Issue 2

This paper deals with the geopolymerization of the red mud generated in the primary
aluminium production and the slag generated in the ferronickel production, in order to develop
inorganic polymeric materials with advanced mechanical and physical properties. In particular,
the effect of the main synthesis parameters of the inorganic polymeric materials on their
mechanical strength and water absorption was investigated. Moreover, the structure of the
inorganic polymeric materials was studied according to X-ray Diffraction analysis, Fourier
Transform Infra Red spectroscopy and Scanning Electronic Microscopy. The inorganic
polymeric materials produced by the geopolymerization of the red mud developed
compressive strength up to 21 MPa and presented water absorption lower than 3 %, while the
geopolymerization of the ferronickel slag resulted in materials with compressive strength
higher than 110 MPa and extremely low water absorption (< 1 %). According to these results,
the developed materials may be viewed as alternatives in the industrial sectors of
construction and building materials.

Coal fly ashes and metallurgical slags are currently widely used as supplementary
cementitious materials in production of Portland cement-based concretes. However, this
application makes very poor use of the intrinsic reactivity of the glassy phases present in the
waste materials, and can hardly therefore be considered ‘valorisation’ in the true sense of the
word. Addition of these materials to Portland cements can also cause difficulties in early
strength development, limiting their use to certain applications. Geopolymerisation, on the
other hand, makes full use of the glassy ash and slag materials by using them as the key
reactants in synthesis of aluminosilicate gel binders for waste-based concrete production. The
activation of the glassy phases by alkaline solutions provides the opportunity to greatly reduce
the Portland cement content of a concrete, but requires a sound understanding of the ash
chemistry and its effects on workability, water demand and setting time if it is to be
implemented successfully on a commercial scale. In this paper, various aspects of fly ash
valorisation via geopolymerisation are discussed, including in particular the determination of
ash reactivity by a recently-developed technique utilising dilatometric data. The correlations
between ash reactivity as measured by dilatometry and geopolymer mechanical strength are
discussed in detail, and comparisons with other measures of ash reactivity presented. Some
commercial examples of geopolymer concrete in-place are also discussed to highlight these
differences in real world usage.

The main objective of this research was to predict expected methane generation in Hellenic
sanitary landfills, in order to evaluate its potential for energy production and to ensure health
and safety in and around these sites on the long term. The study was performed for the
period 2008 – 2028 with the use of a multi-phase model and included also a sensitivity
analysis in order to determine the impact of certain waste parameters. In this context, two
‘extreme’ reference scenarios were formulated and assessed, one anticipating fulfilment of
the EU landfill directive (which sets limits to the amount of biodegradable and packaging
materials to be deposited in sanitary landfills) whereas a second (do-nothing scenario)
assuming no such timely compliance.

This work is aimed at evaluating the potentiality of adding a rhamnolipid biosurfactant in a
petroleum-bearing soil. For this purpose, dehydrogenase activity and seed germination
(Lactuca sativa) testes were performed before the biodegradation assays with different
concentrations of rhamnolipid (1 to 15mg for 1g of soil). The addition of 1 and 15 mg g-1 of
rhamnolipid was harmful to the soil environment. The biodegradation assays were carried out
at room temperature during 45 days in bioreactors containing 450g of a polluted soil with
different rhamnolipid concentrations varying from 1 to 15 mg g-1. The nutrients were corrected
through the addition of NH4NO3 and KH2PO4, in a nutritional ratio of C:N:P=100:15:1. The
humidity was adjusted to 50% of the liquid retention capacity. Besides these assays, a control
test was conducted without adding rhamnolipid. TPH (Total petroleum hydrocarbon) removal
and seed germination were evaluated at the end of these experiments. When 4 mg g-1 of
rhamnolipid were used a TPH removal of about 60% was observed. The biosurfactant
addition improved all treatments, except for the assays with addition of 1 and 15 mg g-1 in
which a decrease of the bioremediations rates was observed in the toxicity tests.