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Item Studies on normal strength concrete cubes subjected to elevated temperatures(2010) Yaragal, S.C.; Babu Narayan, K.S.; Venkataramana, K.; Kulkarni, K.S.; Gowda, H.C.C.; Reddy, G.R.; Sharma, A.Concrete in structures is likely to be exposed to high temperatures during fire. The probability of its exposure to elevated temperatures is high due to natural hazards, accidents and sabotages. Therefore, the performance of concrete during and after exposure to elevated temperature is a subject of great importance and interest to the designer. Popular normal strength grades of concrete produced by Ready Mix Concrete (RMC) India, Mangalore have been used in production of test specimens (150 mm cubes), cured and tested by destructive method for gathering data on strength characteristics. Later, these test samples were subjected to elevated temperatures ranging from 100 C to 800 C, in steps of 100 C with a retention period of 2 hours. After exposure, weight losses and the residual compressive strength retention characteristics are studied. Test results indicated that weight and strength significantly reduces with an increase in temperature. Residual compressive strength prediction equations are proposed for normal strength concretes subjected to elevated temperatures.Item Characteristics of normal strength concrete with and without chemical admixtures at elevated temperatures(CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2011) Yaragal, S.C.; Warad, S.A.; Babu Narayan, K.S.; Venkataramana, K.Fire is one of the most destructive powers to which a building structure can be subjected. Behavior of concrete when exposed to fire in cases like nuclear plants, cooling towers or any accidental fire in industrial buildings, is a serious concern, on the strength retention property of concrete. This work reports strength retention studies on compressive and split tensile strength of normal concrete with and without the chemical admixture (Reobuild 918, BASF make) at elevated temperatures. Concrete cubes of size 100 mm have been cast as per prior mix design for M30 grade of concrete, 28 days water cured and tested by destructive method for strength before exposure. Later these specimen were subjected to elevated temperatures of 200°C, 400°C, 600°C and 800°C with a retention period of 2 hours and were allowed cool within the furnace to reach ambient temperature. Later their appearance, colour and cracks were observed and also weight losses were determined. Further, destructive tests were conducted to estimate residual compressive and residual split tensile strengths and prediction equations are proposed to ascertain splitting tensile strengths from compressive strengths. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Usage potential of melt processed plastic pellets as a substitute to fine aggregate in porous concretes(2012) Maneeth, P.D.; Lokesh, G.; Yaragal, S.C.; Babu Narayan, K.S.Porous concrete (PC) has been used for over 30 years. Because of its high porosity, the most common usages have been in the area of storm water management, but have been limited to use in pavements with low volume traffic, because of its low compressive strength compared to conventional concrete. Domestic and industrial plastic waste management has posed a serious challenge to engineers and scientists today. In this study an attempt is made to utilize plastic waste (melt processed) from small industries as a substitute for fine aggregate (up to 10%) in producing porous concretes. The recycled plastic (melt processed) was produced by drawing industrial and domestic waste plastic into long strands which were cut to small pieces forming granules. The plastic granules (pellets) are used as substitute to sand in this investigation. This experimental investigation reports the scope for plastic waste utilization as a substitute for fine aggregate and its influence on properties like porosity, permeability, compressive strength and tensile strength of porous concretes. © 2012 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Strength characteristics of concrete exposed to elevated temperatures and cooled under different regimes(2012) Yaragal, S.C.; Babu Narayan, K.S.; Adari, S.Concrete loses strength in the event of accidental fires. The residual strength of normal strength concrete is of vital importance for ascertaining serviceability of buildings after the event of fires. Strength loss in concrete is dependent on the temperature of exposure, its duration and the way it gets cooled. In this study concrete cubes of size 100 mm have been cast for M25 grade of concrete, 28 days water cured. The specimens were subjected to elevated temperatures of 150°C, 250°C, 350°C, 450°C and 550°C with a retention period of 1 hour. After 1 hour of exposure, specimens were allowed to cool under different cooling regimes to ambient temperature. Later their appearance, colour and cracks were observed and also weight losses were determined. Further, destructive tests were conducted to estimate residual compressive and split tensile strengths. Important performance changes have been presented and discussed. Split tensile strengths are related to compressive strengths for all the cases of cooling regimes.Item Recuring studies on concretes subjected to elevated temperatures and suddenly cooled by water quenching(Multi-Science Publishing Co. Ltd, 2015) Yaragal, S.C.; Kittur, M.M.; Babu Narayan, K.S.Concrete is found to undergo degradation when subjected to elevated temperatures during an accidental event, such as fire and lose substantial amount of its original strength. The loss of strength in concrete is mainly attributed to the decomposition of Calcium Silicate Hydrate (C-S-H) and release of chemically bound water, which begins when the exposure temperature exceeds 500°C. When such a concrete is supplied with water and allowed to recure, it is found to recover substantial amount of its lost strength. This work is carried out to investigate the effect of recuring on strength recovery of un-blended and blended concrete specimen (100 mm cubes) subjected to elevated temperatures from 400°C to 700°C, in steps of 100°C, for a retention period of two hours at the designated temperatures. The concrete cubes immediately after exposure were subjected to thermal shock by quenching them in water, and then temperature of thermally shocked concrete is allowed to cool to room temperature. The cooled specimen were then recured in water for 1, 3, 7, 14, 21, 28, 56 days and tested for compressive strength recovery. These studies were carried out for Portland Cement (PC) based concrete and Portland & Granulated Blast Furnace Slag (70% PC + 30% GGBS) based concrete (blended concrete), and some interesting results are presented and discussed in this paper. © 2015, Multi-Science Publishing Co. Ltd. All rights reserved.Item Influence of mixing method, speed and duration on the fresh and hardened properties of Reactive Powder Concrete(Elsevier Ltd, 2017) Hiremath, P.N.; Yaragal, S.C.Production methodology of Reactive Powder Concrete (RPC) is not clearly established yet, as several parameters have a varied influence on the resulting fresh and hardened properties of RPC. Even for the same composition, the fresh and hardened properties differ significantly by changing mixing method, mixing speed and mixing time/duration. The present investigation is an attempt to study the effect of mixing method, speed and duration, on the fresh and hardened properties of RPC. The study also deals with the microstructure investigation of RPC mixes. Results indicate that improved mixing techniques prove beneficial in enhancing fresh and hardened properties of RPC. Mixing speed and duration also have significant effect on the fresh and hardened properties of RPC. Higher mixing speed and longer mixing duration decreases flow and strength characteristics of RPC. Microstructure analysis reveals that higher mixing speed and longer mixing duration increases percentage of pores in RPC, leading to reduced fresh and hardened properties. © 2017 Elsevier LtdItem Effect of different curing regimes and durations on early strength development of reactive powder concrete(Elsevier Ltd, 2017) Hiremath, P.N.; Yaragal, S.C.The early strength development of Reactive Powder Concrete (RPC) has been investigated under different curing regimes and compared with standard water curing condition. Four different curing regimes have been considered: ambient air curing, hot air curing, hot water bath curing and accelerated curing. The effect of hot air curing on strength development of RPC at different temperatures and durations are studied in detail. The present study is focused on the effect of combined curing regimes on the early strength development of RPC. Test results indicate that, among the four different curing regimes, hot water bath curing gives higher strength. The combined curing regime has considerably enhanced the compressive strength of RPC by about 63% as is evident by the rise in compressive strength from 110 MPa (standard curing) to 180 MPa (combined curing). Microstructure studies were also conducted to understand the arrangements of hydrated particles and development of other secondary hydrated products under different curing conditions using scanning electron microscope and X-ray diffraction spectroscopy respectively. © 2017 Elsevier LtdItem Assessment of thermally deteriorated concrete by drilling resistance test and sound level(Maik Nauka Publishing / Springer SBM compmg@maik.ru, 2017) Kulkarni, K.S.; Yaragal, S.C.; Babu Narayan, K.S.; Vardhan, H.Concrete being the most versatile and widely used construction material finds application in varied range of structures. Many of these like chimneys, furnaces and reactors have to sustain high temperatures and perhaps all structures have to perform at elevated temperatures in the event of fire accidents. Concrete at elevated temperatures undergoes changes in its physical structure and chemical composition and loses its strength characteristics. Need for quick assessment of fire damaged concrete for strength characteristics, has motivated this work, which explores the potential of drilling resistance test on concrete as a Non Destructive Testing (NDT) tool. Drilling times, penetration depths and sound level measurement while drilling have been recorded and analysed to provide monograms that are handy as reckoners in failure forensics. © 2017, Pleiades Publishing, Ltd.Item Performance evaluation of reactive powder concrete with polypropylene fibers at elevated temperatures(Elsevier Ltd, 2018) Hiremath, P.N.; Yaragal, S.C.Reactive Powder Concrete (RPC) is a type of ultra-high strength concrete. Due to its dense microstructure, is vulnerable to explosive spalling at elevated temperatures. Remarkable application of RPC in special structures throughout the world has drawn the attention to understand the performance of RPC at elevated temperatures, which has not been investigated extensively yet. The main objective of this work was to evaluate the performance of RPC at elevated temperatures from 200 °C to 800 °C, by obtaining residual mechanical properties after exposure. The study aims to find an optimum fiber dosage for spalling protection of RPC. To improve the mechanical properties, RPC incorporating fiber dosage from 0.1% to 0.9% is studied. The thermal deterioration of RPC is assessed using ultrasonic pulse velocity, water absorption and sorptivity. Results shows that 0.1% fiber dosage is enough to control spalling of RPC up to 800 °C. To enhance the residual properties of RPC exposed to elevated temperatures, it is recommended to use fiber dosage of 0.5%. The study also includes microstructural analysis of RPC subjected to elevated temperatures, to assess and evaluate the formation of pores and cracks. © 2018 Elsevier LtdItem Optimization of ferrochrome slag as coarse aggregate in concretes(Techno Press technop2@chollian.net, 2019) Yaragal, S.C.; Kumar, B.C.; Mate, K.The alarming rate of depletion of natural stone based coarse aggregates is a cause of great concern. The coarse aggregates occupy nearly 60-70% by volume of concrete being produced. Research efforts are on to look for alternatives to stone based coarse aggregates from sustainability point of view. Response surface methodology (RSM) is adopted to study and address the effect of ferrochrome slag (FCS) replacement to coarse aggregate replacement in the ordinary Portland cement (OPC) based concretes. RSM involves three different factors (groUnd granulated blast furnace slag (GGBS) as binder, flyash (FA) as binder, and FCS as coarse aggregate), with three different levels (GGBS (0, 15, and 30%), FA (0, 15, and 30%) and FCS (0, 50, and 100%)). Experiments were carried out to measure the responses like, workability, density, and compressive strength of FCS based concretes. In order to optimize FCS replacement in the OPC based concretes, three different traditional optimization techniques were used (grey relational analysis (GRA), technique for order of preference by similarity (TOPSIS), and desirability function approach (DFA)). Traditional optimization techniques were accompanied with principal component analysis (PCA) to calculate the weightage of responses measured to arrive at the final ranking of replacement levels of GGBS, FA, and FCS in OPC based concretes. Hybrid combination of PCA-TOPSIS technique is foUnd to be significant when compared to other techniques used. 30% GGBS and 50% FCS replacement in OPC based concrete was arrived at, to be optimal. © 2019 Techno-Press, Ltd.