Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Department of Structural and Geotechical Engineering

Printed circuit boards (PCB) contain metallic and non-metallic fractions (NMF) that are hazardous and toxic when disposed of in a landfill. This paper emphasizes the feasibility of using NMF reclaimed from waste PCB's as a replacement to fly ash (FA) and metakaolin (MK) in a geopolymer mortar. Geopolymer mortar mixes were prepared with five FA-MK replacement ratios of 100-0, 90-10, 80-20, 70-30 and 60-40 and for each mix FA was also replaced with NMF by 5%, 10%, 15%, and 20%. The compressive strength and microstructures of geopolymer mortar were investigated and it was found that the addition of NMF enhanced the compressive strength. Maximum strength gain was found with 30% of MK and 15% of NMF in FA. The pozzolanic action of alumino-silicates was studied through SEM and XRD which reflected the formation of C-S-H gel with a dense geopolymer matrix along with the formation of CaCO3 crystals resulting in strength gain. The experimental studies provide a practical and sustainable recycling approach for the use of NMF in geopolymers for the construction industry. © 2020 Elsevier B.V.

World University root node

School of Civil Engineering

Vellore Campus

Resources, Conservation and Recycling

A novel approach for the development of sustainable hybridized geopolymer mortar from waste printed circuit boards

This research aims to study the influence of organic additive and aggregate grain size in lime mortar hardening for producing compatible, high-performance and eco-friendly materials for conservation and restoration of heritage structures. Mortar mix with lime to sand ratio of 1:3 by mass and water to binder ratio of 0.75 was considered. Ficus Carica (Moraceae), commonly known as Fig fruit, was used as an organic additive in the mortar mix at 2, 4 and 6% in volume. River sand grounded for 5, 10 and 15 minutes, turning in changes in grain-size distrubution, was used in the mortar mix. Investigations on mortars were performed after 90 curing days; physical and mechanical properties were evaluated, along with mineralogical changes due to organic addition; the influence of organic and aggregate grading in carbonation rate was also assessed. Results indicate that the aggregate with retention value 45 ± 3% in grades between 2 mm to 425 micron and 425 micron to 75 micron; and the addition of organic additive at 4% in volume represents the optimum mix able to assure significant enhansement in carbonation rate and mechanical resistance. Polysaccharides in organic played the central role in the mineralogical transformation responsible for the measured enhanced performances. © 2020 Taylor &amp; Francis.

International Journal of Architectural Heritage

Evaluating the Impact of Organic Addition and Aggregate Gradation on Air Lime Mortar: New Compatible Green Material for Heritage Application

Gainful utilization of mineral admixtures like Metakaolin (MK), Fly Ash (FA) and filler material like Waste Marble Powder (WMP) in various construction practices has become a new topic of interest in research area. This paper presents the studies regarding the use of MK and FA as cement substitution (partial) and WMP as fine aggregate replacement (partial) in Self-Compacting +Concrete (SCC). The pozzolanic nature of the MK and FA due to their high silica and alumina content enables them to be the most valuable Supplementary Cementing Materials (SCM’s) for utilization in the production of SCC. The MK was used as partial replacement of cement in seven different proportions of 5, 7.5, 10, 12.5, 15, 17.5 and 20% while as the FA replacement level (by weight of cement) was kept fixed at 15%. The fine aggregate was partially replaced by 20% WMP. To evaluate the influence of FA, the control mix with 15% FA substitution of cement was also designed. Thus, a total of nine mixes including the reference mix without fly ash were designed. The different tests to evaluate the workability were performed, which are presented in this paper. The specimens were tested in the hardened state at different ages for assessing the mechanical properties of SCC. The use of ternary binding blends consists of OPC+FA+MK and addition of WMP as fine aggregate replacement have shown a positive impact on fresh and mechanical characteristics of SCC. A significant correlation has also been observed between fresh properties and hardened properties of SCC. © 2020, Fundatia Serban Solacolu. All rights reserved.

Revista Romana de Materiale/ Romanian Journal of Materials

Behaviour of self-compacting concrete using different mineral powders additions in ternary blends

The emphasis of this review is to do a parametric analysis for the design of helical piles used in cohesive soils. Also, the enactment of helical piles’ behavior when placed in cohesive soils under various independent loading conditions like compression, uplift, and lateral loads has been discussed. Through a vast gathering of various literatures which is relevant to the design of helical piles, relations were obtained that would be ultimately valuable for future influences associated with the choosing of design parameters and behavioral studies on helical piles. In addition to design parameters, design methods were also considered and comparisons were made. Furthermore, attention is also sought from researchers on the need for further exploration of helical piles subjected to combined loadings and the significance of design parameters. © 2020, Saudi Society for Geosciences.

Arabian Journal of Geosciences

Design parameters and behavior of helical piles in cohesive soils—A review

The article reviews the application of soil living bacteria in concrete. Formation of cracks and subsequent degradation in concrete are the critical durability phenomenon. For protection against cracking, the repair and regular maintenance by traditional methods are found to be costly. Taking notes from biomimicry and biotechnology in concrete from various literature, the role of bacteria on self-healing of cracks and the indirect benefits to strength and durability property of concrete were consolidated and presented. Amid the different microbial species investigated by researchers, bacillus sphaericus have shown greater precipitation of calcium carbonate (CaCO3) with the cell concentration of 105 cells/ml. The hydrolysis of urea has shown a significant result in the precipitation of CaCO3. Thus, the conjunction of bacillus sphaericus with urea hydrolysis could be an optimum way for biomineralization of CaCO3. The shell life of microbes can be extended by encapsulation into the carrier materials (Eg: expanded clay, perlite etc). The large-scale production of bacterial concrete requires sophisticated laboratory for culturing of microbes and preparation of media. Due to these technical constraints, the application of novel bacterial concrete is at the laboratory level. © 2020 Elsevier Ltd.

Materials Today: Proceedings

Microbial precipitation of calcium carbonate in cementitious materials - A critical review

Self-compacting concrete is one of the special concretes that flow in its own weight, which is used in the densely reinforced concrete structures. This concrete requires higher binder content. Higher cement content leads to uneconomical design, higher heat of hydration, higher shrinkage, etc. These factors can be counteracted by addition of mineral admixtures. Hence, Fly ash (30%) and micro silica fume (10%) are mineral admixtures replaced with cement. Concrete is having a poor flexural properties; this can be enhanced by using fibrous materials. Addition of steel fibres improves the strain softening property of composite system. Hence hooked ended micro steel fibres are used in this study. In order, to study the fresh and mechanical properties of SCC, totally eight mix (M1 to M8) designs are developed using Nan Su proposed method of mix design, with varying steel fibres (0.0%, 0.25%, 0.50% and 0.75%) and varying binder content. To evaluate the impact of steel fibres in reinforced concrete; four mixes (C-1 to C-4) of prism dimension 0.1 m × 0.15 m × 1 m were cast with optimized steel fibres and mineral admixtures content and tested using standard UTM. The key properties such as deflection, strain softening and effect of orienting the steel fibres along the direction of flow of concrete were studied. Later the experimental work was virtually modeled and analyzed using ABAQUS. In rheological study, the mix containing mineral admixtures showed better fresh concrete properties. Addition of fibres reduced the flowing ability of SCC. There is no significant change in compression strength due to addition of steel fibres. Flexural strength increased by 63% by addition of 0.75% of steel fibres. The SEM analysis helped to study the hydration process and morphological behaviors in concrete structures. The statistical analysis were carried out and regression equations have been developed for the better understanding in the field of micro steel fibre-reinforced self-compacting concrete containing admixtures. Stress-Strain behavior of mix C3 and C4 is more linear compared to C1 and C2, due to presence of micro steel fibres, which is arrested the development of micro-cracks. C4 shows better strength compared to C3, showing steel fibres are aligned align the direction of flow of concrete in between the reinforced structures. The analyzed theoretical model, developed used ABAQUS showed similar displacement results. © 2020

Construction and Building Materials

Experimental, statistical and simulation analysis on impact of micro steel – Fibres in reinforced SCC containing admixtures

This investigation was carried out to find the effect of various admixtures on the durability properties of Self-Compacting Concrete (SCC) with ternary blends of powders. In this investigation SCC was prepared with Metakaolin (MK), Fly Ash (FA) as partial replacement of cement and Waste Marble Powder (WMP) as a filler material (replacing partial the sand). The MK and FA contains higher concentrations of Silica and Alumina and are therefore considered as congenial Supplementary Cementing Materials (SCM’s). Seven different proportions of MK were used in this investigation. The partial replacement of 15% FA with cement was kept constant for all the mixes (M1-M7) except control mix (M0). The efficiency of FA was evaluated by designing a control mix with 15% FA substitution (M8) of cement. The fine aggregate was replaced partially by 20% WMP. A total of nine mixes were designed. The specimens were tested in the hardened state at different ages for assessing the durability characteristics of SCC such as water absorption and porosity, sorptivity and resistance to acid attack. The results of this investigation revealed that the influence of above admixtures used was quite effective in production SCC with improved durability properties. © 2020, Fundatia Serban Solacolu. All rights reserved.

Durability properties of self-compacting concrete using different mineral powders additions in ternary blends

India is one of the prominent producers of coconuts in the world. Along with the desired products, many undesirable by-products are also generated from the coconut and coir industry. Among the various by-products, coir pith and short coir fibres are the major ones and are obtained during the extraction of long coconut fibres. Raw coir pith was heated in a metallic vessel at 450oC to obtain coir pith ash. In this study, the impact of the presence of CPA as a supplementary cementitious material, on the various mechanical and durability parameters are taken into consideration. The various parameters considered for assessing the mechanical performance include compressive strength, split tensile strength, flexural strength and Ultrasonic pulse velocity. Water absorption and resistance to sulphuric acid environments were considered to evaluate the durability of CPA blended concrete. The resistance of CPA blended concrete against sulphuric acid environment was evaluated by considering the variation in weight, water absorption and percentage loss in compressive strength. Five concrete mixes were used for the study with CPA content ranging from 0% to 20%. Indian standard method of concrete mix design with water-cement ratio 0.45 was adopted. To understand the effect of change in water-cement ratio on the durability parameters of concrete, the study also considered other water-cement ratios like 0.40 and 0.50. Results indicated that the mechanical and durability performance improves when CPA is used as supplementary cementitious material. Also, the specimens with water-cement ratio 0.40 performed better than other ratios. © 2020 by authors, all rights reserved.

Fulltext

Civil Engineering and Architecture

Evaluation of mechanical and durability performance of coir pith ash blended cement concrete

Lightning strikes are prevalent and inevitable natural phenomena that might cause damages during interaction with building structures and, in some cases, culminate in fires. During the last decades, several lightning strikes have caused considerable damages to cultural and heritage buildings. Furthermore, recent studies indicated a plausible connection between climate changes due to global warming and variations in the frequency and intensity of lightning. The evaluation of the structural efficiency and resilience of cultural buildings to global changes and natural risks appears significant in the light of the current scientific debate. This research aims at the assessment of lightning strikes' effects on ancient heritage binding materials through the characterization of their thermal and electrical conductivity properties. This study focused on the performance evaluation of green and low-cost mortars based on the use of organic additives. Lime samples were reverse engineered by using a mixture of organics (fig, jaggery, black grape, banana, kadukai), which comprises the most common additives used in traditional Indian mortars. The reliability of the organic mixture in enhancing the resilience of masonry to lightning strikes was analyzed by using electromagnetic field simulation. © 2020 by the authors.

Sustainability (Switzerland)

Response of organic lime mortars to thermal and electrical shocks due to lightning strikes

The concrete manufactured by using geopolymer technology is considered to be sustainable and economical. The production of geopolymer concrete helps in converting industrial by-product materials into a valuable product. Compared to OPC concrete, geopolymer concrete has superior strength properties. The advantage of using geopolymer concrete is that it is environment-friendly, has low production cost and protects the available natural resources by utilizing industrial by-products and consuming less embodied energy. The ternary blended, low-molarity (2M) geopolymer concrete is manufactured using fly ash, ground granulated blast furnace slag and alccofine, with M-sand as fine aggregate. The present study aimed to find the optimum ratio of Na2SiO3 to NaOH of geopolymer concrete based on the strength and microstructural characterization through scanning electron microscopy/energy-dispersive X-ray spectroscopy, X-ray powder diffraction, Fourier-transform infrared spectroscopy, kinetic ratios and thermogravimetric analysis/differential scanning calorimetry. The results revealed that the Na2SiO3-to-NaOH ratio of 1.5 had a significant increase in the polymerization of geopolymer concrete, which, in turn, resulted in better compressive strength and microstructural features than the other ratios. Although the results of the study are encouraging regarding the use of ternary blended geopolymer concrete by effective utilization of industrial waste products through an environment-friendly route, they also provide a sustainable and economical route for handling the industrial by-products currently generated in various countries. Additionally, it was found that the use of low molarity (2M) and Na2SiO3-to-NaOH ratio of 1.5 reduced the risk involved in handling the alkaline solution.