Gülnahar, Bedirhan İhsan; Alperen Bulut, H.

The purpose of this study is to examine the durability performance of lightweight polymer concrete produced using natural and expanded perlite aggregates under extreme conditions. Within this scope, the effects of perlite aggregates on both the macroscopic performance and microstructural properties of polyester and vinylester resin polymer concrete matrices have been evaluated in an original manner using a comprehensive and comparative approach. In the experimental study, 5% and 10% by volume of quartz aggregates were replaced with natural and expanded perlite. The durability performance of the produced polymer concrete has been tested under extreme environmental conditions, including exposure to high temperatures (50°C, 100°C, 150°C, and 200°C) and freeze-thaw cycles (up to 300 cycles). Additionally, microstructural analyses were performed using weight loss, compressive strength loss, visual evaluations, and scanning electron microscopy (SEM) to investigate the damage mechanisms. The results obtained show that significant changes occur in the durability performance of polymer concrete under extreme conditions, depending on the type of perlite and the ratio of use. Natural perlite aggregates have demonstrated higher durability and minimal performance loss by providing better adhesion with both resin types. However, the high porosity of expanded perlite increased the permeability of the matrix and caused significant deterioration. Vinylester resin polymer concrete has been found to exhibit superior resistance to both high temperatures and freeze-thaw cycles compared to polyester resin concrete. Among all mixtures, vinylester resin polymer concrete containing 5% natural perlite showed the most stable internal structure with the lowest durability losses. These results reveal that natural perlite, a local and sustainable lightweight aggregate, offers an important alternative for the low-carbon building material concept by enhancing the environmental performance of polymer concrete.

Mayda, Sabire; Turan, Ahmet ihsan

The replacement of conventional aggregate in concrete with alternative and waste-based materials has attracted increasing attention due to growing sustainability and waste management concerns. In this study, the combined effects of natural perlite aggregate replacement and fiber reinforcement on the mechanical and microstructural performance of concrete were experimentally investigated. Accordingly, natural perlite aggregate was used to replace conventional stone aggregate at replacement levels of 0%, 30%, 70%, and 100%. In addition, hemp shives and recycled plastic waste, together with commercially available polypropylene (PP) fibers were incorporated at volume fractions of 0.0%, 0.5%, 1.0%, and 1.5% to evaluate the effects of perlite aggregate replacement and fiber reinforcement on the mechanical performance of concrete. After 28 days of curing, compressive strength, elastic modulus, flexural strength, splitting tensile strength, ultrasonic pulse velocity (UPV), stress-strain behavior and scanning electron microscopy (SEM) analyses were conducted. The results showed that compared with the reference mix, 30% fine perlite replacement increased compressive strength and elastic modulus by ∼6.67% and ∼4.08%, respectively, whereas higher replacement levels (70% and 100%) led to strength reductions of ∼3.51% and ∼9.71% due to the porous structure of perlite and the formation of a weaker interfacial transition zone (ITZ). The optimum ratio for fiber reinforcements was 1.0%, and in terms of fiber type, the highest performance in crack bridging and energy absorption was observed in the PP-fiber-reinforced samples. At higher fiber contents, particularly 1.5%, performance losses were observed due to reduced workability, increased void formation, and the resulting deterioration in matrix continuity. Damage images revealed that, with PP fiber use, a widespread crack pattern containing numerous hairline cracks replaced single and wide cracks. Overall, the findings indicate that using natural perlite aggregate at a 30% replacement level in combination with 1.0% PP fiber reinforcement provides an effective and practical solution for producing low-carbon concrete with balanced mechanical performance.

Çolak, Muhammed Ali; Keleş, Ömer Faruk; Baş, Fatih İrfan; Demi̇ri̇z, Ahmet Oğuz

This study investigates the fracture performance of warm mix asphalt (WMA) mixtures modified with Cecabase RT BIO10 and various recycled concrete aggregate (RCA) proportions using laboratory tests and finite element modeling. Semi-Circular Bending (SCB) tests at –15 °C under Mode I loading were performed to measure fracture toughness (KIC), fracture energy (GF, pre-peak and post-peak), stiffness, and flexibility indices. Unlike many prior studies relying on a single approach, fracture toughness was calculated through all major analytical methods and validated with ANSYS finite element simulations. Results showed that increasing Cecabase content notably improved fracture resistance, while higher RCA levels reduced mechanical properties due to the porous nature of RCA. Fracture energy analysis indicated that post-peak deformation parameters correlated more strongly with GF than stiffness indices, highlighting the importance of ductility in asphalt performance. Correlation analyses revealed tensile strength (TS) and tensile stiffness index (TSI) largely evolve independently from post-peak flexibility indicators such as flexibility index (FI), toughness index (TI), and crack resistance index (CRI). Among mixtures tested, the combination of 0.50 % Cecabase and 10 % RCA exhibited the most balanced performance with high TSI, TS, and GF values. These findings emphasize the need to optimize both additive and RCA content to enhance WMA mixtures’ mechanical integrity and sustainability. The proposed approach offers a practical and environmentally friendly framework for designing durable asphalt mixtures suited to low-temperature pavements.

Ciminli, Ahmet Taha; Bulut, H. Alperen

The interest in perlite is increasing significantly in the construction sector in terms of both energy and material in the construction of efficient buildings. This interest arises from the growing demand for environmentally friendly building materials that can mitigate the environmental impact of high cement production. In order for polymer concretes, which have many advantages over traditional concrete, to help reduce damages under earthquake loads and reduce costs, lightweight polymer concrete production should be done using lightweight aggregates. In this study, a new approach for lightweight polymer concrete production was presented for the first time, and the aim was to determine the effect of the compatibility of natural perlite and expanded perlite aggregates with polyester and vinylester resins on the mechanical performance of polymer concrete. For this purpose, natural and expanded perlites were used as fine aggregate in polymer concretes instead of quartz aggregate at the ratios of 0 %, 5 %, and 10 %. As binder materials, unsaturated polyester resin and vinylester resin were selected. Fresh density, compressive, flexural, and splitting tensile strengths, ultrasonic pulse velocity (UPV), modulus of elasticity, and toughness tests were performed on polymer concretes after 7, 28, and 90 days. Furthermore, scanning electron microscope (SEM) analyses were performed to investigate the changes in the microstructure of the polymer concretes. The compressive, flexural, and splitting tensile strength results of polyester resin polymer concretes produced with 5 % natural perlite aggregate were higher than the control concrete. Very high correlations were found between the strength results of polymer concretes and UPV values for all days. Modulus of elasticity and toughness values of vinylester resin polymer concretes with natural perlite aggregate were higher than those of polyester resin polymer concretes. SEM analysis results and experimental results were consistent with each other. Considering all the experimental results, it was revealed that the ideal perlite type and ratio is 5 % natural perlite aggregate. Unlike the literature, and in a unique way, lightweight polymer concretes with high mechanical performance polyester/vinylester resin, especially with natural perlite aggregate, could be produced with a much lower resin ratio (15 %). Thanks to perlite, more sustainable, environmentally friendly, and energy-efficient lightweight polymer concretes can be produced, offering alternative solutions to traditional construction materials.

Keleş, Ömer Faruk; Bayrak, Osman Ünsal; Bayata, Halim Ferit

Different types of solid waste are generated every year due to global industrialization. With the rapid growth of the automobile industry, the disposal of billions of waste rubbers (WR), which pollute the environment and cannot be disposed of properly, is emerging as an urgent matter of concern. Recycling waste rubbers by using them on pavements will contribute to the elimination of ecological and economic problems. In this study, the effects of waste rubbers on the mechanical properties of roller-compacted concrete pavement (RCCP) were investigated by obtaining sustainable RCCP mixtures using different types of waste rubbers as coarse and fine aggregate substitutes. In this context, waste rubbers with three different sizes (powder, crumb and shredded) were substituted for aggregate by volume at seven levels (0%, 2.5%, 5%, 7.5%, 10%, 20% and 30%) with a maximum of 30% in RCC mixtures. Unit weight, mechanical properties, modulus of elasticity and ultrasonic pulse velocity (UPV) were evaluated and compared according to the waste rubber content in the RCC mixtures. In addition, microstructural analysis of the mixtures was performed through scanning electron microscopy (SEM). The experimental results revealed that the compressive, flexural and splitting tensile strength and modulus of elasticity decreased with increasing waste rubber content in RCC. The utilization of waste rubber increased the ductility of RCC and decreased the density to produce lighter concrete. RCC with a compressive strength of about 30 MPa could be obtained by substituting 10% of waste rubber for aggregate. Thus, the utilization of high waste rubber content in pavements was feasible. This study can contribute to a more sustainable RCCP production by replacing natural aggregates with waste rubbers.

Alperen Bulut, H.; Şahin, Remzi

This study was conducted to investigate the hypothesis that radon gas emanation which is harmful to human health may occur more than standard values in Self-Compacting Concrete (SCC) which has a higher amount of dust material than conventional concretes. The SCCs with 5 %, 12.5 %, and 20 % fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBFS) as well as control concretes without mineral additives were placed closed glass environments with dimensions of 150×150×150 mm; average radon activity concentrations (ARACs) were measured passive method by CR-39 nuclear trace detectors after 7–14-21–28-56–90 and 120 days. Radioactivity analyses including annual effective equivalent dose (AEED) calculation of the concretes were also done. The ARAC values of SCCs increased significantly along with the increase of FA and decreased significantly with the increase of SF. So that the ARAC value (131.56 Bq/m3) of SCC with 20 % FA increased 2.40-fold when compared to the control concrete; however, the ARAC value (14.22 Bq/m3) of SCCs containing 20 % SF was found 4.5-fold lower than the control concrete. 5 % of the concretes containing GGBFS reduced the radon gas emanation; however, the rates of 12.5 % and 20 % increased the emanation. The highest AEEDs for each mineral additive type were 7-day samples including 20 % of FA (8.00 mSv/year), 5 % of GGBFS (3.17 mSv/year) and 5 % of SF (2.16 mSv/year). 12.5 % and 20 % FA-added SCCs emit radon gas above the limit levels. The results have confirmed the hypotheses of the present research depending on the mineral additive type and rate.

Ulusu, Hayati; Yılmaz Aruntaş, Hüseyin; Burcu Gültekin, Arzuhan; Dayı, Mustafa; Çavuş, Murat; Kaplan, Gokhan

Nowadays, it is frequently preferred to use pozzolans instead of clinker to reduce the CO2 emissions that increase with cement production. Because in the future, the release of artificial pozzolans, such as fly ash and blast furnace slag, will decrease. Therefore, the demand for natural pozzolanic cement will increase. This study aimed to produce Portland Pozzolan Cement (PPC) by using pumice instead of clinker up to 40%. The Chemical, physical, mechanical, durability, microstructure, and carbon footprint characteristics of PPCs were investigated experimentally. As the pumice volume in the PPCs increased, the CaO/SiO2 ratio and specific gravity decreased. Due to the hygroscopic moisture of the pumice, its grindability has become difficult. While the 40 µm sieve residue of PPCs ranges from 0.8 to 1.7%, the sieve residue ratio generally increases as the pumice volume increases. The porous structure of pumice led to an increase in Blaine fineness as the replacement ratio increased. The Blaine fineness of PPCs containing 40% pumice rose by about 20% more than the reference cement. The consistency water of PCs varies between 29 and 36%. As the water consistency increased, the setting time of the pastes was prolonged. Initial setting times of PPCs are between 150 and 220 min. If the CaO/SiO2 ratio decreased with the pumice volume, the compression strength of the mortars decreased. While the 28-day compression strength of PPC containing 10% pumice was measured as 36.2 MPa, this value was measured as 21.6 MPa for PPC containing 40% pumice. As the pumice volume increased, the mortars' drying shrinkage and sulfate-induced expansion values decreased significantly. According to the sustainability analysis, the CO2 emissions of cement vary between 518 and 880 kg CO2/t. By using pumice instead of clinker, CO2 emissions of cement can be reduced. In SEM examinations, it was determined that pumice concentrated the microstructure. As a result, it has been determined that eco-friendly cement can be obtained by using 10% and 20% pumice in PPC production.

Keleş, Ömer Faruk; Akpinar, Muhammet Vefa

The curing of roller compacted concrete (RCC) pavements requires much more attention and importance than conventional concrete pavements due to its very dry consistency. This research was conducted to determine the effects of different curing types and their application times on mechanical properties of RCC. In addition, the effects on physical properties of RCC were determined in the study, as well. In the experimental study, 4 different curing types as the curing compound, burlap, membrane and water that have been widely used in the market, were applied for 15, 30, and 60 min and immediately after casting. Compressive strength, flexural strength, weight loss, ultrasonic pulse velocity and rebound hammer tests were applied to determine the physical and mechanical properties of RCC specimens. According to the results, the best curing method for compressive and flexural strengths of RCC was determined as water curing, providing approximately 29% and 34% increase in strength compared to uncured mixtures, respectively. In terms of weight loss, the best result was obtained with water curing, increasing the amount of moisture, unlike other curing methods.

Özkal, Fatih Mehmet; Polat, Mehmet; Yağan, Mahmud; Öztürk, Muhammed Orhan

Fiber reinforced polymer (FRP) rebars have recently been gaining popularity in the construction industry all around the world while steel rebars have been widely used so far. FRP bars, which have higher tensile strength compared to steel rebars with the same nominal diameter under normal conditions, are composed of resin matrix and fibers. In this study, mechanical and bonding properties of glass fiber reinforced polymer (GFRP) and steel rebars subjected to elevated temperature effects were investigated throughout a correlative comparison. Axial tensile tests and pull-out tests of these materials were performed subsequent to exposing them into elevated temperature effects in the range of 23–800 °C. Severe effects on the tensile properties of bare steel bars were observed after 600 °C, while this critical limit is 300 °C for bare GFRP bars. Test results show that bond strength degradation is almost linear for both type of rebars, however, 600 °C is also the critical temperature regarding the serious deterioration on concrete. Additionally, an empirical modeling approach on the bond strength degradation of rebars at elevated temperatures was proposed and it was found that comparison results have quite promising consistency based on the modeling process.

Bicer, Kamil; Yalciner, Hakan; Pekrioglu Balkıs, Ayse; Kumbasaroglu, Atila

An experimental study was performed to investigate the effects of polypropylene fibers on uncorroded and corroded reinforced concrete beams. Three different volume fractions of polypropylene fibers having 0, 0.5, and 1.5%, were tested at four corrosion levels of 0% and approximately 5, 7, and 9%. A full scale of an accelerated corrosion pool was used for the accelerated corrosion process. Reinforced concrete beams were used for an under monotonic bending test. The contribution of the actual corrosion levels of transverse and longitudinal reinforcement bars to the total corrosion levels were obtained from reinforcement bars fully extracted from concrete. Flexural strength, bond-slip, and moment-curvature relationships were examined for uncorroded and corroded reinforced concrete beams. A new model was developed to predict the flexural strength of corroded reinforced concrete beams. The proposed model for predicting the residual flexural strength of corroded beams was compared with test data published in previous studies. Furthermore, a novel model is presented for improved predictions between the actual and theoretically estimated corrosion mass losses, based on Faraday's law, with the aid of fully extracted reinforcement bars. The model used to predict the flexural strength of corroded reinforced concrete beams with large sizes demonstrated good agreement with current and previously published literature data. In the case of corroded beams comprising differing amounts of polypropylene fibers, the performance of the corroded beams was limited by a fiber volume fraction of 1.5% at low corrosion levels.