Browsing by Author "Atasever, Muhammet"

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Characterization of Limestone Calcined Clay Cement Made with Calcium Sulfoaluminate Clinker
(SPRINGER, 2024) Atasever, Muhammet; Erdoğan, Sinan Turhan; 0000-0001-7375-8152; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Atasever, Muhammet
This study concentrated on producing limestone calcined clay calcium sulfoaluminate cement by replacing portland cement in limestone calcined clay cement with calcium sulfoaluminate cement, with the goal of increasing the early strength of limestone calcined clay cement. The mineralogy and microstructures of hydrating pastes were investigated using x-ray diffraction and scanning electron microscopy. Heat evolution was studied using isothermal calorimetry. Strength development and workability were assessed on mortar samples. The 1 day strengths of limestone calcined clay calcium sulfoaluminate cement samples exceeded those of limestone calcined clay cement by ~ 30–80%, though its strength gain slows significantly after 1 day due to the lack of calcium silicates, affecting pH and clay dissolution. Despite this, the strength development of limestone calcined clay calcium sulfoaluminate cement, when adjusted for CO2 emissions, is comparable to limestone calcined clay cement. Additionally, limestone calcined clay calcium sulfoaluminate cement provides a 10–15% higher flow and exhibits a lower heat of hydration beyond 12 h, while maintaining a production cost similar to that of limestone calcined clay cement.
Determining datum temperature and apparent activation energy: an approach for mineral admixtures incorporated cementitious systems
(Tulpar Academic Publishing, 2024) Atasever, Muhammet; Tokyay, Mustafa; 0000-0001-7375-8152; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Atasever, Muhammet
The maturity method is used to predict the strength of concrete by monitoring its temperature history. Accuracy of maturity method relies on the dependable determination of the datum temperature and the apparent activation energy. The current study introduces a new approach, complementing those in ASTM C1074-11, for determining the datum temperature and apparent activation energy. The experimental study involved using two different mineral additives to portland cement at 6%, 20%, and 35% replacement amounts. The mortars were then cured at temperatures of 5, 20, and 40 °C, and their strengths were determined. Subsequently, the datum temperatures and apparent activation energies for these mixtures were calculated using both the proposed approach and the alternatives from ASTM C1074-11. Strength estimations were conducted in conjunction with commonly used maturity functions. The results indicate that the proposed approach determines the datum temperature and apparent activation energy reliably for mineral admixture-incorporated mortars. Furthermore, the predicted strengths, derived from the datum temperature and apparent activation energy calculated through the proposed approach, show a closer alignment with the experimental results when applying the Nurse-Saul and HansenPedersen equations, as opposed to the Rastrup and Weaver-Sadgrove models
Effects of clay type and component fineness on the hydration and properties of limestone calcined clay cement
(SPRINGER NATURE Link, 2024) Atasever, Muhammet; Erdoğan, Sinan Turhan; 0000-0001-7375-8152; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Atasever, Muhammet
Limestone calcined clay cement (LC3) is emerging as an alternative to Portland cement, offering economic advantages, reduced CO2 emissions, and mechanical properties on par with Portland cement. Central to the effective utilization of LC3 is understanding how the fineness of its components affects its performance. The current study investigates limestone calcined clay cement mixtures composed of kaolinite, illite, and montmorillonite calcined clays and limestone at two levels of fineness. Strengths of mortar cubes were tested at 1, 3, 7, and 28 d and statistical analysis was performed with a 95% confidence level. Additionally, LC3 pastes were analyzed using x-ray diffraction, mercury intrusion porosimetry, scanning electron microscopy, and isothermal calorimetry. The fineness of the calcined clay along with the fineness of limestone is found to be statistically significant for 28-d strength in LC3 mortars made with kaolinitic and montmorillonite calcined clays. All hydrated blends had a hemicarboaluminate phase, whose intensity was related to the fineness of the calcined clay, and the monocarboaluminate phase formation was found to be dependent on both the fineness and type of calcined clay. Porosimetry revealed that LC3 pastes with illite clay have larger threshold pore diameters than those with kaolinite clay. LC3 pastes containing kaolinite have denser microstructures due to C–S–H and hemicarboaluminate formation. Pastes produced with coarse calcined clay and coarse limestone led to a broader, weaker heat development peak and lower normalized cumulative heat. LC3 with kaolinitic clay has the highest normalized cumulative heat, while that with montmorillonite calcined clay has the lowest. Graphical abstract: (Figure presented.)