Browsing by Author "Yatawara, M."

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Assessment of the potential of incorporating rice husk ash in compressed stabilized earth block manufacturing process
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Athukorala, S. M. W.; Yatawara, M.
Rice husk ash (RHA), an agricultural waste discharged from rice milling industries has become an environmental issue in certain districts in Sri Lanka. Since RHA shows high pozzolanic properties, the present study was designed to determine whether there is a potential to incorporate RHA in compressed stabilized earth block (CSEB) manufacturing process in a production line without changing the proportion of ordinary Portland cement (OPC). Analysis of chemical properties and particle size distribution of RHA and soil texture were done prior to the manufacturing process to confirm the suitability of raw materials. The mixing proportion of OPC and clay soil was, thus, 1:15. Six different types of CSEBs having the size of 300 mm × 150 mm × 100 mm (length, width, height) were manufactured by replacing 0% (control-B1), 5% (B2), 7.5% (B3), 10% (B4), 15% (B5), and 20% (B6) of clay soil by RHA. Properties of CSEBs including dry and bulk densities, water absorption, compressive strength, erosion resistance, acid resistance and percentage weight reduction were determined. Each test was quadruplicated. Data were subjected to One-way ANOVA followed by Tukey’s tests in MINITAB 14. The values were compared with SLS 1382-2009 and British standards. Results revealed that a significant reduction of dry and bulk densities of B3, B4, B5 and B6 (p<0.05) was achieved when compared with controls. The block B3 showed the lowest water absorption, pitting depth, pitting rate and the highest compressive strength. According to SL standard, all the blocks manufactured were suitable for construction of walls (Grade 3), but not for interlocking except B3. When compared with the British statutory minimum compressive strength requirements of bricks for various walls, all types of blocks manufactured were suitable for load bearing walls for one and two storey houses and storey houses divided into flat and non - load bearing walls (both external and internal). Nevertheless, considering acid tolerance of the manufactured blocks, it is recommended to use all types of blocks for load bearing walls for one and two storey houses and storey houses divided into flat and non - load bearing walls (external). The present study suggests that the RHA discharged from rice milling industry can be effectively utilized in CSEB manufacturing by hydraulic compaction at 1.37 x 109 N/m2.
The feeding patterns and food preferences of Aplocheilus parvus: a potential biological control agent for malaria?
(Sri Lanka Association for Fisheries and Aquatic Resources, 2012) Fernando, G.K.A.W.; Jayakody, S.; Wijenayake, W.M.H.K.; Yatawara, M.; Harishchandra, R.D.J.; Deniyage, S.L.; Galappaththy, G.N.L.
The ultimate aim of Anti Malaria Campaign is to eliminate indigenous malaria from Sri Lanka. Better environmental and economic benefits could be achieved by the use of indigenous fish species compared to chemical controlling methods as they have minimum or no impact on the existing aquatic fauna. Aplocheilus porvus is a common indigenous species available in both lotic and lentic systems in wet, intermediate and dry zones and is one of the surface feeding predators. The feeding pattern and food preference of A. parvus was determined to test its efficacy as a biological control agent for malaria larvae. A 24 hour sampling for A. porvus wos conducted (n=12 fish every 2 hours) at a brick pit in Pannala MOH region in Northwestern province positive for potential malaria larvae (Anopheles jomesii, 0.1l6/dip) between September 2011 January 2012. Gut fullness, total and standard length of fish, total weight and gut weight and using copepod as an arbitrary unit, total number of food items per 1ml of dissolved gut was calculated with a Sedgewick Rafter Cell. The time at which active feeding occurred was established from total food particle amount and relative gut weight (gut weight/total weighx100). Diet of A. porvus mainly consisted of adult or larval stages of class Insecta (Coleoptera, Hymenoptera and other unidentified insect parts and insect larvae) and class Maxillopoda (Copepoda). Also, gut had a higher fullness in day time (4.3:t0.121) compared to night (2.4:t0.120) (p
Impact of one month old sludge as top inoculum layer of biogas floe rate in dry batch type digesters
(Sri Lanka Association for the Advancement of Science, 2015) Kodituwakku, K.A.R.K.; Yatawara, M.
Potential of replacing clay soil by rice husk ash (RHA) in enhancing the properties of compressed earth blocks (CEBs)
(Environment, Development and Sustainability, 2020) Yatawara, M.; Athukorala, S.
The present study was planned to assess the potentiality of replacing clay soil with rice husk ash (RHA), in manufacturing of compressed earth blocks (CEBs) while maintaining the required mechanical properties of CEBs. CEBs having the size of 300 mmxl50 mmxl00 mm (length, width and height) were manlrfactured by hydraulic compacrion at 7 .37 x 1 0e N/m2 using ordinary Portland cement (OPC) and clay soil at 1 : 15 ratio and a commercially available resin adhesive (20 mLkg cement). Six different types of CEBs were manufactured by replacing 0% (control and B1),5% (82),1.5% (83), 10% (84), 15% (B5) and 20% (86) of clay soil with RHA. Dry and bulk densities, water absorption, compressive strength, erosion and acid resistance were tested. Each test was quadruplicated. The highest compressive strength, the lowest water absorption and acceptable erosion resistance were recorded fiom B3. Results further revealed that25.7% improvement in the compressive strength of 83 was achieved compared to B 1. Although all types of CEBs recorded compressive strength greater than 2.75 N/mm2, indicating that the blocks were suitable for load bearing walls for one and two story houses and story houses divided into flat and non-load bearing walls (both external and internal), the results of acid tolerance revealed that they were more suitable fbr internal walls. As such, the present study recommends to replace the maximum of 7 5% clay soil with RHA in manufacturing of CEBs for load bearing and non-load bearing internal walls.