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- MakaleAçık Erişim2026Thermochemical Activation of Lightweight Slag–Perlite Alkali-Activated Slag (AAS): Overcoming Aggregate Brittleness and Sulfate Degradation
Eker, Hasan; Demir Şahin, Demet
The successful realization of a circular economy in the cement industry, coupled with a substantial reduction in carbon emissions, relies on the development of sustainable alternative binder systems. This study investigated the physicomechanical performance and sulfate resistance of composites produced by alkali activation of natural perlite and blast furnace slag. The aim of the research was to improve mechanical properties under low- and medium-alkalinity conditions (5–10 M NaOH). The samples were cured at an ambient temperature of 20 °C and then treated with heat at 60 °C. These samples were then mechanically processed and subjected to five soak–dry cycles in 5% and 10% Na2SO4 solutions. The results showed that heat treatment resulted in the formation of a dense C-A-S-H gel, increasing compressive strength approximately eightfold, from 11.64 MPa to 92 MPa. However, perlite’s porous and brittle structure limits its flexural strength to 0.27 MPa; this value is insufficient for structural applications. Under severe sulfate attack (10% Na2SO4), samples cured at ambient temperature showed a 12% mass increase in the first cycle due to solution infiltration into capillary voids. As a consequence of extensive ettringite and gypsum formation, the specimens experienced severe deterioration, resulting in a complete loss of mechanical integrity and a residual compressive strength of 0 MPa. In contrast, heat-treated samples showed limited ion diffusion due to a denser matrix and an improved aggregate interface transition zone, resulting in a 2.6% mass increase and a residual compressive strength of 5.17 MPa. Consequently, the obtained findings indicate that thermally treated alkali-activated slag–perlite composites exhibit high resistance against sodium sulfate attack and may have potential for use in specific industrial environments with high sulfate concentrations. However, the performance of these materials under more complex aggressive conditions, such as mining environments involving magnesium sulfate exposure and acidic drainage waters, should be further validated through future studies.
- MakaleAçık Erişim2025THE REGRESSION ANALYSIS AND DETERMINATION OF MECHANICAL AND PHYSICAL PROPERTIES ON GEOPOLYMER COMPOSITES UNDER THERMAL AND WATER CURING
Cavdar, Ozlem; Temizer, Hulya
Increasing costs due to high energy consumption and the release of harmful CO2 gases in cement production have made it necessary to explore alternative binders. This study aims to investigate the physical and mechanical properties of geopolymer mortars containing different proportions of pozzolanic wastes under different cure conditions. For this objective, fly ash obtained from the Sivas/Turkey thermal power plant and blast furnace slag obtained from the Bolu/Turkey iron-steel industries were used as the binding materials. Thermal curing and water curing were applied, and three different molar ratios (8M, 10M, 12M) of NaOH solution and Na2SiO3 were used. The results showed that the reaction products, types of alkaline activators, and reaction conditions are important factors in geopolymer mortars. The highest compressive strength recorded was 84.7 MPa in the geopolymer sample which consisted of 95% blast furnace slag blast furnace slag and 5% fly ash fly ash. Furthermore, two different binder additives (marble powder and strontium) were used and their time-dependent effects on the main binder were analysed. In addition, according to the ANOVA statistical results, the R2 value of the independent variables (Molarity, main binder ratios) on the compressive strengths accepted as the dependent variable is 81.7%. The significance value is 0.007, and these results were considered quite significant.
- MakaleAçık Erişim2024Performance of different fibre types in alkaline-activated concrete produced with industrial wastes: volcanic rock powder and blast furnace slag
Aksüt, Yavuz Selim; Külekçi, Gökhan; Çullu, Mustafa; Yetgin, Şükrü
The objective of the study is to determine the effects of different fibre types and ratios on the mechanical and physical properties of alkali-activated concrete (AAC) and to optimise important properties such as workability, unit weight, water absorption, compressive strength, modulus of elasticity and abrasion resistance of these concretes. Concrete samples were produced using steel and polyester fibres at ratios of 0.25%, 0.50%, 0.75% and 1%. The fibre ratios were varied, and various tests were conducted to determine the mechanical and physical properties of the concrete samples. The experiments clearly revealed the effects of fibre types and ratios on the performance of concrete. These results clearly demonstrate the effects of different fibre types and ratios on the mechanical and physical properties of AACs. Particularly noteworthy is the water-retaining property of polyester fibres, their effect on workability and their enhancing effect on abrasion resistance. The effects of steel fibres on compressive strength and modulus of elasticity are more pronounced, but they may present disadvantages in terms of workability and abrasion resistance. It is observed that mixed fibre usage provides a good balance in some properties. This study provides a roadmap for evaluating sustainable material options in the concrete industry and guiding future research.
- MakaleYalnız künye2024INVESTIGATION OF THE EFFECTS OF VARIOUS OPERATING PARAMETERS ON GEOPOLYMER MORTARS MADE FROM NATURAL MINERALS AND INDUSTRIAL WASTE MATERIALS
Temizer, Hülya; Çavdar, Özlem
In this study, fly ash (FA) from Sivas/Kangal thermal power plant and blast furnace slag (BFS) from Bolu cement industry were used as the main binder materials. Based on both the literature and preliminary tests, samples were prepared with 85% blast furnace slag and 15% fly ash (85BFS15FA) as the main binder. In addition, the effect of geopolymer main binders and different additives such as mine waste, marble powder, and titanium dioxide were evaluated under various working conditions. The aim was to observe the effect of three different levels and 6 different parameters on the geopolymer samples using the Taguchi optimization method. Accordingly, the L27 orthogonal matrix was created. Three different molar ratios (8M, 10M, 12M) of sodium hydroxide (NaOH) solution and sodium silicate (Na2SiO3) solution were used as alkaline activators. Physical and some mechanical tests such as flexural strength, compressive strength, water absorption, and void ratio were performed on the 7, 28, 56, and 90-day samples, and Taguchi and ANOVA statistical analyses were performed on the 90-day samples. The highest compressive strength observed among 108 samples reached 65.75 MPa in the S20 samples (90-day). Taguchi and ANOVA statistical analyses identified curing temperature as the most significant parameter influencing the geopolymer samples. Additionally, the Signal to Noise ratio data indicated that the optimal curing temperature, determined to be the most effective based on the 'Larger is better' criterion, was found to be 75 ̊C.