Browsing by Author "Tharshigan, T"

Now showing 1 - 5 of 5

item: Conference-Abstract
Development of fine aggregate using coal fly ash with internal curing characteristics
(Department of Civil Engineering, University of Moratuwa, 2020-12) Tharshigan, T; Pradeep, I; Mampearachchi, WK; Perera, HLK
Fly ash is produced as a byproduct from Lakvijaya coal power plant, Norochcholai, Sri Lanka. The daily production of fly ash at Lakvijaya power plant is 950 – 1000 tons. Some part (around 40%) of fly ash is consumed by cement manufacturers, the balance of fly ash is stored without any means of disposal inside the plant. This research study discusses the development of fine aggregate replacement material using sintered coal fly ash with internal curing characteristics. A series of samples were prepared with different composition of fly ash and reservoir sediment material and sintered from 8000C to 13000C temperatures in the interval of 1000C for 30 minutes of sintering time then crushed to prepare fine aggregates. Here reservoir sediment material was used as a binder material and it improved green strength of solidified fly ash. TGA – DSC and XRF analysis was used to investigate the thermal and chemical properties of raw materials, respectively. The microstructure of produced fly ash aggregate was observed using SEM photographs. Water absorption, water desorption and relative density of fine aggregate were measured. Water absorption and relative density aggregates were the range of 21 – 40%, 1.2 – 1.55, respectively. The aggregate with 80% of fly ash and 20% of reservoir sediment material which heated at 11000C had 21.4% water absorption and 74.12% water desorption was selected as suitable replacement material instead of natural river sand. concrete was prepared using wetted fly ash aggregate by replacing 23.5% of natural river sand and external curing has not been done for that concrete. Concrete with wetted fly ash aggregate achieved lower strength at an early stage then after 28 days, it achieved more strength than conventional concrete. Fly ash aggregate supplied internally stored water for hydration reaction of cement after finish the free water present inside the concrete and gave internal curing behavior to the concrete therefore concrete with fly ash aggregate gained more strength than conventional concrete without external curing.
item: Conference-Abstract
Feasibility study of using calicut tile waste as an internal curing fine aggregate in construction industry
(Department of Civil Engineering, University of Moratuwa, 2020-12) Pradeep, KI; Tharshigan, T; Mampearachchi, WK; Perera, HLK
Over recent decades, internal curing concept has become emerging technology and research in this area has increased tremendously. American Concrete Institute described internal curing as “a process by which the hydration of cement continues because of the availability of internal water that is not part of the mixing water”. Internal curing facilitates to minimize autogenous shrinkage as water in the pore structure will work to fill pores which lead to shrinkage. And also, effective cement hydration process will perform inside concrete by maintaining internal relative humidity which leads in to avoid self-desiccation. Over the years, various methods and materials have tested to use as an internal curing aggregate. Calicut tile waste is generated as a wastage (damage tiles) in manufacturing factories and as construction and demolition waste in the construction industry. Waste Calicut tiles cannot be re-used to cast tiles as it is no longer shows clay properties with the phase changed of the material. The development of an internal curing fine aggregates using Calicut tile waste is described in the study. The internal curing fine aggregates are prepared by crushing Calicut tile waste to the size less than 4.75mm. Then crushed calicut tile chips are soaked in water for 48hours to absorb and retain water inside the microstructure. Water absorption, Water desorption, the relative density of pre-wetted Calicut tile chips and microstructure were studied. According to ASTM C1761M, internal curing aggregate shall have a 72-h absorption not less than 5%., the release of at least 85% of its absorbed water at 94% relative humidity. Water absorption of 23%, water desorption of 91% and a relative density of 1.8 showed in the investigations. Scanning electron micrographs images of the aggregate show that tiny pores (> 100nm) are presented in the microstructure which can store water and release for hydration. Initial investigations revealed that Calicut tile waste can be used as an internal curing fine aggregate since it has the required water absorption and desorption capacity.
item: Conference-Abstract
Feasibility study of using industrial waste as an internal curing aggregate for rigid pavements
(Department of Civil Engineering, University of Moratuwa., 2019-09) Pradeep, KI; Tharshigan, T; Mampearachchi, WK; Pasindu, HR
The hydration process of cement in concrete affects the temperature conditions and moisture content which indirectly cause for strength, shrinkage and cracks. Curing starts immediately after setting of concrete. American Concrete Institute describes curing as “action taken to maintain moisture and temperature conditions in a freshly placed cementitious mixture to allow hydraulic-cement hydration and, if applicable, pozzolanic reactions to occur so that the potential properties of the mixture may develop”. In external curing of rigid pavements, water inside the concrete consumed for hydration of cement, some part of water escapes to the atmosphere through concrete surface and some part absorbs to the ground. Thus. Internal drying occurs which reduces the relative humidity while increasing the internal stresses which results in shrinkage and thermal cracks. External supplied water will only affect for top part of the concrete layer. Internal curing method has been introduced as a solution to the problems encountered in external curing. According to American Concrete Institute, they defined internal curing as “a process by which the hydration of cement continues because of the availability of internal water that is not part of the mixing water”. It’s a method which supply water internally through water reservoirs which need for hydration process. This research is to develop a fine aggregate for rigid pavements which performs the internal curing properties using industrial waste. Water treatment sludge (WTS) and Textile Effluent sludge (TES) used as industrial waste to prepare fine aggregates. After several steps in treatment process to remove inorganic, organic contaminants and suspended solid particles in surface water, produce large quantities of sludge by removing impurities from raw water. Sludge removed from above process called ‘water treatment sludge’. Textile industry consume large amount water to convert raw materials and fabric to finished clothing materials. Specially for dyeing. So large quantity of sludge produces in the waste water treatment plants due to this case. The disposal of sludge from water treatment plants and textile dyeing industry is a huge issue for related authorities. Introduce a value-added product for waste sludge will be another solution for the waste. The water treatment sludge and textile effluent sludge was dried under sunlight and crushed in to powder form which passing through 0.6mm sieve. Thermogravimetric analysis and Differential scanning calorimetry are conducted to identify the thermal behaviour of sludges. Different mixtures were prepared by changing two sludge contents (100% WTS, 90% WTS+10%TES, 80%WPS+20%TES). Atterberg limits was initially identified to select the optimum water content need to mix the samples. For laboratory tests, cylindrical samples (Height; 80mm, Diameter; 17mm) were prepared for heating process. Slow heating method used to sinter the samples for different temperature levels (8000C, 9000C, 10000C, 11000C, 12000C). Then samples were crushed to small particles which passes through 4.75mm sieve and retained on 0.6mm sieve. Water absorption test, Relative density test, bulk density test was conducted to observe the physical properties of developed fine aggregates. Scanning Electron Micrographs (SEM) analysis was followed to observe the microstructure of the fine aggregates. Compressive strength test was followed to identify which temperature shows the higher strength of fine aggregates. According to ASTM C1761M, internal curing aggregate shall have a 72-h absorption not less than 5%. Also, the fine aggregate shall release at least 85% of its absorbed water at 94% relative humidity. When Kelvin equation combined with Young’s equation, a relationship between relative humidity and size of the pores being is established. According to the relationship, the pore size should be more than 200nm to release water from aggregate. The fine aggregates which developed using sludge waste shows higher water absorption which need for internal curing property. According to the SEM analysis, it shows that the pore size increases with the temperature and textile effluent sludge content. According to thermogravimetric analysis, compressive strength test and microstructure, it concludes that 1150oC is the optimum temperature to heat the sludge waste. The optimum textile effluent sludge and water treatment sludge were selected as 20% and 80% respectively, while 45% of water content should be added when preparing the mixture. As a conclusion to the above findings, the fine aggregates which developed using sludge waste feasible to use as an internal curing aggregate in rigid pavements.
item: Thesis-Abstract
Investigation of the suitability of sintered fly ash and reservoir sediment materials as a fine aggregate replacement material
(2021) Tharshigan, T; Mampearachchi, WK
Fly ash is produced as a byproduct from Lakvijaya coal power plant, Sri Lanka. The daily production of fly ash at Lakvijaya power plant is 950 – 1000 tons. Around 40% of fly ash is consumed by cement manufacturers, balance of fly ash is stored without any means of disposal inside the plant. This research study discusses about development of fine aggregate replacement material using sintered coal fly ash with internal curing characteristics. A series of samples were prepared with various composition of fly ash and reservoir sediment material and sintered from 8000C to 13000C temperatures in the interval of 1000C for 30 minutes of sintering time the sintered fly ash was crushed to prepare fine aggregates. Reservoir sediment material was used as a binder material and it improved green strength of solidified fly ash. TGA – DSC and XRF analysis were used to investigate the thermal and chemical properties of raw materials, respectively. Microstructure of produced fly ash aggregate was observed using SEM photographs. Water absorption, water desorption and relative density of fine aggregate were measured. Water absorption and relative density of aggregates were in the range of 21 – 40%, 1.2 – 1.55, respectively. The aggregate with 80% of fly ash and 20% of reservoir sediment material which was heated at 11000C had 21.4% water absorption and 74.12% water desorption was selected as suitable replacement material instead of natural river sand. Relative density of selected fly ash aggregate was recorded as 1.46. Concrete was prepared using wetted fly ash aggregate by replacing 17.7% of natural river sand and the concrete was not subjected to external curing. Concrete with wetted fly ash aggregate gained lower strength at early stage then it gained more strength at 28 day than that of conventional concrete. Fly ash aggregate supplied internally stored water for hydration reaction of cement after finishing the free water presence inside the concrete and gave internal curing behavior to the concrete, therefore concrete with fly ash aggregate gained more strength than conventional concrete without external curing. Keywords - coal fly ash, reservoir sediment material, sintering, fine aggregate, water desorption, internal curing concrete.
item: Conference-Abstract
Study on concrete with manufactured sand
(2019) Tharshigan, T; Kajaharan, T; Baskaran, K
Concrete is the most widely used and versatile material of construction all over the world. All these years, natural river sand is being used as fine aggregate, by the Sri Lankan concrete industry. However, the amount of river sand available is inadequate to cater the current demand. This paper is about the application of manufactured sand in concrete as a fine aggregate instead of natural river sand. This study was carried out to compare the compressive strength and durability properties of concrete made up of manufactured sand and river sand as fine aggregates. Also, the physical properties of river sand and manufactured sand were compared. Use of fly ash as a partial replacement material for cement in concrete was also investigated in this study. In total 72 cubes were casted in three sets for experimental purposes. 100% of river sand and 100% of manufactured sand were used in two sets of cubes. Ordinary Portland cement was replaced by 25% of fly ash with 100% of manufactured sand in the third set of cubes. Compressive strength was measured after 7, 28 and 56 days. Water absorption test, water permeability test and sorptivity test were used to investigate the durability properties of concrete. This experimental study shows that replacing manufactured sand instead of river sand in concrete improves the strength and durability properties of concrete.