Grain Size Analysis of Class C Fly ash Used for Aluminium-Silicate Binders

Abstract

Concrete structures are constantly moving in the direction of improving the durability. Durability depends on many factors, which are the composition of concrete mix, the usage of additives and admixtures and also the place, where material will work and carry the load. Taking into account that the consumption of cement on the globe gives way only to the consumption of drinking water, the issue of concrete technology begins to take on an economic and ecological aspect. Mentioned above the aspect of durability is strictly connected to economy. Due to huge amount of greenhouse gasses produced in the process of calcination, the ordinary Portland cements are responsible for even 8% of anthropogenic carbon dioxide production. This paper is focused on properties of materials known as green binders. They can be used to produce aluminium-siliceous binders and green concretes which can also be known as geopolymer concretes. Often used in construction industry, class F fly ashes are also good substratum also for aluminium- siliceous binders. Nevertheless amount of available class F fly ashes do not give the possibility to replace ordinary cements by aluminium-silicate one produced from this type of ash. This raises the need to look for replacement solutions for the substrate of the new green adhesive. As the substrate of new eco-binders there were used fly ash which came from coal and high calcium ash from the burning of lignite, called class C fly ashes. However not processed one, cannot compete with Portland cements due to durability. It surely depends on many aspects of polymerization process, which are for example maturation environment, concentration and type of alkaline activator, but the most important are parameters of fly ash substrate. This is because main attention was paid to granulation of examined class C fly ashes which have been subjected to a grinding process involving milling in a magnetic mill and subjected to ultrasonic waves. The analysis of grain change was presented in the aspect of the possibility of increasing the strength and durability of the cement material.

Full document