Faculty Publications
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Item Numerical study on the effect of steel fibers on fracture and size effect in concrete beams(Elsevier Ltd, 2023) Yadav, D.; Prashanth, M.H.; Kumar, N.The construction sector uses concrete extensively all around the world. Concrete contains a lot of microcracks even before it is loaded. When a tensile force is applied, these microcracks attempt to open up. While designing, the strength of concrete in its tensile zone is ignored. The strength and ductility of the concrete can be improved due to the addition of steel fibers. Steel fibers use a bridge mechanism to restrict the micro-cracks spread. This study uses ABAQUS to numerically analyze the behaviour of the Steel Fiber Reinforced Concrete (SFRC) beams. Two grades of concrete are studied, M20 and M60, for varying volumetric percentages of steel fibers. It was observed from the study that the ultimate load increases by around 52% and 41% for M25 and M60 grade concrete, respectively, by adding 1% of steel fiber. Fracture properties such as fracture toughness and fracture energy are calculated. The addition of steel fibers enhanced fracture toughness and energy significantly. Adding 1% fiber increases fracture toughness by around 56% and 34% and fracture energy by around 169% and 136% for M25 and M60 concrete, respectively. The size effect on SFRC beams is studied to determine the size-independent fracture parameters. © 2023Item Flexural and fracture performance of fiber reinforced self compacting alkali activated concrete– A DOE approach(Elsevier B.V., 2024) Prakash, G.B.; Prashanth, M.H.; Narasimhan, M.C.; Mahendra, K.; Das, A.K.Owing to their much-reduced carbon footprint and lower embodied energy, compared to conventional Portland Cement (OPC-based) Concrete mixes, Alkali Activated Concrete (AAC) mixes represent a pivotal advancement towards achieving sustainability goals. The fracture properties were investigated using Three-Point Bending Tests (3-PBT) under the mode I failure mechanism. This study utilises Taguchi analysis to analyse and optimise Self-Compacting Alkali-Activated Concrete (SAAC), focusing mainly on its flexural strength and fracture characteristics. An L-16 orthogonal array of experiments with three input parameters − replacement of Blast Furnace Slag (BFS) with Fly ash (FA) (0 %, 30 %, 40 %, and 50 %), Steel Fibers (SF) volume content (0 %, 0.25 %, 0.5 % and 0.75 %) and Notch to Depth (a0/d) ratio (0.2,0.3,0.4 and 0.5), at four levels each, was adopted. The Work of Fracture Method (WFM) and Double K Fracture Criterion (DKFC) were utilised to determine the Fracture Energy (GF) and fracture toughness, respectively. The results obtained from all the sixteen mixes showed that the F0-S0.75-N0.5 mix demonstrated better values in several parameters, such as flexural strength of 7.82 MPa,KICini of 0.928 MPa√m, KICuns of 6.99 MPa√m and KICini/ KICuns of 0.133. A maximum GF of 2350 N/m was obtained with F50-S0.75-N0.2 mix. However, all the inferior values of these parameters were observed with F50-S0-N0.5 mix, which recorded a flexural strength of 4.90 MPa, KICini of 0.612 MPa√m,KICuns of 1.16 MPa√m, KICini/ KICuns of 0.528 and GF of 125 N/m. Through Taguchi analysis, the optimal combination for flexural strength was identified as FA 0 %, SF 0.75 %, and a0/d 0.5 and for both Initial Fracture Toughness (KICini) and Unstable Fracture Toughness (KICuns) at FA 0 %, SF 0.75 % and a0/d 0.4. For both the ratio of initial to unstable fracture toughness (KICini/ KICuns) and fracture energy (GF), the optimum combination was FA 0 %, SF 0.75 % and a0/d 0.2. Furthermore, the results indicate that FA significantly influences KICini, while SF predominantly affects all other parameters. The predictive performance of the regression equations demonstrates good agreement with experimental outcomes. © 2024 Elsevier LtdItem Development and performance evaluation of self-compacting lightweight alkali-activated concrete incorporating hydroton clay balls(Elsevier Ltd, 2025) Kuttagola, I.; Prashanth, M.H.Alkali-activated concrete has emerged as a promising alternative in construction due to its enhanced performance characteristics and reduced carbon footprint. This study introduces a novel category of self-compacting lightweight alkali-activated concrete using hydroton clay balls (lightweight expanded clay aggregate, LECA) as coarse aggregate and manufactured sand as fine aggregate. The research investigates the influence of fly ash content in the binder and maximum aggregate size (MAS) on the mechanical properties of the concrete mixes. Three series of mixes were developed with MAS varying at 10 mm, 12.5 mm, and 16 mm, and fly ash proportions at 0 %, 30 %, and 50 %. A novel pre-treatment method involving geopolymer slurry was employed to enhance the stability of LECA by mitigating water absorption, crucial for achieving self-compacting properties. The lightweight concrete mixes demonstrated excellent filling and passing abilities, adhering to EFNARC guidelines, with the mix L10FA50 (smallest MAS and highest fly ash) achieving the highest workability. Compared to the normal-weight mix N16G100, the mix L10FA50 recorded 17 % higher slump flow, 45 % better sieve segregation resistance, and 34 % faster V-Funnel flow times. Dry densities of lightweight mixes ranged from 1851 to 1943 kg/m³, about 19–20 % lower than normal-weight concretes. The pre-treated LECA enhanced the mechanical performance of lightweight mixes, achieving maximum compressive strengths of up to 49.17 MPa, splitting tensile strengths of 3.40 MPa, flexural strengths of 8.60 MPa, and fracture energy of 161.51 N/m, approximately 65 % of the normal-weight mixes. Higher strength gains were particularly notable with higher GGBFS content and larger MAS. The microstructural analysis confirmed dense morphologies with C-S-H and C-A-S-H gel formations, contributing to improved strength. This research establishes the feasibility and performance benefits of utilizing LECA in alkali-activated concrete formulations for sustainable construction practices with enhanced mechanical and microstructural properties. © 2025 Institution of Structural EngineersItem Application of Taguchi's optimization techniques for enhancing the fracture characteristics and brittleness of self-compacting alkali-activated concrete(Elsevier B.V., 2025) Kuttagola, I.; Prashanth, M.H.Alkali-activated concrete has emerged as a promising material for energy-efficient construction, offering a technically viable and eco-efficient alternative that aligns with global sustainability goals. This study explores optimizing fracture properties in self-compacting alkali-activated concrete (SAAC) through controlled variations in maximum aggregate size (dmax) and fly ash. A systematic approach incorporating Taguchi's design of experiments (DOE) and ANOVA analysis was employed to identify optimal mix proportions that enhance fracture performance and ductility. The study employed the Weight-Compensated Work of Fracture Method (WWFM) based on curtailment of the tail of the P–? curve to determine the size-independent fracture energy (GF), enhancing the reliability of SAAC in structural applications. Additionally, the Two-Parameter Fracture Model (TPFM) evaluated the critical stress intensity factor (KsIc) and critical crack tip opening displacement (CTODc), while the MATLAB-based Box-Counting Dimension Method (BCDM) assessed the fractal dimension (D). The findings revealed a higher fracture performance with 0 % fly ash and 16 mm dmax (GF of 206.3 N/m and KsIc of 1.91 MPa?m), suitable for structural applications requiring maximum fracture energy and toughness. The study further tailored a higher ductility mix with 50 % fly ash and 16 mm dmax (CTODc of 0.032 mm and D of 1.144) offering a balanced solution for non-structural applications, providing sufficient strength with enhanced ductility. The closed-form predictive design (CPD) model enables the prediction of ft and KIc under a specified maximum fracture load, offering engineers a practical tool to optimize SAAC formulations by adjusting aggregate sizes and binder proportions for specific project needs. Regression models aligned strongly with experimental and existing literature results, affirming the reliability of predictive performance for future SAAC mix designs. © 2025 Elsevier Ltd