Browsing by Author "Güneyisi, Erhan"

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Citation - WoS: 3
Citation - Scopus: 2
Recycled polypropylene-based waste as fine aggregate in cement-based composites: Engineering and microstructural properties
(ELSEVIER SCI LTD, 2025) Ghassan Subhi Jameel; Muhammed Tanyildizi; Sueleyman Ipek; Erhan Guneyisi; Esra Mete Guneyisi; Tanyıldızı, Muhammed; İpek, Süleyman; Güneyisi, Erhan; Jameel, Ghassan Subhi
Repurposing plastic-based waste materials offers a promising solution to reduce the consumption of natural resources in construction and mitigate environmental risks. This study explored the potential use of polypropylene-based fine aggregate derived from the crushing of waste chairs as a substitute for natural sand in cement-based composites. A series of physical mechanical and microstructural investigations were conducted on specimens where natural sand was partially replaced with polypropylene-based waste chair (PpWC) sand up to 100 %. Besides a sensitive statistical analysis was performed by establishing a relationship between the experimental results and constructing a Pearson correlation matrix to identify the effect of variables on the measured properties. The test results revealed that increasing the PpWC sand content resulted in lighter mixtures and reduced flowability. Additionally a corresponding increase in both water absorption and void content was observed. The incorporation of PpWC sand into the cement-based composites negatively affected its strength properties. Complete replacement of natural sand with PpWC sand reduced the ultrasonic pulse velocity and thermal conductivity values by approximately 50 % and 80 % respectively resulting in a cement-based composite with enhanced acoustic and thermal insulation properties. SEM analyses revealed that higher PpWC sand content led to more porous less dense and cracked interfacial transition zones which negatively affected the mechanical properties of the composites. Despite its relatively low strength performance PpWC demonstrates significant potential for use in cement-based composites for construction applications primarily due to its favorable unit weight and superior acoustic and thermal insulation properties.
Rubber-Modified Self-Compacting Mortar: Evaluating Setting Time and Strength Development
(Yildiz Technical University, 2025) Süleyman İpek; Navvar Makansi; Erhan Güneyisi; İpek, Süleyman; Makansi, Navvar; Güneyisi, Erhan
The influence of using crumb rubber (CR) obtained from the second scraping of used tires as fine aggregate in manufacturing self-compacting mortar (SCM) was investigated experimentally in this study. To explore this natural fine aggregate in SCM mixes was partially replaced with CR at levels ranging from 5% to 25% by total fine aggregate volume. Two mix series one with a total binder of 500 kg/m3 and the other with a 540 kg/m3 binder were designed at water-to-binder ratios of 0.40 and 0.33. Ordinary Portland cement (80% by weight) and fly ash (20% by weight) were used to manufacture mortars. Twelve SCM mixes were cast and tested to evaluate their fresh-state properties including setting times flow diameter and flow time. Moreover the compressive strengths at 3 7 28 56 and 90 days were determined for each mix to investigate their strength development. The test results indicated that the incorporation of CR adversely affected the fresh properties of the SCM mixes and an increase in the CR replacement level systematically diminished their strength characteristics. Nevertheless it was observed that it could be used in a controlled manner to achieve the desired properties.
Citation - WoS: 4
Citation - Scopus: 4
Studying the metakaolin content- fiber type- and high-temperature effects on the physico-mechanical properties of fly ash-based geopolymer composites
(SPRINGERNATURE, 2024) Baris Bayrak; Haluk Gorkem Alcan; Ozge Cigdem Ozelmaci Durmaz; Suleyman Ipek; Gokhan Kaplan; Erhan Guneyisi; Abdulkadir Cuneyt Aydin; Bayrak, Barış; Kaplan, Gökhan; Güneyisi, Erhan; Özelmacı Durmaz, Özge Çiğdem; İpek, Süleyman; Aydın, Abdulkadir Cüneyt; Alcan, Haluk Görkem; Durmaz, Ozge Cigdem Ozelmaci
The study investigated the physicasl characteristics and mechanical performance of fly ash-based geopolymer composites when exposed to high temperatures. Geopolymer composites were produced using fly ash as an aluminosilicate-rich raw material and a combination of sodium silicate and sodium hydroxide as an alkaline activator. In this context the study also examined the impact of partially replacing metakaolin (7.5% and 15% by weight). Furthermore the study aims to examine the impact of adding fiber (basalt and carbon types) on the physical mechanical and high-temperature properties of geopolymer composites. The physical properties investigated were unit weight apparent porosity water absorption and capillary water absorption while the strength performances investigated were flexural and compressive strengths. To monitor the effect of high temperatures on the strength characteristics of the geopolymer composites the mixtures were exposed to temperatures of 200 degrees C 400 degrees C and 600 degrees C. Besides SEM images were provided to illustrate the degree of geopolimerization. The results indicated that metakaolin replacement yielded mixtures having higher unit weight but lower apparent porosity and water absorption. The results indicated that metakaolin replacement yielded mixtures having a higher unit weight reaching an increase of about 5% but lower apparent porosity and water absorption with decreases reaching 18.3% and 20% respectively. The metakaolin-blended geopolymer composites resulted in better strength performance and resistance to high temperatures. Raising the metakaolin replacement level from 0 to 15% led to an increase of 17.3% in flexural strength. The compressive strength of the composites subjected to a temperature of 200 degrees C exhibited an increase of over 10%. Notably this rate of increment was observed to be nearly 20% higher in nonfibrous composites. Fiber addition decreased the compressive strength up to about 21% while increasing the flexural strength up to 65%. Strength performance improved at 200 degrees C but decreased at higher temperatures up to 600 degrees C. The geopolymer composites experienced significant mass loss when exposed to high temperatures.