Abstract:
Global warming and climate change are significant concerns nowadays. One of the primary causes of climate change is CO2 emissions. Cement production is responsible for 8% of global CO2 emissions. So, reducing CO2 emissions associated with cement production is the most critical and urgent challengefacing the cement industry.One sustainable solutionis replacing cement with supplementary cementitious materials (SCMs), which will reduce carbon footprint.SCMs such as silica fume (SF), fly ash (FA), and ground granulated blast furnace slag (GGBS) are industrial byproducts that possess pozzolanic properties. Another concern is construction and demolition waste (CDW) which creates severe environmental and landfill issues. The growing demand for construction has led to a shortage of natural aggregates. Converting CDW into recycled aggregate can help address this issue by reducing dependency on natural resources and minimizing waste, thereby promoting a more sustainable construction industry.Urbanization and rising construction demand in Bangladesh have led to increased demolition of old structures, many of which were built with brick chips due to limited stone availability. Demolition of these old structures results in a significant increase in CDW, including brick chips. So, the possibility of reusing brick chips needs to be explored. Additionally, since concrete is inherently brittle, enhancing its ductility is important for specific applications. This can be achieved by incorporating fibers such as different types of fibers such as nylon fiber, steel fiber, and glass fiber.
This study investigates the use of silica fume (SF), fly ash (FA), and nylon fiber (NF) to improve the performance of recycled brick concrete aggregate (RBCA) concrete. The effects of cement replacement by SF (10% and 20%), cement replacement by FA (10%, 20%, and 30%) with varying NF content (0.1%, 0.2%, 0.35%, and 0.5% volume fraction) on 100% RBCA concrete was examined. The compressive, tensile, and flexural strength of RBCA concrete reinforced with NF and SCMs were determined.
This study investigates the impact of SCMs on RBCA concrete. Cement replacement by 10% SF enhanced RBCA concrete compressive strength by 12.7% and 0.7% over only RBCAconcrete and clay brick chip (CBC) concrete, respectively. At this replacement level, tensile and flexural strength were0.7% and 3.8% higher, respectively,than only RBCA concrete.Cement replaced by 20% FAshowed7.2% compressive strength improvements over only RBCA concrete, though 4.2% lessthanonly CBC concrete.Although tensile strength was lower than only RBCA concrete at this replacement,flexural strength was equivalent to only CBC concrete and 10.4% higher than only RBCA concrete.
The study also investigated the compressive, tensile, and flexural strengthof RBCA concrete reinforced with NF and SCMs.The study found that incorporating both SF and NF significantly enhanced the properties of RBCA concrete. The highest compressive strength of 33.8 MPa was achieved with 10% SF replacement and 0.2% NF at 90 days of curing; strength increased by 10.8% and 24.0% compared to only CBC and RBCA concrete, respectively. Additionally, this mix showed an 11.6% increase in tensile strength and an 8.2% rise in flexural strength compared to only RBCA concrete. Further, maximum tensile and flexural strength was found with 20% SF replacement and 0.5% NF achieved, showing 4.7% and 2.6% improvements over only CBC concrete.Incorporating FA and NF also improved the mechanical properties of RBCA concrete. The maximum compressive strength of 32.9 MPa was obtained with 20% FA replacement and 0.1% NF at 90 days of curing, representing a 7.9% and 20.8% improvement compared to only CBC and RBCA concrete, respectively. Additionally, this mix showed a 14.3% increase in tensile strength compared to only RBCA concrete and a 1% increase over only CBC concrete. The flexural strength also improved by 11.7% compared to only RBCA concrete and 1.1% compared to only CBC concrete with the same mix.
Considering environmental sustainability, recycled brick aggregate can be effectively used in concrete if silica fume or fly ash as SCMs and nylon as short discrete fibers are used in concrete mixes. The research findings contribute to sustainable cement production and resource conservation efforts.