Flexural Behaviour of RC Beams Strengthened by FC Laminates

This paper investigates the flexural behaviour of reinforced concrete beams strengthened by ferrocement laminates. Totally five beams of length 3200mm, width 150mm and depth 250mm were cast and tested. A flat ferrocement laminate 125mm wide, 25mm thick and 3000mm long was cast using cement mortar as binder and weld and woven mesh as reinforcement. The experimental study shows that the ferrocement laminate increases the flexural bahaviour of the distressed reinforced concrete beams. The aim of this project is to bond ferrocement laminates to reinforced concrete beams and strengthen it against flexure.

B.Sivagurunathan, Selection Grade Lecturer in Civil Engineering, Thiagarajar College of Engineering, Madurai. Dr.B.Vidivelli, Professor in Civil and Structural Engineering, Annamalai University, Annamalai Nagar.

Introduction

Increase in service loading, environmental degradation, damage of structure due to poor quality of material and inferior design, upgrading of old structures as per new code and need of seismic retrofit leads to the need of repair and rehabilitation. Rehabilitation of deteriorated civil engineering infrastructure such as beams, girders, bridge decks, parking structures, marine structures, roads etc has been the major issue in the last decades. The need to upgrade the deteriorated civil engineering infrastructure greatly enhances with the ever increasing demands. Therefore rehabilitating existing civil engineering infrastructure has been identified as an important issue to be addressed. The strengthening of concrete structures to resist higher design loads, correct deterioration-related damage, or increased ductility has been traditionally accomplished using conventional materials and construction techniques. Externally bonded steel plates, FRP and ferro-cement laminates are some of the traditional techniques available. In the context of strengthening problem, advanced composites have the potential to prove another promising solution.

Introduction to Ferrocement

Ferrocement is a form of reinforced cement mortar (micro concrete) that differs from conventional reinforced or pre-stressed concrete primarily by the manner in which the following elements are dispersed and arranged. It consists of closely placed, evenly distributed multiple layers of mesh or fine rods completely embedded in cement mortar. Widespread use of ferrocement in construction industry has occurred during the last 40 years. The main worldwide application of ferrocement construction to date has been for silos, tanks, roofs, irrigation channels, manholes & covers, and mostly boats. The construction of ferrocement can be divided in to four phases:

  • Fabricating the steel rods to form a skeletal (cage) framing system;
  • Tying or fastening rods and mesh to the skeletal framing;
  • Plastering and
  • Curing.

Review of Previous Work

Ong.K.C.G, Paramasivam.P and Lim.C.T.E. (1992),

In this study the methods of strengthening of reinforced concrete beams using ferrocement laminates with skeletal bar attached onto the soffit of the beams are reviewed. The methods of anchorage of the ferrocement laminates in the strengthened beams have been investigated. The methods of increasing the ultimate load of the original beams using ferrocement laminate and to control the cracking behavior of the beams as well the effect of the damage of original beams prior to repair are examined.

It is concluded that the strengthened beams have performed better in cracking behavior, reduction in mid-span deflection and increased ultimate load. Further, the pre-cracked beams prior to repair did not affect the ultimate loads of the strengthened beams tested.

Mohd Zamin Zumaat and Ashraful Alam (2006),

In this study, methods of strengthening of reinforced concrete beams using ferrocement laminates with skeletal bar attached on to the soffit of the beams are reviewed. The addition of ferrocement laminates with skeletal bar to the soffit (tension face) of the beams substantially delayed the formations of first crack, restrained the crack widths and increased the flexural stiffness and load capacities of the strengthened beams. The effects of curtailing the ferrocement laminate short of the supports were studied. In the strengthening carried out in the present work, the ferrocement laminates were extended over the supports. This however would be difficult to achieve in practice.

Vidivelli.B, et al (2001),

In this study, the damage due to overloading is considered. A total of three beams were cast and tested. One beam (control beam) was tested to ascertain the load deflection behaviour and ultimate load. The remaining two beams were damaged by overloading. After unloading the damaged beam specimens were repaired with ferrocement laminates with single layer at tension face using epoxy. Static test was conducted on all the beams to determine the load deflection behaviour and ultimate load. A comparison was made on crack width, deflection and ultimate strength at different load stages between control, damaged and repaired beams.

Experimental Investigation on Flexural Behaviour of Reinforced Concrete Beams Strengthened by Ferrocement Laminates

 

Experimental Programme

Material Used

For the beam specimen, the concrete with design compressive strength of M20 was used. The concrete mix proportions are given in Table1. 43 grade Portland Pozzalana Cement (PPC) confirming to IS: 1489 – 1991, having a specific gravity of 2.92 was used. Locally available river sand having a fineness modulus of 2.61, specific gravity of 2.65 and coarse aggregates of 20mm maximum size, having a fineness modulus of 6.97 and specific gravity of 2.9, were used. High yield strength deformed bars of Fe 415 were used as reinforcement in the concrete beam

Experimental Investigation on Flexural Behaviour of Reinforced Concrete Beams Strengthened by Ferrocement Laminates Figure 1: Cross section and reinforcement details of RC Beams


For casting of the ferrocement laminates Portland cement mortar matrix, woven and welded meshes of size 24 gauge are tied together to act as reinforcement. Ferrocement may require chemical additives to reduce the reaction between the matrix and the reinforcement.

Experimental Investigation on Flexural Behaviour of Reinforced Concrete Beams Strengthened by Ferrocement LaminatesFigure 2: Preparation of distressed beam surface

 

Details of Test Specimen

Five beams were cast for flexural test out of which one beam was control beam the second and third were tested for service load and rehabilitated and the fourth and fifth beams are retrofitted. For rehabilitation and retrofitting ferrocement laminates were used. The details of reinforcement used in the beam are as shown in the Fig.1. Wooden moulds satisfying the above specimen size were used. Before casting, machine oil was applied on the inner surfaces of moulds. Concrete was mixed using tilting type laboratory concrete mixer and was poured into the moulds in layers. Each layer of concrete was compacted well. The specimens were removed from mould after 24 hours of casting and then cured using jute bags. All specimens were moist cured for 28 days.

Experimental Investigation on Flexural Behaviour of Reinforced Concrete Beams Strengthened by Ferrocement Laminates Figure 3: Ferrocement laminate

 

Bonding of Ferrocement laminate to beam

Before bonding the fabricated ferrocement laminates on the soffit (tension side) of the concrete beam, surface was made rough using sand blasting and cleaned with an air blower to remove all dirt and debris. Once the surface was prepared to the required standard, the epoxy resin was mixed in accordance with manufacturer's instructions. Mixing was carried out in a metal container with base to hardener ratio of 1:2 and was continued until the mixture obtained uniform colour. Then it was applied both on laminate and beam surface and bonded properly without any air gap.

Experimental Investigation on Flexural Behaviour of Reinforced Concrete Beams Strengthened by Ferrocement LaminatesFigure 4: Bonding of laminnates to the beam

 

Experimental set-up

Two-point loading system was adopted for the tests. At the end of each load increment, deflection and ultimate load were carefully observed and recorded. The ultimate load for the control beam was found out. Then the other two beams (S) were tested for service load and rehabilitated with ferrocement laminates. The other two beams (R) were retrofitted with ferrocement laminates. The rehabilitated and retrofitted beams were again tested by two point loads and at the end of each load increment; the deflection was carefully observed and recorded. The recorded values are graphically represented and are shown in Fig.6.

Experimental Investigation on Flexural Behaviour of Reinforced Concrete Beams Strengthened by Ferrocement LaminatesFigure 5: Experimental setup

 

Results and Discussions

Experimental Investigation on Flexural Behaviour of Reinforced Concrete Beams Strengthened by Ferrocement LaminatesFigure 6: Load vs Deflection

From the test results summarized in Fig.6, it can be concluded that the rehabilitated beam with ferrocement laminates 12% lesser load than the controlled beam. The retrofitted beam carries 18% more load than that of control and 24% of rehabilitated beam. Fig.6 shows the ultimate load carrying capacity of the beams with different configuration.

Acknowledgements

The experimental work was carried out in the Structural Engineering Laboratory of Thiagarajar College of Engineering, Madurai and Tamilnadu. We would like to thank the faculty members of Structural engineering Department, AnnamalaiUniversity, Annamalai nagar.

References

  • Mohammad taghi kazemi and Reza morshed (2005), "Seismic shear strengthening of RC columns with ferrocement jacket", Journal of structural Engineering, Vol.1.
  • Ong, K.C.G, Paramasivam. P and Lim, C.T.E (1992), "Flexural strengthening of Reinforced concrete beams using ferrocement laminates", Journal of Ferrocement, Vol.22, No.4, PP. 331 - 342.
  • Vidivelli.B, Antony Jeyasehar.C, Srividya P.R. (2001),"Repair and Rehabilitation of Reinforced concrete beams by Ferrocement," In proceedings of the Seventh International conference on ferrocement, Singapore, PP. 465 – 470.
NBM&CW March 2011

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

Advancing Concrete Durability in Coastal and Aggressive Environments

Advancing Concrete Durability in Coastal and Aggressive Environments

Professor (Dr.) S B Hegde provides a thorough examination of the challenges faced by concrete infrastructure in India’s coastal and harsh environments; the impact of salt, humidity, pollution, and extreme weather on concrete durability

Read more ...

Concrete Distress Maintenance & Repair Techniques

Concrete Distress Maintenance & Repair Techniques

Concrete structures deteriorate over time due to environmental factors, leading to issues like cracks and corrosion. Effective repair and maintenance are vital for restoring strength and durability. In this article, Sasanka Dey

Read more ...

Durability and Sustainability of Hardened Concrete

Durability and Sustainability of Hardened Concrete

Concrete is widely used in construction, yet its longevity and sustainability often go unnoticed until signs of premature deterioration appear. To truly understand how to extend its service life, it is crucial to explore the factors

Read more ...

Role of Chemical Admixtures in Enhancing Construction Durability

Role of Chemical Admixtures in Enhancing Construction Durability

“In modern construction, the integration of chemical admixtures is not just an enhancement—it's a necessity. By improving durability, performance, and sustainability, these innovations are shaping the future of infrastructure.

Read more ...

ICrete by Amazecrete: A Game-changer Concrete Additive

ICrete by Amazecrete: A Game-changer Concrete Additive

With the introduction of ICrete, we are pushing the boundaries of concrete technology with solutions that address both performance and environmental challenges. Kowshika V R, Executive Director, Amazecrete

Read more ...

Grinding Aids as Energy Saver in Cement Production

Grinding Aids as Energy Saver in Cement Production

The benefits of using different grinding aids in cement production are improved output, decreased energy consumption, cost reduction, and minimizing the carbon footprint- all of which are steps forward in bringing greater sustainability

Read more ...

Thermax Acquires BuildTech to Expand its Footprint in Construction Chemicals

Thermax Acquires BuildTech to Expand its Footprint in Construction Chemicals

The recent acquisition of BuildTech by Thermax exemplifies a significant trend within the industry towards strategic expansion and enhanced capabilities in construction technologies.

Read more ...

Icrete By Amazecrete Enhances Strength & Durability of Concrete

Icrete By Amazecrete Enhances Strength & Durability of Concrete

Icrete has emerged as a new age material for Concrete Construction given its efficacy in increasing the strength and durability of concrete, bringing value additions and greater profitability to the users.

Read more ...

Cement Industry Targets Net Zero with 25% Emissions Reduction by 2030

Cement Industry Targets Net Zero with 25% Emissions Reduction by 2030

The Cement Industry is embarking on a Net Zero pathway, aiming for a 25% reduction in CO2 emissions by 2030 and a full decarbonization by 2050, driven by technological innovations, use of alternative raw materials, and circular economy

Read more ...

Determining Plastic Hinge Length in Precast Seismic Force-Resisting Systems

Determining Plastic Hinge Length in Precast Seismic Force-Resisting Systems

Plastic hinges form at the maximum moment region of reinforced concrete columns. A reasonable estimation of the plastic hinge length is key to successfully modeling the lateral load-drift response and conducting a proper seismic

Read more ...

Properties and Applications of Geopolymer Masonry Blocks

Properties and Applications of Geopolymer Masonry Blocks

Radhakrishna, Professor and Head, Department of Civil Engineering, RV College of Engineering, Affiliated to Visvesvaraya Technological University, Bengaluru. Block masonry is one of the oldest methods of construction. It is composed

Read more ...

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 ...

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