Browsing by Author "Yavuz Bayraktar O."

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Basalt fiber-reinforced foam concrete containing silica fume: An experimental study
(2022-04-04) Gencel O.; Nodehi M.; Yavuz Bayraktar O.; Kaplan G.; Benli A.; Gholampour A.; Ozbakkaloglu T.
Foam concrete refers to a type of low-density concrete that is commonly known to have favorable insulation and thermal performance due to its intentionally increased porosity. However, foam concrete is known to generally have a very low physico-mechanical and durability performance mainly due to its high porosity and the connectivity of the pores that can allow the entrance of unfavorable substances into the concrete medium. As a result, most often, foam concrete is considered inapplicable to major load bearing structural elements. To counter this tendency, this study adopted the use of basalt fibers with silica fume to increase the structural integrity of foam concrete. In that respect, 18 mixes with varying content of foaming agent, basalt fiber and silica fume have been prepared. Apparent porosity, water absorption, compressive, flexural and splitting tensile strength, sorptivity, ultrasonic pulse velocity (UPV), drying shrinkage, freeze–thaw, thermal conductivity, and thermal resistance tests were performed to evaluate the physico-mechanical, durability, and insulation properties of the produced foam concretes. Based on the results, a highly durable foam concrete with a maximum compressive, flexural and splitting tensile strength of ∼ 46, 6.9 and 3.07 MPa, respectively, has been developed. Furthermore, it is observed that the inclusion of silica fume can significantly influence the pore network and enhance fiber-paste matrix. The effect of basalt fiber, however, is found to be more dependent on the use of silica fume, potentially due to its low integration with cementitious paste. The results of this study are significant and point out to the great potential for producing a highly durable and lightweight insulating foam concrete through the use of basalt fiber and silica fume.
Characteristics of hemp fibre reinforced foam concretes with fly ash and Taguchi optimization
(2021-08-02) Gencel O.; Yavuz Bayraktar O.; Kaplan G.; Benli A.; Martínez-Barrera G.; Brostow W.; Tek M.; Bodur B.
This study presents investigation on microstructural, mechanical, durability and thermal characteristics of hemp fibers (HFs) reinforced foam concrete with fly ash (FA) and Taguchi optimization approach. Three series of foam concretes mixtures were produced with foam contents of 50, 75 and 100 kg/m3. There is a reference mixture without HFs and FA. Thus, mixtures contain FA as cement replacement at the concentrations of 0%, 10%, 20%, 30%, 40% and 50%. HFs with varying fiber length were introduced into mixes at concentrations of 0.75%, 1.5% and 3% by weight of cement. Slump test was done to see workability. Compression and flexural properties were determined at 7, 28 and 91 days. Durability was investigated by high temperature, freeze–thaw and sulphate exposures. Thermal conductivity, drying shrinkage, porosity, water absorption and dry unit weight properties of foam concretes were also investigated. Experimental results were analyzed using Taguchi optimization approach. Addition of HFs provides very large compressive and flexural strength enhancements. FA addition reduces the drying shrinkage and thermal conductivity while it increases the high temperature resistance of foam concretes.
Investigation of physico-mechanical, thermal properties and solar thermoregulation performance of shape-stable attapulgite based composite phase change material in foam concrete
(2022-04-01) Gencel O.; Ustaoglu A.; Benli A.; Hekimoğlu G.; Sarı A.; Erdogmus E.; Sutcu M.; Kaplan G.; Yavuz Bayraktar O.
Thermal energy storage (TES) by means of phase change materials (PCM) is of great concern to decrease heating and cooling loads. In building envelopes, one of the most efficient TES methods is integration of PCMs with construction materials for preventing temperature fluctuations by taking advantage of energy storage/release feature of PCMs. Aim of this research was to develop novel foam concretes containing shape-stable attapulgite (ATP) based composite PCM as TES material. Shape-stable ATP/Capric-Myristic acid eutectic mix composite (ATP/C-M) was incorporated into foam concrete at three different ratios (15, 30 and 45 wt%) and characterized. Impacts of ATP/C-M inclusion on physico-mechanic and TES characteristics of foam concretes including composite PCM (FCPCM) were worked systematically. DSC results showed that ATP/C-M composite melts at 22.12 °C with latent heat storage capacity of 74.97 J/g, whereas FCPCM-45 melts at 21.05 °C with latent heat storage ability of 10.98 J/g. Inclusion of ATP/C-M instead of silica sand decreased flow diameter of foam concretes. Compared to reference mixture FCPCM-0, compressive strengths of FCPCM-15, FCPCM-30 and FCPCM-45 samples were reduced in the range of 11–46% while reduction in flexural strength was found to be about 35–57% at 28th day. All FCPCM samples showed lower thermal conductivity values than the specified value and could be defined as better insulation materials. Solar thermoregulation performances of foam concretes containing ATP/C-M were comparatively tested in laboratory and also actual ambient conditions. Results showed that foam concretes with acceptable mechanical properties can be used for internal temperature controlling and energy saving in buildings.
Lightweight foam concrete containing expanded perlite and glass sand: Physico-mechanical, durability, and insulation properties
(2022-02-21) Gencel O.; Yavuz Bayraktar O.; Kaplan G.; Arslan O.; Nodehi M.; Benli A.; Gholampour A.; Ozbakkaloglu T.
Foam concrete refers to a type of concrete with high porosity that can be produced with or without aggregate. Foam concrete has generally superior thermal insulation properties compared to conventional concrete. Despite its major thermal benefits, the high content of Portland cement, as well as its very high porosity, makes foam concrete prone to physico-durability concerns such as drying shrinkage by allowing the entrance of chemicals and free water to the concrete pores. To address this and reduce the pore network connectivity, in this study, expanded perlite and fine-sized waste glass sand were used as the main aggregates in concrete mixes. In that respect, 10 mixes of foam concrete were produced with two foam contents of 50 and 100 kg/m3, with a constant water-to-binder ratio (w/b) of 0.5. In each mix, the dominated expanded perlite aggregate was replaced by waste glass sand having a size of < 2.36 mm. Apparent porosity, water absorption, compressive and flexural strength, sorptivity, ultrasonic pulse velocity (UPV), drying shrinkage, freeze–thaw, alkali-silica reaction, thermal conductivity, and thermal resistance tests were performed to investigate the physico-mechanical, durability and insulation properties of the foam concrete. Based on the results, it is found that the addition of glass sand improves physico-mechanical and durability properties of foam concrete. The addition of expanded perlite increases the insulating properties of foam concrete, potentially due to the high porosity of expanded perlite compared to that of glass sand. The findings of this study point to the suitability of producing sustainable insulating foam concrete through the use of waste glass sand.
Physico-mechanical, durability and thermal properties of basalt fiber reinforced foamed concrete containing waste marble powder and slag
(2021-06-21) Yavuz Bayraktar O.; Kaplan G.; Gencel O.; Benli A.; Sutcu M.
Recently, the usage of industrial wastes for concrete production has played an important role for developing environmentally friendly building materials. This work focused on investigating physico-mechanical, durability and thermal properties of basalt fibers (BF) reinforced foamed concrete containing waste marble powder (WMP) and ground granulated blast furnace slag (GGBFS). Foamed concretes were fabricated with 50 kg/m3 and 100 kg/m3 contents of a protein-based foaming agent at 0.75 water/binder (w/b) ratio. Two control mixtures in which silica sand used as fine aggregates and containing no BF were developed at each foam content. Other foamed mixtures were produced with WMP as fine aggregates and GGBFS as white Portland cement (WPC) replacement at the rates of 0%, 30% and 60%. BF were also added to the mixtures at the rates of 0%, 1% and 2% by weight of cement. Fresh properties of mixtures investigated were slump and fresh unit weight. Experiments were also fulfilled to evaluate 7, 28, 90 and 180-day water-cured mechanical strengths. Porosity, water absorption and sorptivity were studied after 28 aged cured specimens. Dry unit weight, thermal conductivity and drying shrinkage properties of foamed concrete specimens were assessed on 28 aged specimens. High temperature and freeze–thaw durability of foamed concrete specimens were also examined. Results indicated that very high compressive and flexural strength enhancements of 179.49%, 141.79% and 139.91%, 93.18%, at 7 and 28 days were obtained using WMP and BF addition respectively. Coupling use of 30% GGBFS and 1%BF revealed the highest compressive strength of 32.57 MPa and lowest porosity value of 14.8% at foam content of 50 kg/m3.
Physico-mechanical, thermal insulation and resistance characteristics of diatomite and attapulgite based geopolymer foam concrete: Effect of different curing regimes
(2023-04-10) Kaplan G.; Yavuz Bayraktar O.; Bayrak B.; Celebi O.; Bodur B.; Oz A.; Aydin A.C.
This study investigated the physicomechanical, durability and microstructure characteristics of geopolymer foam concrete (GFC) with a unit weight of less than 1500 kg/m3 produced using attapulgite and diatomite. In the blends, as the main binder was used 10, 20 and 40% attapulgite instead of ground blast furnace slag (GBFS). In addition, 30, 40 and 50 kg/m3 foam were used in the blends. Three alternative curing methods were used on GFC: steam (80 °C), water (∼22 °C), and an oven (80 °C). Thermal curing regimens last 24 h at a temperature of 80 °C. The blends’ porosity ranges from 36.8 to 53.3%, while their levels of water absorption range from 32.5 to 49.4%. Unit weights of hardened GFC samples range from 475 to 1226 kg/m3. On the 28th day, after applying the steam curing to blends with a 30 kg/m3 foam dosage, the compressive strength is greater than 5 MPa. After 900 °C heat treatment (elevated temperature effect), a blend with a foam dosage of 30 kg/m3 and 40% attapulgite produced compressive strengths of greater than 4 MPa. The blends’ depths of water penetration range from 22.1 to 27.8 mm. The drying shrinkage of the blends was increased by adding more foam and attapulgite. GFC's thermal conductivity coefficient varies from 0.134 to 0.354 W/m.K. Increasing the attapulgite and foam decreased the thermal conductivity coefficient. Reaction products such as CASH and NASH gels were observed in SEM examinations. As a result, it has been determined that the most suitable results (In terms of physico-mechanical, thermal insulation and strength Properties) can be obtained if steam curing is applied in blends with 20% attapulgite and 30 kg/m3 foam dosage.
The effect of steel fiber aspect-ratio and content on the fresh, flexural, and mechanical performance of concrete made with recycled fine aggregate
(2023-03-03) Yavuz Bayraktar O.; Kaplan G.; Shi J.; Benli A.; Bodur B.; Turkoglu M.
In order to solve the problem of low toughness and easy cracking of recycled aggregate concrete, steel fibers were incorporated to recycled fine aggregate concrete (RAC) to prepare a sustainable fiber-reinforced concrete. Steel fibers of various contents (20, 35, 50 and 65 kg/m3) and aspect ratios (l/d = 40 and 55) were incorporated to the RAC, and their fresh properties, mechanical properties and microstructure were investigated. The results show that the slump of RAC decreases with increasing fiber aspect ratio and content. Meanwhile, incorporating a small amount of steel fibers (l/d = 40, 20 kg/m3) improves the 28-d compressive strength of RAC, but with further increase in fiber aspect ratio and content, the compressive strength of RAC decreases. The incorporation of steel fibers greatly improves the splitting tensile strength and flexural strength of RAC, and the steel fibers with high aspect ratio have a higher gain in strength. The 28-d flexural strength of concrete with 65 kg/m3 steel fibers (l/d = 40) increases by 148.11 % relative to plain RAC, while the 65 kg/m3 steel fibers with an aspect ratio of 55 makes RAC with increases by 243.78 %. The mass loss of fiber-reinforced RAC under abrasion is also lower than that of plain RAC, and the steel fiber with high aspect ratio performs better. For the load–deflection response, the incorporation of fibers increases the peak load, and also increases the flexural toughness and post-cracking toughness, with the greatest gain for high aspect ratio fibers.
The impact of RCA and fly ash on the mechanical and durability properties of polypropylene fibre-reinforced concrete exposed to freeze-thaw cycles and MgSO4 with ANN modeling
(2021-12-27) Yavuz Bayraktar O.; Salem Taher Eshtewı S.; Benli A.; Kaplan G.; Toklu K.; Gunek F.
An experimental study has been conducted to investigate the impact of recycled coarse aggregate (RCA) and fly ash (FA) on the transport, mechanical and durability properties of polypropylene fiber reinforced concretes. In this context, nine concrete mixtures with 25% FA as cement replacement (by wt.) and nine mixtures without FA were produced. RCA was used to replace natural coarse aggregates (NCA) at 0, 25 and 50% by wt. in all concrete mixtures. In addition, polypropylene fiber (PPF) was added to concrete mixtures at 0, 3 and 6% by volume. Mechanical performance was evaluated by compressive, splitting tensile strength at 7, 28 and 90 days and Schmidt rebound hammer at 90 days. Dry bulk density, water absorption, apparent porosity and sorptivity of concrete were also evaluated. Durability performance of concretes was evaluated by exposing to 50,100 and 150 freeze-thaw cycles and MgSO4 attack. Abrasion test on the concretes was also performed. After performing durability tests, compressive, splitting tensile strength, ultrasonic pulse velocity, microstructural observations and mass loss of the concretes were assessed. An artificial neural network (ANN) was also modeled for predicting experimental data. The results indicated that combined use of RCA, FA and PPF improved the compressive strength considerably and approximately 60 MPa was obtained in concretes with 25 and 50% RCA. The use of RCA in concretes with 25% FA has improved the mechanical properties. The mixture with 25% RCA, 6%PPF and without FA and the mixture with 50% RCA, 3%PPF and FA showed the best abrasion resistance. Reference and the mixture with 0% RCA, 25% FA and 6% PPF exhibited the lowest strength loss after the MgSO4 attack. Reference and the mixture with 25% RCA, 25% FA and 3% PPF performed the best after 100F-T cycles in terms of compressive strength. With the Bayesian regularized algorithm, material quantities for the target concrete properties can be obtained. The main outcome of this study is that using RCA, FA and PPF in concrete can give better performance in terms of mechanical and durability performance than normal concrete.
The use of waste marble for cleaner production of structural concrete: A comprehensive experimental study
(2022-12-26) Gencel O.; Nodehi M.; Yavuz Bayraktar O.; Kaplan G.; Benli A.; Koksal F.; Bilir T.; Siddique R.; Ozbakkaloglu T.
Waste marble is a byproduct that is produced as a result of cutting and reshaping marble stone that is commonly used in the construction sector. From a sustainability perspective, waste marble can be a potential alternative to limestone sand with slightly reduced ecological footprint which is aligned with novel concepts, such as circularity of construction industry. To provide a comprehensive outline of marble's use as coarse aggregate in concrete production, this study adopted utilizing waste coarse marble aggregate (WCMA) at a quantity of 50% and 100% to substitute coarse limestone aggregates (also natural coarse aggregate (NCA)). Likewise, since marble stone is considered as a metamorphic rock with slightly different microspores, compared to limestone, three different water-to-cement ratios (w/c) of 0.35, 0.42 and 0.49 have also been used. Results show that concretes incorporating WMCA exhibit a slightly better mechanical performance than concretes incorporating NCA, given that the w/c ratio is enough to lubricate WMCA's surface but not to the point of increasing free water in concrete's microstructure. In other words, it is found that WMCA is relatively sensitive to the mixture's w/c ratio which can have a large impact on the resulting physico-mechanical and thermo-durability properties of the specimens. In this regard, despite the WMCA's slightly enhanced performance in certain thermo-durability tests, the interfacial transition zone (ITZ) areas are found to be more susceptible to deteriorating factors. Nonetheless, the result of this study is found to be significant and point to the suitability of utilizing WMCA as an alternative to NCA.