Browsing by Author "De Silva, SD"

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    item: Conference-Abstract
    Non-destructive evaluation of strength gain of ordinary portland cement mortar by ultrasonic pulse velocity method
    (Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 2016-04) De Silva, SD; Sivahar, V; Jayasekara, AGBP; Amarasinghe, YWR
    This paper presents results of the study of ultrasonic pulse velocity and compressive strength of ordinary Portland cement mortar. Objectives of this study are to determine correlations between ultrasonic pulse velocity and compressive strength of cement mortar and to predict strength of cement mortar at 28 days within 02 days using ultrasonic pulse velocity of cement mortar. Water/cement ratio, sand content, method of specimen preparation, curing conditions were kept constant throughout the experiment. Portable Ultrasonic Nondestructive Digital Indicating Tester with transducers of 54 kHz frequency was used to measure ultrasonic pulse velocity. In this research it was found that the relationship between ultrasonic pulse velocity and compressive strength was linear and Lime Saturation Factor (LSF) of cement has an influence on this relationship. Further it was seen that, with the increase of curing period ultrasonic pulse velocity of all samples increased. At the end it was possible to obtain an equation that can predict the cement strength at 28 days within 02 days and that equation was verified using another five (05) cement samples.
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    item: Conference-Extended-Abstract
    The role of the mottled water hyacinth weevil (neochetina eichhorniaes on biological control of water hyacinth in Sri Lanka
    (2003) Gamage, NPD; Jayaweera, MW; De Silva, SD; Kasige, AP
    Water hyacinth (Eichhornia crassipesi has become one of the most obnoxious freshwater weeds \~ith numerous widespread infestations occurring in the North Western. Central and Southern provinces in Sri Lanka. Water hyacinth competes with native plants and phytoplankton in aquatic system for essential nutrients and space due to its rapid grow tho Further it clogs waterways thereby restricting recreational activities including fishing and navigation. lowers dissolved oxygen in water and limits light penetration due to the formation of an extensive network of mats.