Browsing by Author "Manjunath, B."

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Areca nut husk biochar as a sustainable carbonaceous filler for cement: Pyrolysis temperature and its effect on characterization, strength, and hydration
(Elsevier B.V., 2024) Manjunath, B.; Ouellet-Plamondon, C.M.; Das, B.B.; Rao, S.; Bhojaraju, C.; Rao, M.
This study addresses the gap in sustainable agro-based materials for cement by exploring locally available areca nut husk pyrolyzed into areca nut husk biochar (AB). The research investigated the effect of pyrolysis temperature (300°C, 400°C, and 500°C) on the characteristics of AB and its impact on cementitious performance. The study found that increasing pyrolysis temperatures led to lower yield, greater aromaticity, and increased surface area of AB. Fourier Transform Infrared Spectroscopy (FTIR) analysis showed decreased functional groups in AB at higher temperatures, confirming enhanced carbonization. Thermogravimetric analysis (TGA) revealed greater thermal stability of AB. X-ray diffraction (XRD) indicated a carbon-rich amorphous structure and crystalline graphite carbon formation in AB. Incorporating AB at 2 % into cementitious composites substantially increased the compressive strength compared to the control mortar. At 7 and 28 days, the compressive strength increased by 8 % and 12 % for AB 300, 16 % and 21 % for AB 400, and 27 % and 34 % for AB 500. This improvement was due to the micro filler effect of AB, which improved the compactness of the cementitious matrix. Hydration studies from TGA showed that the addition of AB accelerated early-stage hydration, with the degree of hydration increasing from 46 % (in control mix) to 48–53 % in AB blended mixes using Bhatty's method. FTIR analysis demonstrated improved hydration of silicate phases and C-S-H formation in the presence of AB, supported by XRD analysis. AB blended mortar reduced the CO2 equivalent emission by 22 % compared to the control mortar attributed to its carbon sequestration capacity. These results highlight the potential of AB as a sustainable carbonaceous filler for cementitious composites, offering an environmentally friendly option for future research in construction materials. © 2024 Elsevier B.V.
Development of sustainable conductive cementitious composite using graphite-coated spent catalyst waste
(Elsevier Ltd, 2024) Bhagithimar, Y.; Manjunath, B.; Das, B.B.; Bhojaraju, C.
This study presents an innovative approach to developing sustainable conductive composites by coating graphite onto the surface of spent catalyst waste through nano-surface engineering techniques. The process ensures uniform adsorption of graphite onto the surface of the spent catalyst waste particles, followed by oven treatment and milling. This results in better integrity and effective bonding, leading to the production of graphite-coated spent catalyst waste (G-SCW). Scanning electron microscopy indicates the successful coating of spent catalyst waste with graphite. The research investigates the effect of G-SCW on the cementitious properties of paste and mortar. Incorporating G-SCW results in acceptable workability and setting time, while the compressive strength increases at early and later stages, with up to 20 % G-SCW content. The addition of G-SCW in the mortar significantly reduces the electrical resistivity, resulting in a 63 % reduction in resistivity compared to the reference mix, thereby enhancing the conductivity. Hydration studies confirm the presence of pozzolanic reaction in blended paste, as evidenced by a decrease in calcium hydroxide content. The sustainability assessment indicates a substantial reduction in embodied carbon and possibly producing mortar with lower cement content. These findings suggest great potential for developing sustainable conductive mortar with G-SCW, enabling smart building construction, and supporting sensor networks for structural health monitoring. © 2024 Elsevier Ltd
Optimizing nutmeg shell biochar production temperature for enhanced cement composite performance
(Taylor and Francis Ltd., 2025) Bhavya; Manjunath, B.; Ouellet-Plamondon, C.M.; Das, B.B.; Bhojaraju, C.
The growing focus on sustainability has driven research into converting agricultural waste into biochar (BC) for concrete applications. As cement manufacturing contributes significantly to global CO2 emissions, BC offers a promising replacement solution. This study investigates nutmeg shell BC as a sustainable cement alternative produced through pyrolysis at temperatures of 400 °C, 500 °C, and 600 °C, and incorporates it at concentrations of 1%, 2%, and 3% by weight. The main findings reveal that 2% BC prepared at 500 °C achieved optimal performance, with 23% and 27.57% increase in compressive strength and electrical resistivity, respectively, at 28 days. Additional benefits included enhanced water absorption resistance, reduced chloride permeability. Hydration analysis confirms BC’s porous structure provides nucleation sites for cluster formation during early hydration, representing a novel mechanism for accelerated strength development. This research demonstrates BC as a sustainable alternative to cement, offering environmental benefits through CO2 reduction and the valorization of agricultural waste. © 2025 Informa UK Limited, trading as Taylor & Francis Group.
Potential utilization of regional cashew nutshell ash wastes as a cementitious replacement on the performance and environmental impact of eco-friendly mortar
(Elsevier Ltd, 2023) Manjunath, B.; Ouellet-Plamondon, C.M.; Das, B.B.; Bhojaraju, C.
Globally, agro-waste ashes are increasing significantly due to the rapid implementation of biomass-based power plants. In the present trend, agro-wastes are disposed of in an unsustainable manner. The recycling of agro-waste has significantly contributed to sustainable goals. In the construction sector, it is possible to dispose of waste more efficiently. However, the efficiency of locally available agro-residual waste in cementitious composites is not well understood. In the present investigation, the practicability of using agro-residual ash obtained from the burning of cashew nutshells on the properties of eco-friendly blended cement paste and mortars is explored. Blended cement mixtures containing cashew nutshell ash (CNSA) were prepared at five replacement levels, 5, 10, 15, 20, and 25%, relative to the weight of the cement. To understand the characteristics of CNSA, microstructure investigations such as X-ray diffraction, thermogravimetric analysis (TGA), scanning electron microscopy, and energy-dispersive spectroscopy analyses were performed. Paste properties of CNSA-based cement are observed through consistency, setting time, mini-slump flow, and expansion tests. For the CNSA-based mortars flow table, compressive strength, ultrasonic pulse velocity (UPV), electrical resistivity (ER), water absorption, bulk density, and porosity tests were performed to understand its efficiency. The strength indices of mortars were used to quantify the pozzolanic effect of CNSA. With the incorporation of CNSA, water demand increased by 57%, initial and final setting time decreased by 90% and 83%, respectively. Results showed that CNSA-based mortars absorbed more water and had higher porosity, which reduced compressive strength, UPV, and ER values. CNSA blended mortar is more suitable for applications that do not require high compressive strength. Results indicated that the compressive strength, UPV, and ER are within the limit specified. Strength indices indicated that CNSA has a positive and negative pozzolanic effect during early and later ages, respectively. Further, the sustainable assessment showed that the introduction of CNSA in mortar could substantially reduce embodied carbon, embodied energy, and strength efficiency over the control mortar. The inadequate amount of SiO2, Fe2O3, and Al2O3 in CNSA makes it an unsuitable pozzolanic material. However, it can be utilized in smaller amounts as a fractional replacement of cement and is found to be promising for specific desired properties of cement as a cost-effective accelerator. © 2023 Elsevier Ltd
Utilization of Laterite Waste in Concrete
(CRC Press, 2022) Manjunath, B.; Ram Chandar, R.C.
Laterite is one of the major quarrying activities in giving construction material the form of laterite bricks. In this process, large quantity of waste is being produced causing environmental problems; the waste causes reddishness of land and the water also looks reddish in colour once laterite comes in contact with water. So, it’s better to use such waste for some useful purpose like replacing fine or coarse aggregates in concrete. Such systematic research is presented in this chapter explaining the various uses of laterite waste, optimum percentage use of it in concrete keeping under different strength conditions. © 2022 Ram Chandar Karra, Gayana B.C and Shubhananda Rao P.
Valorization of coffee cherry waste ash as a sustainable construction material
(Elsevier Ltd, 2024) Manjunath, B.; Ouellet-Plamondon, C.M.; Ganesh, A.; Das, B.B.; Bhojaraju, C.
This study explores the potential of treated coffee cherry waste (T-CCW) as a partial replacement of cement in mortar. T-CCW was characterized and incorporated into pastes and mortars at 5 %–25 % cement replacement. The main objectives were to examine the fresh and hardened properties, hydration, and environmental assessment. Results showed that the high specific surface area and porous structure of T-CCW particles increased water demand and accelerated setting times. T-CCW incorporation of up to 15 % enhanced compressive strength at all curing ages due to improved hydration and limited pozzolanic reactions. Ultrasonic pulse velocity indicated good homogeneity and compactness in T-CCW blended mortars. Microstructural analysis revealed that T-CCW enhanced cement hydration, leading to a denser matrix. Environmental analysis showed a reduced embodied carbon and cement intensity index compared to the control mix. Overall, the optimal performance was observed at 15 % T-CCW replacement, significantly improving engineering properties and environmental impact. Further, the fishbone diagram addresses various factors to optimize the use of T-CCW as a cementitious composite. These findings demonstrate the potential of T-CCW as a sustainable construction material, offering a promising pathway towards environmentally friendly and resource-efficient building practices while addressing waste management in the coffee industry. © 2024 Elsevier Ltd