Bolat, Hakan; Şimşek, Osman; Çullu, Mustafa; Durmuş, Gökhan; Can, Ömer

Attempts to find a construction material having increased strength, ductility, toughness, and durability have led to interest in high performance fiber reinforced concrete. The use of such materials increases day by day. When the fibers are distributed in a homogeneous way and used in appropriate quantity inside the concrete, they reduce cracks, contribute to tensile strength, toughness, ductility and durability, and improve other mechanical properties. In this study, four types of concrete were produced: steel fiber (SFRC), polyester fiber (PYFRC), polypropylene fiber (PPFRC) reinforced concrete and a reference sample made of plain concrete (R1); these were then compared to one another. The ratio of fibers was used 4.25% of volume of concrete. The effects of the different types of fiber on hardened concrete were determined by conducting physical and mechanical experiments. Compressive strength, surface hardness, ultrasonic pulse velocity, carbonation, abrasion, capillarity and freeze-thaw resistance experiments were conducted on hardened concretes. SFRC had higher 12.4%, PYFRC 3.4% higher and PPFRC 4.3% lower compressive strength with respect to R1. PPFRC showed 8.04% higher compressive strength than R1 when it was determined by the surface hardness method. SFRC showed 5.4% higher compressive strength than R1 when we applied the ultrasonic pulse velocity method. In the abrasion experiment, the highest abrasion was found in SFRC with ∼0.5%, while the lowest was found in PPFRC at ∼0.18%. The highest and lowest amount of capillary water absorption was seen in R1 and PYFRC, respectively. In a carbonation experiment, SFRC was determined ∼130.8% higher than R1. It was concluded that the types of fiber used for reinforcement influenced the physical and mechanical properties of the concrete.

Arslan, Metin; Çullu, Mustafa; Durmuş, Gökhan

This study aims to determine the effect of antifreeze admixture used in the concretes subjected to frost action on the concrete compressive strength. Three groups of concrete samples of C30 class were prepared with antifreeze admixtures by using the mixture of 30% calcium nitrate and 5% hydroxy ethoxy amin (A), calcium nitrate (B), Polyhydroxy amine (C). Concrete samples are put in the freezer in a fresh state 15 min after the mixing. Samples are subjected to frost action in 0, -5, -10, -15 and -20°C degrees for 48 hours. On the concrete samples water cured after 48 hours, compressive strength tests of 28 day are conducted. Consequently, it is seen that with the increase of the set temperature that concrete is cured, compressive strength of concrete is decreased and among all types of antifreezes the maximum decrease is seen between 0 and -5°C while the decrease in compressive strength is relatively less for -10, -15 and -20°C.