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- ArticleAçık Erişim2025Investigation of the Mechanical Properties of Self-compacting Concretes Containing Mineral Additives Produced by Substituting Fine Recycled Aggregate in Different Rates
Kandil, Ufuk; Erdoğdu, Şakir
In the study, the effect of fine recycled concrete aggregate (FRCA) replaced by natural fine aggregate on some mechanical properties of self-compacting concrete (SCC) containing different types and amounts of mineral additives was evaluated. In the concretes produced for this purpose, natural fine aggregate was replaced with FRCA at the ratios of 35%, 70% and 100% by weight. For comparison, concretes without FRCA were also produced. Three different mineral additives, namely fly ash (FA), metakaolin (MK) and silica fume (SF), were used in different ratios. In order to determine the fresh state properties of concretes, unit weight, slumpflow, T500 time, J-ring and sieve segregation tests were carried out, while compressive strength, splitting tensile strength, flexural strength, Böhme abrasion and dynamic elasticity modulus determination tests were carried out on hardened concretes. Based on the findings obtained, there is no significant adverse effect on the mechanical properties of concrete with 35% FRCA replacement. However, when FRCA is used at higher ratios, the negative effect on mechanical properties becomes evident. In particular, Böhme abrasion is quite high at high FRCA replacement ratios. Provided that the conditions in which the research was carried out are valid, the negative effects of FRCA substitution on the mechanical properties of concrete can be eliminated by changing the type and combination ratios of mineral additives used.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024The Effect of Different Proportions of Waste Rubber Substitution on Alkali-Silica Reaction and Mechanical Properties in Mortars
Kandil, Ufuk; Bulut, H. Alperen
This study investigates the alkali-silica reaction (ASR) and mechanical properties of mortars containing crumb and powder rubber instead of river sand. In this regard, mortars were produced using waste rubber whose ratios in the mixture are 0%, 3%, 6%, 9%, 12%, 15%, 18%, and 21%. ASR expansion, compressive and flexural strength tests were conducted on the samples. ASR measurements were performed on days 3, 7, 14, 21, and 28. Besides, at the end of the ASR experiment, the microstructures of the mortars were examined using scanning electron microscope (SEM) images. Examining the results of this study reveals that the use of waste rubber in rising portions in the mortars led to an increase in the ASR expansions of the mortars. The study shows that the ASR expansions of the mortar samples that have 9% and 15% waste rubber replacement are comparatively higher than the other mortar samples. Furthermore, the results of the SEM analysis verified this finding. The study demonstrates that 3% of waste rubber mortar samples have the highest compressive and flexural strengths. On the other side, the ASR expansion of the mortars with 3% substituted waste rubber was considerably low compared to other mortars containing waste rubber. These findings (ASR, compressive and flexural strength tests results) show that using 3% waste rubber is ideal for producing mortars and supports a sustainable production approach in the sector.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Mechanical properties of cement-based composites incorporating eco-friendly aggregate of waste rubber
Bulut, H. Alperen; Kandil, Ufuk
The purpose of this study is to evaluate the waste tires that harm the environment as aggregate in concrete and to examine the effect on the mechanical properties of concrete. Three different classes (powder, crumb and chips) of waste rubber with seven different ratios (0%, 4%, 8%, 12%, 16%, 20% and 24%) and two different water to cement ratio (0.4 and 0.5) were used in concrete production. In this regard, this study conducted various experiments consisting of 28 and 90 days of the curing process to determine the properties of unit weight, compressive, flexural, and splitting tensile strength, along with ultrasonic pulse velocity (UPV) and dynamic modulus of elasticity. The waste rubber concrete with the highest compressive strength at the end of 90 days is the concrete that includes 4% waste rubber (0.4WR4) with 58.81 MPa. Concrete containing 8% waste rubber has the highest UPV of 5660 m/s after 90 days. The increase in the water/cement ratio from 0.4 to 0.5 and the waste rubber ratio cause deterioration in the mechanical properties of concrete. Although the use of waste rubbers does not bring an increase in strength, it is feasible to produce high strength concretes with 4% and 8% waste rubber substitution ratios. The water/cement ratio and curing time were highly effective on the mechanical properties of rubberized concrete.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024Examination of the permeability of rubberized concrete with different water/cement ratios and their resistance against acid and sulfate attack
Kandil, Ufuk; Bulut, H Alperen
This study aims to examine the permeability and acid and sulfate attack of waste rubber-substituted concrete containing recycled rubber in three different grain size classes (chips, crumb and powder) with two different water/cement (w/c) ratios (0.4 and 0.5). Waste rubber at different ratios (0%, 4%, 8%, 12%, 16%, 20%, and 24%) was used in concrete by replacing fine and coarse aggregates. Sorptivity, electrical resistivity, and acid and sulfate attack tests were conducted on concrete cured for 90 days. Although the capillarity coefficient values increased with the waste rubber replacement ratio increase, a decrease occurred after the 20% waste rubber replacement ratio. In 12% waste rubber-substituted concrete (0.4WR12) with a water/cement ratio of 0.4, the electrical resistivity value (8.3 kΩ.cm) was the highest, and concretes with low permeability could be produced. As a result of the use of 16% waste rubber in the concrete, 75% less compressive strength loss was observed after the acid attack compared to the control concrete. In concrete with a water/cement ratio of 0.5, when the waste rubber ratio increased by up to 16%, the compressive strength losses caused by the sulfate attack decreased dramatically (95.76% less) compared to the control concrete. The rubberized concrete with a water/cement ratio of 0.5 showed high resistance to acid and sulfate attacks. The experiment results showed that 12% to 16% waste rubbers are ideal ratios. In this study, the water/cement ratio was a valuable parameter for the waste rubber ratio in rubberized concrete.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2020EVALUATION OF THE DEPENDENCY OF THE COMPRESSIVE STRENGTH OF CONCRETE ON THE CORE DRILLING DIRECTION THROUGH ANOVA TEST
Erdoğdu, Şakir; Nayir, Safa; Kandil, Ufuk; Kurbetci, Şirin; Nas, Memduh
Determination of the compressive strength of concrete in existing reinforced concrete structures is important, particularly in some cases. Destructive and non-destructive test methods are used to determine the compressive strength in such structures. Amongst these, coring is the most widely used method as a destructive method in determining the compressive strength in existing reinforced concrete structures. However, even though numerous studies have been carried out on the variation of the determined compressive strength depending on the coring direction, the discussions continue. In this study, concrete blocks containing fly ash (FA) and silica fume (SF) and aggregates of different maximum sizes were produced. In the mixtures, cement was replaced by fly ash at ratios of 20%, 40%, and 60% and silica fume at ratios of 5%, 10%, and 15%, respectively. Two aggregates with the maximum aggregate sizes of 16 mm and 31.5 mm were used in the production of the concrete blocks. The concrete blocks were kept in a laboratory by covering them with burlaps moistened intermittently for 28 days and then cores of 10 cm diameter were taken and cut to have 20 cm height then capped and tested to determine compressive strength. Core drilling was carried out parallel and perpendicular to the casting direction and then the compressive strengths were determined. Cubes of 15 cm were also prepared and tested to determine the compressive strength level of concrete and to make comparisons accordingly. The compressive strength of mineral-added core samples taken parallel to the casting direction is higher than those of taken perpendicular to the casting direction, in all mixtures. The ANOVA test applied on the results obtained, it was found that the maximum aggregate size (Dmax) and the core drilling direction with respect to casting direction is statistically significant in terms of the compressive strength of concrete produced using fly ash and silica fume at certain substitution ratios.
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