A comparative investigation on the mechanical and durability properties of concrete incorporating class C and F type fly ash

Key Words: Fly Ash, Mechanical Properties, Efficiency, Strength, Durability.Fly ash is the waste product of the thermal power plants, where coal is burned for generating electricity. Using fly ash in concrete production is one of the important ways of reducing its negative effects. When fly ash is used alone, it doesn?t show binder property. However, if it is added to concrete mixture with cement, it improves the mechanical and durability properties of concrete.In this study, F and C type fly ashes efficiencies and their effects on the mechanical properties and durability of concrete are compared. For this study, 39 different mixtures were produced. Çatalağzı Thermal Plant fly ash (F type), Çayırhan Thermal Plant fly ash (C Type) and CEM I 42,5 R type cement were used as binder. Three reference concrete mixtures were produced with 260, 320, 400 kg/m3 cement dosage and six fly ash (F and C type) including mixtures were produced for each reference mixture. Cement dosages were reduced with 10% ratio in half of mixtures and 17% ratio in other half of mixtures. Fly ash was added instead of reduced cement. Added fly ash / reduced cement ratios by mass were (1.5), (2), (2.5) for 260 kg/m3 cement dosage and (1), (1.5), (2) for 320 and 400 kg/m3 cement dosages. Mechanical properties of concretes, which were produced according to same workability method, were examined and their efficiency factor were determined with Bolomey formulas. Six cube specimens with 15/15/15 cm dimensions, six cylinder specimens with 10 cm diameter and 20 cm height and six prismatic specimens (pins were placed to two sides of there of these specimens) with 7/7/28 cm dimensions are produced for each mixtures. After demolding, concrete specimens were cured in water tank at 23±2 ºC. Water contents of all mixtures are determined by casting trial mixtures. On fresh concrete, slump, bulk density and air content tests and on hardened concrete compression strength, bending strength, ultrasound pulse velocity, modulus of elasticity, capillary water absorption, freeze-thaw, sulphate effect, rapid chloride permeability tests were done.Tests results showed that using F and C type fly ash contributed workability . On the other hand, pozzolanic reaction need to wait the formation of free lime and the reactions of F and C type fly ash including mixtures are slower than reference mixtures. So, increasing of strength in these mixtures are more at further ages.