Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

Steel fibre reinforced concrete (SFRC) is widely recommended where fatigue is a predominant mode of failure, such as concrete bridges, offshore structures and concrete pavements. From a detailed literature review, it was observed that the different fibre parameters like fibre type, fibre volume, aspect ratio, etc., influence the crack resistance performance and thus, the fatigue endurance limit. This paper attempts to understand the effect of various test parameters (stress ratio, frequency) and fibre parameters (length, diameter, volume of fibres, aspect ratio and reinforcing index) on the fatigue life of SFRC based on available literature data. Studies involving SFRC with volume fractions of 0.13–2.0% are included in the analysis. The objective of the current study is to propose a generalized fatigue model, based on statistical analysis of data available from literature, for pre-cracked SFRC with the consideration of the above variables. A multiple linear regression (MLR) analysis using SPSS software was used to perform analysis of variance (ANOVA). The most significant parameters, obtained from the analysis, for the prediction of fatigue life of pre-cracked SFRC are stress ratio, length of fibre and reinforcing index. The generalized expression can be used for the prediction of the post cracking fatigue life of SFRC for volume fractions within the range of 0.13–2.0%. It is envisaged that these generalized models could be integrated into any SFRC design methodology requiring fatigue response prediction, leading to better-optimized designs. Overall, this study expands the state-of-the-art on fatigue behaviour of SFRC and its analysis.

World University root node

Environmental Sciences and Sustainable Engineering Centre (ESSENCE)

Department of Civil Engineering

RILEM Bookseries

Statistical Modelling of Flexural Fatigue Response of Steel Fibre Reinforced Concrete

This paper reviews the feasibility of using low grade clay for developing geopolymer mortar by partially replacing conventional source material. The study intends to develop a framework for identification, classification and utilization of various clays and suggest suitable processing techniques to qualify for geopolymerization. The influence of source clay based on the reactivity of silica, physical, chemical and mineralogical characteristics on the properties of geopolymer mortar is extensively studied based on existing literature. Characteristics of clay after various treatment methods (calcining and lime treatment) are also reviewed so as to identify the extent of its effectiveness on geopolymers. Characteristics based on micro-structural studies such as energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD) along with geotechnical characterization are reviewed. The paper highlights the significant characteristics of clay that is significant for geopolymerization and its implication on the properties of geopolymer mortar. The manifestation of geopolymer characteristics and its relation to crystallography and microstructure is explored to develop strategies for the qualification of clays. The influence of parameters such as alkali concentration and sodium silicate to sodium hydroxide ratio on compressive strength is presented. Based on the review, an attempt has been made to characterize different types of clay obtained from few sources in India, and a study has been conducted to assess the qualification technique proposed. © RILEM 2020.

Qualifying of Low Grade Clay for Geopolymer Mortar: A Preliminary Assessment

Use of fibre reinforced concrete (FRC) for pavements is advocated since the higher crack resistance could lead to lower slab thickness and higher joint spacing. The post-cracking capacity of FRC allows pavements to be designed and analysed considering the response beyond the elastic regime. The current paper presents possible failure patterns in FRC pavement slabs, which are governed by the slab dimensions, loading type and boundary conditions and the appropriateness of inelastic design methodologies for these failure patterns. Subsequently, a mechanistic-empirical design methodology developed for FRC pavements, based on yield line analysis incorporating fatigue in the moment calculation, is discussed. The proposed design methodology gives specific checks for the different failure patterns and the consequent design strategy to be adopted. The method incorporates material parameters, such as the first crack and post crack flexural strengths and fatigue correction factors for the evaluation of the moment carrying capacity. Cumulative fatigue damage analysis is also done as a serviceability check. The final design solution satisfies both the inelastic moment capacity requirement and fatigue life required without excessive damage accumulation.

Sadhana - Academy Proceedings in Engineering Sciences

Mechanistic-empirical design of fibre reinforced concrete (FRC) pavements using inelastic analysis

CONSTRUCTION MATERIALS AND SYSTEMS

In order to enable the adoption of fibre reinforced concrete (FRC) in applications such as slabs-on-grade, it is imperative to develop comprehensive guidelines that address different facets of the slab behavior. The current study aims at providing a design methodology for FRC slabs-on-grade and pavements, which incorporates suitable material parameters and considers various failure conditions. The approach is based on inelastic analysis since the presence of fibres imparts sufficient rotation capacity to the slabs. The equivalent flexural strength, fiflα150fifl is used to incorporate the crack resisting potential in the design. The required expressions are developed based on yield line analysis for different types of loads and lead to performance requirements in terms of the equivalent flexural strength, for a minimum thickness and chosen grade of concrete, by using appropriate limiting moment equations. The methodology also accounts for stresses due to temperature variations and restraint to shrinkage. A detailed calculation is also given to illustrate the use of the design procedure.

Indian Concrete Journal

Design methodology for fibre reinforced concrete slabs-on-grade based on inelastic analysis

The effective utilization of pseudo‐ductile materials like Fibre Reinforced Concrete (FRC) depends on the incorporation of suitable material parameters in appropriate design approaches. A design methodology has been developed for slabs‐on‐grade addressing various failure patterns and giving a performance requirement as the design output. This opens up the choice of fibres, allowing the use of combinations of fibres to suit the service requirements. In this context, the current study explores the use of hybrid combinations of conventional steel fibres (SF) and a genre of corrosionresistant amorphous metallic fibres (AMF) that have the ability to significantly enhance the flexural strength of concrete, even at relatively low dosages. It is shown that AMF, when used in combination with SF, results in a synergistic response with respect to toughness; mixes with 15 kg/m3 of SF and 20 kg/m3 of AMF exhibit about 50% higher characteristic flexural strength and more than double the characteristic equivalent flexural strength than the mix with 15 kg/m3 of SF alone, in the concrete considered here. Consequently, when FRC with a hybrid combination of fibres (AMF+SF) was considered in design, a significant reduction in thickness of slab was possible, in comparison to FRC with only SF.

Fulltext

RILEM Technical Letters

Benefits of using amorphous metallic fibres in concrete slabs‐on‐grade

Doctoral Thesis, Department of Civil Engineering, Indian Institute of {\ldots}

Design of Fibre Reinforced Concrete Slabs-ongrade and Pavements

A study on the use of amorphous metallic fibers (AMFs) in concrete was undertaken to combine its action with that of hooked-ended steel fibers for improving flexural strength and toughness. Tests on mixtures with various dosages of AMF (10, 20 and 30 kg/m3 [16.9, 33.7 and 50.6 lb/yd3]) and 15 kg/m3 (25.3 lb/yd3) of steel fibers were carried out, along with hybrid mixtures with two dosages of AMF. The results showed a significant increase in the flexural strength of concrete with the addition of AMF, even at low dosages. The performance of concretes with the hybrid combinations is significantly enhanced. For example, the equivalent flexural strength for the concretes with just 10 kg/m3 (16.9 lb/yd3) of AMF and 15 kg/m3 (25.3 lb/yd3) of steel fibers is 35% higher than with only steel fibers and is approximately 3.5 times that obtained with only 10 kg/m3 (16.9 lb/yd3) of AMF. The load-deflection behavior and the toughness parameters clearly indicate a significant synergy in the hybrid combination.

ACI Materials Journal

Synergy in toughness by incorporating amorphous metal and steel fibers

The use of fibre reinforced concrete (FRC) for applications such as slabs-on-grade and pavements has been established to be advantageous due to the superior crack resistance properties, enhanced post cracking moment carrying capacity, and higher performance under fatigue, shrinkage and temperature stresses. In this context, the goal of this doctoral work is to develop and propose a comprehensive methodology for the design of fibre reinforced concrete pavements/slabs-on-grade incorporating the inelastic design techniques and material characteristics specific to FRC. The material parameter adopted in design is the equivalent flexural strength at a specified deflection. A database of flexural toughness parameters based on existing codes has been prepared for typical fibre concretes incorporating various fibres in different dosages and also used for comparison of material performance. The paper discusses the proposed design methodology based on yield line analysis, which results in an economical solution with fibre concretes in comparison to plain concrete. Emphasis has also been given to fatigue stress design in the case of pavements by incorporating a stress correction factor based on S-N relations of FRC. The need to determine the actual temperature differential in slabs has also been illustrated based on the results from experimental program performed at IIT Madras.

Proceedings of the 10th fib International PhD Symposium in Civil Engineering

A design methodology for fibre reinforced concrete pavements and slabs-on-grade

Use of fibre-reinforced concrete for pavements, though widely established, lacks comprehensive standardization with respect to both design as well as implementation. Most widely used design methods have adopted the established techniques used for slab-on-grade, mostly due to lack of studies specific to pavements. This is a major drawback since the failure of slabs-on-grade is predominantly caused by static loading whereas the failure of pavements, more often than not, occurs at much lower stresses due to fatigue. In this context, a comprehensive design methodology exclusively for FRC pavements is proposed here including the effect of fatigue in conjunction with inelastic analysis. The static load design equation is based on Meyerhofs ultimate load (yield line) analysis. The material capacity is estimated using the flexural capacity factored by a stress reduction factor for FRC in the cracked and the uncracked state obtained from suitable S-N relations to account for the fatigue stresses. The material parameters incorporated in the design equations include the flexural strength and the equivalent flexural strength of FRC obtained using the unnotched prisms as per Japanese standards (JSCE-SF4).

American Concrete Institute, ACI Special Publication

A comprehensive methodology for the design of fibre-reinforced concrete pavements

Increased use of fibre reinforced concrete (FRC) in India has resulted in the urgent need to standardise testing and characterisation. The current paper addresses the different available techniques and gives pre-normative suggestions for toughness characterisation. The use of an unnotched beam test is advocated here considering the dearth of laboratories for performing more sophisticated tests and the use of FRC being by-and-large restricted to slabs-on-grade and other non-structural applications. In this study, different types of steel fibres were incorporated in a typical M35 concrete used in India in flooring applications. Flexural tests were conducted to obtain the load-deflection curves and determine various toughness parameters, viz., flexural strength, equivalent flexural strength, equivalent flexural strength ratio and residual strength. The load-deflection curves of FRC with undulated fibres differed significantly from those with straight hookedended fibres in that the concrete failure often occurred with significant crack branching and spalling. The tests indicate no significant change in compressive strength due to addition of fibres while the flexural strength of FRC is slightly higher than that of plain concrete emphasising the need for determining the flexural strength by testing rather than using values from empirical equations or from tests of plain concrete. Specifically, the results illustrate that hooked-ended fibres do not influence the behaviour until after the peak and are more efficient in improving toughness, especially at larger deflections resulting in higher equivalent flexural strengths, in comparison with the undulated fibres. As expected, the higher aspect ratio and higher dosage of steel fibres impart more toughness to the concrete. It is shown that different combinations of fibre type and dosage can yield similar equivalent flexural strength ratios (Re,n) and different fibres at same dosage can have different Re,n values. It was observed, in general, that the variability of flexural strength is much higher than that of the compressive strength and that the variation of results is lower for straight hooked-ended fibres. The scatter in the residual strengths is much higher than that in the equivalent flexural strength, which results in a relatively lower characteristic value for the former in comparison to the latter at similar deflections. Based on the study, recommendations have been made for consideration in an Indian test standard.

Characterisation of the toughness of fibre reinforced concrete - Revisited in the Indian context

A methodology for the design of steel fibre reinforced concrete (SFRC) pavements and slabs-on-grade is suggested incorporating the equivalent flexural strength to account for the residual moment carrying capacity. The design methodology is a modification of the yield line theory proposed by Concrete Society Report TR34 (2002). The methodology proposed has the advantage that it extends the familiar design methods of plain concrete slabs-on-grade design. Based on cost analysis, optimization of dosage of fibres and thickness has also been attempted to obtain economical solutions for typical loading.

8th RILEM International Symposium on Fibre Reinforced Concrete: Challenges and Opportunities (BEFIB2012)

On the Design of Steel Fibre Reinforced Concrete Pavements and Slabs-on-Grade

The current scenario of depleting resources has lead to a major thrust in developing and applying highly sustainable solutions to construction industry. Therefore, it has become essential to devise designs based on materials that cost the least for the transportation network and at the same time have a minimum environmental impact. Though there are a few modern material solutions that may meet these criteria, like the use of steel fibre reinforced concrete (SFRC) for pavement constructions, a proper evaluation of the performance and impact of utilization of such materials is lacking. Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) offer the means to evaluate the sustainability, and have been used in this paper to provide frameworks analysing Asphalt, Jointed Plain concrete (JPC) and Steel Fibre Reinforced Concrete pavements. In this work, asphalt, JPC and SFRC pavement sections have been designed as per the respective IRC guidelines so as to get equivalent designs for the given traffic loading, environmental and material conditions. Subsequently, LCCA is done as per the procedure provided in the Federal Highway Administration’s Interim Technical bulletin and LCA is done by using the process approach for each of the pavements. The assessment indicates where sustainable practices can be directed to so as to minimize environmental impacts in the initial stage of the pavement life cycle. The paper also discusses the limitations and difficulties of carrying out life cycle assessment and life cycle cost analysis for highways in India.&nbsp;