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SUStainable, innovative and energy-efficient CONcrete, based on the integration of all-waste materials

Periodic Report Summary 1 - SUS-CON (SUStainable, innovative and energy-efficient CONcrete, based on the integration of all-waste materials)

Project Context and Objectives:

Concrete industry plays a predominant role in the huge environmental impact of construction sector. Binder is mostly responsible for energy consumption and CO2 emissions, while aggregates have the highest impact on the concrete thermal resistance which, in turns, heavily affects the energy consumption of the building in service.
Preliminary tests demonstrated the possibility, on the one hand, to reduce the embodied energy and CO2 footprint of concrete by totally replacing the current binders by novel ones (geo-polymers) made of waste or by-products only, on the other hand to produce light thermally efficient aggregates, composed completely of waste.
This framework led to the SUS-CON project idea of boosting and linking the two research lines (binders and aggregates), resulting in an innovative light-weight, eco-compatible and cost-effective construction material, made by all-waste raw materials and characterized by low embodied energy and CO2 and by improved thermal insulation performances. The target of low embodied energy and CO2 will be mainly achieved through working on the binders side, while the target of energy efficiency (heat insulation) will be mainly achieved through working on the aggregates side. Target applications are both pre-casting and casting-in-situ concrete.
The use of lightweight recycled aggregates will allow making the target material lightweight and heat-insulating. The focus will be on waste materials that currently cause huge socioeconomic problems and which are, at the same time, available in quantities large enough for feeding the concrete industry. This will lead to improve sustainability and cost-efficiency of concrete industry, as well as to reduce the environmental/social impact of waste. On the binder side, the aim is the complete replacement of cement by waste materials of high silicon dioxide content, e.g. municipal
incinerator ash, ash disposed from coal-fired thermal power plants, and/or in combination with by-products such as ferronickel slag and natural or man-made pozzolans like µ-silica and metakaolin. Properties regulators will also be studied, consisting of highly active products that will regulate the performance of the binder, taking into account the waste raw materials variability, in order to achieve and stabilize the required properties of final products.
The project results, while setting-up a novel low-cost material for producing energy-efficient buildings components, will also contribute to solving the issue of “waste pressure” on towns and to reducing the consumption of not-renewable natural raw materials.
The [*]project’s[/*] goal will be achieved through a number of intermediate objectives including an EU overview of the candidate waste materials to produce lightweight aggregates from solid wastes. In addition the project seeks to completely replace Portland cement with waste binders. A specific mix-design methodology and working procedures, pilot plants, decision-support tool and application guidelines will also help to achieve the goal.

Project Results:
The first part of the Project (WP1) was preparatory, leading to the following main results:
• Complete framework of regulations and policies across EU27 on waste management;
• Complete framework of technical specifications on the use of recycled materials as aggregates and binders in concrete production;
• Complete framework of HSE regulations concerning reuse and recycling of the kinds of wastes of interest to the project;
• Identification of availability in EU27 Countries of the thirteen candidate waste materials;
• Identification of the possible future trends of the candidate waste materials streams;
• Creation of SUS-CON geographical database, also in a version consultable trough free software.

The second part of the Project (WP2) was devoted to develop light weight concrete aggregates from solid waste materials, integrating and testing them in concrete made with ordinary Portland cement.
So far, the following main results were achieved in WP2:
• The Remix production process has been optimized and its applicability to different EU waste streams was demonstrated;
• Conditions for using tyre rubber, e-plastics and PU as light aggregates for concrete was identified;
• The properties of each aggregate typology were measured, providing data for the mix-design;
• The geo-polymer production process from different waste materials was well defined;
• The most promising surface treatment on Remix was identified, namely treatment with acrylic emulsions;
• Heat treatments on Remix aggregates were successfully performed with the use of natural fill waste and thermosetting waste powders;
• First outcomes of the trial mixes in terms of workability, compressive strength, air content and thermal conductivity are available.

The third part of the Project (WP3) was devoted to design and test geopolymer binders by identifying blends of waste materials that, combined with an alkali, will result in suitable concrete. So far, the following main results were achieved in WP3:
• Significant conclusions as to the suitability of aluminosilicate rich materials to be used as alkali activated binders are available, with reference to different materials group:
o Low calcium pfa and ggbs based binders
o Perlite tailings
o Bentonite tailings
o Industrially solid wastes, like high calcium fly ash, ferronickel slag and red mud.
• It was shown that all the materials that were assessed, but the red mud, proved to be good candidate materials for geopolymeric synthesis;
• Optimum lab-scale recipes were obtained;
• The material- related problems during the synthesis process were identified and tests to overcome them by material- redesigning were performed (co-geopolymerisation of different raw materials);
• It was found that the source materials with silicates that have a significant amount of framework silicates with a medium amount of aluminium incorporated, give the strongest geopolymers;
• The cost analysis showed that the cost of geopolymer concrete is reduced significantly when considering large quantities of the alkali activators delivered in bulk to the site, as well as that geopolymeric concretes can compete, at least in terms of price, with Portland cement concrete;
• Possible blending of different materials so as to produce geopolymer concretes with the desired engineering properties has been determined, showing that strengths between 20 and 80 MPa can be achieved with the optimum alkali dosage and modulus;
• The linear relation between geopolymer strength and the relative amount of particular aluminium-silicate types in the source material as measured using FT-IR as well as 29Si-NMR, has the potential to be a successful screening tool for assessing the suitability of secondary resource materials for high quality geopolymers.

The following part of the Project (WP4) is devoted to develop concrete with 100% waste materials, namely the waste aggregates and waste binder. So far, the following main results were achieved in WP4:
• A framework for a performance based design and assessment of SUS-CON Concrete;
• A numerical model for predicting the properties of SUS-CON concrete on the basis of the properties on the aggregates on the one hand and the binder paste on the other hand;
• A feeling for the new concrete in practice on the basis of the first trial mixtures;
• A first version of a practical design model for the SUS-CON concrete.

A further part of the Project (WP7) aims at assessing, for each of the Project products, on one hand the real reduction of Embodied Energy and CO2 Emission, and on the other hand the health, safety and environmental (HSE) implications of the proposed solutions. So far, the following main results were achieved in WP7:
• Identification of hazard pictograms and statements to comply with the CLP Regulation
• Comparison of environmental impacts of traditional concrete and preliminary SUS-CON solutions

Potential Impact:
The main expected final result of the Project will consist in an innovative light-weight, eco-compatible and cost-effective construction material, made by all-waste raw materials and characterized by low embodied energy and CO2 emissions, with good thermal insulation properties.
Nevertheless, in addition to the main result of the project (all-waste concrete) there will be further self-standing industrially exploitable results, i.e. concrete obtained with recycled aggregates and traditional binders, and concrete obtained with traditional aggregates and recycled binders.
Further self-standing industrially exploitable results can be considered the aggregates obtained from the different waste streams considered in the project (at least three of them will be developed up to the demonstration stage).
Moreover, some non-industrial results are expected from the Project, mainly related to the specific know-how and tools developed by the scientific partners, which will be in the condition to exploit such know-how in further R&D Projects and in consulting activities.
The expected final results of the Project, in addition to the direct impact on the project partners, will lead to significant impacts in terms of environment, socio-economic and societal implications, in line with the most recent EU policy trends regarding pollution, energy efficiency, waste management and products quality.
In particular, sustainability of concrete industry will be enhanced, mainly thanks to the decrease of embodied energy and CO2 footprint, as well as to the reduction of raw materials consumption. Moreover, the waste prevention and recycling policies supported by the Project will contribute to giving clean affordable and societal benefits to EU citizens, mainly by reducing the quantity of waste destined to landfill or incineration.

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