A. S. Santhi
Other affiliations: A.V.V.M Sri Pushpam College
Bio: A. S. Santhi is an academic researcher from VIT University. The author has contributed to research in topic(s): Fly ash & Compressive strength. The author has an hindex of 9, co-authored 21 publication(s) receiving 207 citation(s). Previous affiliations of A. S. Santhi include A.V.V.M Sri Pushpam College.
Abstract: Electroless deposition process has undergone numerous changes to meet the challenging needs for a variety of industrial applications ever since the invention of the process during 1947. Among the various metals that can be electrolessly plated, electroless nickel has proved its supremacy for producing coatings with high corrosion resistance, hardness, wear resistance and uniformity. Electroless nickel can be deposited from a variety of baths and the coating properties depends upon the type of reducing agents and other deposition conditions. Electroless nickel–boron coatings have received considerable interest nowadays because of the superior hardness, corrosion and wear resistance characteristics. In this paper, the authors have reported on the development of a biodegradable electroless Ni–B bath and evaluated its characteristic properties. The influence of bath constituents, temperature and pH on the rate of deposition was studied. Scanning electron microscopy, X-ray diffraction, X-ray fluoresce...
Abstract: Many researches have been carried out in the area of fly ash utilization in the past. It mainly concentrated on replacement of cement with fly ash but production of artificial aggregates with fly ash helps in utilizing large volume of ash in concrete. The world is much interested in this part recently due to this large-scale utilization which also reduces environmental pollution and dwindling of natural resources. This paper mainly focuses on manufacturing process of light weight aggregates using pelletizer and curing has been done in cold bonded technique. The properties of these fly ash aggregates have been tested and compared with natural gravel and the study shows that cold bonded fly ash aggregates can be used as an aggregate replacement material in concrete. The strength property and density of concrete made with artificial fly ash aggregates and natural gravel were also studied which confirms that introduction of fly ash aggregates in concrete reduces the compressive strength but meets the required strength to be used as a structural material.
Abstract: This paper presents an experimental investigation on the Impact failure energy and strength reliability of fiber reinforced concrete (FRC) by using a simple drop weight test which was based on the testing procedure recommended by ACI committee 544. Two different steel fibers were used as the reinforcing material in various volume fractions such as 0%, 0.5%, 1.0% and 1.5% with a water cement ratio of 0.42. Furthermore, the two-parameter weibull distribution was used to analyze the experimental data in order to sort out a variation of test results. Using the weibull distribution, the impact failure strength reliability, in other words, the probability distribution according to which the concrete will fail, was obtained. The results indicated that the concrete containing a 1.5% volume fraction of fiber gave the best performance followed by 1.0% and 0.5% under impact loading. It was proven that the probabilistic distributions of the impact failure energy of seven types of samples approximately follow two-parameter Weibull distribution.
Abstract: Geopolymers are a new type of artificial polymer which is developed when an aluminosilicate source is triggered or activated by the application of alkaline hydroxide and silicate solution. They have shown good mechanical properties and shows good resistance to chemicals, lesser shrinkage, no damage to environment and shows formidable durability. Ground granulated blast furnace slag(GGBS) is a good aluminosilicate source as it contains high amounts of alumina and silica which are necessary for the geopolymerisation reaction to take place. In this paper, three variations in terms of weight percentages of GGBS and metakaolin clay have been taken with 80%-20%,50%-50%, and 20%-80% respectively. A 10M solution of sodium hydroxide with sodium silicate was used as alkaline activator solution. For practical purposes ambient curing of the geopolymer samples has been adopted. The Degree of reaction was evaluated for all the percentage variations of the geopolymer concrete at 7 days of curing. The mechanical properties of geopolymer concrete have been studied by compressive test, split tensile test and four-point loading test. To understand the structural integrity of the casting of the geopolymer specimens, ultrasonic pulse velocity test was performed. The study of micro-structure of geopolymer concrete was carried out by Fourier transform infrared spectroscopy (FTIR) technique.
Abstract: Portland cement is a highly energy intensive material. Therefore, considerable effort is being made to find substitutes for partial replacement of cement in concrete. This paper reports the results from experimental studies on the compressive strength and resistance to chloride ion penetration of concrete containing ternary blends of Portland cement, silica fume (SF) and wide range of fly ash (FA) Class C fly ash is used in this study in various proportions (i.e.) 30%, 40% and 50% and that of silica fume by 6% and 10% by weight of cement. The mix proportions of concrete had constant water binder ratios of 0.4 and super plasticizer was added based on the required degree of workability. The concrete specimens were cured on normal moist curing under normal room temperature. The compressive strength was determined at various ages and the resistance to chloride-ion penetration was measured at different ages up to 90 days. The results indicate that the concrete made with these proportions generally show excellent fresh and hardened properties since the combination is somewhat synergistic. The addition of silica fume with fly ash was found to increase the compressive strength of concrete at early age when compared to concrete made with fly ash alone. Moreover the incorporation of fly ash and silica fume in concrete increases the resistance to chloride ions and produced concrete with low permeability.
Abstract: Concrete is a unique composite material that is porous and highly heterogeneous. The durability of steel reinforced concrete in chloride environments is of great interest to design engineers, infrastructure owners and maintainers, and researchers. This review reports recent advances in the knowledge base relevant to the durability of steel reinforced concrete in chloride environments, including: the role of mineral admixtures in concrete durability, the methods of measuring the chloride ingress into concrete, the challenges in assessing concrete durability from its chloride diffusivity, and the service life modeling of reinforced concrete in chloride-laden environments. It concludes with a look to the future, including research needs to be addressed.
Abstract: Electroless coating is different from the conventional electrolytic coating as the former does not require any electricity for its operation. The advantages include uniform coating and also nonconductive materials can be coated. Electroless nickel coatings possess splendid tribological properties such as high hardness, good wear resistance and corrosion resistance. For this reason, electroless nickel has found wide applications in aerospace, automobile, electrical and chemical industries. Quest for improved tribological performances has led many researchers to develop and investigate newer variants of electroless nickel coatings like Ni–W–P, Ni–Cu–P, Ni–P–SiC, Ni–P–TiO2, and so on. Also the enhancement of tribological characteristics through modification of the coating process parameters has remained a key point of interest in researchers. The technological advancement demands the development of newer coating materials with improved resistance against wear and tear. Electroless nickel has shown huge potential to fit in that space and so the study of its tribological advancement deserves a thorough and exhaustive study. The present article reviews mainly the tribological advancement of different electroless nickel coatings based on the bath types, structure and also the tribo testing parameters in recent years.
Abstract: A design scheme for self-reinforced cementitious composites to be used for building-scale 3D printing processes is introduced. The design is based on that of engineered cementitious composites, which include dispersed short polymer fibers to generate robust tensile strain-hardening. The mechanical property profile of these printable ECC materials is meant to eliminate the need for steel reinforcement in printed structures, providing more freedom and efficiency for building-scale 3D printing processes. The fresh state rheological properties have been systematically manipulated to allow printability. Effects on fresh state workability of several compositional ingredients and processing parameters are investigated herein. To maintain consistent printing performance with a batch mixing approach, thixotropy in the fresh state is exploited to temporarily decouple hardening behavior from the processing timeline. Minimal workability loss under continued shear agitation is achieved. Mechanical properties of the printable materials are characterized and the printability of the materials is demonstrated.
Abstract: Electroless nickel coating is an autocatalytic coating whose characteristics are very much dependent on the composition of electroless bath. The present study is an attempt to minimize the friction and wear characteristics of electroless Ni–B coatings simultaneously by optimizing the three coating parameters viz. bath temperature, concentration of reducing agent and concentration of nickel source together with the annealing temperature. Taguchi based grey relational analysis is employed for the optimization of this multiple response problem using an L 27 orthogonal array. Analysis of variance reveals that concentration of reducing agent has the maximum contribution in controlling the friction and wear behaviour of Ni–B coating. The interaction between bath temperature and nickel source concentration is also found to possess significant contribution in controlling the friction and wear characteristics. The surface morphology, composition and phase structure analysis are done with the help of scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD), respectively. Moreover the wear mechanism is studied and found to be in general abrasive in nature.
Abstract: In this study, cement has been partially replaced with a Class F fly ash (FA) at a level of 70% to produce high-volume fly ash (HVFA) concrete (F70). F70 was modified by partially replacing FA with silica fume (SF) at levels of 10% and 20%, by weight. All HVFA concrete types were compared to the neat Portland cement (PC) concrete. After curing, the specimens were exposed to elevated temperatures ranging from 400 °C to 1000 °C with an interval of 200 °C. Weight and compressive strength before and after firing have been thoroughly explored. The various decomposition phases formed were identified using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated higher relative strength of all HVFA concrete types. F70 exhibited the highest relative strength. The SF blends exhibited good fire performance up to 600 °C, then severe degradation in the residual strength was observed at 800 and 1000 °C.