The investigation of durability properties on geopolymer concretes

In this study, fly ash (FA), a thermal power plant waste with pozzolanic characteristics, was used as the main raw material. The fly ash used was obtained from the Kütahya Tunçbilek Thermal Power Plant. The sodium hydroxide (NaOH) and sodium silicate solution (Na2SiO3) (SS) were used as the alkali activator in the preparation of the samples. The aggregates used in the production of concretes are in two different grades as 0 - 4 mm (thin) and 4-8 mm (medium). These aggregates were obtained from a special concrete company in Afyon. In the preparation of geopolymer concrete samples, the mixture design of the alkaline activators (NaOH and SS), which are used as raw materials, are determined by experiments. Mixtures prepared in laboratory type pan mixer are placed on hard plastic molds with dimensions of 10 x 10 x 10 cm by vibration method. Then, the relevant samples were placed the laboratory type oven in order to carry out thermal curing process. In order to apply the thermal curing process, geopolymer concrete samples were cured at three different times (5, 8 and 24 hours) and three different temperatures (50 oC, 60 oC and 70 oC). After the curing process was completed, samples were taken from the molds after one day in laboratory. Then geopolymer concretes were placed in the water tank for 24 hours to determine the physical properties of the samples. Then the samples; physical properties such as water absorption, apparent porosity, unit weight and apparent density were determined according to Archimedes' principle. In the determination of physical and mechanical properties of samples, 28-day geopolymer concrete samples were used. Following the determination of the physical and mechanical properties of geopolymer concretes; According to ASTM C 672-84, freezing dissolution has been subjected to some durability tests such as high temperature and resistance to sulphate (NaSO4 and MgSO4) attacks according to TS EN 13501-1.