Porosity of expanded clay manufactured with addition of sludge from the brewing industry

Int J Energy Environ Eng (2014) 5:341–347 DOI 10.1007/s40095-014-0112-6 ORIGINAL RESEARCH Porosity of expanded clay manufactured with addition of sludge from the brewing industry Carmen Martı́nez Garcı́a • Teresa Cotes Palomino • Francisco J. Iglesias Godino • Francisco A. Corpas Iglesias Received: 28 September 2013 / Accepted: 29 April 2014 / Published online: 2 August 2014 Ó The Author(s) 2014. This article is published with open access at Springerlink.com Abstract This study describes the industrial use of waste generated from the brewing industry, specifically sludge from a wastewater treatment plant. The processing technique was developed to produce ceramic material with the potential for use as a lightweight aggregate in construction. This waste is usually dumped in landfills, but the current increase in restrictions on dumping and interest in improving the environment make our proposal for gaining value from this sludge a significant contribution. The chemical composition of the raw materials was analyzed (using X-ray fluorescence and elemental analysis) and their thermal behavior evaluated (thermogravimetric analysis and differential thermal analysis). To determine the effect of adding sludge to the aggregate, different compositions were then prepared and tested. To obtain the material’s final resistance and cohesion, the dried sample was subjected to a firing process in a kiln. The samples were prepared without special pre-treatment steps, such as milling, and without the addition of expansive additive. The new aggregate has a low bulk density, due to the formation of an internal cellular structure, a porous internal and a partially vitrified C. M. Garcı́a (&)
T. C. Palomino
F. J. I. Godino
F. A. C. Iglesias Department of Chemical, Environmental and Materials Engineering, E.P.S. Linares, University of Jaen, C/Alfonso X, el Sabio, 28, 23700 Linares, Jaén, Spain e-mail: T. C. Palomino e-mail: F. J. I. Godino e-mail: F. A. C. Iglesias e-mail: external shell. As waste is added, water absorption increases by values of 17–26 %, as does the porosity, resulting in a linear relationship between the pore volume and percentage of sludge added. Keywords Sludge
Lightweight aggregate
Waste reuse Introduction European legislation encourages the development of a variety of ceramic building materials, such as expanded aggregates, that incorporate waste. For example, the national integrated waste plan for 2007–2015 requires implementing not only measures to reduce generation of the waste, but also recycling and reuse at all levels. The technical building code (TBC) seeks to respond to social demand to improve the quality of construction, while also achieving better protection of the user and promotion of sustainable development. European policies such as the Lisbon and Göteborg Agendas also propose a sustainable development strategy that assumes responsibility for management of natural resources. Other technologies that have been developed successfully include using wastes such as fly ash, scrap tire rubber, and sludge from the paper industry in the production of lightweight concrete aggregates [1–3] and expanded clay [4] for structural applications. The use of waste has the advantage of both optimizing the properties of ceramic products and reducing cost and environmental problems involved in depositing this waste in landfills. It is currently estimated that industrial waste in Europe exceeds 900 million tonnes per year. Further, using this waste in ceramic building materials could help structures to obtain sustainable building certification. 123 342 Int J Energy Environ Eng (2014) 5:341–347 Lightweight aggregates (LWAs) are increasingly in demand, particularly in the precast concrete industry, where they are used in a range of construction products. The lighter weight of concrete components made with LWAs aids in off-site manufacturing has significant advantages, both during construction and throughout the life of the building [5]. Development of LWAs also fulfils the need for alternate waste disposal methods. Research into the economical reuse of various wastes published in recent years includes studies of the incorporation of these wastes in clay-based products [6]. Because the final LWA product varies in shape and size, and because production rates are very high, LWA production has the potential for high levels of incorporation. Further, research shows the reuse of several wastes in expanded clay-based formulations. These wastes include quarry minerals, industrial wastewater sludge, paper-pulp and wood or incinerator bottom ash, and pulverized fuel ash [7–14]. Various types of waste are being investigated for use in the manufacture of construction materials. These include sewage sludge waste, waste products in power generation processes and food industry remains [15–18]. The sludge is used as a partial replacement of clay, or in the manufacture of cement [19–22]. All studies to date have used \30 % sludge. Some authors have investigated the use of sludge in mortar and concrete [23–25]. Others propose lightweight aggregate (LWA) of sewage sludge and clay [26–30]. The manufacturing principle used is based on the occluded expansion undergone and the gases formed during treatment of a mass of clay mixed with waste when it is subjected to a temperature increase. Firing is the most important stage in the ceramic process for the production of lightweight aggregate. It is during this phase that decomposition of the clay mineral reticle causes instability in the joint. This leads to the formation of amorphous phase, liquid at this temperature, which serves as a unifying element in the array. This phase will remain until the end of sintering, and some of it often creates very stable crystalline phases. During ceramization, the inorganic portion of the waste enters the amorphous phase of the ceramic matrix. All solid state reactions, as is the case of ceramics, have extremely slow reaction kinetics. The factor that can speed up the process is particle size. The finer the particle, the greater the surface area and the greater the reaction capacity. In contrast, a large enough particle will not react. When the goal is to inertize a waste due to its toxicity, the waste must be ground very fine. In this case, the waste melts partially and is integrated into the ceramic matrix. If the particle size is coarse, the waste particle does not interact with the ceramic matrix and is simply encapsulated [31, 32]. The thermal process for sintering conventional clay usually consists of constant and gradual increase in the temperature until the clay mass reaches approximately 123 950–1,000 °C. The process is radically different for the formation of the expanded clay. Here, the temperature rise is very sharp so that the surface layer of clay vitrifies before ceramization of the inner layers begins. Vitrification of the outer layer prevents escape of the gases formed in (...truncated)