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- MakaleYalnız künye2025Scopus SJRQ1Dunite powder as a green precursor in one-part alkali-activated composites: Effects on mechanical and durability properties
Benli, Ahmet; Bayraktar, Oğuzhan Yavuz; Karataş, Mehmet; Bodur, Burak; Yılmazoğlu, Mehmet Uğur; Kaplan, Gökhan
Natural pozzolans are a sustainable alternative to Portland cement, offering abundant alumina and reactive silica for geopolymer production. Due to their simple extraction methods, they are cost-effective and environmentally friendly. This study explores the utilization of dunite powder (DP) as a sustainable precursor in one-part alkali-activated slag-based composites (AAC), aiming to evaluate its potential to partially replace granulated blast furnace slag (GBFS). The mechanical, fresh, and durability properties of the composites were investigated by varying DP replacement levels (0%, 15%, 30%, and 60%) under an activator dosage of sodium metasilicate, with the mixtures cured at 80 °C for 24 h and subsequently exposed to ambient conditions. The compressive and flexural strengths were evaluated at 7, 28, and 91 days, while the fresh properties (flowability and setting time), durability under sulfate attack, high-temperature resistance, freeze-thaw resistance, dry shrinkage, sorptivity and microstructural characteristics (SEM, XRD, and FT-IR) were also examined. The compressive strength decreased with higher DP content, with the 60% DP mixture showing a 43% strength reduction at 28 days compared to the reference mixture. However, the 30% DP mixture achieved a favorable balance between strength and sustainability, demonstrating a compressive strength decrease of only 11% at 91 days. The mixture containing 15% DP demonstrated the best performance under high-temperature conditions and freeze-thaw cycles. The 60% DP mixture exhibited the highest mass and strength loss when exposed to temperatures above 400 °C and a 15% compressive strength reduction after 120 days of immersion in a 10% MgSO4 solution.
AtıfScopus29OpenAlex22
İncele - MakaleYalnız künye2024Scopus SJRQ1Resistance to magnesium sulphate attack of binary and ternary cementless self-compacting alkali-activated mortar
Şahin Yön, Merve; Karataş, Mehmet
The aim of this study is to investigate the effect of sulphate on self-compacting alkali-activated mortars (SCAAMs) produced using volcanic scoria (V), boron waste (B) and granulated blast furnace slag (G) together with alkali activators. Thus, the production of cement-free alkali-active mortar by recycling waste and reducing the CO2 effect increases the importance of this study. The fact that the waste material is provided free of charge and that V is readily available from nature provides economic advantages in the production of these mortars. In this experimental study, magnesium sulphate solution was utilized to define the sulphate resistance of SCAAMs. In binary SCAAMs, B was used with G in a ratio of NS:NH = 3.0, with an increase from 5 % to 15 %; in ternary mixtures, B was used together with G and V in the same proportions, in a ratio of NS:NH = 1.0. The tests involved immersion in 5 % magnesium sulphate solution for 1, 3 and 6 months. Mass development, compressive strength, visual inspection and microstructural changes were investigated. In general, the binary SCAAMs performed better in magnesium sulphate solution than the ternary SCAAMs, except in the 6th month. Considering the samples with the highest B content, a 100 % loss of compressive strength occurred in the B15G85 sample under the influence of sulphate for 6 months, while a loss of compressive strength of about 15 % occurred in the B15G40V45 sample. The results showed that the increase in B content caused a severe deterioration of the sulphate effect in the samples over time and that the V additive had a positive effect on the sulphate resistance.
AtıfScopus26WoS23OpenAlex19İncele - MakaleAçık Erişim2022Scopus SJRQ1Evaluation of the mechanical properties and durability of self-compacting alkali-activated mortar made from boron waste and granulated blast furnace slag
Yön, Merve Şahin; Karataş, Mehmet
The production of high-strength alkali-activated mortar and concrete by using waste materials instead of cement in order to reduce the amount of carbon dioxide released to nature in cement production is an important study that attracts the attention of researchers. In this study, self-compacting alkali-activated mortar samples were produced using boron waste (BW) and granulated blast furnace slag (GBFS). Prismatic samples of 40 × 40 × 160 mm and cubes of 50 × 50 × 50 mm were produced, in which 0%, 5%, 10%, 15%, 20%, 25% of BW were used. To achieve self-compacting alkali-activated mortar (SCAAM) slump-flow test method was conducted by per The European Federation of Specialist Construction Chemicals and Concrete Systems (EFNARC) guidelines. The samples prepared using Na2SiO3 (NS)/NaOH (NH) = 3.0 were exposed to oven curing at 60 °C and 100 °C for 3 days. The flexural and compressive strength (CS) values of 3, 28 and 90 days were obtained for the samples whose curing period was completed. According to the mechanical strength results, influence of capillary water absorption, porosity, water absorption and density and freeze-thaw from durability tests were carried out. After experimental tests, Scanning Electron Microscope (SEM) and Energy-dispersive X-ray Spectroscopy (EDS) images were utilized to determine microstructures of the samples. As a result of the study, it was determined that the highest strengths were obtained at the curing temperature of 60 °C. Also, it was seen that mechanical strengths and durability decreased with the increase in the BW ratio in the mixtures.
AtıfScopus31WoS28OpenAlex33İncele