In this study, the effects of different fibre types on the workability and mechanical properties of self-compacting concrete were investigated. Fresh and hardened properties of self-compacting concrete, different fibre content 0.90, 1.35 and 1.80 kg/m3 were evaluated using basalt, polypropylene and macro synthetic fibres with different fibre lengths of 24, 19 and 40 mm, respectively. The properties of fresh concrete were evaluated in terms of slump flowing, viscosity and flowability. In addition, compressive, flexural and splitting tensile strength were obtained from hardened concrete properties. To characterize mechanical properties 90 specimens were experimentally tested. The results show that the use of fibre reduces the workability of self-compacting concrete. On the other hand, tensile and flexural strength of the self-compacting fibre reinforced concrete increased with increasing fibre content, but it was determined that the fibre addition had no significant effect on the compressive strength.

The cement production process contributes significantly to CO2 gas emissions and environ- mental pollution. To reduce this adverse effect, the substitution of waste marble powder as a cement additive was investigated. In this study, the properties of mortar specimens were analyzed by using waste marble powder as a partial substitute for three different cement types: CEM I 42.5R Ordinary Portland Cement (OPC), CEM II/B-L 42.5R White Cement (WC) and CA-40 Calcium Aluminate Cement (CAC). Waste marble powder has been replaced with ce- ment at 5%, 10%, and 15%. The compressive and flexural strength, capillary water absorption, and sorptivity values of the prepared mixtures were determined before and after freezing and thawing. It was carried out after 28 days of water curing on 50 x 50 x 50 mm specimens for compressive strength and 160 x 40 x 40 mm specimens for flexural strength test. Freeze-thaw testing of the mixture samples was conducted according to ASTM C666 Procedure A. Test re- sults showed that the highest compressive strength before freeze-thaw was obtained in calcium aluminate cement-based mortars containing 10% by weight waste marble powder replacement for cement. The appropriate waste marble powder ratio was determined as 10% in all cement types used in the study. Before freeze-thaw, the mechanical properties of CAC-based mixtures were higher than those of other cement types. However, as the number of freeze-thaw cycles increased, the strength losses were more significant compared to OPC and WC.

The world's largest boron deposits are in Turkey, Russia, and the U.S.A. Türkiye holds about 73% of the world's reserves of oil. The tincal mineral accounts for approximately 25.3% of Türkiye's boron reserves. Annually, around 900,000 tons of boron-derived waste are produced to obtain 1 million tons of borax pentahydrate from the tincal mine. This waste is stored in pools, causing considerable environmental issues. This study investigates the potential use of tincal waste, an environmental problem, in cement and concrete applications. Tincal waste (T.W.) was utilized to produce geopolymer mortar. Geopolymer samples were created by replacing ground blast furnace slag (G.B.F.S.) with 10%, 20%, 30%, and 40% tincal waste (T.W.) by weight. The mixture samples were cured at room temperature and 60 °C. After curing, the samples were exposed to high temperatures of 200 °C, 400 °C, and 600 °C. The samples' unit weight, compressive strength, ultrasonic pulse velocity (U.P.V.), and mass loss values were measured. A mathematical model was also developed to describe the relationship between compressive strength and U.P.V. before and after high temperatures. The samples underwent Fourier Transform Infrared Spectroscopy (FTIR) microstructural analysis. The results showed that using up to 20% T.W. enhanced the properties of the samples before and after high-temperature exposure. A strong correlation was found between compressive strength and U.P.V. These findings suggest that T.W. has potential as a novel material for use in geopolymer technology.