Conductivity (EC) and total dissolved solids (TDS) are water quality parameters, which are used to describe salinity level. These two parameters are correlated and usually expressed by a simple equation: TDS = k EC (in 25 °C). The process of obtaining TDS from water sample is more complex than that of EC. Meanwhile, TDS analysis is very important because it can illustrate groundwater quality, particularly in understanding the effect of seawater intrusion better than EC analysis. These conditions make research in revealing TDS/EC ratios interesting to do. By finding the ratio value, TDS concentration can be measured easily from EC value. However, the ratio cannot be defined easily. Previous research results have found that the correlation between TDS and EC are not always linear. The ratio is not only strongly influenced by salinity contents, but also by materials contents. Furthermore, the analysis of TDS concentration from EC value can be used to give an overview of water quality. For more precision, TDS concentrations need to be analyzed using the gravimetric method in the laboratory.

https://iopscience.iop.org/article/10.1088/1755-1315/118/1/012019/pdf

Correlation between conductivity and total dissolved solid in various type of water: A review

Successes and challenges in non-destructive testing of aircraft composite structures

Evaluation of groundwater quantity and quality in the Kashan Basin, Central Iran

This work describes a novel method of embedded damage detection within glass fiber–reinforced polymer composites. Damage detection is achieved by monitoring the spatially distributed electrical conductivity of a strain-sensitive multiwalled carbon nanotube thin film. First, thin films were spray-deposited directly upon glass fiber mats. Second, using electrical impedance tomography, the spatial conductivity distribution of the thin film was determined before and after damage-inducing events. The resolution of the sensor was determined by drilling progressively larger holes in the center of the composite specimens, and the corresponding electrical impedance tomography response was measured by recording the current–voltage data at the periphery of the monitored composite sample. In addition, the sensitivity to damage occurring at different locations in the composite was also investigated by comparing electrical impedance tomography spatial conductivity maps obtained for specimens with sets of holes drilled at different locations in the sensing area. Finally, the location and severity of damage from low-velocity impact events were detected using the electrical impedance tomography method. The work presented in this study indicates a paradigm shift in the available possibilities for structural health monitoring of fiber-reinforced polymer composites.

Detection of Spatially Distributed Damage in Fiber-Reinforced Polymer Composites.

Investigation on mechanical properties of fly ash-ground granulated blast furnace slag based self curing bio-geopolymer concrete

The study aims at establishing the correlation ratio between Total Dissolved Solids (TDS )and Electrical Conductivity ( EC ) for natural waters such as fresh water , sea water and tender coconut .The EC value can be obtained from in situ conductivity measurements since it is quick reliable and relatively of low cost . Twenty four fresh water , fifteen sea water and twenty eight ( eight from pollution free area and twenty from textile industrial belt) tender coconut samples were considered for the analysis various water quality parameters. In sea water, the result indicates 96 % of the variability in TDS could be ascertained to the variable EC. The regression equation for sea water is in the form of y = bx + c where b is the correlation ratio due to ionic species and the intercept c values are assigned to unionic species. In the case of tender coconut, the correlation ratio was found to be 0.63 for samples taken from pollution free residential areas where as the ratio found to be varied between 0.59 to 0.93 in textile industrial belt.

Correlation between Electrical Conductivity and Total Dissolved Solids in Natural Waters

In the present study, lime mortar samples from the restoration site of Vadakumnathan temple, Kerala, India have been analyzed. Samples from three different locations of the temple such as ancient wall, gopuram and arch have been taken. Traditional methods such as chemical analysis, acid loss analysis and organic test were conducted on mortar samples. Modern instrumental techniques such as electronic particle size distribution, X-ray Diffraction (XRD), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDX), Thermo Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Infrared Spectroscopy (FT-IR) were employed in the study. The binder used in the mortar is calcium high with 30% of clay mineral. A binder to aggregate ratio in the range of 1:1.5–2.5 has been established from acid loss analysis. Particle of the aggregate are mostly silt in nature, hence nominal sand would have been grinded to reduce the particle size and to induce pozzolanic reaction. The presence of carbohydrate, protein and fats are identified by organic test that are in agreement with FT-IR analysis and TGA. Calcite, aragonite and calcium complexes of silicate and aluminates in form of hydro thermal product namely gyrolite and okenite are present in wall and gopuram samples. The formation of hydrothermal products confirms that the mortar was produced by hot lime technology. In TGA, the decomposition of CaCO 3 to CO 2 between 600 and 770 °C reveals the transformation of calcite from complex forms of CSH (gyrolite and okenite) and CAH. The presence of degraded products such as syngenite and gypsum in arch sample shows that the lime mortar is in complete deterioration where as mortar remained in good condition in gopuram and wall samples.Texture along with elemental analysis (EDX) confirms the results of chemical analysis.

Knowing from the past – Ingredients and technology of ancient mortar used in Vadakumnathan temple, Tirussur, Kerala, India

The implementation of health monitoring in various structures proves to be beneficial in numerous ways like providing enhanced public safety, improving life span of structures, cutting costs, and early detection of risks thus helping in improving the overall performance of the structures. The improved performance of structures is also essential for the nation and its development. Increased usage of various sensors in different bridges like as Tsing Ma Bridge, Confederation Bridge, and Commodore Barry Bridge structures leads to effective structural health monitoring, which further ensures their long life span. Despite using sensors in the structures, there are some factors like environmental factors, misinterpretation of collected data by mixing of various structural health monitoring (SHM) techniques, and on-site construction defects which affects the conclusions related to the nature of damage and its location. In this chapter, a detailed study of benefits of structural health monitoring and thus the need to meet recent requirements by various recent trends is done. With the progress in trends of structural health monitoring techniques challenges which de-toured the final results of SHM techniques are reviewed in detail. This chapter on recent trends in structural health monitoring includes an elaborate study of advanced technology such as optical fiber Bragg grating (OFBG) strain sensors to monitor damages in civil infrastructures, carbon fiber reinforced polymer (CFRP)-OFBG sensing unit to measure the interface strain and fiber optic sensors for measuring small cracks. These recent trends are extremely effective in meeting various requirements for a modern SHM system, but they still encounter various challenges that affect the measurement data and final conclusions. Therefore various research studies are taking place in the SHM field to achieve an absolutely error-proof monitoring system in the near future.

Recent advances and trends in structural health monitoring

Printed circuit boards (PCB) contain metallic and non-metallic fractions (NMF) that are hazardous and toxic when disposed of in a landfill. This paper emphasizes the feasibility of using NMF reclaimed from waste PCB's as a replacement to fly ash (FA) and metakaolin (MK) in a geopolymer mortar. Geopolymer mortar mixes were prepared with five FA-MK replacement ratios of 100-0, 90-10, 80-20, 70-30 and 60-40 and for each mix FA was also replaced with NMF by 5%, 10%, 15%, and 20%. The compressive strength and microstructures of geopolymer mortar were investigated and it was found that the addition of NMF enhanced the compressive strength. Maximum strength gain was found with 30% of MK and 15% of NMF in FA. The pozzolanic action of alumino-silicates was studied through SEM and XRD which reflected the formation of C-S-H gel with a dense geopolymer matrix along with the formation of CaCO3 crystals resulting in strength gain. The experimental studies provide a practical and sustainable recycling approach for the use of NMF in geopolymers for the construction industry.

S. Thirumalini

Papers

Correlation between Electrical Conductivity and Total Dissolved Solids in Natural Waters

Knowing from the past – Ingredients and technology of ancient mortar used in Vadakumnathan temple, Tirussur, Kerala, India

Recent advances and trends in structural health monitoring

A novel approach for the development of sustainable hybridized geopolymer mortar from waste printed circuit boards

Experimental and numerical investigation of short GFRP- reinforced steel tubular short columns