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Maria Bignozzi

Associate Professor

Department of Civil, Chemical, Environmental, and Materials Engineering

Academic discipline: ING-IND/22 Materials Science and Technology

Research

Keywords: durability alkali activated materials corrosion protection systems waste recycling sustainable building materials geopolymer corrosion behaviour ceramic materials ceramic tiles/slabs

  1. Civil and industrial waste creates many problems for disposal. The use of waste to produce new materials based on polymer, ceramic or cement matrices through new technologies is an attracting route to obtain new eco-sustainable materials with high performances.
  2. Low environmental impact materials with high performances are investigated and designed for industrial and civil engineering sector, exploiting innovative technologies (alkali activated materials/gepolymers).
  3. Materials durability is a very important feature for all the engineering fields: corrosion rate and degradation mechanisms are investigated by means of electrochemical measurements and environmental chambers.
  4. Investigations are carried out on corrosion behavior and protection of ferrous and non-ferrous alloys for applications in the construction and industrial sectors, in architecture and cultural heritage fields.
  5. Investigations are carried out on the production process of ceramic tiles/slabs and their functionalizations from the environmental point of view.

 

1. New building materials based on industrial waste for the sustainable development of construction industry.

The large exploitation of natural raw resources, the carbon dioxide emissions, the great amount of industrial waste yearly disposed to landfill are some of the reasons to carry out research for the development of sustainable materials suitable for the construction industry and industrial sector. The possibility to use waste as unconventional constituent for building materials makes necessary studying the compatibility between natural raw materials and waste. Moreover, waste chemical reactivity and relevant modifications introduced in materials microstructure also need to be investigated. Glass and ceramic industrial waste have been successfully used to produce new blended cement: these new constituents exhibit pozzolan activity and the relevant cements result more resistant to environment attacks. Recycled glass can be also used as fine aggregates (sand) for concrete. In this case as well as when recycled glass is used as supplementary cementing materials, the chemical composition of the glass plays a very important role in promoting or hindering alkali silica reaction and/or pozzolan activity. Indeed, both these reactions depend on glass dissolution and relevant products formed in the alkaline environment of concrete. In order to improve the development of sustainable concrete, the research is also focused on the mix design and characterization of traditional and self-compacting concrete containing concrete and demolition waste (C&D waste) as aggregates replacement. In particular, the results of physical and mechanical characterizations at early and long age highlighted how large content of recycled aggregates (coarse and fine, coming from concrete demolition) can be successfully used in concrete mix design, thus potentially overcoming the limits set by European regulations.

2. Alkali activated materials/geopolymers: a new class of inorganic materials suitable for construction industry.

The interest of recycling waste of different origin and nature follows European directives and, in this framework, geopolymers can be a very interesting solution. Geopolymers are inorganic materials obtained by alkali activation of alumino-silicate precursors, such as metakaolin. Metakaolin is obtained by caolin calcining and the different conditions of activation (temperature and reaction time, concentration and types of activating alkali solutions, etc.) can lead to products differing for physical and mechanical properties. The control of porosity and its distribution are key parameters if geopolymers are thought for building sector, where these new materials can be interesting for producing tiles, panels, insulating products, binder for mortar and conglomerates, etc.. Alkali activation can be also extended to precursors based on calcium containing alumino-silicates and the resulting products are named alkali activated materials. Many waste based on calcium-alumino-silicates (ceramic waste, ladle slag, etc.) can be thus potentially recycled by means of alkali activation, even though the process parameters must be properly set and the final properties of the resulting materials need to be deeply investigated. Alkali activated materials/geopolymers consolidate at room or slightly higher temperature (T< 100°C) making this process particularly attractive in terms of saving carbon dioxide emissions and natural resources combustion. The research activity is mainly focused on innovative precursors in order to: (i) set up their mix design and process parameters (time, temperature, types and concentration of alkaline solutions, molar ratios, etc.); (ii) provide fresh state characterizations and optimize moulding technology; (iii) provide physical-mechanical characterizations of the final products at the hardened state (with special focus on porosity and its control; (iv) study their physical and mechanical behaviour after high temperature treatments; (v) investigate final products durability by means of climate chambers with temperature, humidity and ultraviolet controls.

3/4. Corrosion and protection of metals

This research field has been developed in the last six years. The first studies were initially focused on corrosion behaviour of reinforcing steel bars in concrete prepared with alternative blended cements. Then, investigations of protective systems of different nature (natural patina, organic and inorganic layers, geopolymers, etc.) have been carried out on ferrous and non-ferrous alloys suitable for applications in the sector of constructions, cultural heritage, industrial plants, etc. In particular, the evaluation of the corrosion behaviour and the protective efficiency of coatings are performed through accelerated ageing, surface analyses, thermal analyses, electrochemical measurements. Research activities are carried out in collaboration with research groups of the Interdepartmental Center for Industrial Research of the University of Bologna for Advanced Applications in Mechanical Engineering and Materials Technology CIRI-MAM (Corrosion Unit: Dr. Cristina Chiavari), of the Industrial Engineering (Dr. Carla Martini) and Industrial Chemistry «Toso Montanari» (Dr. Elena Bernardi) Departments of the University of Bologna, of the Corrosion Center “Daccò”, University of Ferrara (Prof. Cecilia Monticelli). Moreover, research projects supported by national and international companies are developed in order to solve technological problems due to unexpected corrosion phenomena.

On the topic of corrosion, the European project B-IMPACT ( Bronze-IMproved non-hazardous PAtina CoaTings) submitted to 2013 M-ERA.net call has been recommended for funding. The project, coordinated by the Slovenian National Building and Civil Engineering Institute, Ljubljan, Slovenian, will start on March,1st, 2015.

5.  Production process of ceramic tiles/slabs and their functionalizations from the environmental point of view.

In collaboration with Centro Ceramico, the main industrial and scientific issues related to ceramic sector are investigated.

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