Remzi Şahin

THE EFFECTS OF DIFFERENT CEMENT DOSAGES, SLUMPS AND PUMICE AGGREGATE RATIOS ON THE COMPRESSIVE STRENGTH AND DENSITIES OF CONCRETE

Abstract Compressive strengths of concretes made up of mixtures of pumice aggregate (PA) and normal aggregate were measured. To determine the effect of PA ratio, different cement dosage and slumps on the compressive strength of concrete, (1) 25%, 50%, 75% and 100% pumice ratios were used instead of normal aggregate by volume, (2) 200, 250, 350, 400 and 500 kg/m 3 cement dosages were used and (3) 3±1, 5±1 and 7±1 cm slumps were also used in this study. The analysis of the test results leads to the conclusion that PA decreased the density of concretes up to 41.5% and reductions occurred due to the increase of the PA ratio in the mixes. With the increase of cement dosage in the mixes, both density and compressive strength of concretes increased up to 3.2% and 265%, respectively, when compared to the control sample that contain 200 kg/m 3 cement dosage. The effect of the slump on the density and compressive strength was varied. Elasticity moduli were decreased with an increase of PA ratio and increased with an increase of cement dosage. Water absorption improved with an increase of cement content.

Neutron Equivalent Dose Rate Measurements of Gypsum-Waste Tire Rubber Layered Structures

The neutron equivalent dose rates (µSv/h) of gypsum, steel-reinforced rubber waste tire, and gypsum-waste tire rubber sandwich composite samples were investigated. Prepared samples were irradiated with 241Am-Be neutrons and transmission values were obtained using dose equivalent rates measured with a BF3 neutron detector. Results were compared to those of concrete, and as a result of neutron shielding, the performance of gypsum, waste tire, and waste tire (steel-reinforced rubber) embedded gypsum samples was higher than that of concrete. This information may be useful for shielding design of nuclear application areas.

Taze Beton Özelliklerinin Optimizasyonu / Optimization of Fresh Concrete Properties

OZET : Bu calismada; su-cimento orani, cimento dozaji ve hava surukleyici katki maddesinden olusan parametrelerin betonun taze haldeki ozellikleri uzerindeki etkileri incelenmistir. Deney tasarimi asamasinda ve sonuclarin istatistiksel analizinde Taguchi Yontemi kullanilarak optimizasyon yapilmistir. Optimizasyon sonucunda betonun islenebilirligi icin cimento dozaji; birim agirlik ve hava icerigi icin ise hava surukleyici katki maddesi en onemli parametre olarak bulunmustur. Genellikle betonun donmacozulmeye karsi direncini artirmasi icin kullanilan hava surukleyici katki maddesi, taze betonun akiskanligini da artirmistir. Deneylerde kullanilan Taguchi Yontemi; deney sayisini azaltmis, her uc deney icin gecerli olacak sekilde parametrelerin optimum seviyelerinin belirlenmesini saglamis ve yapilmayan deneylerin sonuclarinin kestirimini mumkun kilmistir. Anahtar kelimler: Taze beton, cokme, dozaj, birim agirlik, hava icerigi, Taguchi Metodu ABSTRACT : In this study, the influence of water-cement ratio, cement dosage and air-entrainment admixture (AEA) on the properties of fresh concrete was investigated using Taguchi Method. The Method was used for both experimental design and statistical analysis of the results to optimize the parameters mentioned. The optimisation results showed that the most important parameter is cement dosage for the workability, is AEA for the unit weight and for the air content. AEA which is generally used to improve the resistance of concrete exposed to freezing and thawing increased the workability of fresh concrete. Taguchi Method decreased the number of experiments, enabled to determine the optimum levels of the parameters for all the three experiments and to estimate the results of not conducted experiments. Keywords: fresh concrete, slump, dosage, unit weight, air content, Taguchi Method