Application of ceramic waste in brick blocks with enhanced acoustic properties

Abstract

High environmental noise level is currently affecting an increasing amount of people in urban areas, industrial areas, or places with heavy traffic. Therefore, there is a righteous demand for design of building materials and construction elements with improved acoustic properties that ensure a sufficient protection of people affected by noise. Ceramic brick blocks with a system of incorporated voids, which are widely used in the region of Central Europe, can present a prospective solution in that respect. The well-organized manufacturing process, good mechanical and thermal properties and durability of these ceramic products can be considered as supporting arguments for their utilization. The optimization of acoustic properties of brick blocks can be achieved by using waste bulk fillers originating directly in the brick production. This approach generally brings environmental benefits, together with the economic benefits for the producers. In this study, two waste materials of brick-production origin, namely brick rubble and brick microparticles, were characterized in terms of chemical and mineralogical composition at first, along with the characterization of the brick body itself. Then, they were utilized at different dosages as bulk fillers for modified brick blocks. The acoustic properties of the blocks represented by the sound pressure level were determined in the designed small-sized reverberation chambers. It was observed that the utilization of tested waste fillers led to a 10.6–11.7 dB decrease of the average sound pressure level in the frequency range of 50 Hz–5 kHz while the mass increase of the studied brick blocks was 40–47%. The obtained results indicate a successful design of environmental-friendly brick-based materials with enhanced acoustic insulation ability, which was achieved without any significant additional costs.

Introduction

Brick is a traditional construction and building material used worldwide for a long time. The dried-clay bricks were used in 8000 BC and the fired-clay bricks as early as 4500 BC (Zhang, 2013). During medieval times the application of fired-clay bricks was already common. As many such bricks were preserved until now, their properties were analyzed in many scientific studies. For instance, Blain et al. (2010) tested brick samples from French medieval churches dated to 10th – 11th century A.D. using the luminescence method. Evans (2018) focused on the fortifications of Hull port in England that was fronted by a circuit of brick walls. The utilization of bricks continued through 19th and 20th century until the present days. Shu et al. (2017) comprehensively described the composition and properties of various types of bricks used in China between 1866 and 1983. Grifa et al. (2017) studied traditional brick production in Madagascar in terms of raw materials processing and firing technology. Fired-clay bricks production was continuously improved during the time, so that the quality of bricks is currently much higher than in the past. It is mainly due to an improved production technology using more sophisticated procedures and methods for creating the desired shapes of bricks (Guzman and Munno, 2015), controlled temperature of sintering (Vlasova et al., 2018), using supplementing admixtures (Gencel et al., 2013), or quick firing of hypercompacted bricks at moderate temperatures (Bruno et al., 2019). However, energy consumption of fired-clay bricks production together with its negative impact on the environment represented by emissions and produced waste is still very high. Nath et al. (2018) assessed the environmental impact of brick production in India which is the 3rd top brick exporter with 250 billion bricks per year (Barasa, 2018). Kulkarni and Rao (2016) compared carbon footprints of bricks manufactured in India (Karad) with the corresponding data provided by Athena Sustainable Materials Institute, Ottawa for bricks produced in the USA and Canada. They concluded that the carbon footprint of bricks manufactured in Karad location (195 g CO₂/kg of fired brick including bagasse combustion and transportation of raw materials) was lower than carbon footprint of brick manufactured in tunnel kilns in the USA and Canada (232.25 g CO₂/kg of fired brick by using natural gas as fuel, 338.19 g CO₂/kg of fired brick by using light-fuel oil as fuel) and tunnel kilns in UK (234.24 g CO₂/kg of fired brick). In order to lower the environmental impact of bricks production, much scientific effort has been devoted to the design and materials characterization of bricks with various waste admixtures. Raut et al. (2011) summarized 18 widely used waste materials used for the design of bricks, compared material properties of waste-based bricks and concluded that the main advantages lied mainly in lower density, lower thermal conductivity and in the case of brick with waste paper pulp in higher compressive strength, in a comparison with common bricks. Murmu and Patel (2018) identified in their review 43 different types of wastes and concluded that the production of bricks from waste materials still relies on firing to enhance the strength of bricks which is an energy intensive process emitting greenhouse gases into the atmosphere and that lightweight, energy efficient autoclaved bricks possess good insulating properties. However, specialized equipment is required for their manufacturing and the current production cost per unit is still higher than that of conventional bricks. Zhang et al. (2018), based on an extensive review of brick-related studies, divided innovative bricks into two groups (material-oriented and process-oriented) and concluded that fired and cement- and lime-based calcium-silicate-hydrate bricks were not sustainable. Therefore, in the future clay-based geopolymer bricks could be a promising alternative to the fired bricks due to the less energy-intensive way of production. Bullibabu et al. (2018) aimed at bagasse, the waste material originating from the sugar industry that was used within the production of thermally insulating fired bricks. Boltakova et al. (2017) were dealing with utilization of inorganic industrial wastes with special emphasis on Russian research between 2000 and 2015. Abbas et al. (2017) studied the influence of fly ash in amount up to 25% of clay in the production of bricks and concluded that utilization of such waste material can lead towards economical and sustainable construction. Study performed by Taurino et al. (2017) was focused on the sintering process and technological properties of fired bricks based on high amount of post-treated municipal solid waste incinerator bottom ash and refractory clay. Karayannis (2016) was investigating steel industry electric arc furnace dust as an admixture into standard clayey raw materials typically used by ceramic industries and figured out that according to the results, the development of extruded and fired bricks with up to 15 wt% recycled steel industry byproduct is feasible without significant variations in their technological properties. Sutcu et al. (2019) utilized fly- and bottom ash (FA, BA) in bricks fired at 950 °C and 1050 °C. They observed a significant decrease in the compressive strength of bricks with higher amount of FA and BA (20%, 30%), but bricks containing 5% FA, 5% BA, and 10% BA exhibited similar compressive strengths to the reference bricks. An increasing amount of FA/BA also led to the decrease in thermal conductivity which was related to the increase in porosity.

In the present, acoustic deterioration of the environment exhibits significantly increasing tendency due to an industrial and a traffic growth (Gupta et al., 2018). Such phenomenon was proved by various measurements all around the world in industrial areas, big cities and places close to the main traffic roads or airports. Therefore, monitoring of noise level in such places and successive proposal of measures leading to improvement of local situation is a very important task. Several studies were dealing with such a topic, e.g. Hueso et al. (2017) measured noise sources mainly produced by the traffic in the city of Valencia for several years, Gozalo et al. (2015) carried out continuous acoustic measurements in 21 different locations in Madrid for one year, Malec and Borowski (2018) measured road noise in the city of Lublin, Glekas et al. (2016) monitored noise level on two main airports in Cyprus and Vogiatzis et al. (2018) monitored noise level in Athens underground in order to define policies to protect inhabitants in the vicinity of worksites and tunnel surroundings.

Human well-being and health are negatively influenced by noise which was proved by studies performed at different places around the world, e.g. in Korea (Oh et al., 2019) or Brazil (Paiva et al., 2019). Christensen et al. (2015) in their study concluded that long-term exposure to residential traffic noise leads to changes of body weight, it was observed that exposure to residential road traffic noise is associated with higher risk of diabetes (Sorensen et al., 2013) and postmenopausal breast cancer (Sorensen et al., 2014) and Babisch (2014) found out that road traffic noise is a significant risk factor for cardiovascular diseases. In the light of these observations and taking into account the negative influence of high acoustic load on constructions condition (Binal, 2018), it exists a legitimate demand for people and construction protection by convenient urban planning (Gozalo et al., 2013) and designing of building materials with good acoustic properties.

Considering the latter, Schiavoni et al. (2016) introduced a comprehensive review dealing among others with acoustic properties of various natural and artificial building materials. Asdrubali et al. (2015) focused on acoustic properties of natural and recycled materials. Marcelino-Sadaba et al. (2017) introduced a comprehensive LCA analysis revealing that various types of brick blocks were better ranked than cement-based concrete blocks in a wide range of environmental-based indicators. They concluded that the preference of clay-based materials for sustainable construction is justifiable, based on the obtained observations. In the field of determination of acoustic properties of bricks, Guzman and Munno (2015) tested two commercial bricks and two brick-prototypes with triangle- and hexagonal holes in the ceramic body in terms of sound absorption ability by means of 50 dB and 62.4 dB sound exposition. The designed bricks exhibited higher sound absorption than the commercial bricks, therefore, these findings support the importance of the optimized design of bricks. Granzotto et al. (2020) focused on research dealing with experimental determination of sound reduction index of hollow brick walls and proposal of a model that provided good estimation of the sound reduction index up to 2500 Hz which can accelerate the design process of brick blocks with enhanced acoustic properties.

In this paper, the influence of two waste bulk fillers originating in brick production on the acoustic properties of brick blocks, represented by the sound pressure level decrease (Δ SPL), was studied. Acoustic measurements were conducted in the designed small-size reverberation chambers for a reference brick block and three brick blocks with different dosages of waste fillers. The contribution of the paper to the state of the art consists in several aspects. Bulk waste materials originating directly in brick production possess a potential to attenuate acoustic waves due to the scattering effect but their application in acoustic bricks was not investigated yet. Moreover, such materials can be considered as wastes free of costs, since they are directly reutilized at the brick company production site which is an undisputable advantage from both economic and environmental points of view. Prior studies were dealing with waste materials originating from other than brick production and in such a case, transportation costs and environmental impact must be taken into consideration (Talang and Sirivithayapakorn, 2018) or with utilization of waste materials used primarily as a partial replacement of clay which usually leads to deterioration of materials properties of the final fired bricks.