K. Karthikeyan

Bio: K. Karthikeyan is an academic researcher from VIT University. The author has contributed to research in topics: Weibull distribution & Aggregate (composite). The author has an hindex of 6, co-authored 21 publications receiving 146 citations.

Development of a novel low carbon cementitious two stage layered fibrous concrete with superior impact strength

Abstract: This study proposes a novel low carbon cementitious two stage layered fibrous concrete (LCCTSLFC) derived from clinker, flyash, calcined clay and steel fibres . In two stage fibre reinforced concrete (TSFRC), the volume of steel fibres together with coarse aggregates are pre-mixed and pre-placed into the mold. Henceforth, filling of voids in-between the aggregates is done by grouting that flows through gravity. The short and long steel fibres used throughout the thickness (layered), manufactured low carbon cement, X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis were considered here in. For the first time, this research develops the concept of impact resistance of LCCTSLFC under falling weight collision. For this purpose, short crimped fibres and long hooked end steel fibres were used in two stage layered concrete and tested as per ACI committee 544 guidelines. The results reveal that the proposed layered LCCTSLFC specimen shows superior impact strength compared to that of fully reinforced cross-section with equivalent dosages of fibre. This study emphasizes the potential to engineer a new layered LCCTSLFC with superior compressive and impact strength properties for the safety of civil and military infrastructure during terrorist attacks.

Two statistical scrutinize of impact strength and strength reliability of steel Fibre-Reinforced Concrete

Abstract: The variations in impact strength of steel Fibre Reinforced Concrete (FRC) were statistically, commanded in this research. For this purpose, the experimental impact test results of earlier researchers were investigated using two statistical approaches. Firstly, normality test was carried out on first crack strength (N1) and failure strength (N2) using distribution plot and its accuracy was verified with Kolmogorov-Smirnov, Shapiro-Wilk and Chen-Shapiro test. Secondly, strength reliability analysis was carried out using two parameter Weibull distribution and their Weibull parameters were determined using three methods viz., Empherical Method of Justus (EMJ), Method of Moments (MOM) and Empherical Method of Lysen (EML). Results suggested that, if three samples are used to determine the N1 value for researchers’ data, at 95% levels of confidence, then the error in the measured value is about 50%. The 0.1 reliability level of the impact strength values of EMJ, EML and MOM were 153, 120 and 153 respectively in case of N1 and were 198, 156, and 198 respectively in case of N2 based on earlier researcher’s data.

Comparative Experimental and Analytical Modeling of Impact Energy Dissipation of Ultra-High Performance Fibre Reinforced Concrete

Abstract: This study examines the impact energy dissipation capacity of Ultra High Performance Fibre Reinforced Concrete (UHPFRC). For this purpose, nine different mixes were fabricated with hooked end and crimped steel fibres at a dosage of 0.5, 1.0, 1.5 and 2.0 percentage and tested under pendulum impact test. The impact energy dissipation capacity is assessed based on test (Charpy U-notch) procedure suggested by ASTM E23. Also, an analytical model was adopted to predict the impact energy dissipation value of UHPFRC and its performance is verified against experimental results. Based on the test results, the impact energy dissipation capacity of the mixtures containing crimped and hooked end steel fibres were significantly higher than that of Plain Concrete (PC). The hooked end steel fibres had an increased impact energy dissipation capacity compared to crimped steel fibres, which implies that hooked end steel fibre is more appropriate for enhancing the impact energy dissipation of UHPFRC. Also, the modelling data compared well with experimental data for the fibre volume fraction beyond 0.5%.

Influence of MgO on the Hydration and Shrinkage Behavior of Low Heat Portland Cement-Based Materials via Pore Structural and Fractal Analysis

Abstract: Currently, low heat Portland (LHP) cement is widely used in mass concrete structures. The magnesia expansion agent (MgO) can be adopted to reduce the shrinkage of conventional Portland cement-based materials, but very few studies can be found that investigate the influence of MgO on the properties of LHP cement-based materials. In this study, the influences of two types of MgO on the hydration, as well as the shrinkage behavior of LHP cement-based materials, were studied via pore structural and fractal analysis. The results indicate: (1) The addition of reactive MgO (with a reactivity of 50 s and shortened as M50 thereafter) not only extends the induction stage of LHP cement by about 1–2 h, but also slightly increases the hydration heat. In contrast, the addition of weak reactive MgO (with a reactivity of 300 s and shortened as M300 thereafter) could not prolong the induction stage of LHP cement. (2) The addition of 4 wt.%–8 wt.% MgO (by weight of binder) lowers the mechanical property of LHP concrete. Higher dosages of MgO and stronger reactivity lead to a larger reduction in mechanical properties at all of the hydration times studied. M300 favors the strength improvement of LHP concrete at later ages. (3) M50 effectively compensates the shrinkage of LHP concrete at a much earlier time than M300, whereas M300 compensates the long-term shrinkage more effectively than M50. Thus, M300 with an optimal dosage of 8 wt.% is suggested to be applied in mass LHP concrete structures. (4) The addition of M50 obviously refines the pore structures of LHP concrete at 7 days, whereas M300 starts to refine the pore structure at around 60 days. At 360 days, the concretes containing M300 exhibits much finer pore structures than those containing M50. (5) Fractal dimension is closely correlated with the pore structure of LHP concrete. Both pore structure and fractal dimension exhibit weak (or no) correlations with shrinkage of LHP concrete.