http://ir.lib.ruh.ac.lk/handle/iruor/7340 This community contains all other publications produced by the University Academic Members. Sun, 19 Jul 2026 11:23:22 GMT 2026-07-19T11:23:22Z http://ir.lib.ruh.ac.lk/handle/iruor/21498 Improvement of the performance of recycled concrete powder-based artificial aggregates through the acceleration carbonation effect induced by polyethyleneimine admixture Shuqing, Tao; Qijun, Yu; Yang, Yu; Appuhamy, J.M.Ruwan S. Abstract Manufactured sand, recycled concrete powder, and cement were used as raw materials to produce recycled concrete powder-based artificial aggregates (RCP-AA) via cold-bonding granulation technology. The effects of curing methods and polyethyleneimine (PEI) dosage on the macro performance and microstructure of RCP-AA were analyzed. The recycled concrete powder contains a small number of active substances that can react with CO₂ to form CaCO3, thereby enhancing the performance of the artificial aggregates. Additionally, the secondary and tertiary amine groups in PEI molecules react with CO₂ to promote the carbonation process and form carbonates. This process not only improves carbonation efficiency under milder conditions, reducing the dependence on high CO₂ concentrations and pressure, but also significantly enhances the microstructure and performance of the aggregates. The results showed that carbonation and PEI addition significantly increased aggregate density, reduced water absorption, and enhanced single particle strength by promoting CaCO3 formation and improving the microstructure. Specially, the water absorption of RCP-AA reduced from 13.9 % to 9.8 %, and the early strength reached 3.07 MPa at an 8 % PEI dosage. Microstructural characterization further confirmed the effects of carbonation, showing a reduction in Ca(OH)2 content, an increase in CaCO3 formation, significant pore structure optimization, and improved carbonation efficiency and structural uniformity. The maximum CaCO3 generation occurred within the PEI dosage range of 8–12 %, while a 16 % dosage hindered carbonation due to the formation of overly dense polymer films. Considering both performance and practical applicability, an 8 % PEI dosage was recommended as the optimal level for improving the structure and mechanical properties of RCP-AA. This study provides a theoretical foundation for the preparation and curing of sustainable building materials, with the proposed method not only enhancing material performance but also offering significant potential for promoting the application of low-carbon, green materials, thereby supporting the construction industry's environmental sustainability. Fri, 13 Jun 2025 00:00:00 GMT http://ir.lib.ruh.ac.lk/handle/iruor/21498 2025-06-13T00:00:00Z http://ir.lib.ruh.ac.lk/handle/iruor/21487 A Review on Novel Approaches to Enhance Sound Absorbing Performance Using Textile Fibers Madushika, J.W.A.; Lanarolle, W.D.G. Fibreglass, foam, mineral fibres and their composites are the conventional materials used in applica tions that require absorption of sound. However, due to the health risks associated with the traditional materials, textile fibrous structures are becoming a valid alternative in spite of their comparatively lower sound absorption properties. The existing textile structures and textile structures specifically modified physically or chemically to enhance sound absorption properties have been experimented for better performance in sound-related properties. The fibres have been chemically modified using plasma treatments and alkali treatments, while microfibres, nanofibres, hollow fibres, bicomponent fibres, crimp fibres and aerogel-treated fibres are produced to modify the physical structures of fibres. The basic principle employed in these fibre modifications to enhance sound absorption is the increase of energy dissipation by increasing the fibre surface area, fibre roughness and tortuosity of the mater ial. This article critically reviews the techniques of modifying the fibrous structures to enhance sound absorption properties and their effectiveness. The sound absorption coefficient of natural fibres can be enhanced up to 0.9 in mid and high frequencies by alkali treatments, while the sound absorption coefficients of microfibres, hollow fibres, bicomponent fibres and nanofibres significantly higher than regular fibres. Sat, 01 Jan 2022 00:00:00 GMT http://ir.lib.ruh.ac.lk/handle/iruor/21487 2022-01-01T00:00:00Z http://ir.lib.ruh.ac.lk/handle/iruor/21486 Mathematical Modeling and Simulation of Acoustic Properties of Knitted Fabrics Backed by an Air Cavity Madushika, J.W.A.; Wijerathne, J.K.; Lanarolle, W.D.G. Noise pollution has become a critical issue in the modern world of ever-increasing industries and machinery. Noise should be controlled due to the physical and psychological health effects associated with noise. Textiles as lightweight and cost-effective porous structures have received increasing interest for acoustic controlling applications. In-room acoustics, knitted fabrics represent a strong source of innovation due to drapability and aesthetic appearance. However, in general, the sound absorption performance of knitted fabrics is relatively low. Therefore, the primary goal of this work is to enhance sound absorption by introducing an air gap between the fabric and a solid wall. The diffuse incident sound absorption coefficient of knitted fabrics was mathematically modeled and simulated using basic equations of fluid dynamics where the fabric is acoustically described by its porosity, thickness, density and airflow resistivity. The air gap varied from 10 to 25 mm in 5 mm increments. Modeling predictions were compared with the experimental data obtained from the literature for sound absorption of knitted fabrics. The modeling predictions were in good agreement with the experimental data for different values of air gap thicknesses. The simulation results indicated that when the air layer thickness increases, the sound absorption coefficient of knitted fabrics increases significantly at low frequencies. The peak value of the sound absorption coefficient moves in the direction of a lower frequency. The sound absorption coefficient reached a maximum value of 0.45 at a resonance frequency equivalent to the quarter wavelength of the air layer thickness. Fri, 01 Jan 2021 00:00:00 GMT http://ir.lib.ruh.ac.lk/handle/iruor/21486 2021-01-01T00:00:00Z http://ir.lib.ruh.ac.lk/handle/iruor/21485 Development of a small-scale reverberation chamber and validation of the diffuse field Madushika, J.W.A.; Wijerathne, J.K.; Lanarolle, W.D.G. Noise absorbers are in a growing demand in the automotive, aerospace and building construction industries. Testing acoustic properties of materials is mandatory for developing an efficient acoustic controlling product design. Two main methods available to measure acoustic properties of materials are impedance tube method and reverberation room method. Impedance tube method uses small test specimens (usually less than 10 cm in diameter) and measures only normal incidence sound absorption, whereas reverberation room method is a relatively expensive setup which usually requires a large space (100-200 m3 ) and allows large samples (10-12 m2 ). To overcome the drawbacks of the current test methods and to make a comparative analysis of the test samples, a small scale reverberation room was designed. A chamber with 2.06 m3 volume was constructed. All the inner surfaces including the door were lined with highly reflective ceramic tiles to obtain maximum reflectivity. The randomness of the incident angles was achieved by an asymmetric shaped room with an inclined roof to obtain all walls non parallel. A modal analysis was performed to validate the small scale reverberation chamber for acoustic measurements. The pressure variations inside the enclosure within resonance frequencies are too small. Even though the cut-off frequency of a purely rectangular chamber with the same volume is 270 Hz, the new design of the reverberation room allows taking measurements below 270 Hz. Sun, 01 Jan 2023 00:00:00 GMT http://ir.lib.ruh.ac.lk/handle/iruor/21485 2023-01-01T00:00:00Z