Browsing by Author "Konthesingha, C"

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item: Article-Full-text
Effects of blending manufactured sand and offshore sand on rheological, mechanical and durability characterization of lime-cement masonry mortar
(Taylor & Francis, 2022) Arulmoly, B; Konthesingha, C; Nanayakkara, A
The environment and ecological systems are suspected of serious drawbacks as a result of the over-extraction of river sand for construction activities. An attempt was made in this research on completely replacing river sand in lime-cement masonry mortars with blended sands comprised of manufactured sand and offshore sand. The S and N types (as defined in the standards) were selected for producing masonry mortars with different sand contents. For each type, five mortars were prepared to contain river sand alone (reference mortar), manufactured sand alone, and three blended sands (replacing manufactured sand by offshore sand at 25%, 50%, and 75%). Because of the dominant roles of particle angularity, surface roughness, and gradation of the alternatives, the performance of mortars was evaluated and compared based on these sand characteristics. Furthermore, the level of statistical significance of the experiment results was analyzed from a single factor one-way ANOVA test. Outcomes of this research revealed that the blended sands and manufactured sand declined the fresh state performance of mortars than the river sand mortars. However, most of the stiffened and durability properties of alternative mortars were significantly advanced than the reference mortars.
item: Article-Full-text
Effects of microfine aggregate in manufactured sand on bleeding and plastic shrinkage cracking of concrete
(Springer Science+Business Media, 2022) Arulmoly, B; Konthesingha, C; Nanayakkara, A
Construction industries have started to utilize manufactured sand (MS) as an effective alternative for river sand in concrete. High-grade parent rocks are crushed to obtain MS, which also produces a considerable amount of microfine aggregate (MFA). The higher percentage of MFA could lead to both positive and negative effects on the performance of cement-based mixes. This research was done to examine the influence of varying MFA levels, specifically 0%, 3%, 6%, 9%, and 12% (by weight) as the partial replacements of MS on bleeding and plastic shrinkage cracking of concrete. In addition to the varying MFA levels, some concrete mixes also included fly ash (FA) and superplasticizer to investigate the effect of free-water content in the mixes. The bleeding test data were taken as on-site measurements, while the cracks from the plastic shrinkage cracking test were evaluated using an image processing technique. The results concluded that the MFA replacements and the effective water-to-cement ratio have a significant effect on the selected concrete properties. With the increasing replacement levels, cumulative bleeding and crack initiation life gradually decreased, while a progressive increase was observed for crack width, crack length, and crack area.
item: Conference-Full-text
influence of blended fine aggregates on the performance of lime - cement mortar — a statistical approach
(IEEE, 2021-07) Arulmoly, B; Konthesingha, C; Nanayakkara, A; Adhikariwatte, W; Rathnayake, M; Hemachandra, K
This study investigates the performance evaluation of lime-cement mortar comprised of manufactured sand and offshore sand as the river sand alternatives. The most common mortars suggested by the standards such as S and N types were selected and five mixes were prepared for each type. Different sand compositions such as river sand, manufactured sand, and blended sand with manufactured sand and offshore sand were used in the mixes. The performance of mortars with sand replacements was investigated based on the fresh and hardened properties. The experimental results were undergone for a one-way analysis of variance (ANOVA) test to check whether the selected sand types and replacements statistically and significantly impacted the properties of mortar. Results revealed that the selected replacements statistically and significantly influenced the workability, compressive strength, and flexural strength while no significant improvements were noticed with the workable life of mortars. Mortars with blended sand considerably improved the performance against capillary water absorption than a mortar with river sand.
item: Article-Full-text
Performance evaluation of cement mortar produced with manufactured sand and offshore sand as alternatives for river sand
(Elsevier, 2021) Arulmoly, B; Konthesingha, C; Nanayakkara, A
This study investigates the fresh and hardened state properties of cement-sand mortar comprising manufactured sand and offshore sand as alternatives for a complete replacement of river sand. Two types of manufactured sand were selected based on different rock types such as Hornblende-Gneiss and Charnockite. Offshore sand was collected from an open stock pile after required period of washing. Mortars were manufactured with a binder of Portland Limestone Cement. Binder-to-aggregate ratios of 1:3, 1:4 and 1:6 were considered in this study and manufactured sand was replaced at 0%, 25%, 50% and 75% with offshore sand. To check the influence of sand alternatives and blending ratios, fresh and hardened state properties of alternative mortars were analyzed and compared with reference mortars which were made with river sand alone. Wet and dry bulk densities of mortars were increased with lower replacement levels with offshore sand. Most mortars with blended sand improved the workability while consistency and initial setting time of mortars were not significantly affected. Inflated bleeding of mortars was noticed with the alternatives and replacement levels. Workable life was decreased at small replacements. When manufactured sand in mortar content was 25% and 50%, the water retentivity was significantly improved than other replacements and control mixes. Mortars at lower replacements greatly advanced the flexural strength, compressive strength and capillary water absorption. Linear shrinkage and thermal expansion of mortars were also affected with the selected replacement levels. Based on the overall performance of mortars, blended sand at 25% replacement of manufactured sand with offshore sand was deduced as the feasible solution for completely replacing river sand and to produce economical mortars.
item: Article-Full-text
Plastic settlement and hardened state assessments of manufactured sand made concrete for varying microfine levels
(Wiley-Blackwell, 2022) Arulmoly, B; Konthesingha, C; Nanayakkara, A
Manufactured sand (MS) has been started utilizing as an alternative in constructions due to the escalated demand for river sand (RS). The microfine aggregate (MFA) is a salient constituent in manufactured sand, which is a crushed reactive form of parent rocks having particles less than 0.075 mm. This paper presents the effects of varying microfine aggregate levels on bleeding, plastic shrinkage cracking (PSC) and compressive strength of MS made concrete. Two types of MS were utilized: MS from Hornblende-Gneiss rock (MH) and MS from Charnockite rock (MC) and the MFA level was ranged from 0% to 12% at 3% increments and the reference concrete was prepared with RS alone. With the MFA levels, the bleeding of MS concretes was reduced where, at 0% MFA level the maximum bleeding rates were observed for MC (1.63 kg/m2) and MH (0.84 kg/m2) concretes. PSC results were analyzed from an image processing technique, which revealed an increasing trend of mean and maximum crack widths, crack length and crack area with the MFA levels. At 0% MFA, the mean crack width of MC (0.19 mm) and MH (0.17 mm) concretes manifested marginally similar to RS concrete (0.17 mm). The decreasing bleeding with the MFA levels can be attributed to the increasing severity to PSC. Moreover, the optimum 28 days compressive strength of MC (57.5 MPa) and MH (56.1 MPa) concretes was achieved at 3% MFA level which are higher than RS concrete (51.5 MPa). Consequently, the MFA level should be limited to 3% for better plastic and hardened performance of MS made concrete.
item: Article-Abstract
Web crippling behaviour of cold-formed carbon steel, stainless steel, and aluminium lipped channel sections with web openings
(MDPI, 2022) Weerasinghe, H; Konthesingha, C; Nanayakkara, A; Poologanathan, K; Perampalam, G; Kanthasamy, E
This paper reviews the research advancements and design practices related to the structural web crippling response of lipped Cold-Formed (CF) carbon steel, stainless steel, and aluminium channels with web perforations. The web crippling response differs among each material based on the non-linear stress-strain characteristics and degree of strain hardening. Therefore, the reduction in the web crippling strength of web-perforated CF channel sections made of different materials may not be equivalent. The research activities surrounding the web crippling response of CF channels with and without web openings were reviewed initially. Despite the limited design provisions given in the international specifications for the web crippling design of lipped CF channels with web openings, web crippling studies conducted across the world have developed suitable design equations in the form of reduction factors. Past research studies have substantially captured the web crippling response of carbon steel channels with web openings while that of stainless steel and aluminium are limited, as identified in this paper. Lastly, numerical models were developed for simulating the web crippling behaviour of lipped CF carbon steel, stainless steel, and aluminium channels with web opening and validated with past experimental data, with a view for developing unified design guidelines.