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In recent years, the use of self-compacting concrete has been a great advantage and garnered undoubted interest in construction. Due to the environmental impact caused by the consumption of natural aggregates in the manufacture of concrete, a more sustainable approach is needed. An approach for more sustainable construction is to use industrial waste such as bottom ash from the combustion of biomass as a replacement for natural aggregates. This research aims to use biomass bottom ash as a replacement for natural sand (10%, 20% and 30% replacement); in addition, by utilizing a crushing process of the bottom ash, the ash has been used as a filler replacement (replacement 20%, 40% and 60%). The fresh and hardened properties have been evaluated according to the standard. The results show the feasibility of using biomass bottom ash in self-compacting concrete, providing a sustainable alternative in order to minimise environmental impacts related to the extraction and depletion of natural resources., FEDER/ Ministry of Science, Innovation and Universities—Agencia Estatal de Investigación (State Research Agency)/Valorisation of biomass bottom ash for sustainable construction applications (1264457-R)—BIOCEM

The use of industrial byproducts as construction material can help to achieve sustainability in this industry. Phosphogypsum (PG) is a waste obtained in the phosphoric acid (PA) manufacturing process, produced in large quantities, especially from the soil fertilizer industry. Alternatively, in the disposal of these materials in landfill, several investigations have applied PG as a substitute for natural gypsum in the production of Portland cement to control the hydration reaction rate of cement and also in concrete, bricks, plaster panels, and others. The composition and characteristics of PG are closely related to both the composition and origin of the feedstock used (phosphate rock), showing high gypsum content, and high levels of natural radionuclides, especially from U-series. These properties depend on the PA production process and the origin of the raw material. In this chapter, the possibilities of using this waste in cement-based materials are presented, to encourage future research lines based on this waste/byproducts.

This document studies replacing cement by stainless steel slag waste and improving the mechanical properties of the slag waste by using different types of treatments. The application of stainless steel slag waste reduces the use of raw materials for manufacturing cement and provides a profit from the large amount of waste generated. This study analyses the cementation and pozzolanic reaction characteristics of stainless steel slag waste to evaluate its strength activity index and its environmental impact. The cement was replaced with different substitution percentages of untreated stainless steel slag waste and slag waste that was processed through crushing, burning and both treatment to determine the optimum replacement ratio according to its mechanical properties. A study based on multivariate factor analysis was developed to compare these processed wastes according to their mechanical behaviour. The decision mechanism consists of a feature extraction method to evaluate the wastes used as a cement substitute.

The use of biomass for power generation is increasingly common. However, one of the most important problems when using biomass is the amount of waste produced in the combustion process such as ash, which must be transported to landfills for deposition. Biomass bottom ash may contain a large amount of organic matter which is the most restrictive property for reusing this by-product. The potential reuse is determined by chemical and physical properties. The presence of light particles and organic matter confer to biomass bottom ash certain physical and chemical characteristics which significantly reduce the possibility of reuse. Previous studies have demonstrated the possibility of using biomass bottom ash in cement-treated materials, but its properties imply a decrease of compressive and flexural strength. Therefore, this paper reported the study of the mechanical and durability properties of mortars containing biomass bottom ash applying different processing methods. Cement was replaced with different rates of substitution of biomass bottom ash and several samples were treated applying different techniques, such as grinding, elimination of lightweight particles and combustion. The results showed significant improvements in the mechanical and durability properties of mortars in which some treatment were applied. Lightweight particle extraction and organic matter removal by burning considerably improved the mechanical behaviour of the manufactured mortars. Therefore, mortars with crushed biomass bottom ash without floating particles and without organic matter led to a 10% of compressive strength decrease with respect to the control mortar. Thus, this study displays a possibility of waste valorisation by means of to the reuse of this type of by-product in mortars and concretes manufacture.

Recycled aggregates (RA) have been extensively studied in the production of concrete. Normally, the coarse fraction of recycled concrete aggregates (RCA) is the most commonly used to manufacture recycled concretes. The manufacturing of concrete with fine fraction of RCA and/or recycled mixed aggregates (RMA) (from a mix of concrete, asphalt, masonry, etc.) has not been studied in depth. In most cases, the recycling plants produce RA with an ALL-IN particle size distribution. These recycled materials could be named as ALL-IN RECYCLED CONCRETE AGGREGATES (aiRCA) and ALL-IN RECYCLED MIXED AGGREGATES (aiRMA). Applying these aiRCA or aiRMA, limiting the percentage of the substitution of natural aggregates (NA) by the aiRCA, is more beneficial for both the production costs and the environment. In recent studies, other by-products, such as biomass bottom ash (BBA) were used in concretes, substituting natural sand (NS) and improving the mechanical properties in concretes with low quantities of cement. It is possible to improve the properties of the BBA via mechanical processes (like screening or flotation) to reduce the organic matter content and there by obtain processed BBA (Pr-BBA). This study provides interesting data on the mechanical and durability properties of the concretes manufactured with 30% aiRCA and aiRMA, and also by applying different replacement rates (0, 15, and 30%) of NA by BBA and Pr-BBA. The mechanical and durability properties were analysed over different time durations in different mixtures. It was demonstrated that it is possible to apply these recycled materials in non-structural concrete mixtures by limiting the replacement rate. The application of BBA and Pr-BBA reduced the properties of the concrete. However, this reduction was less significant with the use of Pr-BBA.

In the last 15 years, new types of display technologies have increasingly replaced cathode ray tube (CRT) screens, which has led to an increase in landfill of old discarded CRT televisions, which present a great environmental challenge throughout the world due to their high lead content. In addition, environmental awareness has led to greater use of recycled aggregates to reduce the exploitation of existing reserves. This document aims to study the feasibility of incorporating CRT glass waste with recycled aggregate (RA) in combinations for use in civil engineering, more specifically in road bases and sub-bases. For the mechanical and environmental assessment of all of the samples and materials, the following procedures have been performed: the compliance batch test of UNE-EN 12457-4:2004 for RA, CRT, and mixtures, the Percolation Test according CEN/TS 14405 for the mixtures, CRT, and RA, Modified Proctor and load capacity (the California Bearing Ratio, or CBR) in all mixtures without cement addition, and finally, compressive strength of the material treated with cement at different ages of curing. The analysis of the mechanical and environmental properties through different techniques of lixiviation was positive, showing the ability to use CRT for certain dosage percentages mixed with recycled aggregates.

In recent years the use of biomass for electricity generation in thermal and cogeneration plants has increased worldwide because it is an environmentally clean fuel whose impact measured in greenhouse gas emissions is practically zero. However, biomass bottom ash, a waste produced during combustion, has also increased considerably, which has both a negative economic and environmental impact, due to landfill transport and management of this by-product. Although biomass bottom ash has potential characteristics for application in the manufacture of construction materials, its full-scale application is difficult because of the wide range in physicochemical properties, depending on the type of biomass burned, such as wood residue, olive waste, waste paper sludge, cocoa shell, etc., and the type of combustion process in the plant. This study reviews the influence on the physicochemical properties, mechanical behavior, and durability of different cement-based materials, such as mortars, concrete, and cement-treated granular material, manufactured from biomass bottom ash. The previous studies demonstrate the feasibility of substituting natural materials for biomass bottom ash in cement-based materials, presenting adequate mechanical behavior and durability properties to comply with the required technical specifications in different building materials.

Green philosophy is gaining popularity worldwide. Recycling materials from building demolitions, reutilizing by-products from industrial facilities and exploring the potential uses of waste during a second life cycle are the objectives of this philosophy. In the present article, bottom ashes from electric power generation plants using biofuel combustion were evaluated to verify their potential use as expansive clay stabilizers. Two objectives are pursued: (1) finding a new use for waste that is typically landfilled despite its great potential arising from its technical properties and (2) improving the mechanical properties and reducing the expansive nature of the expansive clays identified during the construction of a motorway. Based on this framework, the present study demonstrated the potential of biomass bottom ashes to stabilize expansive clays. The optimum dosage to improve the properties of clays was determined based on performance parameters, such as plasticity, free swelling or soil collapse. Afterwards, the contaminating potential of ashes was evaluated, being classified as hazardous waste. However, the stabilized mixtures were classified as inert products, thus guaranteeing the environmental feasibility of their use. Finally, the technical application of the stabilized clays as filling materials for embankments and subgrade for light traffic roads was proved. Graphical abstract.

Biomass is a renewable energy source that is increasingly being used worldwide. However, because of recent increases in production, waste products from biomass combustion are becoming a relevant environmental and economic problem. Other wastes from the construction and demolition sectors have been extensively studied. For this, several research studies have been performed to study the mechanical and some durability properties in concrete manufacturing with recycled concrete and mixed aggregates from different construction origins. In previous works, the lower density of recycled mixed aggregates (RMA) and biomass bottom ash (BBA) with respect to natural aggregates was studied. This feature can be exploited for the production of construction elements that require the use of low-density materials, such as lightweight concrete. For this, the aim of this work was to study the influence of the use of recycled mixed aggregates and biomass bottom ash, as replacements for the natural aggregates, on the mechanical behaviour, durability properties and environmental risk of recycled lightweight concrete. Several replacements for natural aggregates through recycled aggregates and biomass bottom ash were applied in the manufacture of lightweight concretes. To study the concrete behaviour, properties such as density, absorption, compressive strength, flexural strength, UPV, water penetration and drying shrinkage were measured. Due to the incorporation of RMA and BBA, a decrease of the density and mechanical properties of the recycled concrete manufactured was obtained with respect to the control mix. Therefore, the results showed the possibility of applying these types of recycled materials in lightweight concretes for their application in specific constructive elements. Through this study the possibility of reuse of waste and industrial by-products (RMA and BBA) that have so far been accumulated mainly in landfill is demonstrated. The positives results show the possibility of manufacture of lightweight concrete with these by-products, achieving a material with a lower density and mechanical requirements that comply with the current standards for concrete.

A focus on environmental sustainability during the last decade has led to greater use of recycled aggregates to reduce the exploitation of existing reserves. In addition, environmentally consciousness has led to an increased use of renewable energy. Biomass is an important source of energy, and it also leads to high generation of waste products from biomass combustion. Previous studies have investigated the use of recycled aggregates from construction and demolition in road bases and sub-bases with positive results. This paper aims to study the feasibility of incorporating biomass bottom ash produced in the combustion process mixed with natural aggregates and recycled aggregates for use in civil engineering. The analysis of the mechanical properties was positive, showing the ability to use biomass bottom ash mixed with natural or recycled aggregates in specified ratios. Valuing biomass bottom ash can reduce waste generation and may lead to economic and environmental benefits.