Abstract
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.
Highlights
The Construction and Demolition Wastes (CDWs) comprise one of the heaviest and most voluminous solid wastes worldwide generated by the construction industry [1]
This study presents an effort on controlling the alkali leachability of waste brick geopolymers which is responsible for the efflorescence phenomenon
The results showed that the alkalinity of the activation solution plays an important role on the free alkali content
Summary
The Construction and Demolition Wastes (CDWs) comprise one of the heaviest and most voluminous solid wastes worldwide generated by the construction industry [1]. Due to the high SiO2 and Al2O3 content of many CDWs (bricks, tiles concrete, ceramics etc), they can be utilized in the production of alkali activated materials or geopolymers [3,4]. Geopolymers are a class of inorganic materials which possess a three-dimensional polymeric-type structure. They are formed by the reaction of an alkaline solution with an aluminosilicate material at ambient or slightly elevated temperature [5]. The alkalis play a dual role in the geopolymerization process First of all, they generate a high pH solution by releasing hydroxyl ions in order to dissolve the aluminosilicate precursors and to produce small reactive silico and alumino species. The mechanical strength of the produced specimens was measured through compressive strength tests
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