Mehran Khan - Academia.edu (original) (raw)

Papers by Mehran Khan

Cement and Concrete Research, 2022

Case Studies in Construction Materials, 2022

Structural Concrete, 2021

Construction and Building Materials, 2021

Abstract The bond at fiber–matrix interface is considered as one of the most important factors in... more Abstract The bond at fiber–matrix interface is considered as one of the most important factors influencing the performance of fiber reinforced cementitious composites (FRCC). To improve such bond, adding silica fume is considered as an effective and efficient method. In modern FRCC, CaCO3 (calcium carbonate) whisker and basalt fibers witnessed increasing popularity due to their effectiveness in improving mechanical performance at multi-scales. However, systematic research still lacks for the bond improvement at their fiber–matrix interface. In this regard, silica fume of various contents was added to plain concrete (PC), CaCO3 whisker reinforced cementitious composites (CWRCC) and basalt fiber reinforced cementitious composites (BFRC). The bond strength at the fiber–matrix interface and mechanical properties of PC, CWRCC and BFRC were evaluated. Test results show that the addition of silica-fume up to 10% could enhance the interface bond and mechanical properties of CWRCC and BFRC up to 30% and 34%, respectively. SEM analysis revealed improved bond at the fiber–matrix interface with addition of silica fume as evidenced by the fact that the whisker after pulled out from the matrix was encapsulated by cement paste, as compared to that of plain composite without silica fume. Moreover, EDS energy spectrum of whisker and basalt fiber surface show that the Si content increased noticeably as a result of the increased hydration products adhering to the whisker and basalt fiber surface, thus improving the bond at the fiber–matrix interface. The incorporation of silica-fume in BFRC lead to a large number of attached hydration products to the surface of fiber after pulling out. At the initial stage of cement hydration, dispersed silica-fume particles play a role of “crystal nucleus”, which can absorb Ca + and OH– ions, and increase the number of CH nuclei. Furthermore, silica-fume continuously reacts with CH and procedure C-S-H gel which decreases the porosity of the interface layer, makes the structure more compact and improves the interfacial adhesion. The microstructure of the interface layer is enhanced by C-S-H which is generated by “secondary reaction” and increase the interfacial bond strength of fiber and matrix. Lastly, a microstructure schematic representation for the fiber–matrix interface was developed to understand the mechanism between the fiber and the cement matrix.

Materials, 2021

Fracture characteristics were used to effectively evaluate the performance of fiber-reinforced ce... more Fracture characteristics were used to effectively evaluate the performance of fiber-reinforced cementitious composites. The fracture parameters provided the basis for crack stability analysis, service performance, safety evaluation, and protection. Much research has been carried out in the proposed study field over the previous two decades. Therefore, it was required to analyze the research trend from the available bibliometric data. In this study, the scientometric analysis and science mapping techniques were performed along with a comprehensive discussion to identify the relevant publication field, highly used keywords, most active authors, most cited articles, and regions with largest impact on the field of fracture properties of cement-based materials (CBMs). Furthermore, the characteristic of various fibers such as steel, polymeric, inorganic, and carbon fibers are discussed, and the factors affecting the fracture properties of fiber-reinforced CBMs (FRCBMs) are reviewed. In ad...

Journal of Building Engineering, 2020

Abstract In order to ensure safety of confined brick masonry structures, researchers have recomme... more Abstract In order to ensure safety of confined brick masonry structures, researchers have recommended the use of reinforced-concrete (RC) stiffeners. Most of the time, the seismic demand is much less than the provided strength even with the use of minimum stiffeners cross-section, concrete strength and reinforcement re-bars. Thus, there is a need to correlate the seismic demand with the stiffeners design. In this paper, the optimization of RC stiffeners is proposed using a diagonal approach and validated numerically. The purpose of this effort is to ensure both structural safety and economy at the same time. A total of 50 macro-models of brick masonry structures are developed and analyzed in SAP2000 for different seismic parameters. The principle critical stress and top maximum displacement (in-plane) are studied in detail. The prediction of cracks propagation is also made. The behaviour of different confined brick masonry structures (CBMS) are compared with that of unconfined brick masonry structure (UBMS). As anticipated, CBMS (with proposed stiffeners) performed better compared to UBMS for respective seismic loadings. It is concluded that the proposed optimized stiffeners in CBMS meet the required seismic demand for combinations of seismic loadings.

Construction and Building Materials, 2020

Abstract Calcium carbonate whisker (CW) is used to modify the steel-PVA hybrid fibers reinforced ... more Abstract Calcium carbonate whisker (CW) is used to modify the steel-PVA hybrid fibers reinforced cementitious composites (SPFRCC). The addition of CW result in excellent mechanical properties and considerable economic benefit owing to its microscopic reinforcement effect and low cost. In this study, the flexural behavior, fiber distribution characteristics and compression response of CW modified steel-PVA hybrid fibers reinforced cementitious composites (CW-SPFRCC) are investigated by three-point bending test, image processing technique and uniaxial compression test, respectively. The results indicate that the addition of CW can effectively improve the flexural properties of SPFRCC because of the crack resistance and filling effect at microscale. The best fiber distribution characteristics are observed in CW10-S15P05 due to the presence of CW that modify the adhesion and flowability of cement matrix. The uniaxial compression strength, peak strain, elastic modulus and Poisson's ratio of CW-SPFRCC are increased by 37.1%, 40.2%, 3.7% and 30.7%, respectively. Meanwhile, the uniaxial compression constitutive model is proposed to describe the compression stress–strain relationship of CW-SPFRCC based on the experimental results. Moreover, the microstructure analysis demonstrates that the modification mechanism of CW in SPFRCC is attributed to the interface improvement, CW pull-out, CW slippage, and CW rupture.

Journal of Building Engineering, 2020

Journal of Building Engineering, 2020

Materials, 2020

Recently, the addition of natural fibers to high strength concrete (HSC) has been of great intere... more Recently, the addition of natural fibers to high strength concrete (HSC) has been of great interest in the field of construction materials. Compared to artificial fibers, natural fibers are cheap and locally available. Among all natural fibers, coconut fibers have the greatest known toughness. In this work, the mechanical properties of coconut fiber reinforced high strength concrete (CFR-HSC) are explored. Silica fume (10% by mass) and super plasticizer (1% by mass) are also added to the CFR-HSC. The influence of 25 mm-, 50 mm-, and 75 mm-long coconut fibers and 0.5%, 1%, 1.5%, and 2% contents by mass is investigated. The microstructure of CFR-HSC is studied using scanning electron microscopy (SEM). The experimental results revealed that CFR-HSC has improved compressive, splitting-tensile, and flexural strengths, and energy absorption and toughness indices compared to HSC. The overall best results are obtained for the CFR-HSC having 50 mm long coconut fibers with 1.5% content by cem...

Magazine of Concrete Research, 2019

Nowadays, basalt fibre is gaining popularity in the field of construction materials due to its lo... more Nowadays, basalt fibre is gaining popularity in the field of construction materials due to its low production cost and enhanced mechanical properties. However, research is still needed into the use of a single type of fibre with different lengths in composite materials. Therefore, in this paper the hybridisation of basalt fibre of various lengths and contents is studied in order to take full advantage of multi-scale characteristic(s) with a single type of fibre, while the fundamental mechanical properties of single-length basalt-fibre-reinforced cementitious composites and hybridisation of different-length basalt-fibre-reinforced composites are investigated. Additionally, a hybrid fibre coefficient is developed to evaluate the effect of hybrid fibre in cementitious materials. A total of 17 mix proportions were made containing either a single length or a combination of four different lengths of basalt fibre (3, 6, 12 and 20 mm) with various total volume contents. The paper shows that...

Magazine of Concrete Research, 2019

Nowadays, basalt fibre is gaining popularity in the field of construction materials due to its lo... more Nowadays, basalt fibre is gaining popularity in the field of construction materials due to its low production cost and enhanced mechanical properties. However, research is still needed into the use of a single type of fibre with different lengths in composite materials. Therefore, in this paper the hybridisation of basalt fibre of various lengths and contents is studied in order to take full advantage of multi-scale characteristic(s) with a single type of fibre, while the fundamental mechanical properties of single-length basalt-fibre-reinforced cementitious composites and hybridisation of different-length basalt-fibre-reinforced composites are investigated. Additionally, a hybrid fibre coefficient is developed to evaluate the effect of hybrid fibre in cementitious materials. A total of 17 mix proportions were made containing either a single length or a combination of four different lengths of basalt fibre (3, 6, 12 and 20 mm) with various total volume contents. The paper shows that...

Construction and Building Materials, 2018

Construction and Building Materials, 2019

Construction and Building Materials, 2018

Construction and Building Materials, 2018

INTRODUCTION: While science has taken giant strides over time, people in our society are still un... more INTRODUCTION: While science has taken giant strides over time, people in our society are still unable to define and identify stress. A lot of people are victims of stress in our society today, including medical students who are constantly coping with the challenges of medical education in tandem with the demands of personal and social life. <br>OBJECTIVE: The main objective of the study was to determine the level and cause of stress and the coping strategies used by medical students of Khyber Pakhtunkhwa. <br>METHODOLOGY: A cross-sectional study was conducted in five private medical colleges of Khyber Pakhtunkhwa. The study sample was 300 medical students of first and second-year MBBS. Probability stratified sampling technique was used to collect data. The period of study was from October 2017 to January 2018. Data was analyzed by SPSS version-20.0. <br>RESULTS: A total of 300 medical students participated in the study of which of 55% were male and 45% females. The...

Proceedings of the 31st Annual ACM Symposium on Applied Computing - SAC '16, 2016

Software architecture design and requirement engineering are core and independent areas of engine... more Software architecture design and requirement engineering are core and independent areas of engineering. A lot of research, education and practice are carried on Requirement elicitation and doing refine it, but it is a major issue of engineering. QSMSR model act as a bridge between requirement and design. There is a huge gap between these two areas of software architecture and

Cement and Concrete Research, 2022

Case Studies in Construction Materials, 2022

Structural Concrete, 2021

Construction and Building Materials, 2021

Abstract The bond at fiber–matrix interface is considered as one of the most important factors in... more Abstract The bond at fiber–matrix interface is considered as one of the most important factors influencing the performance of fiber reinforced cementitious composites (FRCC). To improve such bond, adding silica fume is considered as an effective and efficient method. In modern FRCC, CaCO3 (calcium carbonate) whisker and basalt fibers witnessed increasing popularity due to their effectiveness in improving mechanical performance at multi-scales. However, systematic research still lacks for the bond improvement at their fiber–matrix interface. In this regard, silica fume of various contents was added to plain concrete (PC), CaCO3 whisker reinforced cementitious composites (CWRCC) and basalt fiber reinforced cementitious composites (BFRC). The bond strength at the fiber–matrix interface and mechanical properties of PC, CWRCC and BFRC were evaluated. Test results show that the addition of silica-fume up to 10% could enhance the interface bond and mechanical properties of CWRCC and BFRC up to 30% and 34%, respectively. SEM analysis revealed improved bond at the fiber–matrix interface with addition of silica fume as evidenced by the fact that the whisker after pulled out from the matrix was encapsulated by cement paste, as compared to that of plain composite without silica fume. Moreover, EDS energy spectrum of whisker and basalt fiber surface show that the Si content increased noticeably as a result of the increased hydration products adhering to the whisker and basalt fiber surface, thus improving the bond at the fiber–matrix interface. The incorporation of silica-fume in BFRC lead to a large number of attached hydration products to the surface of fiber after pulling out. At the initial stage of cement hydration, dispersed silica-fume particles play a role of “crystal nucleus”, which can absorb Ca + and OH– ions, and increase the number of CH nuclei. Furthermore, silica-fume continuously reacts with CH and procedure C-S-H gel which decreases the porosity of the interface layer, makes the structure more compact and improves the interfacial adhesion. The microstructure of the interface layer is enhanced by C-S-H which is generated by “secondary reaction” and increase the interfacial bond strength of fiber and matrix. Lastly, a microstructure schematic representation for the fiber–matrix interface was developed to understand the mechanism between the fiber and the cement matrix.

Materials, 2021

Fracture characteristics were used to effectively evaluate the performance of fiber-reinforced ce... more Fracture characteristics were used to effectively evaluate the performance of fiber-reinforced cementitious composites. The fracture parameters provided the basis for crack stability analysis, service performance, safety evaluation, and protection. Much research has been carried out in the proposed study field over the previous two decades. Therefore, it was required to analyze the research trend from the available bibliometric data. In this study, the scientometric analysis and science mapping techniques were performed along with a comprehensive discussion to identify the relevant publication field, highly used keywords, most active authors, most cited articles, and regions with largest impact on the field of fracture properties of cement-based materials (CBMs). Furthermore, the characteristic of various fibers such as steel, polymeric, inorganic, and carbon fibers are discussed, and the factors affecting the fracture properties of fiber-reinforced CBMs (FRCBMs) are reviewed. In ad...

Journal of Building Engineering, 2020

Abstract In order to ensure safety of confined brick masonry structures, researchers have recomme... more Abstract In order to ensure safety of confined brick masonry structures, researchers have recommended the use of reinforced-concrete (RC) stiffeners. Most of the time, the seismic demand is much less than the provided strength even with the use of minimum stiffeners cross-section, concrete strength and reinforcement re-bars. Thus, there is a need to correlate the seismic demand with the stiffeners design. In this paper, the optimization of RC stiffeners is proposed using a diagonal approach and validated numerically. The purpose of this effort is to ensure both structural safety and economy at the same time. A total of 50 macro-models of brick masonry structures are developed and analyzed in SAP2000 for different seismic parameters. The principle critical stress and top maximum displacement (in-plane) are studied in detail. The prediction of cracks propagation is also made. The behaviour of different confined brick masonry structures (CBMS) are compared with that of unconfined brick masonry structure (UBMS). As anticipated, CBMS (with proposed stiffeners) performed better compared to UBMS for respective seismic loadings. It is concluded that the proposed optimized stiffeners in CBMS meet the required seismic demand for combinations of seismic loadings.

Construction and Building Materials, 2020

Abstract Calcium carbonate whisker (CW) is used to modify the steel-PVA hybrid fibers reinforced ... more Abstract Calcium carbonate whisker (CW) is used to modify the steel-PVA hybrid fibers reinforced cementitious composites (SPFRCC). The addition of CW result in excellent mechanical properties and considerable economic benefit owing to its microscopic reinforcement effect and low cost. In this study, the flexural behavior, fiber distribution characteristics and compression response of CW modified steel-PVA hybrid fibers reinforced cementitious composites (CW-SPFRCC) are investigated by three-point bending test, image processing technique and uniaxial compression test, respectively. The results indicate that the addition of CW can effectively improve the flexural properties of SPFRCC because of the crack resistance and filling effect at microscale. The best fiber distribution characteristics are observed in CW10-S15P05 due to the presence of CW that modify the adhesion and flowability of cement matrix. The uniaxial compression strength, peak strain, elastic modulus and Poisson's ratio of CW-SPFRCC are increased by 37.1%, 40.2%, 3.7% and 30.7%, respectively. Meanwhile, the uniaxial compression constitutive model is proposed to describe the compression stress–strain relationship of CW-SPFRCC based on the experimental results. Moreover, the microstructure analysis demonstrates that the modification mechanism of CW in SPFRCC is attributed to the interface improvement, CW pull-out, CW slippage, and CW rupture.

Journal of Building Engineering, 2020

Journal of Building Engineering, 2020

Materials, 2020

Recently, the addition of natural fibers to high strength concrete (HSC) has been of great intere... more Recently, the addition of natural fibers to high strength concrete (HSC) has been of great interest in the field of construction materials. Compared to artificial fibers, natural fibers are cheap and locally available. Among all natural fibers, coconut fibers have the greatest known toughness. In this work, the mechanical properties of coconut fiber reinforced high strength concrete (CFR-HSC) are explored. Silica fume (10% by mass) and super plasticizer (1% by mass) are also added to the CFR-HSC. The influence of 25 mm-, 50 mm-, and 75 mm-long coconut fibers and 0.5%, 1%, 1.5%, and 2% contents by mass is investigated. The microstructure of CFR-HSC is studied using scanning electron microscopy (SEM). The experimental results revealed that CFR-HSC has improved compressive, splitting-tensile, and flexural strengths, and energy absorption and toughness indices compared to HSC. The overall best results are obtained for the CFR-HSC having 50 mm long coconut fibers with 1.5% content by cem...

Magazine of Concrete Research, 2019

Nowadays, basalt fibre is gaining popularity in the field of construction materials due to its lo... more Nowadays, basalt fibre is gaining popularity in the field of construction materials due to its low production cost and enhanced mechanical properties. However, research is still needed into the use of a single type of fibre with different lengths in composite materials. Therefore, in this paper the hybridisation of basalt fibre of various lengths and contents is studied in order to take full advantage of multi-scale characteristic(s) with a single type of fibre, while the fundamental mechanical properties of single-length basalt-fibre-reinforced cementitious composites and hybridisation of different-length basalt-fibre-reinforced composites are investigated. Additionally, a hybrid fibre coefficient is developed to evaluate the effect of hybrid fibre in cementitious materials. A total of 17 mix proportions were made containing either a single length or a combination of four different lengths of basalt fibre (3, 6, 12 and 20 mm) with various total volume contents. The paper shows that...

Magazine of Concrete Research, 2019

Nowadays, basalt fibre is gaining popularity in the field of construction materials due to its lo... more Nowadays, basalt fibre is gaining popularity in the field of construction materials due to its low production cost and enhanced mechanical properties. However, research is still needed into the use of a single type of fibre with different lengths in composite materials. Therefore, in this paper the hybridisation of basalt fibre of various lengths and contents is studied in order to take full advantage of multi-scale characteristic(s) with a single type of fibre, while the fundamental mechanical properties of single-length basalt-fibre-reinforced cementitious composites and hybridisation of different-length basalt-fibre-reinforced composites are investigated. Additionally, a hybrid fibre coefficient is developed to evaluate the effect of hybrid fibre in cementitious materials. A total of 17 mix proportions were made containing either a single length or a combination of four different lengths of basalt fibre (3, 6, 12 and 20 mm) with various total volume contents. The paper shows that...

Construction and Building Materials, 2018

Construction and Building Materials, 2019

Construction and Building Materials, 2018

Construction and Building Materials, 2018

INTRODUCTION: While science has taken giant strides over time, people in our society are still un... more INTRODUCTION: While science has taken giant strides over time, people in our society are still unable to define and identify stress. A lot of people are victims of stress in our society today, including medical students who are constantly coping with the challenges of medical education in tandem with the demands of personal and social life. <br>OBJECTIVE: The main objective of the study was to determine the level and cause of stress and the coping strategies used by medical students of Khyber Pakhtunkhwa. <br>METHODOLOGY: A cross-sectional study was conducted in five private medical colleges of Khyber Pakhtunkhwa. The study sample was 300 medical students of first and second-year MBBS. Probability stratified sampling technique was used to collect data. The period of study was from October 2017 to January 2018. Data was analyzed by SPSS version-20.0. <br>RESULTS: A total of 300 medical students participated in the study of which of 55% were male and 45% females. The...

Proceedings of the 31st Annual ACM Symposium on Applied Computing - SAC '16, 2016

Software architecture design and requirement engineering are core and independent areas of engine... more Software architecture design and requirement engineering are core and independent areas of engineering. A lot of research, education and practice are carried on Requirement elicitation and doing refine it, but it is a major issue of engineering. QSMSR model act as a bridge between requirement and design. There is a huge gap between these two areas of software architecture and