Journal Articles
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Item Sand spit and shoreline dynamics near Terekhol River mouth, Goa, India(National Institute of Science Communication and Policy Research, 2014) C, C.; Kumar, S.J.; Gowthaman, R.; Jishad, M.; Yadhunath, E.M.; Pednekar, P.S.Evolution of shoreline and sand spit at the mouth of the Terekhol River, near Keri beach, located in the Indian state of Goa has been investigated. From the analysis of the data collected, the shoreline oscillation (accretion & erosion) is seasonal up to 2010. A sand spit of 2 m height has been stabilized in 2012 during monsoon in the southern bank of the river which obstructs the natural flow of the river and also hindrance to the ferry transport system. This leads to the unbalanced scenario between the sediment discharge from the river and the littoral transport. Around 2 km stretch of shoreline is under severe erosion in which a stretch of 500 m of sea wall is completely damaged. Sand spit present in the northern part of the shoreline plays a vital role in the shoreline oscillation. Tetrapods were placed recently to protect the eroding part of the coast. Due to the unbalanced littoral movement, the erosion is still persisting and started damaging the new tetrapod protective measure. © 2014, National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved.Item Studies on the dynamic response of coastal sediments due to natural and manmade activities for the Puducherry coast(National Institute of Science Communication and Policy Research, 2014) Vijayakumar, G.; C, C.; Sundararajan, T.; Govindarajalu, D.This paper presents the response of the coastal sediments by the impact of waves and construction of manmade structures in the Puducherry coastal stretch, East coast of India. Based on the real time wave climate data which was collected from the nearshore region of coast using wave rider buoy and wave direction indicator. The quantum of sediment movement is calculated using CERC formula for three years (2007, 2008, and 2009) and compared with Kamphuis method for one year i.e., 2009. In order to achieve a more reliable value on the sediment movement a sand trap was used at the littoral zone to collect the actual sediment samples for a period of two months i.e., February and March 2009. For all the three observation period the predominant sediment transport rate is Northerly. Estimated sediment transport rates were also determined by Kamphuis method. From the results obtained, CERC formula ‘over predicts’ the sediment transport rate when compared with Kamphuis method. The actual sediment transport calculated using sand trap was found to be 60% reliable when compared with theoretical sediment transport rate which has been determined by using Kamphuis method. © 2014, National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved.Item Surfzone currents at candolim and Miramar beaches of Goa, India: Measurements and comparisons(National Institute of Science Communication and Policy Research, 2014) Yadhunath, E.M.; Seelam, J.K.; Jishad, M.; Gowthaman, R.; C, C.; Pednekar, P.S.Measurements in the surfzone current are often carried out using Acoustic Doppler Velocimeters, Electromagnetic current meters, as well as visual observations based on floats. A simple approach is used to install an Aanderaa current meter in water depths less than a meter and the surfzone currents are measured for a period of about 2 hours during a rising tide. Surfzone wave heights and tide were also simultaneously measured and used to compute wave induced currents based on appropriate equations. The obtained current velocity compared with measured RCM data. Measurements were carried out separately at two beaches (Candolim and Miramar) which have varying topography and different surfzone conditions. © 2014, National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved.Item Surfzone Wave Characteristics during Flood Tide on the Central West Coast of India(World Scientific Publishing Co. Pte Ltd michael.wagreich@univie.ac.at, 2015) Seelam, J.K.; Jishad, M.; Yadhunath, E.M.; C, C.; Gowthaman, R.; Pednekar, P.S.; Luis, R.; Mehra, P.Surfzone wave characteristics, measured using a wave and tide gauge (WTG) during a flood tide, were studied at three different beaches having different nearshore slopes. The spectral wave characteristics viz., wave-height and mean wave period were estimated considering different sample sizes. Inter-comparisons of wave climate between each of three beaches for a similar tide level are presented. The wave-height and mean wave period values obtained from the wave analysis for each of the record using waves by wave method show that surfzone wave-height increased with time during a flood tide and the mean wave period decreased with time up to mid tide and then increased during the rest of the measurement period at Keri and Miramar beaches. At Candolim, the reversing trend of mean wave period increase is observed to occur much before reaching the mid tide level. The surfzone waves during a flood tide indicated that the wave-heights increased with time while the mean wave period showed a decreasing trend in general. The variation of breaker index showed a decreasing trend from low tide to high tide ranging between 0.45 and 0.23. The surf similarity parameter estimated corroborates with the visual observations. © 2015 World Scientific Publishing Company.Item Mechanical properties of recycled aggregate concrete produced with Portland Pozzolana Cement(Techno Press technop2@chollian.net, 2016) Saha, S.; C, C.The quantity of construction and demolition waste has been greatly increasing recently. It causes many problems to the environment. For this reason, demolition waste management becomes inevitable in order to overcome the environmental issues. The present study aims to evaluate the effects of using recycled coarse aggregate, which is generated from construction and demolition waste, on the properties of recycled aggregate concrete. An experimental investigation on the strength characteristics of concrete made with recycled coarse aggregate is presented and discussed in this paper. In this study, Portland Pozzolana Cement (fly ash based) is used instead of ordinary Portland cement. The results of this investigation show the possibility of the use of recycled coarse aggregates in the production of fresh concrete. Use of demolition waste as coarse aggregate will lead to a cleaner environment with a significant reduction of the consumption of natural resources. A comparative study on the strength characteristics of recycled aggregate concrete made with Ordinary Portland Cement and Portland Pozzolana Cement is presented and discussed in this paper. © 2016 Techno-Press, Ltd.Item Enhancement of the properties of fly ash based geopolymer paste by incorporating ground granulated blast furnace slag(Elsevier Ltd, 2017) Saha, S.; C, C.Research efforts have been made continuously to establish fly ash based geopolymer as an alternative binder material for the production of fresh concrete because production of Ordinary Portland Cement degrades the environment by huge emissions of carbon-di-oxide and also by consuming lot of natural resources. But most of the study reveals, fly ash based geopolymer paste needs more time to get set when it is cured at ambient temperature. As a result, it is quite impractical to use fly ash based geopolymer paste as an alternative to Ordinary Portland Cement in faster construction. In this study, an effort has been made to enhance the properties of fly ash based geopolymer paste by incorporating ground granulated blast furnace slag at various percentage levels. Microstructure of the geopolymer paste is studied using Scanning Electron Microscopy. Result of this investigation shows that significant improvement on setting time and compressive strength can be obtained by adding ground granulated blast furnace slag in the mixes. © 2017 Elsevier LtdItem Investigation on the potential use of recycled fine aggregate to produce geopolymer mortar mix(ASTM International, 2019) Saha, S.; C, C.The utilization of construction and demolition waste (C&DW) partially or fully for various purposes in construction industries is one of the most significant solutions to overcome the scarcity of raw materials and disturbances of the environmental system. On the other hand, geopolymer is being tried to be established as an alternative sustainable binder material for ordinary portland cement. In the present study, with the thought of promoting of sustainability, an attempt has been made to use concrete wastes as recycled fine aggregate (RFA) partially to produce fly ash (FA)-based geopolymer mortar. The workability, water absorption, compressive strength at 3, 7, 28, and 56 days, volume change behavior, and chloride permeability of the produced FA-based geopolymer mortar were determined. The effects of RFA, the ratio of alkali liquid (AL) to FA, and different curing regimes on these properties of mortar mix also discussed. The morphology and microstructures of the samples taken from the mortar mix, which were observed having the highest strength under different curing regimes, were studied using scanning electron microscopy (SEM). The experimental results indicate lower workability, higher water absorption capacity, and higher drying shrinkage of geopolymer mortar mix that has more RFA content in the mix, but the compressive strength of the geopolymer mortar mix started decreasing after a certain percentage of RFA content in the mix. Utilization of that certain percentage of RFA will help us to minimize the consumption of natural fine aggregates and reduce the disturbances generated by unorganized dumping of C&DW. © 2019 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.Item Characterization and performance of processed lateritic fine aggregates in cement mortars and concretes(Elsevier Ltd, 2019) Yaragal, S.C.; Basavana Gowda, S.N.; C, C.Availability of river sand is becoming scarce, due to rapid increase in infrastructure projects in India. Acute shortage of river sand, has led to indiscriminate sand mining. Adverse effect of sand mining includes river bank erosion, river bed degradation, loss of biodiversity and deterioration of river water quality and ground water availability. To address the above issues, research efforts are on, to find substitutes for river sand to be used as fine aggregate in mortars and concretes. One among the locally available resources is laterite. Laterite is a product of tropical or sub-tropical weathering, which is an abundant soil material in many parts of India. An attempt has been made to characterize the processing technique to obtain good quality lateritic fine aggregates (lateritic FA). Experiments were designed and conducted to study the performance of lateritic FA as replacement to river sand, in cement mortars and concretes. Processed lateritic FA in replacement levels of 0, 25, 50, 75 and 100 wt% to river sand at all fineness levels (Zone I to Zone IV as per Indian standards) is considered. Microstructure studies were conducted to understand the arrangement of river sand and lateritic FA with cement matrix and their Interfacial Transition Zones (ITZ) using Scanning Electron Microscope (SEM). The workability and compressive strength characteristics of cement mortars and concretes are evaluated. Laterized mortars with Zone III and Zone IV fine aggregates, at all replacement levels, result in the same compressive strengths as those of control mortars. Suitable strength enhancement technique has been attempted to achieve strengths of Zone I and Zone II lateritic fine aggregates based mortars at 100 wt% replacement, to achieve strength at least equal to or more than those of control mortars. Laterized concretes have achieved nearly the same strengths as those of control concretes, at all replacement levels and for all fineness levels (Zone I to Zone IV). © 2018 Elsevier LtdItem Volume change characteristics of eco-friendly mortar mixes produced with geopolymeric binder and recycled fine aggregate(ASTM International, 2020) Saha, S.; Shaik, N.; C, C.The production of geopolymer mortar using recycled fine aggregate (RFA) generated from concrete waste has significant potential to be a sustainable construction material. In this article, the volume change properties of the produced geopolymer mortar mixes are studied in terms of drying shrinkage up to the age of 180 days and reported as the percentage increase with respect to the shrinkage value of 3 days. The influence of RFA content, alkaline liquid (AL) in terms of the concentration of sodium hydroxide (SH) solution, the ratio of sodium silicate (SS) solution to SH solution, and the ratio of AL to fly ash (FA) were investigated on the drying shrinkage properties of the geopolymer mortar mixes. All the cast specimens were cured at 80°C for 24 hours. Higher drying shrinkage values were observed for the mortar mixes produced with higher RFA content, AL/FA, SS/SH ratio, and lower concentration of SH solution. Scanning electron microscope images were studied for the samples taken from the geopolymer mixes showing lower drying shrinkage values to understand the microstructure. © 2019 by ASTM International.Item Performance of eco-friendly mortar mixes against aggressive environments(Techno-Press info@techno-press.com, 2020) Saha, S.; C, C.; Gupta, P.Past research efforts already established geopolymer as an environment-friendly alternative binder system for ordinary Portland cement (OPC) and recycled aggregate is also one of the promising alternative for natural aggregates. In this study, an effort was made to produce eco-friendly mortar mixes using geopolymer as binder and recycled fine aggregate (RFA) partially and study the resistance ability of these mortar mixes against the aggressive environments. To form the geopolymer binder, 70% fly ash, 30% ground granulated blast furnace slag (GGBS) and alkaline solution comprising of sodium silicate solution and 14M sodium hydroxide solution with a ratio of 1.5 were used. The ratio of alkaline liquid to binder (AL/B) was also considered as 0.4 and 0.6. In order to determine the resistance ability against aggressive environmental conditions, acid attack test, sulphate attack test and rapid chloride permeability test were conducted. Change in mass, change in compressive strength of the specimens after the immersion in acid/sulphate solution for a period of 28, 56, 90 and 120 days has been presented and discussed in this study. Results indicated that the incorporation of RFA leads to the reduction in compressive strength. Even though strength reduction was observed, eco-friendly mortar mixes containing geopolymer as binder and RFA as fine aggregate performed better when it was produced with AL/B ratio of 0.6. © 2020 Techno-Press, Ltd.