Mineralogical and chemical properties of the volcanic rocks of Afyon region and their usage of construction sector

The investigated area is located central and nearby of Afyonkarahisar, NW-SE trending Afyon zone. Early Miocene aged volcanic rocks crop out dominantly intermediate-felsic rocks as a N-S extending orientation in the centrl segment of the Afyon zone. The volcanics are flows (lavas) and pyroclastics, namely Afyon lavas, and volcanic tuffs/ash. In other words, the Afyon volcanites are observed predominantly as trachytic flows associated with scarce trachytic-porphiroidal trachyte-trachyandesite-andesite to porphiroidal andesite necks/plugs. They ocur as sucessive flow units with thicknesses of 2.0 m. to 100 m., and have porphyric texture with grey colour in fresh samples, and light-brownish grey colour in altered samples. It is determined that the volcanic rocks in this region is a product of island arc volcanism according to result of the mineralogical-petrographic investigations and chemical analysis samples taken rocks cropping out in bold levels especially in areas where Omer-Gecek springs, in and around the province of Afyon, Turkey. The results revealed that the volcanic rocks that makes up mechanisms of volcanism completely to have different mineralogical compositions from volcanic ash and formed in genesis in different conditions. We present mineralogical and petrographical characteristics of pyroclastic material and lava flows from north and south of areas. Petrographically, the Afyon volcanics are mainly trachyte, porphiroidal trachyte, trachyandesite, trachytic tuff, and less basalt, consisting of primarily of alkali feldspar (sanidine), plagioclase (oligoclase, andesine), amphibole (brown hornblende), clinopyroxene and biotite. Rapid cooling and solidification of trachytic lava produces the fine texture of the groundmass. The groundmass is composed of sanidine, plagioclase (rarely), clinopyroxene (augite), and volcanic glass with fluidal texture. The secondary epidote, calcite and rarely quartz are also present at the Afyon volcanics. The south of volcanic rocks are mainly trachyte-trachyandesite and less andesite, whereas, the north of volcanic rocks are trachyandesite, porphiroidal trachyte, andesite, and basalt composition. The chemical analyzes of the volcanic rocks show that the total content of SiO2+Al2O3+Fe2O3 of the meterial is trachyandesite from volcanic origin (80.99%) and the total content of SiO2+Al2O3+Fe2O3 of the volcanic ash is trachyte-trachyandesite (75.61%) composition. In the of scanning electron microscope (SEM) investigations, it was determined that the volcanic tuffs/ashes in the investigated area occurred from altered minerals sanidine, plagioclase, ignimbrite and biotite. The matrix is a fine-grained structure. X-ray diffraction (XRD) studies have shown that all volcanic tuffs/ashes are composed the mineralogical composition of the alkali feldspar (sanidine), biotite and smectite group clay minerals. In this study; especially to determine the availability of volcanic ash in cement as well as major oxide values, physical and pozzolanic activity tests were conducted. This volcanic ash participated in portland cement in different proportions (5%, 10%, 15%). Mineralogical, chemical, physical and mechanical tests were applied to the samples obtained from this cement. The compressive strength tests (1.85-2.82 MPa) and tensile strength tests results (0.82-0.92 N/mm²) were obtained on the examples of all produced blended cement samples. The pozzolanic activity tests carried out with lime reveal that according to the trash standards required by TS EN 197-1, volcanic ash samples were not suitable. At the end of our research it was determined that the volcanic ashes from Afyon province and near surroundings Ömer- Gecek mixed with Portland cement at 5%, 10% and 15% will not be suitable for the production of Pozzolano mixed cement. As a result, in the physicomechanic experiment such as the pressure and the inflection resistance of cement mortar containing pozzolano which was done by using 20% Radiolarite additive, it was revealed that volcanic ashes were not in the standard required by TS EN 196. Keywords: Alkaline, Cement, Lava, Mineralogy, Pozzolano, Volcanic Ash, Volcanics, Trachyandesite, Trachyte.