Industrial symbiosis, which is characterised mainly by the reuse of waste from one company as raw material by another, has been applied worldwide with recognised environmental, economic, and social benefits. However, the potential for industrial symbiosis is not exhausted in existing cases, and there is still a wide range of opportunities for its application. Through a comprehensive literature review, this article aims to compile and analyse studies that focus on potential industrial symbiosis in real contexts, to highlight the margin of optimisation that is not being used. The cases reported in the publications identified here were characterised and analysed according to geographic location, type of economic activity, waste/by-products, main benefits, and the methods employed in the studies. From this analysis, we conclude that there is great potential for applications involving industrial symbiosis throughout the world, and especially in Europe, corresponding to 53% of the total cases analysed. Manufacturing stood out as the sector with the highest potential for establishing symbiosis relationships, and the most common types of waste streams in potential networks were organic, plastic and rubber, wood, and metallic materials. This article also discusses the main drivers and barriers to realising the potential of industrial symbiosis. The diversity of industries, geographical proximity, facilitating entities and legislation, plans, and policies are shown to be the main drivers.

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The Potential of Industrial Symbiosis: Case Analysis and Main Drivers and Barriers to Its Implementation

Rad istražuje mogucnost koristenja celicanske zgure, nastale kao nusproizvod iz proizvodnje željeza i celika u hrvatskim celicanama, kao agregata u betonu. S tim ciljem, spravljene su betonske mjesavine sa celicanskom zgurom kao krupnim agregatom te su njihova svojstva u svježem (gustoca, udio pora, konzistencija) i ocvrsnulom stanju (tlacna cvrstoca, savojna cvrstoca, staticki modul elasticnosti, volumne promjene, korozivno djelovanje) uspoređena sa svojstvima betona spravljenog s uobicajeno koristenim dolomitnim agregatom. Rezultati prethodno navedenih ispitivanja potvrđuju da su istraživane celicanske zgure prikladna zamjena za agregat iz prirodnih izvora.

Utilisation of steel slag as an aggregate in concrete - Croatian experiences

Purpose
While circular economy (CE) is fast becoming a political and economic agenda for global urban development, there are still substantial knowledge gaps in possible strategies to speed up such transition, especially in the construction industry. This study analyses literature surrounding CE to unpack current trends possible future research directions to foster CE implementation in the construction industry.

Design/methodology/approach
The study undertakes a systematic review of CE literature published between 1990 and 2019. It adopts a five-stage procedure as a methodological approach for the review: formulation of the research question(s), locating and identifying relevant studies, selection and evaluation of studies, analysis or synthesis and results reporting.

Findings
The findings on CE research in the construction industry show extensive focus on resource use and waste management. There are limited investigations in other areas of construction such as supply chain integration, building designs, policy, energy efficiency, land use, offsite manufacturing, whole life costing, and risk, cost reduction, cost management, health and safety management. The study findings provide evidence that current CE practice fails to incorporate other areas that would facilitate the network of true circular construction industry.

Originality/value
This research provides a comprehensive overview of research efforts on CE in the construction context, identifying areas of extensive and limited coverage over three decades. Besides, it identifies possible pathways for future research directions on CE implementation, towards the accelerated transition to a true circular construction industry for the benefit of funding bodies and researchers.

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A systematic review of circular economy research in the construction industry

Cementitious activity optimization studies of iron tailings powder as a concrete admixture

Minimizing the cement amount used to produce concrete significantly reduces non-renewable raw materials, primarily clays and limestone or chalk, used in cement production. Equally reduced is the large amount of energy used in clinker production and CO2 emission released to the atmosphere during the calcination of limestone, which results in global warming. On the other hand, large amounts of industrial and agricultural waste with little alternative use are produced in large quantities worldwide. Both strength and durability have been observed to increase significantly when these materials are combined in concrete in modest amounts, which allows them to be used in structural members. This research investigates the effect of high-volume sugarcane bagasse ash (SCBA) replacement of Portland cement from 10%–50% in concrete production. It was observed that structural grade concretes with 28-day cube crushing strengths of more than 25 MPa could be obtained, with strength increasing with age to more than 30 MPa at 180 days. In addition, good heat insulation, stability at high temperatures up to 600 °C, and reduced density were observed as added advantages. 

Mechanical and durability properties of concrete incorporating silica fume and a high volume of sugarcane bagasse ash

The main goals of this work were to verify the potential of reuse of steel slag and iron ore tailings as secondary raw materials to produce solid brick and to evaluate whether this application can consume the amount of slag generated in Brazil. The feasibility of this application was verified through a comparative study. The mechanical behavior of concrete artifacts and pressed bricks made from residues was compared with others described in the literature. The residues were initially characterized using chemical and granulometric analysis. The bricks were produced by mixing different compositions of the residues with the addition of cement in the contents of 0 and 5%. The bricks were pressed in a manual mechanical press and sent to curing. The values of flexural strength of the bricks were higher than 2.0 MPa, and the average weight of the bricks was like those found in the ecological bricks. The simulation with the construction of houses showed that the proposed application can consume the amount of slag generated in Brazil. The generation of the income from carbon credits associated with CO2 reduction is an incentive to implement environmental management tools in Quadrilatero Ferrifero territory, specifically, industrial symbiosis and the carbon market.

Steel slag and iron ore tailings to produce solid brick.

BFS-MK-based alkali-activated materials are well established as an alternative for sustainable and green construction. This work aims to collaborate and encourage the use of biomass ashes, such as sugarcane bagasse ash (SCBA), as a precursor in alkali-activated materials (AAM). This ash is a rich source of aluminosilicate, which is a primary requirement for this application. In addition, this waste is still an environmental liability, especially in developing countries, and with a large volume of annual production. Thus, in this research, alkali-activated pastes (AA) were produced using sugarcane bagasse ash (SCBA), granulated blast furnace slag (BFS) and metakaolin (MK) as precursors. In addition, environmental gains were encouraged with energy savings, with no extra reburn or calcination steps in the SCBA. Thus, the precursors were characterized by laser granulometry, X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The pastes were produced by mixing the precursors with the activator, composed of a mixture of sodium hydroxide 8 mol/L and sodium silicate. Aiming to study the incorporation of SCBA, all samples have a precursor/activator ratio and a BFS/(BFS + MK) ratio constant of 0.6. The compressive strength analysis, FTIR, XRD, TGA, SEM and isothermal calorimetry analyses pointed out the occurrence of alkaline activation in all proposed samples for curing times of 7, 28 and 91 days. The sample GM0.6-BA0 (15% SCBA) achieved the highest compressive strength among the samples proposed (117.7 MPa, at 91 days), along with a good development of strength throughout the curing days. Thus, this work presents the properties of alkaline-activated pastes using SCBA as a sustainable and alternative precursor, seeking to encourage the use of raw materials and alternative waste in civil construction.

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Effect of Non-Calcined Sugarcane Bagasse Ash as an Alternative Precursor on the Properties of Alkali-Activated Pastes

Reaction Mechanisms in Geopolymers Produced from Sugarcane Bagasse Ash

This work presents a technical and economic study using sugar cane bagasse ash (SCBA) to partially replace Portland cement clinker. To evaluate the technical viability, the replacement rates of 10, 20, and 30% of Portland cement were used in the experiments. The ashes used were in the following conditions: (i) as collected (AC), (ii) ground (G), and (iii) re-burnt and ground (RG). Three composition parameters were used in the mortar mix procedures: (i) mix with water factor/fixed binder in volume, (ii) mix with water factor/fixed binder in weight, and (iii) mix with the fixed flow. After the technical feasibility analysis, the benefit of the substitutions and an analysis of the relationship between cement consumption and the acquired compressive strength, correlating with possible economic costs, were discussed. SCBA AC was not suitable for the partial replacement of Portland cement clinker. SCBA G presented a satisfactory performance and SCBA RG was the ash that presented the best performance in the partial replacement of Portland cement clinker. For the same levels of compressive strength, the consumption of Portland cement per cubic meter of concrete reduced; from this, the cost of concrete and mortar could be reduced by 8%, with the ash having the same value as cement. Furthermore, the use of SCBA RG at 30% inhibited the alkali–silica reaction (ASR) in concretes with a reactive basalt and quartzite aggregate. SCBA G (20 and 30%) and SCBA RG (10 and 20%) inhibited the ASR in concretes with a reactive basalt aggregate and reduced the expandability in concretes with a reactive quartzite aggregate. Another point to highlight was the durability shown by the cements with SCBA, which, 900 days after the accelerated test of expansion by the alkali–aggregate reaction, maintained high levels of flexural strength when compared to the results obtained before the accelerated test of expansion. The present work concluded that using sugar cane bagasse ash to replace Portland cement is feasible from a technical, environmental, and economic perspective.

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Feasibility of Using Sugar Cane Bagasse Ash in Partial Replacement of Portland Cement Clinker

Alkali-activated materials (AAMs) result from the dissolution process and polycondensation of precursors in high pH solutions. This material is considered alternative cement with similar properties and lower environmental impact than Portland cement. However, AAMs are subjected to the same standardization applied to cement-based materials since no formal methods exist to characterize this material and/or the precursor reactivity. Therefore, this work aims to develop a method to characterize the reactivity of the main precursors used to produce AAMs. Hence, the precursors were assessed in two steps after chemical, physical, and mineralogical characterization. The first step evaluated the crystallinity change of the material after the acid attack by mixing 1 g of each material in 100 mL of 1% HF solution for 6 h at ambient temperature. The crystallinity change was evaluated by comparing the X-ray diffraction of the materials before and after the acid attack. The second step involved evaluating the formation of geopolymerization products in the pastes of studied precursors through FTIR test. The pastes were produced with Na2SiO3 and NaOH as activators. After 28 days of curing, the pastes were submitted to a FTIR test for structural analysis. This method was tested evaluating the reactivity of traditional precursors for alkali activation (i.e., silica fume (SF), blast furnace slag (BFS), and metakaolin (MK)), in addition sugarcane bagasse ash mechanically treated (SCBAM) and sugarcane bagasse ash mechanically and heat treated (SCBAMH) since SCBA is a promising precursor for alkali activation. Considering the crystallinity change of precursors (step 01), the formation of geopolymerization products (step 02), and the chemical composition of precursors (preliminary characterization), it could be concluded that: (i) surface area is not relevant to materials with small particle size (<23 µm); (ii) amorphous area is only relevant if the material exhibits the optimal chemical composition; and (iii) the chemical composition is a crucial parameter for alkali activation. In addition, the potential precursors for alkali activation should have a significant amorphous halo and a SiO2/Al2O3 ratio of 2 to 5. Also, it could be concluded that SF and SCBAMH do not exhibit adequate reactivity while BFS, MK, and SCBAM can be classified as reactive precursors.

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Leila Nobrega Sousa

Papers

Steel slag and iron ore tailings to produce solid brick.

Effect of Non-Calcined Sugarcane Bagasse Ash as an Alternative Precursor on the Properties of Alkali-Activated Pastes

Reaction Mechanisms in Geopolymers Produced from Sugarcane Bagasse Ash

Feasibility of Using Sugar Cane Bagasse Ash in Partial Replacement of Portland Cement Clinker

Preliminary Reactivity Test for Precursors of Alkali-Activated Materials