Engineering and acoustical properties of gypsum composite materials containing pineapple leaf fibres

Abstract

Gypsum is one of the most widely used interior building materials, notably as a finishing material. However, because to its brittle nature, as well as low compressive and flexural strength, there has been a reduction in interest in the prospective use of gypsum as an interior finish in buildings in recent years. In order to meet other mechanical and technical characteristics that are acceptable for use as interior building materials, gypsum must have high ductility characteristics and good sound energy absorption capabilities. Therefore, it is important to reduce these engineering issues using environmentally friendly and economic solutions through the use of natural fibres in the gypsum composite mixture. This study aims to characterize the engineering and acoustic properties of gypsum composites containing pineapple leaf fibres (PALF) with 5 mm and 15 mm in sizes. In determining the physical chemical and mechanical properties of gypsum-PALF composites, five different configurations containing PALF of 2%, 3%, 5%, 10%, and 20% based on the weight of the gypsum composition were prepared for both sizes of PALF. The composite specimens were tested under normal conditions after 7 and 28 days of curing. The microstructural characteristics of the composites were further examined using a Scanning Electron Microscope and an Energy Dispersive X-ray Spectroscopy (SEM/EDX), X-Ray Diffraction (XRD), and X-ray Fluorescence (XRF). The test results show that the materials reinforced with 2% PALF of 15mm in size provides composite materials with better mechanical properties of 3.70 MPa and 2.60 MPa, respectively for compressive and flexural strength. However, the compressive strength values are seen to decrease when more PALF content is mixed. The compressive strength increased up to 12.4% when 2% PALF was used in the gypsum composite. The flexural strength has increased up to 59% compared to ordinary gypsum when 2% PALF is added to the gypsum mixture. In comparison to materials reinforced with 5 mm fibre size, test results demonstrate that materials containing 15 mm PALF size provides a PALF-gypsum material with significantly better mechanical properties in terms of flexural strength. The optimum composition of the composite material was found to exist for a PALF content of 2% in the weight of the fibre size of 15 mm. Next, the study focused only on the optimal mix with 2% PALF of 15mm size tested for its sound absorption and sound loss capabilities. The series of specimens from the optimal mix are made based on market thicknesses of 9 mm, 12 mm, and 15 mm. The sound absorption and loss properties of the specimens were measured using an impedance tube instrument based on ASTM C384-04 in the frequency range between 60 Hz to 1600 Hz. As a result, it was found that there is an increase in sound absorption especially in the frequency range of 1000 Hz with a maximum value equal to 0.24. The average value of the sound absorption coefficient at 250 Hz, 500Hz, 1000 Hz and 1600 Hz or the noise reduction coefficient (NRC) shows an increase of 50% in the composite sample when compared to the gypsum sample without PALF. i.e., with a maximum value of 0.18. Sound transmission loss (SLT) also increases by 26% at a frequency of 1000 Hz. In general, adding 2% PALF to the gypsum results in greater level of STL. Based on the result of acoustical and mechanical test, it is concluded that the novel composite developed has the potential to be used to reduce agricultural waste, i.e., pineapple leaf waste. and energy savings from the use of non-natural fibres. Finally, design guidelines for gypsum-PALF composite materials in the future have also been proposed.