CERS - 2021
Permanent URI for this collectionhttp://192.248.9.226/handle/123/17780
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Browsing CERS - 2021 by Author "Gamage, JCPH"
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- item: Conference-AbstractComposite effects of pozzolans in producing high strength recycled aggregate concrete(Department of Civil Engineering, University of Moratuwa, 2021-11) Fernando, AM; Gamage, JCPH; Hettiarachchi, POver the years, the unceasing growth and development in the construction industry has resulted in both positives and negatives. The extensive use and disposal of many of the materials used in construction have resulted in the depletion of natural resources, together with piling up of large amounts of construction and demolition waste in landfills, causing adverse effects on the environment, the economy as well as society. The most extensively consumed material in the construction industry can be identified as concrete. Procurement and transportation of raw materials for cement and aggregates which are the two major constituents used in concrete production add significant disturbances to the ecological system. Thousands of research studies have shown the feasibility of using recycled aggregates to produce both normal and high strength concrete with comparable properties to conventional concrete. However, it requires a more allinclusive approach in producing an environmentally friendly solution. This paper discusses the procedure followed in producing cost effective and economical high strength concrete through the composite use of pozzolans namely fly ash, silica fume and rice husk ash (RHA), in both stages of aggregate treatment and concrete production. Results from aggregate testing showed a 26%and 59% reduction in aggregate water absorption and porosity, respectively. Further, enhancements in terms of aggregate specific gravity and crushing value were obtained. Concrete which contained RHA in both stages, attained a compressive strength of 55.4 MPa, which was even higher than the control mix containing natural aggregates. The same mix of concrete showed a 12% increase in its surface resistivity. This indicates the possibility of achieving high strengths, even with the use of RA derived from parent concretes of lower grades, and not many studies have focussed on this aspect of high strength recycled aggregate concrete production (HS-RAC).
- item: Conference-AbstractDevelopment of a plastering mortar using waste bagasse and rice husk ashes with sound mechanical and thermal properties(Department of Civil Engineering, University of Moratuwa, 2021-11) Srikanth, G; Gamage, JCPH; Hettiarachchi, PThe concept of using cleaner production technologies has become prominent in the present context for achieving sustainability in construction. It has been proven that by incorporating agricultural waste as cement replacement, mechanical and durability properties of the resulting mortar have been enhanced. A comparative study on the mechanical, thermal, and environmental performance of a newly developed lightweight mortar containing agro-wastes namely Bagasse Ash (BA) and Rice Husk Ash (RHA) were investigated. Ordinary Portland cement was partially replaced by BA at dosages of 0%, 5%, 15%, 20%, and 30% and RHA at dosages of 0%, 5%, and 15% by weight. A detailed investigation was carried out to determine the best suited material mix which can achieve very good material properties. Results indicated that the mixtures with the replacement percentages up to 30% by both BA and RHA for cement had compressive strength confined to the standard recommended range (~5.2 MPa) while maintaining the adequate water absorption and acid alkaline resistance. This indicates that BA can be used to replace the cement up to 30% and BA and RHA of each 15% of cement replacements also can be used to manufacture the mortar for wall plaster and addition of 30% BA as a partial replacement for cement improved the thermal performance by causing a decrease in the thermal conductivity about 33%. However, the combination of BA and RHA (15% each) decreased the thermal conductivity up to 31% compared to the conventional mortar and results indicated that acid resistance also increased with the increase the percentage of BA and RHA, Further, the assessment of environmental impact reveals a noticeable reduction in embodied GHGE with the increasing replacement of BA and RHA in mortar. When the cement in conventional mortar was substituted with 30% BA and, 15% BA and 15% RHA, both cases reduced the CO2 emissions by about 28% than the control mix. The cost of control for both mortar containing 30% BA and mortar containing 15% BA and 15% RHA production is 16.6% of conventional mortar mix. However, the energy to produce BA mortar is less than BA and RHA mortar. Thus, BA falls more under the prospective of energy effective, cost-effective, and environmentally friendly construction materials.
- item: Conference-AbstractDevelopment of sandwich roof panels: a review(Department of Civil Engineering, University of Moratuwa, 2021-11) Bandaranayake, SS; Gamage, JCPH; Hettiarachchi, PSandwich panels (modular panels) promote optimal solutions to some major issues prevailing in the construction industry such as increased energy consumption by building elements, excessive disposal of construction waste and unproductive time spent during construction. Hence the inclination towards sandwich elements has been increased vastly deviating from conventional building construction materials and methods. However, the potential of using locally available natural materials for the development of sandwich panels is a salient sustainable approach that needs to be addressed. The research methodology was composed of a detailed literature review followed by a series of thermal simulations using a commercially available finite element analysis programme. The potential materials used in modular panels and key properties of sandwich panels which include mechanical, thermal and sound insulation properties were identified. Moreover, various test methods followed, and standards specified to investigate the mechanical, thermal, and acoustic insulation properties were also discussed. Secondly, the possibility of using coconut fibre as a locally available natural alternative core material to polyurethane core of sandwich panels has been evaluated using the aforesaid thermal simulation software based on the material properties obtained from literature. The study identifies coconut fibre as a potential alternative core material for sandwich roof panels which reflects similar thermal behaviour to polyurethane. However, these results can be further validated, and panels can be optimized structurally by performing further experimental studies based on the test methods and standards identified in the study.
- item: Conference-AbstractPerformance of CFRP/concrete composites after conditioning under accelerated alkaline exposure(Department of Civil Engineering, University of Moratuwa, 2021-11) Aponsu, GMDN; Gamage, JCPH; Hettiarachchi, PEnvironmental exposure leads to the degradation of the adhesive bond between externally bonded Carbon Fibre Reinforced Polymer (CFRP) and concrete in reinforced concrete (RC) structures strengthened with CFRP. Moisture penetration is a major factor that is detrimental to the durability of CFRP composites due to the high susceptibility of the resin matrix to moisture-induced damage. Furthermore, alkaline solutions pose a threat to CFRP-strengthened structures due to ionic compounds present in them which accelerate the process of deterioration. A series of single-lap shear tests were conducted to evaluate the bond performance of CFRP/concrete composites exposed to accelerated alkaline exposure. Strengthening of concrete samples was done by following the wet layup method. The conditioning was done by immersing the shear lap test specimens in an alkaline solution with a pH value of 12.6 to provide equivalent conditions as in concrete pore water solution for a period of 60 days. At the end of exposure, the specimens were left to cure under ambient conditions to provide equivalent conditions to the bond line during destructive testing. Then, a transient tensile load was applied at the displacement rate of 0.5 N/mm till failure. Scanning Electron Microscopy (SEM) was employed to assess the microstructure level degradation of CFRP laminates, bond, and interfaces after exposure. A maximum bond strength reduction of 23.8% was observed following the 60-day exposure period. The results indicated an accelerated drop of 20% within the initial 15 days of exposure. Microstructure analysis exhibited substantial damage, characterised by disintegration, swelling and cracking, of the resin matrix by the penetration of moisture and alkaline ions. Further evidence was provided by the observed failure mechanism which indicated the poor interface between concrete and epoxy.