Recent innovations in geopolymer technology have led to the development of various different types of geopolymeric products, including highly porous geopolymer-based foams, which are formed by the addition of foaming agents to a geopolymer fly-ash based matrix. These agents decompose, or react with the liquid matrix or oxygen in the matrix, resulting in the release of gases whichform pores prior to the hardening of the gel. The hardened structure has good mechanical and thermal properties, and can therefore be used for applications in acoustic panels and in lightweight pre-fabricated components for thermal insulation purposes. This study presents the results of the pore-forming process in the case when two different foaming agents, i.e. aluminium powder amounting to 0.07, 0.13 and 0.20 mass. % and H2O2 amounting to 0.5, 1.0, 1.5 and 2.0 mass. %, were added to a fly-ash geopolymer matrix. Highly porous structures were obtained in the case ofboth of the investigated foaming agents, with overall porosities up to 59% when aluminium powder was added, and of up 48% when H2O2 was added. The mechanical properties of the investigated foams depended on their porosity. In the case of highly porous structures a compressive strength of 3.3 MPa was nevertheless achieved for the samples containing 0.2% of aluminium powder, and 3.7 MPa for those containing 2.0% of H2O2.
COBISS.SI-ID: 2168679
This paper investigates the value of different industrial by-products and residues in the production of lightweight alkali activated materials (AAM). Waste metakaolin, recycled waste glass, aluminium scrap recycling waste, and steel-plant waste (SPW) were considered as secondary raw materials. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and X-ray micro-tomography examinations were performed in order to analyse the reaction products, to identify their phase composition, and to observe the micromorphology. The results showed that highly porous lightweight building materials could be obtained, with densities ranging from 380 to 470 kg/m3, heat conductivities ranging between 0.14 and 0.15 W/mK, and compressive strengths ranging between 1.1 and 2.0 MPa. It was also shown that the main hydration products were amorphous aluminosilicate gels, whereas the crystalline compounds from the SPW remained in the structure of the AAM. The results of X-ray micro-tomography showed that lightweight AAM contained 72.0 to 89.0 vol% of pores, with sizes ranging between 1 and 5 mm. In the paper a brief description is given of the waste management method which can be applied to obtain materials that can be used in the building industry as lightweight load-bearing insulation materials.
COBISS.SI-ID: 2265447
The implementation of repair works on concrete structures is on the increase since many existing concrete buildings have been exposed for long periods of time to different climates, as well as to other severe conditions, and have consequently deteriorated. Repair mortars need to fulfil the requirements of the EN 1504 series before being used in practice. Different mixtures, based on three different precursors (fly ash, ground granulated blast furnace slag, and metakaolin) and processed by alkali activated technology, have been assessed with regard to their suitability for the repair of concrete. Whereas the slag-based repair mortar delaminated from the substrate, and was thus unsuitable for its intended use, the other two mortars which were based on the precursors fly ash and metakaolin exhibited good mechanical properties and good adhesion. The bond strength of the metakaolin and fly ash mortars ranged from 1.8 to 2.3 N/mm2, and thus met these criteria for both structural and non-structural repair mortars. The capillary absorption of all three mixtures was too high to fulfil the criteria of EN 1504-3 for structural repair products, but the fly ash and metakaolin mixtures still have the potential to be used for non-structural repair works. The problem of efflorescence in all three mixtures was also assessed.
COBISS.SI-ID: 2231911
This study deals with the porous refractories based on alkali activated chamotte with addition of aluminium scrap recycling waste as a pore forming agent and firebrick sawing residues as a heat resistant filler for the application in temperature up to 850°C. These newly developed porous lightweight materials can be potentially used in the industrial field, since they display good thermal insulation, density range from 541 to 618 kg/m3 and resistance to elevated temperatures (material shrinkage at the temperature of 850°C did not exceed 0.05%). The refractoriness of alkali activated materials was studied by differential thermal analysis (DTA/TG) and dilatometry tests. Pore microstructure was examined by SEM. Mineralogical composition of the raw materials and physical properties of the produced samples were determined.
COBISS.SI-ID: 2258023