strength test four methods are described in the literature11. Out of these methods drop weight method was used owing to its simplicity. A steel ball weighing 20 N was dropped from the height of 1m over the specimen. The number of blows required to cause complete failure were noted. The impact energy was calculated as follows.

Impact energy = w x h x N (N-m).

Where

w = weight of the ball = 20 N

h = height of fall = 1 m

N = number of blows required to cause complete failure

After 28 days of curing, the specimens were taken out of the water. Then they were tested for their respective strengths.

Test Results

Tables 3 to 6 give the compressive strength, tensile strength, flexural strength and impact strength test results respectively, for SIFCON with and without replacement of cement by silica fume. The tables also indicate the percentage increase in the strength of SIFCON due to replacement of cement by silica fume.

Effect of Replacement of Cement by Silica Fume on the Strength Properties of SIFCON Produced From Waste Coiled Steel Fibres

The Figures 1 to 4 give variation of compressive strength, tensile strength, flexural strength, and impact strength respectively, for SIFCON with and without replacement of cement by silica fume.

Discussions on Test Results

1) It has been observed that the compressive strength, tensile strength, flexural strength and impact strength of SIFCON goes on increasing as the aspect ratio of fibers in it goes on increasing. This is also true for SIFCON with and without replacement of cement by silica fume.

Effect of Replacement of Cement by Silica Fume on the Strength Properties of SIFCON Produced From Waste Coiled Steel Fibres

This may be due to the fact of optimum infiltration of slurry for fibres having more aspect ratio.

Thus it can be concluded that the SIFCON produced with fibres having an aspect ratio of 120 yields the maximum strength.

Effect of Replacement of Cement by Silica Fume on the Strength Properties of SIFCON Produced From Waste Coiled Steel Fibres
2) It has been observed that maximum compressive strength for SIFCON is obtained when 20% of cement is replaced by silica fume. Also it is observed that percentage increase in the compressive strength of SIFCON with 8% fibres, due to 20% replacement of cement by silica fume is 20.07%, 20.19%, 20.49%, 20.63% and 20.91% respectively for different aspect ratios of fibres.

It has been observed that maximum tensile strength for SIFCON is obtained when 20% of cement is replaced by silica fume. Also it is observed that percentage increase in the tensile strength of SIFCON with 8% fibres, due to 20% replacement of cement by silica fume is 20.98%, 21.16%, 21.43%, 21.74%, 22.07% respectively for different aspect ratios of fibres.

It has been observed that maximum flexural strength for SIFCON is obtained when 20% of cement is replaced by silica fume. Also it is observed that percentage increase in the flexural strength of SIFCON with 8% fibres, due to 20% replacement of cement by silica fume is 20.41%, 20.63%, 20.91%, 21.14%, 21.55% respectively for different aspect ratios of fibres.

It has been observed that maximum impact strength for SIFCON is obtained when 20% of cement is replaced by silica fume. Also it is observed that percentage increase in the impact strength of SIFCON with 8% fibres, due to 20% replacement of cement by silica fume is 20.84%, 21.17%, 21.46%, 21.65%, 21.88% respectively for different aspect ratios of fibres.

The increase in various strengths of SIFCON due to replacement of cement by silica fume may be attributed to pozzolanic activity of silica fume. Silica fume is highly reactive pozzolana. Further due to its fineness it fills the small pores of the cement paste giving very dense concrete. Due to these facts an increase in the strength properties is seen. However, beyond 20% replacement the strengths decrease. This may be due to less quantity of cement in the mix. Hence it may be concluded that the optimum percentage of replacement of cement by silica fume for SIFCON is 20%.

Conclusions

  • The SIFCON produced with waste coiled steel fibres having an aspect ratio of 120 yields the maximum strength.
  • Optimum percentage of replacement of cement by silica fume for SIFCON is 20% when waste coiled steel fibres are used.
  • Waste coiled steel fibres can be efficiently used in the production of SIFCON.
Effect of Replacement of Cement by Silica Fume on the Strength Properties of SIFCON Produced From Waste Coiled Steel Fibres

Acknowledgment

The authors would like to thank and Dr. A. N. Chapgaon and Dr.S. C. Pilli, Principals of D. Y. Patil College of Engineering and Technology, Kolhapur and KLE Society's College of Engineering and Technology, Belgaum for their encouragement throughout the work. Authors are also indebted to management authorities of both the colleges for their wholehearted support, which boosted the moral of the authors. Thanks are also due to HODs of the Civil Engineering Department and other staff for their kind cooperation.

References

  • Chaid R. et al, 'Influence of natural pozzolana on the properties of high performance mortar,' The Indian Concrete Journal, August 2004, pp 22-26.
  • Tiwari A. K., 'Advances in high performance concrete–the fifth ingredient,' Civil Engineering & Construction Review, June 2005, pp 28-38
  • Sikdar P. K., Saroj Gupta and Satander kumar, 'Application of fibres as secondary reinforcement in concrete,' Civil Engineering & Construction Review, December 2005, pp 32-35.
  • Kieth Carr, 'Polypropylene and steel fibres combinations,' Concrete, September 2004, pp 60-61.
  • Ziad Bayasi and Henning Kaiser, 'Steel fibres as crack arresters on concrete.' The Indian Concrete Journal, March 2001, pp 215-219.
  • Marc Wandewalle N.V., Bekaert S.A., Choudhari G.P., 'Fibres in concrete-Dramix steel fibres for SFRS & SFRC,' The Indian Concrete Journal, March 2003, pp 939-940.
  • Fibre reinforced concrete, A report published by cement and concrete institute, Midrand, 2001.
  • Prakash K. B. et al, 'Performance evaluation of slurry infiltrated fibrous silica fume concrete', Proceedings of International conference on Fibre Composites, HPC and smart materials', Chennai, India, pp 201-211.
  • Saluja S. K. et al, 'Compressive strength of fibrous concrete', The Indian Concrete Journal, February 1992, pp99-102.
  • I. S. 516-1959, 'Methods of tests for strength of concrete', Bureau of Indian standards, New Delhi.
  • Balsubramanain K. et al, 'Impact resistance of steel fibre reinforced concrete', The Indian Concrete Journal, May 1996, pp257-262.2
NBM&CW March 2009

No comments yet, Be the first one to comment on this.

×

Terms & Condition

By checking this, you agree with the following:
  1. To accept full responsibility for the comment that you submit.
  2. To use this function only for lawful purposes.
  3. Not to post defamatory, abusive, offensive, racist, sexist, threatening, vulgar, obscene, hateful or otherwise inappropriate comments, or to post comments which will constitute a criminal offense or give rise to civil liability.
  4. Not to post or make available any material which is protected by copyright, trade mark or other proprietary right without the express permission of the owner of the copyright, trade mark or any other proprietary right.
  5. To evaluate for yourself the accuracy of any opinion, advice or other content.
Advancing LC3 Cement Technology for Sustainable Construction in India

Advancing LC3 Cement Technology for Sustainable Construction in India

Dr S B Hegde provides a deep, research-driven analysis of LC3 cement, emphasizing its chemistry, process innovations, global applicability, and success stories, and evaluates its technical advantages, performance, cost savings

Read more ...

Supplementary Cementitious Materials Improving Sustainability of Concrete

Supplementary Cementitious Materials Improving Sustainability of Concrete

Concrete is the second most consumed material after water in the world and cement is the key ingredient in making concrete. When a material becomes as integral to the structure as concrete, it is important to analyze its environmental impacts.

Read more ...

Alite & Belite in Portland Cement: A Key to Sustainability & Strength

Alite & Belite in Portland Cement: A Key to Sustainability & Strength

Dr. S B Hegde guides construction industry stakeholders on balancing cement’s early strength with long-term durability and sustainability and advocates optimized cement formulations and supplementary materials for more resilient infrastructure

Read more ...

Amazecrete: Offering Sustainable Concrete Solutions like ICRETE

Amazecrete: Offering Sustainable Concrete Solutions like ICRETE

V.R. Kowshika, Executive Director, Amazecrete, discusses the economic and environmental benefits of eco-friendly and sustainable products like ICRETE and the positive impact on the construction industry.

Read more ...

Admixture-Cement Compatibility For Self-Compacting Concrete

Admixture-Cement Compatibility For Self-Compacting Concrete

An admixture is now an essential component in any modern concrete formula and plays a significant role in sustainable development of concrete technology. Dr. Supradip Das, Consultant – Admixture, Waterproofing, Repair & Retrofitting

Read more ...

Amazecrete's Icrete: New Age Material for Concrete Construction

Amazecrete's Icrete: New Age Material for Concrete Construction

By maximizing the durability and use of supplementary cementitious materials, Icrete has emerged as a new age material for Concrete Construction V. R. Kowshika Executive Director Amazecrete

Read more ...

Nanospan’s Spanocrete® Reduces Cement & Curing Time in Fly Ash Bricks

Nanospan’s Spanocrete® Reduces Cement & Curing Time in Fly Ash Bricks

Hyderabad-based Ecotec Industries is a leading manufacturer of fly ash bricks and cement concrete blocks in South India under the trademark NUBRIK. Their products are known for their consistency and quality. Ecotec was earlier owned

Read more ...

Ready-Mix Concrete: Advancing Sustainable Construction

Ready-Mix Concrete: Advancing Sustainable Construction

A coordinated approach by the government, industry stakeholders, and regulatory bodies is needed to overcome challenges, implement necessary changes, and propel the RMC sector towards further growth such that RMC continues to play a vital

Read more ...

Advancements & Opportunities in Photocatalytic Concrete Technology

Advancements & Opportunities in Photocatalytic Concrete Technology

Research on photocatalytic concrete technology has spanned multiple decades and involved contributions from various countries worldwide. This review provides a concise overview of key findings and advancements in this field

Read more ...

Self-Compacting Concrete

Self-Compacting Concrete

Self-compacting concrete (SCC) is a special type of concrete which can be placed and consolidated under its own weight without any vibratory effort due to its excellent deformability, which, at the same time, is cohesive enough to be handled

Read more ...

Nanospan's Spanocrete® Additive for Waterproofing & Leak-Free Concrete

Nanospan's Spanocrete® Additive for Waterproofing & Leak-Free Concrete

Nanospan's Spanocrete Additive for Waterproofing & Leak-Free Concrete has proven its mettle in the first massive Lift Irrigation project taken up by the Government of Telangana to irrigate one million acres in the State.

Read more ...

Accelerated Building & Bridge Construction with UHPC

Accelerated Building & Bridge Construction with UHPC

UHPC, which stands for Ultra High-Performance Concrete, is a testament to the ever-evolving panorama of construction materials, promising unparalleled strength, durability, and versatility; in fact, the word concrete itself is a misnomer

Read more ...

Innovative Approaches Driving Sustainable Concrete Solutions

Innovative Approaches Driving Sustainable Concrete Solutions

This paper explores the evolving landscape of sustainable concrete construction, focusing on emerging trends, innovative technologies, and materials poised to reshape the industry. Highlighted areas include the potential of green concrete

Read more ...

GGBS: Partial Replacement Of Cement For Developing Low Carbon Concrete

GGBS: Partial Replacement Of Cement For Developing Low Carbon Concrete

Dr. L R Manjunatha, Vice President, and Ajay Mandhaniya, Concrete Technologist, JSW Cement Limited, present a Case Study on using GGBS as partial replacements of cement for developing Low Carbon Concretes (LCC) for a new Education University

Read more ...

Behaviour of Ternary Concrete with Flyash & GGBS

Behaviour of Ternary Concrete with Flyash & GGBS

Evaluating the performance of concrete containing Supplementary Cementitious Materials (SCM) like FlyAsh and Ground Granulated Blast Furnace Slag (GGBS) that can be used in the production of long-lasting concrete composites.

Read more ...

Nanospan's Spanocrete®: nano-admixture for concrete

Nanospan's Spanocrete®: nano-admixture for concrete

Nanospan’s Spanocrete, a Greenpro-certified, award- winning, groundbreaking nano-admixture for concrete, actualizes the concept of “durability meets sustainability”. This product simplifies the production of durable concrete, making it cost-effective

Read more ...

The Underwater Concrete Market in India

The Underwater Concrete Market in India

India, with its vast coastline and ambitious infrastructural projects, has emerged as a hotspot for the underwater concrete market. This specialized sector plays a crucial role in the construction of marine structures like bridges, ports

Read more ...

The Path to Enhanced Durability & Resilience of Concrete Structures

The Path to Enhanced Durability & Resilience of Concrete Structures

This article highlights a comprehensive exploration of the strategies, innovations, and practices for achieving concrete structures that not only withstand the test of time but also thrive in the face of adversity.

Read more ...

Self-Curing Concrete for the Indian Construction Industry

Self-Curing Concrete for the Indian Construction Industry

The desired performance of concrete in the long run depends on the extent and effectiveness of curing [1 & 2]. In the Indian construction sector, curing concrete at an early age is a problematic issue because of lack of awareness or other

Read more ...

To get latest updates on whatsapp, Save +91 93545 87773 and send us a 'Saved' message
Click Here to Subscribe to Our eNewsletter.