No abstract

No abstract

The main purpose of this study was to investigate the compressive strength and microstructure characteristic of alkali-activated metakaolin cement (AAMC). In accordance with this purpose, besides the pure metakaolin activation five other mixtures were designed by substitution of different OPC ratios instead of metakaolin (MK) from 0 to 25 (5, 10, 15, 20, 25% OPC). AAMC was activated with sodium silicate (Na2SiO3) of modulus Ms = SiO 2 /Na2O = 3.1 and NaOH solutions (32% of NaOH, 68% of water by mass). The ratio of liquid/solid (L/S) was kept constant at 0.65. All specimens were cured at 70 °C for 72 hours then kept in room conditions until the days that experiments were performed. Compressive strength and UPV experiment tests were carried out on all specimens at different curing periods of 3,14,28 and 90 days. In addition, the microstructure of 28 days alkali-activated metakaolin cements were analyzed with scanning electron microscope (SEM). The results showed that AAMC specimens reached the desired strength and major part of the final strength was gained at the end of 3 days of curing.

This study reports the results of high temperature effects on the properties of steel fiber reinforced self-compacting concrete (SFRSCC) fabricated by replacing cement with ground pumice powder (GPP) as mineral additive at different substitution rates. The mixtures had the same amounts of steel fiber and the binding material with constant water to binder (w/b) ratio of 0.37. In this context, five SFRSCC series were prepared by replacing Portland cement (PC) with 5, 10, 15, and 20% of GPP including the control mix. Sixty cube samples with a dimension of 150 × 150 × 150 mm were fabricated and exposed to curing aged 3, 7, 28, and 90 days to conduct compressive strength tests and a total of 100 × 100 × 350 mm 18 beam samples cured at 28 days were fabricated to perform the flexural strength tests. Durability tests were performed on the 18 cube samples of 100 × 100 × 100 mm subjected to water curing at 28 days. In addition, the relation between the compressive strength and Ultrasonic Pulse Velocity (UPV) of SFRSCC samples was compared aged 1, 3, 14, and 28 days. Samples of SFRSCC were subjected to the temperatures of 200, 400, 600, and 800 C after being cured at 28 days then cooled to room temperature before conducting tests. The results revealed that the compressive strength of all SFRSCC mixes enhanced at 200 C by 5.34 and 3.55% for control and GPP10 mixes respectively. The strength loss of mixes incorporating GPP is about 60% at 800 C. K E Y W O R D Scompressive strength, elevated temperature, ground pumice powder, steel fiber reinforced selfcompacting concrete, UPV

Bu çalışmanın amacı; manyetize edilmiş suyun, lifli ve lifsiz reaktif pudra betonların (RPB) basınç ve eğilme dayanımı üzerindeki etkisini incelemektir. Farklı manyetik alan şiddetleri manyetik su üretimi için kullanılabilmektedir. Bu çalışmada; 0.8-1 ve 1.2 Tesla şiddetindeki üç farklı manyetik alan şiddeti seçilmiştir. Manyetik su üretimi için farklı manyetik alan şiddetlerinde bekletme süresi 20 dakika olarak sabit alınmıştır. Elde edilen sonuçlar incelendiğinde; normal su kullanımı yerine manyetik su kullanımı, 7 ve 28 günlük basınç ve eğilme dayanımlarının artmasını sağladığı görülmüştür. Ayrıca manyetize edilmiş suyun, RPB'lerin basınç ve eğilme dayanımına olumlu etkisi olduğu ve dayanımı artırmak için en verimli manyetik alan şiddetinin 1 Tesla olduğu tespit edilmiştir.