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This study regards the synthesis of waste brick geopolymers and the evaluation of their alkali leaching potential. Geopolymers with varied alkali to Al molar ratios were prepared and their alkali leaching potential was measured. In order to improve the efflorescence of the waste brick geopolymers, KOH was used instead of NaOH in the activation solution, Ca cations were incorporated through the partial substitution of the brick powder by ground granulated blast furnace slag or extra Al was introduced in the activation solution. The results showed that the leachability of the products is close related to the alkali content of the activation solution while the use of K ions in the starting mixtures reduced the leachability potential. The same effect was observed in the case of the extra Al ions incorporation. The partial substitution of the wastes bricks by slag showeda slight increase of leachability even though denser materials with enhanced strengths were prepared.

The aim of this work is to propose the methodology and the mathematical tools for the design and development of geopolymeric materials from industrial wastes and by-products. The applied methodology follows the Taguchi fractional experimental design allowing the investigation of the combining effect of selected parameters in the response of the experimental system by conducting the minimum number of experiments. Two cases of geopolymer synthesis optimization based on the mechanical strength and the apparent density of the products, to which the Taguchi methodology has been successfully applied, are presented in the paper.

Insulation elements are distinguished in inorganic fibrous and organic foamed materials. Foamed insulation materials are of great acceptance and use, but their major disadvantage is their flammability. In case of fire, they tend to transmit the flame producing toxic gases. In this paper, the synthesis and characterization of innovative inorganic insulation materials with properties competitive to commercial is presented. Their synthesis involves the mixing of inorganic raw material and water with reinforcing agent or/and foaming agent leading to the formation of a gel. Depending on raw materials nature, the insulation material is produced by freeze drying or ambient drying techniques of the gel. The raw material used are chemically benign and abundantly available materials, or industrial by-products and the final products are non-toxic and, in some cases, non-flammable. Their density and thermal conductivity was measured and found 0.02-0.06 g/cm3 and 0.03-0.04 W/mK, respectively.

This study concerns the development of lightweight fly ash based geopolymers which can be applied as alternatives to the traditional lightweight concrete. Different kinds of expanded polystyrene were used as lightweight agents. The results showed that lightweight geopolymers were successfully prepared, exhibiting compressive strength and density in the range 7.70 – 29.57 MPa and 0.97 – 1.57 g/cm3, respectively. The product containing 3% w/w of commercial expanded polystyrene possesses low thermal conductivity (0.16 W/mK) combined with sufficient mechanical strengths (11 MPa), excellent stability and fire resistance while its water absorption is comparable to that of conventional construction materials (cement mortars, concrete).