Shubham Raj | Indian Institute of Technology Madras, Chennai (original) (raw)

Papers by Shubham Raj

Cement and Concrete Composites, 2023

Foam concrete is prone to instability during mixing, casting, and curing. Besides preformed foam ... more Foam concrete is prone to instability during mixing, casting, and curing. Besides preformed foam stability characteristics and volume, several geopolymer mix parameters, viz., precursor composition, silica modulus, alkali content, and water content, influence the overall foamed concrete stability, the understanding of which is still limited. This study evaluates the effect of the above parameters on the physical, hydrolytic, and mechanical stability of fly ash and slag-based foamed geopolymer. Physical stability was assessed by the design of experiments using a central composite design (inscribed), while systematic laboratory experiments assessed hydrolytic and mechanical stability characteristics. The foamed geopolymer behavior is sensitive to silica modulus and solid alkali-to-binder ratio, showing maximum interaction effects for producing stable foamed geopolymer for i) target to actual fresh density difference and ii) settlement along the height. The water-to-binder ratio was the most significant factor affecting the homogeneity across the cross-section along the height.

Further, the alkali and slag content significantly affected the hydrolytic and mechanical stability characteristics. An optimum proportion of slag content, silica modulus, solid alkali-to-binder ratio, and water-to-binder ratio is suggested for the maximum benefit of fly ash and slag-based foamed geopolymer. This study provides a framework for comprehensive stability assessment of foamed geopolymers and can aid in developing sustainable lightweight materials for industrial applications.

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2022

Foam characteristics, including density, stability, and texture, influence the properties of end ... more Foam characteristics, including density, stability, and texture, influence the properties of end products like foamed concrete. The present work investigates the individual and combined influence of xanthan gum and low-cost sodium-based admixtures (NaOH, NaCl, and Na2CO3) on the viscosity of sodium lauryl sulfate (SLS) foaming solution and the foam characteristics. Where xanthan gum induced its characteristic pseudo-plastic behavior to the foaming solution, the addition of sodium-based admixtures did not affect the Newtonian behavior of the SLS solution. The addition of sodium-based admixtures elevated the critical turbidity and Krafft temperature of the surfactant solution. Xanthan gum substantially reduced the liquid drainage and improved stability to a great extent. However, the increment in foam density was more gradual with increasing xanthan gum dosage, following an increase in lamella thickness. Sodium-based admixtures significantly increased the density of foam while reducing the bubble sizes. Further, the SLS solution admixed with xanthan gum and sodium-based admixture resulted in foam with properties intermediate to the foams stabilized with individual admixtures. The resulting foam had a higher density and a smaller mean bubble size than unstabilized or xanthan gum stabilized foam. In contrast, the stability was more increased compared to unstabilized or sodium-based admixture stabilized foam.

World Journal of Engineering, 2018

Industrial wastes such as copper slag and fly ash are being generated in tons every year and disp... more Industrial wastes such as copper slag and fly ash are being generated in tons every year and disposed mainly by land fillings, resulting in wastage of useful land. Copper slag in itself is a granular cohesionless sand-like material, while fly ash is highly pozzolanic. The purpose of this paper is to investigate copper slag and fly ash mixes with cement as stabilizer for their proper use in road construction.,Different trial mixes of copper slag and fly ash were tested for obtaining the optimum mix having maximum dry density. Cylindrical specimens were prepared using optimum mix with different proportion of cement (3, 6 and 9 per cent) and cured for period of 7, 14 and 28 days in desiccator. Several tests such as proctor test, unconfined compressive strength test, splitting tensile strength test and soaked CBR test were carried out.,After analyzing the variation of test results with varying cement content and curing period, maximum compressive strength of 10 MPa and maximum tensile strength of 1.5 MPa was found for specimen having 9 per cent cement content cured for a period of 28 days. It was concluded that copper slag and fly ash when mixed in optimum proportion and stabilized with 6 and 9 per cent cement can be effectively used as granular material in sub base and base layer of road pavement.,A typical flexible pavement section was designed and checked using IITPAVE software which gave desired results. This paper may add value in the areas of pavement design, waste utilization, etc.

SP-326: Durability and Sustainability of Concrete Structures (DSCS-2018), 2018

This study investigates the effect of recycled coarse aggregate (RCA) as replacement of natural c... more This study investigates the effect of recycled coarse aggregate (RCA) as replacement of natural coarse aggregate on the strength properties of concrete. The investigation was carried out by conducting unconfined compressive strength (UCS) test, indirect tensile strength (ITS) test, flexural strength test and bond strength test on five concrete mixtures using 0%, 25%, 50%, 75% and 100% by weight of RCA as replacement of natural coarse aggregate. The test samples were prepared with a target strength of 40 MPa (6000 psi). Water-cement ratio (w/c) and slump was adopted as 0.40 and 100 mm (4.0 in.) respectively. It was observed that as the percentage of RCA in concrete mixtures increased, the strength properties of concrete decreased. There was a decrease of 1.92%, 5.43%, 10.46% and 27.13% in UCS for RCA 25%, 50%, 75% and 100% respectively. Tensile strength of concrete decreased considerably on addition of RCA. All samples achieved target strength except 100% replacement. Also, as the percentage of RCA increased in concrete mixtures, the rate of strength gain over time decreased. However, RCA can be efficiently used as a replacement of natural coarse aggregate up to 25% without any major laboratory testing and up to 50% with proper testing and care for concreting where high strength is not a priority.

World Journal of Engineering, 2017

Purpose This study aims to investigate the optimum proportion of coconut fibre and cement suitabl... more Purpose This study aims to investigate the optimum proportion of coconut fibre and cement suitable for rammed earth wall construction. Coconut fibres and cement can be easily incorporated into the soil mixture which adds strength and durability to the wall. This paper highlights the salient observations from a systematic investigation on the effect of coconut fibre on the performance of stabilized rammed earth blocks. Design/methodology/approach Stabilization of soil was done by adding Ordinary Portland Cement (2.5, 5.0, 7.5 and 10.0 per cent by weight of soil), whereas coconut fibre in length about 15 mm was added (0.2, 0.4, 0.6, 0.8 and 1.0 per cent by weight of soil) as reinforcement. Thirty types of mixes were created by adding different proportions of cement and fibre to locally available soil and compacting the mix at constant compaction energy in three layers with Proctor rammer. Findings Samples were tested for compressive strength and tensile strength, and failure patterns ...

Cement and Concrete Composites, 2023

Foam concrete is prone to instability during mixing, casting, and curing. Besides preformed foam ... more Foam concrete is prone to instability during mixing, casting, and curing. Besides preformed foam stability characteristics and volume, several geopolymer mix parameters, viz., precursor composition, silica modulus, alkali content, and water content, influence the overall foamed concrete stability, the understanding of which is still limited. This study evaluates the effect of the above parameters on the physical, hydrolytic, and mechanical stability of fly ash and slag-based foamed geopolymer. Physical stability was assessed by the design of experiments using a central composite design (inscribed), while systematic laboratory experiments assessed hydrolytic and mechanical stability characteristics. The foamed geopolymer behavior is sensitive to silica modulus and solid alkali-to-binder ratio, showing maximum interaction effects for producing stable foamed geopolymer for i) target to actual fresh density difference and ii) settlement along the height. The water-to-binder ratio was the most significant factor affecting the homogeneity across the cross-section along the height.

Further, the alkali and slag content significantly affected the hydrolytic and mechanical stability characteristics. An optimum proportion of slag content, silica modulus, solid alkali-to-binder ratio, and water-to-binder ratio is suggested for the maximum benefit of fly ash and slag-based foamed geopolymer. This study provides a framework for comprehensive stability assessment of foamed geopolymers and can aid in developing sustainable lightweight materials for industrial applications.

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2022

Foam characteristics, including density, stability, and texture, influence the properties of end ... more Foam characteristics, including density, stability, and texture, influence the properties of end products like foamed concrete. The present work investigates the individual and combined influence of xanthan gum and low-cost sodium-based admixtures (NaOH, NaCl, and Na2CO3) on the viscosity of sodium lauryl sulfate (SLS) foaming solution and the foam characteristics. Where xanthan gum induced its characteristic pseudo-plastic behavior to the foaming solution, the addition of sodium-based admixtures did not affect the Newtonian behavior of the SLS solution. The addition of sodium-based admixtures elevated the critical turbidity and Krafft temperature of the surfactant solution. Xanthan gum substantially reduced the liquid drainage and improved stability to a great extent. However, the increment in foam density was more gradual with increasing xanthan gum dosage, following an increase in lamella thickness. Sodium-based admixtures significantly increased the density of foam while reducing the bubble sizes. Further, the SLS solution admixed with xanthan gum and sodium-based admixture resulted in foam with properties intermediate to the foams stabilized with individual admixtures. The resulting foam had a higher density and a smaller mean bubble size than unstabilized or xanthan gum stabilized foam. In contrast, the stability was more increased compared to unstabilized or sodium-based admixture stabilized foam.

World Journal of Engineering, 2018

Industrial wastes such as copper slag and fly ash are being generated in tons every year and disp... more Industrial wastes such as copper slag and fly ash are being generated in tons every year and disposed mainly by land fillings, resulting in wastage of useful land. Copper slag in itself is a granular cohesionless sand-like material, while fly ash is highly pozzolanic. The purpose of this paper is to investigate copper slag and fly ash mixes with cement as stabilizer for their proper use in road construction.,Different trial mixes of copper slag and fly ash were tested for obtaining the optimum mix having maximum dry density. Cylindrical specimens were prepared using optimum mix with different proportion of cement (3, 6 and 9 per cent) and cured for period of 7, 14 and 28 days in desiccator. Several tests such as proctor test, unconfined compressive strength test, splitting tensile strength test and soaked CBR test were carried out.,After analyzing the variation of test results with varying cement content and curing period, maximum compressive strength of 10 MPa and maximum tensile strength of 1.5 MPa was found for specimen having 9 per cent cement content cured for a period of 28 days. It was concluded that copper slag and fly ash when mixed in optimum proportion and stabilized with 6 and 9 per cent cement can be effectively used as granular material in sub base and base layer of road pavement.,A typical flexible pavement section was designed and checked using IITPAVE software which gave desired results. This paper may add value in the areas of pavement design, waste utilization, etc.

SP-326: Durability and Sustainability of Concrete Structures (DSCS-2018), 2018

This study investigates the effect of recycled coarse aggregate (RCA) as replacement of natural c... more This study investigates the effect of recycled coarse aggregate (RCA) as replacement of natural coarse aggregate on the strength properties of concrete. The investigation was carried out by conducting unconfined compressive strength (UCS) test, indirect tensile strength (ITS) test, flexural strength test and bond strength test on five concrete mixtures using 0%, 25%, 50%, 75% and 100% by weight of RCA as replacement of natural coarse aggregate. The test samples were prepared with a target strength of 40 MPa (6000 psi). Water-cement ratio (w/c) and slump was adopted as 0.40 and 100 mm (4.0 in.) respectively. It was observed that as the percentage of RCA in concrete mixtures increased, the strength properties of concrete decreased. There was a decrease of 1.92%, 5.43%, 10.46% and 27.13% in UCS for RCA 25%, 50%, 75% and 100% respectively. Tensile strength of concrete decreased considerably on addition of RCA. All samples achieved target strength except 100% replacement. Also, as the percentage of RCA increased in concrete mixtures, the rate of strength gain over time decreased. However, RCA can be efficiently used as a replacement of natural coarse aggregate up to 25% without any major laboratory testing and up to 50% with proper testing and care for concreting where high strength is not a priority.

World Journal of Engineering, 2017

Purpose This study aims to investigate the optimum proportion of coconut fibre and cement suitabl... more Purpose This study aims to investigate the optimum proportion of coconut fibre and cement suitable for rammed earth wall construction. Coconut fibres and cement can be easily incorporated into the soil mixture which adds strength and durability to the wall. This paper highlights the salient observations from a systematic investigation on the effect of coconut fibre on the performance of stabilized rammed earth blocks. Design/methodology/approach Stabilization of soil was done by adding Ordinary Portland Cement (2.5, 5.0, 7.5 and 10.0 per cent by weight of soil), whereas coconut fibre in length about 15 mm was added (0.2, 0.4, 0.6, 0.8 and 1.0 per cent by weight of soil) as reinforcement. Thirty types of mixes were created by adding different proportions of cement and fibre to locally available soil and compacting the mix at constant compaction energy in three layers with Proctor rammer. Findings Samples were tested for compressive strength and tensile strength, and failure patterns ...