An experimentally evaluating the mechanical behavior concrete incorporating macadamia nutshells = Đánh giá thực nghiệm về tính chất cơ lý của bê tông kết hợp vỏ hạt mắc ca

Abstract

This study focuses on the application of macadamia nut shells - an agricultural waste - as lightweight aggregate in concrete (MNC), to propose a new environmentally friendly construction material option, minimizing the environmental impact of the construction industry. With its light and durable properties, macadamia shells are considered a potential alternative to traditional aggregates, while contributing to reducing the amount of waste from the macadamia production industry. In this study, macadamia shells were collected and crushed into sizes of 5-20 mm and combined with high-grade mortar mixture (with a flow rate of ≥ 240 mm and a compressive strength of ≥ 100 MPa) to create lightweight concrete. Concrete samples were cast and cured for 28 days, then tested for mechanical properties such as compressiveand flexural strength according to TCVN standards. The results showed that the MC1 concrete mixture (53.7% mortar and 46.3% macadamia shell) had a density of 1800 kg/m³, 15-20% lighter than conventional concrete, and a compressive strength of 25.87 MPa after 28 days. However, the MC2 mixture with a higher mortar ratio (62.9%) had a better compressive strength (33.97 MPa) but suffered from segregation problems, and therefore needed further optimization. The study concluded that MNC concrete, especially MC1, has great potential in sustainable construction due to its low density and being a recycled material from waste. However, further research is needed to improve durability and optimize mix design to expand its application. The development of production standards and efficient macadamia shell collection and processing systems is also key to making MNC a popular building material, especially in major macadamia producing areas.