The mineral and chemical composition of aluminosilicates used in geopolymer systems is critical for optimal structure formation and the overall performance of the geopolymer products. The composition of alumosilicates can be altered during the technological processing, especially, at the stage of fine milling. This study investigated the effect of aluminosilicate contamination with Fe from milling yield, the characteristics of the aluminosilicates with a metal lining, structure formation, and hardened properties of geopolymers based on different natural and technogenic persilicic aluminosilicates. The formation of Fe-phases due to milling yield was detected by the XRF analysis and the XRD investigation revealed the formation of nanosized ferrous hydroxide or bernalite Fe(OH)3(H2O)0.25. The volume of an elemental cell of the nanosized bernalite per Fe atom is 4.5 times larger than that of the metallic iron. This results in the disintegration of the matrix, which was observed by SEM and then confirmed by reduced strength performance of geopolymer composites. Based on this study, the negative effect of Fe-phases from milling and nanosized ferrous hydroxide on structural characteristics and service performance of geopolymer composites based on natural and technogenic raw materials was concluded.
-The industrial powder waste from thermal power plants such as fly ash is used as asphalt or mineral filler due to its properties and dispersibility. However, the conflicting data on the fly ash usage are due to the different compositions, dispersibility, reaction capacity of the used fly ash. This paper presents the detailed research of the structuring process in bitumen-mineral compositions experimentally studied under the water saturation tests. The water saturation for the asphalt cements evaluates the strength of adhesion of the binder film to the particle surface as well as the stability of the bitumen-mineral structure when saturating water under the reduced pressure and elevated temperature. Depending on the fly ash composition, the structure formation operates differently at the component cohesion stage and during the swelling test. In bitumen-mineral composites, based on the high-lime ash, the mineral hydration leads to the binder film liftoff as well as to the change of the ash phase composition due to the low adhesion of bitumen and mineral particles. That results in undesirable formations in the system such as calcium sulfate dihydrate and ettringite, particularly. These formations cause the structural softening and the swelling of asphalt cements. The higher bitumen -low-lime ash adhesion provided the more stable structure of asphalt cements under testing. That resulted just in the binder film deformation without its liftoff. The swelling of the bitumen compositions was provided by the low packing density of ash particles in the asphalt cement.Keywords-the thermal power plant fly ash, swelling test; asphalt cement; structure formation; new formation.
One of the main factors is the structure of asphalt concrete. The most important structural component in asphalt concrete is mineral powder, the quality of which depends on the technical and operational characteristics of the road surface. Different methods of processing mineral materials are used to improve the performance of asphalt concrete in Russia and abroad. In most cases, mechanical activation with organic substances is used during the grinding process.
The article presents the results of research on the effect of treatment of mineral powder with the preparation GF-1 on its characteristics and on changes in the physical and mechanical properties of asphalt concrete, as well as on indicators for long-term water saturation.
It is shown that as a result of modification, the mineral powder becomes hydrophobic, which has a positive effect on the physical and mechanical characteristics of asphalt concrete with its use. It is found that hydrophobization of mineral powder significantly reduces water saturation and swelling; increases water resistance during long-term water saturation (up to 90 days) of asphalt concrete samples. As a result of hydrophobization, the temperature sensitivity of asphalt concrete increases significantly. Therefore, the composite will work reliably in a wider temperature range.
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