Alkali Activation of HCFA Mixtures with Aluminosilicate Additives - Mechanical Characteristics

Abstract

Over the last years, the increasing need of cost saving and environmental protection has led to finding alternative methods and materials in construction. One of these methods is the alkali-activation, which can transform alumino-silicate binders, like siliceous fly ashes, blast furnace slags, into useful materials. On the other hand, little focus has been given to study the potential uses of high calcium fly ashes (HCFAs), which are also produced in Europe and constitute the half of total fly ash output.In this paper, a calcareous fly ash (F) from Agios Demetrios power plant in Greece was studied in combination with different alumino-silicate materials such as pozzolan, diatomite and brick dust in order to improve their physico-mechanical characteristics. Pastes were mixed with an alkaline activator, which consists of a sodium silicate solution and sodium hydroxide solution 10M. The weight ratio of NaOH:Na2SiO3was 1:1. At the fresh state, setting time of the mixture was measured after mixing. Prismatic specimens were matured at different temperature conditions (25°C for 2 days and 65°C for 2 days). The samples were tested under flexural and compressive strength at the ages of 2, 7 and 28 days. Volume deformation and open porosity were also determined.

­­­Mechanical behavior of textile reinforced alkali-activated mortar based on fly ash, metakaolin and ladle furnace slag

“…Recent studies have demonstrated the applicability of recycling industry byproducts in the construction sector, which can result in further reduction of CO 2 emissions and preservation of natural resources 24 . Furthermore, the ever-growing demand for construction supplies has led to a large-scale scarcity of natural resources and major sustainability concerns 25 .…”

Long-Term Behavior and Durability of Alkali-Activated Clay Mortars

“…Usually, the preferable heating temperatures to achieve the polymerization of an aluminosilicate precursor such as clay are between 60 °C and 90 °C [ 7 ]. However, scientific studies prove that the alkali activation reaction of calcium–aluminosilicate systems can also take place in ambient conditions [ 6 , 8 , 9 ].…”