153 Cerâmica 65 (2019) 153-161 http://dx.doi.org/10.1590/0366-69132019653732551 INTRODUCTION Today, the need for the production of new ecofriendly building materials from each country’s natural resources and/ or waste by-products increased vastly with the increasing general awareness concerning the environment which led to a growing concern about the waste generation and the realization that such materials must be treated, eliminated or re-used. Rising consumption and the concomitant increase in industrial production has occasioned both a rapid decline in natural resources and generation of large volumes of waste or by-products [1]. Recent researches into the economically viable re-use of wastes have given rise to different proposals, including the possibility of its inclusion in building materials [2, 3]. Alkali-activated materials, commonly known as geopolymer if their resources are from nature geological origins rich in silicon and aluminum, whilst if their resource from industrial by-products rich in alumina and silica oxides such as coal fy ash, silica fume and granulated blast furnace slag can be considered as alkali-activated materials which is the major category, whilst geopolymers can be considered a subset of this mother set as coincide with the pioneer scientists Davidovits in 1970s [4, 5]. The basic binding phase in geopolymers is an amorphous aluminosilicate gel that consists of a three-dimensional framework of SiO 4 and AlO 4 tetrahedra linked by corner-shared O atoms [6-8]. Geopolymer binders exhibit improved properties compared to traditional binding materials although the most important is their low manufacturing energy consumption and low CO 2 *hkhater4@hbrc.edu.eg https://orcid.org/0000-0002-9832-5895 Abstract Production of lightweight building materials attract the attention of the scientists worldwide with the need for reducing the structure deadweight, provide better thermal insulation for buildings, and cost less to transport. The current work focused on the production of lightweight geopolymer composites by the incorporation of aluminum powder and aluminum slag in various ratios for water-cooled slag/kaolinite sand composite; the activators used were 6% of equal ratio from sodium hydroxide and sodium silicate. The properties of the produced lightweight geopolymer composites were studied by measurement of compressive strength, bulk density, water absorption, FTIR, XRD and SEM imaging. Results showed the enhancement for both physicomechanical and microstructural characteristics with using aluminum powder and aluminum slag forming lightweight composites with densities below 2.15 g/cm 3 depending on the studied mix composition. Keywords: lightweight, geopolymer, activation, aluminum, slag. Resumo A produção de materiais de construção leves atrai a atenção dos cientistas em todo o mundo com a necessidade de reduzir o peso morto das estruturas, fornecer melhor isolamento térmico para edifícios e ter menor custo de transporte. O presente trabalho centrou na produção de compósitos geopoliméricos leves pela incorporação de pó de alumínio e escória de alumínio em várias proporções para o compósito de escória resfriada a água/areia de caulinita; os ativadores utilizados foram 6% de igual proporção de hidróxido de sódio e silicato de sódio. As propriedades dos compósitos geopoliméricos leves produzidos foram estudadas pela medição da resistência à compressão, densidade aparente, absorção de água, FTIR, DRX e MEV. Os resultados mostraram que as características físico-mecânicas e microestruturais aumentaram com a utilização de pó de alumínio e escória de alumínio, formando compósitos leves com densidades abaixo de 2,15 g/cm 3 , dependendo da composição da mistura estudada. Palavras-chave: material leve, geopolímero, ativação, alumínio, escória. Development and characterization of sustainable lightweight geopolymer composites (Desenvolvimento e caracterização de compósitos geopoliméricos leves e sustentáveis) H. M. Khater 1 * 1 Housing and Building National Research Center, 87 El-Tahrir St., Dokki, Giza, P.O. Box 11511, Cairo, Egypt