Browsing by Author "Bayraktar O.Y."

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Basalt fiber reinforced foam concrete with marble waste and calcium aluminate cement
(2023-02-01) Bayraktar O.Y.; Yarar G.; Benli A.; Kaplan G.; Gencel O.; Sutcu M.; Kozłowski M.; Kadela M.
As a typical cellular lightweight material, foam concrete is produced by mixing cement, water, aggregate and a suitable foaming agent and has a density usually below 1600 kg/m3. The large number of air spaces present in foam concrete ensures that the concrete has advantages such as lightweight, high fluidity during pouring, excellent thermal and sound insulation, superior fire resistance, and outstanding energy absorption capacity. Its high porosity and the connectivity of the pores, which can allow the entry of negative substances into the concrete environment, cause foam concrete to have a very low physico-mechanical and durability performance. To eliminate or reduce these disadvantages, this study adopted the use of basalt fibers (BF) as eco-friendly fiber type and calcium aluminate cement (CAC) as aluminous cement with waste marble powder (WMP) as aggregates in foam concrete. In that respect, 9 mixes with varying content of foaming agent (FC) and basalt fiber have been prepared. Assessment of mechanical performance was based on compressive and flexural strength after 6 h, 1, 7, and 28 days. Dry bulk density, thermal conductivity, porosity, water absorption, and sorptivity of the concretes were determined. Durability characteristics of the concretes were examined by dry shrinkage, high temperature, magnesium sulfate, sulfuric, and hydrochloric acids. The obtained results showed that the content of BF affected the compressive strength of the mixtures slightly negatively or positively depending on the FC. The lowest value in thermal conductivity was gained as 0.645 (W/m K) for the mixture incorporating 1% BF and 50 kg/m3 foam quantity. In addition, the foam concrete incorporating foam of 30 kg/m3 and 1% BF showed the best resistance against MgSO4. The mixture with 2% BF and 30 kg/m3 FC exhibited the lowest mass loss after HCI exposure.
Characteristics, energy saving and carbon emission reduction potential of gypsum wallboard containing phase change material
(2022-11-25) Yaras A.; Ustaoglu A.; Gencel O.; Sarı A.; Hekimoğlu G.; Sutcu M.; Erdogmus E.; Kaplan G.; Bayraktar O.Y.
Phase change materials (PCM) used in the development of building materials with thermal energy storage (TES) capacity can minimize temperature fluctuations by reducing the heating and cooling load in building envelopes due to their energy storage/release properties. The present study aims to produce, characterize and measure energy performance under real weather conditions of novel gypsum wallboard containing shape-stable attapulgite (ATP) based composite PCM as TES material. Shape-stable composite PCM was prepared by impregnating 1-Dodecanol (DD) into attapulgite (ATG) and then incorporated with gypsum in volume fraction of 25 and 50 %. The impacts of the shape stable ATG/DD composite PCM additive on the thermo-physical and mechanical properties were systematically assessed. The DCS measurements revealed that the shape-stable ATG/DD composite melts at 20.06 °C with a melting enthalpy of 115.9 J/g while the gypsum/shape-sable ATG/DD (50 v/v%) melts at 20.03 °C with melting enthalpy of 20.06 J/g. Thermoregulation tests demonstrated that the indoor temperatures of the test room made by gypsum/shape-stable composite PCM were about 1.2 °C–2.66 °C warmer than that of the reference gypsum room for about 6–12 h in a cold weather. Theoretical calculations showed that the thermal enhanced gypsum wallboard, because of its TES capability, has a favorable future in terms of energy savings and low CO2 emission.
Development, characterization, and performance analysis of shape-stabilized phase change material included-geopolymer for passive thermal management of buildings
(2022-12-01) Gencel O.; Harja M.; Sarı A.; Hekimoğlu G.; Ustaoğlu A.; Sutcu M.; Erdogmus E.; Kaplan G.; Bayraktar O.Y.
The cooperation between phase change materials (PCMs) and geopolymer (GP) is energy-efficient way for improving the thermal performance of construction materials. This study discusses the effect of PCM combination with GP matrix on obtained concretes' mechanical and thermal properties. Attapulgite/lauric-capric acid eutectic mixture (ATP/LCEM) composite was fabricated as shape-stable composite phase change material (SSPCM) and then integrated with GP concrete (GPC) for improvement of the thermal mass of buildings. Thermal, mechanical, physical, morphological, thermal energy storage (TES) characteristics, and solar thermoregulation performances of the developed GPC-SSPCMs were experimentally characterized. The compressive strength was found over 6 MPa for GPC without aggregates (only SSPCM). The compressive and flexural strengths were relatively low, but above the requirements of the current standards. Other properties as thermal conductivity and solar performance make the produced GPC-SSPCMs promising materials for advanced TES applications in buildings. The apparent porosity was around 45% for GPC-SSPCM-50 and 63% for GPC-SSPCM-100, while water adsorption around 21% for GPC-SSPCM-50 and 30% for GPC-SSPCM-100. Thermal conductivity values of 0.375 W/mK for GPC without aggregates recommended this material as an insulator. The produced SSPCM composite melts at 19.00°C with corresponding latent heat of 73.9 J/g, while the GPC-SSPCM melts at 18.30°C with corresponding latent heat of 6.57 J/g. Based on the obtained outcomes, the energy-saving was determined as 5.56 kWh, which is corresponding to the CO2 saving of 15 kg-CO2, 14.68 kg-CO2, and 2.41 kg-CO2 in case of using coal, natural gas, or electricity, respectively as energy source.
Effect of cement clinker type, curing regime and activator dosage on the performance of one-part alkali-activated hybrid slag/clinker composites
(2023-06-01) Turkoglu M.; Bayraktar O.Y.; Benli A.; Kaplan G.
One candidate for a novel binder is alkaline hybrid cement, which has more than 70% supplemental cementitious materials (SCMs) and a trace amount of an alkali activator but less than 30% Portland cement. This cementitious material offers high early strength, a more compact microstructure, and outstanding resistance to chloride penetration and sulphate attack, in addition to the benefits of alkali-activated materials (AAMs) and Portland cement. This study presents the findings of an experimental investigation that aims to clarify the effect of cement clinker type, curing regime, and activator dosage on the fresh, mechanical, durability, and microstructure properties of one-part alkali-activated hybrid slag/cement clinker composites (AAHC). Flow diameter, setting time, compressive strength, dry unit weight, flexural strength, drying shrinkage, sorptivity, and transport properties were evaluated. It was also aimed to investigate its effectiveness at high-temperatures, sulphate exposure, alkali-silica reaction (ASR), and freeze-thaw (F-T) cycles. A total of twelve AAHC mixtures were made with two GBFS/Clinker ratios of 70/30 and 90/10 and an external addition of 10% and 20% one-part alkali activator. Three cement clinker types and three curing regimes were adopted including oven, water, and steam. The results indicated that the water-cured mixture with GBFS/C3 ratio of 90/10 and activated by 20%MS had the greatest compressive strength of about 65 MPa. Steam and oven-cured mixtures with GBFS/C3 ratio of 90/10 and activated by 10%MS performed the best high-temperature resistance. The same mixtures cured in steam also had the best F-T resistance.
Effect of cement dosage and waste tire rubber on the mechanical, transport and abrasion characteristics of foam concretes subjected to H2SO4 and freeze–thaw
(2021-10-04) Bayraktar O.Y.; Soylemez H.; Kaplan G.; Benli A.; Gencel O.; Turkoglu M.
This paper presents an experimental study of the effects of cement dosage and waste tire rubber as aggregate on the mechanical, transport and abrasion characteristics of foam concretes subjected to H2SO4 and freeze–thaw cycles. Foam concrete mixtures were made with two percentages 0, and 20 of silica fume (SF) as partial substitution of Portland cement (PC) and with 100% of waste tire rubber (WRA) as substitution of fine aggregates. Two groups of mixtures were prepared with SF contents of 0% and 20%. At each group of mixtures, three cement contents of 300, 400 and 500 kg/m3 and three foam contents of 20, 40 and 60 kg/m3 were used to produce concretes mixtures having water/binder (w/b) ratio of 0.75. Workability of fresh concretes were assessed by performing slump test. Compressive and flexural strength of the mixtures were determined after 7 and 28 days and transport properties were measured by means of porosity and water absorption after 28 days. Tests for shrinkage, sorptivity, abrasion, acid attack and freeze–thaw cycles of 30 and 60 were also performed in addition to microstructure investigations. An optimization was also performed. The results exhibited that increase in cement dosage resulted in the compressive strength by 204.50% maximum increment at cement content of 500 kg/m3 as compared to the mixture with dosage of 300 kg/m3 at foam content of 20 kg/m3. Based on the results, it was concluded that the lowest and highest shrinkage values of 5032 × 10−6 and 7065 × 10-6 mm/mm were gained for the mixtures with cement dosages of 300 kg/m3 and 500 kg/m3 and foam content of 20 kg/m3 respectively. The results also indicated that SF blended mixture with cement content of 500 kg/m3 foam content of 20 kg/m3 showed the best resistance after abrasion, F-T cycles and acid attack exposure.
Effect of high volume fly ash and micro-steel fiber on flexural toughness and durability properties in self-compacting lightweight mortar (SCLM)
(2021-11-08) Kaplan G.; Bayraktar O.Y.; Memis S.
In this study, high volumes of fly ash and micro-steel fiber were used to improve lightweight aggregate mixes' strength and durability properties that can be used in the prefabrication industry. The developed composite can be used in roof truss flooring of steel structures and bridge decks. Although the unit weight of the mixtures was reduced below 2000 kg/m3, micro steel fibers were used to improve the behaviour against seismic effects. The increase in fly ash content increased the porosity, water absorption, and water penetration depths of the mixes. The increase in the steel fiber content created a micro-filter effect, reducing the water absorption and water penetration depths. The hardened unit weights of the mixes vary between 1305–1723 kg/m3, while their 91-day compressive strength varies between 30.9 and 46.4 MPa. It has been observed that the mixes using steel fiber are in the medium and good class in the residual strength factors specified in ASTM C 1018. The carbonation depth of the mixes using 50% fly ash increased more than 5.5 times compared to the reference mix. After the freeze–thaw effect, spills occurred on the surfaces of the mixes due to fiber corrosion.
Effect of using wastewater from the ready-mixed concrete plant on the performance of one-part alkali-activated GBFS/FA composites: Fresh, mechanical and durability properties
(2023-10-01) Bodur B.; Bayraktar O.Y.; Benli A.; Kaplan G.; Tobbala D.E.; Tayeh B.
Water scarcity is the world's most pressing issue, as concrete batching facilities and concrete mixer trucks produce massive amounts of wash water every day. Recycling waste water from ready-mix concrete factories' concrete washing water is critical for conserving hundreds of millions of tons of water and preventing water and soil contamination. This study examined the impact of waste washing water on the microstructural, durability, fresh, and mechanical characteristics of one-part alkali-activated ground blast furnace slag (GBFS)/fly as (FA) composites (AAC) containing partial and complete replacement of tap water under ambient conditions. GBFS was used as the main binder in the production of AAC. FA was also used as a binder at 0%, 25%, and 50% instead of GBFS. Sodium metasilicate (MS) was used as a one-part activator at two dosages 7.5% and 15% of the total binder. The fresh properties (setting time and flowability), physical properties, compressive and flexural strength (3, 7, 28, 90, and 180 days) and durability (high-temperature resistance, freeze, and thaw resistance, drying shrinkage, sorptivity, HCl and MgSO4 resistances, NaCl effect and alkali-silica reaction) and microstructure analysis were investigated. The findings showed that the use of wastewater (WW) instead of tap water (TW) contributed positively or had no serious negative effect on the mechanical and durability properties of AAC. Compressive strength of 72.37 MPa and 81.67 MPa was gained with the inclusion of 50%WW at 7.5 and 15 %MS content respectively. The findings showed that WW improved the workability of fresh ACC containing FA, reduced dry shrinkage and sorptivity of ACC with 15%MS content, and refined the pores of hardened ACC. The results also supported that WW contributed to the decrease in expansion due to ASR and sulfate expansion. Using WW improved the high temperature and F-T resistance of ACC mixtures containing 15%MS content.
Effect of waste marble powder and rice husk ash on the microstructural, physico-mechanical and transport properties of foam concretes exposed to high temperatures and freeze–thaw cycles
(2021-07-12) Gencel O.; Benli A.; Bayraktar O.Y.; Kaplan G.; Sutcu M.; Elabade W.A.T.
An experimental program was performed to evaluate the impact of rice husk ash (RHA) as cement replacement and waste marble powder (WMP) as sand replacement on the microstructural, mechanical and transport properties of foamed concrete exposed to high temperature and freeze–thaw cycles. For this, Portland Cement (PC) was replaced by RHA at 10% and 20%wt of binder and silica sand was replaced by WMP at 25% and 50%wt of fine aggregates to cast foamed concrete mixtures. Two different foam contents of 40 kg/m3 and 80 kg/m3 were used in the production of foamed concretes with water/binder (w/b) ratio of 0.70. Two reference mixtures were produced from silica sand and without RHA at each foam content. Other foam concretes were fabricated from 25% and 50% WMP instead of silica sand and 10% and 20% RHA instead of cement. Fresh properties of mixtures were evaluated by performing slump test. Transport properties of foam concretes were investigated, including porosity, sorptivity and water absorption after 90 days curing. Mechanical properties of foam concretes were investigated, including compressive and flexural strength ultrasonic pulse velocity (UPV) after 7, 28 and 90 days. Drying shrinkage and thermal conductivity of concretes were also studied after 90 days. Durability of concretes were also investigated after exposure to the temperature of 200, 400, 600 and 800 °C and freeze–thaw (F-T) cycles of 100 and 200 in addition to microstructure investigations. Results show that 10% RHA as cement substitute and 50% WMP as sand substitute give optimum percentage especially at late-age of 90 days at foam content of 40 kg/m3. The lowest drying shrinkage and sorptivity were obtained by using 10%RHA and 25%WMP. The results also indicate that water cooled specimens showed more strength loss than air cooled specimens after 200 °C. The worst F-T performance was obtained for the mixture containing 10% RHA and without WMP by 43.8 and 59.8% strength reductions.
Foam Concrete Produced with Recycled Concrete Powder and Phase Change Materials
(2022-06-01) Gencel O.; Nodehi M.; Hekimoğlu G.; Ustaoğlu A.; Sarı A.; Kaplan G.; Bayraktar O.Y.; Sutcu M.; Ozbakkaloglu T.
In construction industry, phase change materials (PCMs), have recently been studied and found effective in increasing energy efficiency of buildings through their high capacity to store thermal energy. In this study, a combination of Capric (CA)-Palmitic acid (PA) with optimum mass ratio of 85–15% is used and impregnated with recycled concrete powder (RCP). The resulting composite is produced as foam concrete and tested for a series of physico-mechanical, thermal and microstructural properties. The results show that recycled concrete powder can host PCMs without leaking if used in proper quantity. Further, the differential scanning calorimetry (DSC) results show that the produced RCP/CA-PA composites have a latent heat capacity of 34.1 and 33.5 J/g in liquid and solid phases, respectively, which is found to remain stable even after 300 phase changing cycles. In this regard, the indoor temperature performance of the rooms supplied with composite foams made with PCMs, showed significantly enhanced efficiency. In addition, it is shown that inclusion of PCMs in foam concrete can significantly reduce porosity and pore connectivity, resulting in enhanced mechanical properties. The results are found promising and point to the suitability of using RCP-impregnated PCMs in foam composites to enhance thermo-regulative performance of buildings. On this basis, the use of PCMs for enhanced thermal properties of buildings are recommended, especially to be used in conjunction with foam concrete.
Hemp fiber reinforced one-part alkali-activated composites with expanded perlite: Mechanical properties, microstructure analysis and high-temperature resistance
(2023-01-11) Bayraktar O.Y.; Tobbala D.E.; Turkoglu M.; Kaplan G.; Tayeh B.A.
The objective of the current research is to find out what impacts hemp fibers (HF) lengths and percentages have on the fresh, physical, mechanical, sorptivity, dry shrinkage, and thermal properties of HF-reinforced alkali-activated composite (AAC) reinforced with ground blast furnace slag (GBFS). Two groups of AAC mixes with 10 and 20 mm HF lengths were produced. Each group contained different percentages of HF with varying fiber lengths added to mixes at 0.5 %, 1 %, 2 %, and 3.0 % by weight of cement, respectively. Flow diameters were measured to determine the fresh-state properties of the AACs. Water absorption and apparent porosity were determined as physical properties. The unit weights of AAC mixtures are between 1045–1672 kg/m3. Measurements were made on compression and flexural characteristics at 7 and 28 days. The 28-day compressive strengths of AAC mixtures vary between 1.28 and 2.73 MPa, and the bending strengths vary between 0.48 and 1.65 MPa. AAC was also tested for water absorption, drying shrinkage, thermal conductivity, fresh and dry unit weight and porosity. The resistance of high temperatures at 250, 500, and 750 °C was determined. There is a significant improvement in compressive and flexural strength and thermal conductivity when HF is added at a 20 mm length. This improvement was confirmed and emphasized through scanning electron microscopy (SEM). According to study results, high-temperature alkali cooking treatments up to 250 °C may improve the thermal stability of HF cellulose. The best HF mix, M2-2 %, increased the 28-day compressive strength by 28.8 % and produced the best results at temperatures as high as 750 °C. The compressive strength of the mixtures exposed to 750 °C was obtained as approximately 2 MPa.
Improving the eco-efficiency of fiber reinforced composite by ultra-low cement content/high FA-GBFS addition for structural applications: Minimization of cost, CO2 emissions and embodied energy
(2023-10-01) Kaplan G.; Bayraktar O.Y.; Li Z.; Bodur B.; Yılmazoglu M.U.; Alcan B.A.
Influence of bottom ash and polypropylene fibers on the physico-mechanical, durability and thermal performance of foam concrete: An experimental investigation
(2021-11-01) Gencel O.; Kazmi S.M.S.; Munir M.J.; Kaplan G.; Bayraktar O.Y.; Yarar D.O.; Karimipour A.; Ahmad M.R.
Recently, foam concrete (FC) has been widely considered due to higher workability, lightweight, lower cost, thermal and fire resistance relatively to conventional concrete. This study intends to measure the properties of FC incorporating bottom ash (BA) as fine aggregates (FA) and polypropylene fibers (PPF). A total of 18 concrete mixes were produced with two cement contents: 300 and 400 kg/m3. In addition, three foam agent contents (40, 50, and 60 kg/m3) and three PPF contents (0, 0.5, and 1% in terms of volume) were used and considered to investigate the physical, mechanical, thermal, and durability properties of PPF-reinforced FC incorporating BA. Furthermore, the effect of elevated temperature on the properties of specimens was also examined. Results show an increase in apparent porosity, water absorption, and sorptivity of FC with the increase in foam agent content. Conversely, a reduction in thermal conductivity, porosity, and shrinkage is observed with an increase in foam agent, cement, and PPF contents, respectively. The rise in foam agent content declines the mass loss while improves both compressive and flexural strengths of FC under an elevated temperature. Scanning electron microscopic (SEM) analysis of the FC specimens after exposure to the elevated temperature shows the cracks and inter-connected pores due to the thermal stresses by decomposing calcium silicate phases. Results show that all the FC mixes incorporating BA as FA and PPF can be used as moderate-strength concrete following American Concrete Institute guidelines, leading to enhanced FC performance and sustainable construction.
Insulating and fire-resistant performance of slag and brick powder based one-part alkali-activated lightweight mortars
(2022-01-01) Koksal F.; Bayraktar O.Y.; Bodur B.; Benli A.; Kaplan G.
Waste brick powder (WBP) has enough pozzolanic characteristics to be employed as a supplemental cementing material in Portland cement-based concrete or as a precursor in the manufacture of alkali activated materials. This study was aimed to study the strength, thermal, microstructural and durability properties of ground blast furnace slag (GBFS) and WBP based one-part alkali-activated lightweight mortars (AAMs) produced with expanded vermiculite. One-part AAM mixtures were produced by using GBFS and WBP as binary precursors. Sodium metasilicate powder was used as the alkali activator. Two curing regimes namely heat curing at 75°C for 24 h and air curing at ambient conditions were adopted. GBFS was used as main binder and WBP was added at the rates of 0%, 10%, 25%, and 50% instead of GBFS. Four different mixtures were prepared by replacing GBFS at the rates of 0%, 10%, 25%, and 50% with WBP for each curing regime (totally eight mixtures). Expanded vermiculite powder were used as lightweight aggregates in all mixtures. The effects of WBP on AAM mixtures properties, including flowability, compressive strength, flexural strength, dry bulk density, thermal conductivity, porosity, and water absorption were studied. The effects of WBP and curing regime on drying shrinkage, sorptivity were also investigated. High temperature performance of the produced mixtures were determined. Results showed that air-cured WBP incorporated AAM mixtures exhibited better compressive strength, flexural strength, shrinkage, and sorptivity performance than the heat-cured WBP incorporated AAM mixtures. The air-cured AAM mixtures containing 25% WBP achieved the best results of 5.69 and 1.43 MPa for compressive strength and flexural strength at test age of 28 days. The heat-cured 50% WBP incorporated AAM mixture showed the best high temperature resistance and the lowest thermal conductivity.
Investigation of effect of brick DFST and silica FFME on the properties of portland cement mortar
(2019-01-01) Bayraktar O.Y.; Citoglu G.S.; Belgin C.M.; Cetin S.; Cetin M.
In this study, the mechanical behaviors that can occur under the influence of high temperature in the mortars produced by silica fume and waste brick dust were investigated. For this purpose, Portland cement (CEM I), brick dust (BD) of brick factory waste, silica fume (SF) of ETİ electrometallurgy INC. industrial waste CEN standard sand and water were used in the production of mortar. Blended cements were obtained by using BD, SF and SFBD at 5.0%, 10.0%, 15.0% and 20.0% ratio with substitution method in Portland cement. Density, Blaine, initial set and final set tests were performed on the produced mortars and 40x40x160 mm sized mortar prism samples were obtained using these cements. These samples were exposed to five temperature effects as 20, 150, 300, 700 and 900 ° C. The mortar samples kept at 20 ° C were accepted as reference mortar. A total of 1053 samples were studied in two different ways of cooling mortars as air-cooling (spontaneously at 20 ° C ± 2 in laboratory environment) and sprinkling (water spraying). After the mortar samples reached at room temperature, flexional resistance and compressive strength tests were carried out on 7th, 28th and 90th days. According to the test results; it was determined that BD, SF and SFBD can be used as pozzolanic additives in cement mortars both alone and together and can be evaluated in buildings with high probability of fire up to certain temperature values.
Investigation of the mechanical properties of marble dust and silica fume substituted portland cement samples under high temperature effect
(2019-01-01) Bayraktar O.Y.; Citoglu G.S.; Belgin C.M.; Cetin M.
The mechanical behaviors that can occur under the influence of high temperature in the mortars produced by silica fume and waste marble dust were investigated in this study. For this purpose, Portland cement (CEM I), waste marble dust (MD) from Afyon Çavdarlar Marble Factory, silica fume (SF) of ETİ electrometallurgy INC. industrial waste, CEN standard sand and water were used in the production of mortar. Mechanical experiments such as high temperature effect and cooling process with some physical experiments were performed on MD, SF and SFMD. Blended cements were obtained by using MD, SF and SFMD at 5.0%, 10.0%, 15.0% and 20.0% ratio with substitution method in Portland cement. Density, Blaine, initial set and final set were performed on the produced mortars and 40x40x160 mm sized mortar prism samples were obtained using these cements. These samples were exposed to five temperature effects as 20, 150, 300, 700 and 900 ° C. The mortar samples kept at 20 ° C were accepted as reference mortar. A total of 1053 samples were studied in two different ways of cooling mortars as air-cooling (spontaneously at 20 ° C ± 2 in laboratory environment) and sprinkling (water spraying). After the mortar samples reached at room temperature, flexional resistance and compressive strength tests were carried out on 7th, 28th and 90th days. According to the test results; it was determined that MD, SF and SFMD can be used as pozzolanic additives in cement mortars both alone and together and can be evaluated in buildings with high probability of fire up to certain temperature values.
Mechanical and durability properties of steel fiber-reinforced concrete containing coarse recycled concrete aggregate
(2021-10-01) Kaplan G.; Bayraktar O.Y.; Gholampour A.; Gencel O.; Koksal F.; Ozbakkaloglu T.
The focus of this study is to investigate the effect of using coarse recycled concrete aggregates (RCAs) as an alternative material to natural coarse aggregate on the fresh, mechanical and durability behavior of concrete reinforced with steel fiber. Eighteen unique concrete mixes with RCA content of 0%, 50%, and 100% and steel fiber content of 0%, 1%, and 2% were prepared, and tests were performed to study slump, density, compressive and splitting tensile strengths, flexural behavior, surface hardness, surface abrasion resistance, water absorption, and sorptivity of each mix. It is shown that concrete containing RCA has a lower unit weight, compressive, splitting tensile and flexural strength, flexural toughness, surface hardness, and abrasion resistance, and a higher water absorption and sorptivity in comparison with conventional concrete. An increased compressive, splitting tensile and flexural strength, flexural toughness, surface hardness, and abrasion resistance, and a decreased water absorption and sorptivity of concrete with an increased steel fiber content from 1% to 2% is less significant compared to those from 0% to 1%. The results also show that, at RCA content of 50%, incorporating 1% steel fiber develops a concrete mix with similar or even better properties compared to unreinforced conventional concrete. At 100% RCA content, incorporating 2% steel fiber develops a concrete mix with similar properties to unreinforced conventional concrete having water to cement ratio of 0.3, but inferior properties to unreinforced conventional concrete having water to cement ratio of 0.5. These findings indicate that recycled aggregate concrete with similar or even better properties compared to concrete with natural aggregate can be developed through properly designing mixes, providing a great avenue toward the production of green construction material for structural applications.
Optimization of foam concrete characteristics using response surface methodology and artificial neural networks
(2022-06-27) Kursuncu B.; Gencel O.; Bayraktar O.Y.; Shi J.; Nematzadeh M.; Kaplan G.
In this study, influences of waste marble powder (WMP) and rice husk ash (RHA) partially replaced instead of fine aggregate and cement into foam concrete (FC) on compressive and flexural strength, porosity, and thermal conductivity coefficient were investigated using Response Surface Methodology (RSM) and Artificial Neural Networks (ANN) methods. The foam parameter was determined as two levels in the experimental design, and the WMP and RHA parameters were determined as three levels. With the RSM analysis, the most influential parameters for compressive and flexural strength were determined as Foam WMP and RHA, respectively. Likewise, the order of effective parameters for porosity and thermal conductivity coefficient was found as foam WMP and RHA. With the RSM method, R2 values were obtained as 0.9492 for compressive strength, 0.9312 for flexural strength, 0.9609 for porosity, and 0.9778 for thermal conductivity coefficient. Correlation coefficients with the ANN method were found as 0.98393, 0.96748, 0.9933, and 0.96946 for compressive and flexural strength, porosity, and thermal conductivity coefficient, respectively. The ANN method was found to be suitable for estimating the responses. The RSM method was found to be suitable both for estimating the responses and for determining the effective parameters. In addition, the optimum parameters were determined by the RSM method.
Optimization of without SCM concrete exposed to seawater according to minimum cost and CO2 emissions: Sustainable design with ABC algorithm
(2023-06-01) Kaplan G.; Bayraktar O.Y.; Bayraktar T.
The service life of marine concrete structures is relatively shorter due to various salts in seawater. In this context, assistance is obtained from the exposure classes in standards such as EN 206. In this study, an ABC-based (artificial bee colony) algorithm was developed that considers the CO2 emissions and cost analysis of concrete designed according to EN 206 standards. The number of studies involving algorithms in designs according to regulations and standards is very few in the literature. In addition, Supplementary Cementitious Materials (SCMs) are generally used in concretes exposed to sea water. This study investigated the physical, mechanical, durability, microstructure, cost and sustainability properties of concretes without SCM. This study produced nine concrete mixes with different cement dosages (260–300–340 kg/m3) and a water/cement ratio (0.45,0.55, and 0.65). The mixes were cured in normal water (NWC) and seawater (SWC). As the cement mixes’ cement dosage increased, the water absorption and apparent porosity values decreased. Since the increase in the w/c ratio increased the capillary void content of the mixes, it enhanced the porosity and sorptivity values. While the 28d compressive strength of NWC-applied concretes varies between 31.3 and 39.8 MPa, the compressive strength of SWC-applied concrete varies between 30.7 and 36.8 MPa. After 80 wetting-drying cycles, the compressive strength of the concretes decreased below 20 MPa. The CO2 emission values of the concrete vary between 270 and 343 kg and their costs range between 17.9 and 21.5 $/m3. According to the ABC algorithm, it was determined that cement dosage should be 260 kg/m3, w/c ratio should be 0.45 for high compressive strength, low cost, and CO2 emission. As a result, it has been determined that a lower cost and more durable concrete design can be made if methods such as the ABC algorithm are combined with EN 206 standards.
Performance assessment of fiber-reinforced coral aggregate-based lightweight foam concrete for sustainable marine construction
(2024-10-25) Bayraktar O.Y.; Danish A.; Bodur B.; Kaplan G.; Aydın A.C.; Ozbakkaloglu T.
Possibilities of disposing silica fume and waste glass powder, which are environmental wastes, by using as a substitute for Portland cement
(2021-04-01) Bayraktar O.Y.
In this study, the possibilities of disposal of environmental waste, silica fume, and waste glass powder as substitutes in the mortar samples in Portland cement were investigated. For this purpose, Portland cement (CEM I), silica fume (SF), waste glass powder (WGP), CEN standard sand, and water were used in mortar production. Additive cements were obtained by using the SF, WGP, and SFWGP substitution methods in Portland cement at the rates of 10, 20, 30, and 40%. The flexural strength, compressive strength, radiation permeability (determination of linear absorption coefficient), high temperature, and alkali-silica reaction (ASR) effect on SF, WGP, and SFWGP were examined and compared with the control PC 42.5R samples. Mortar samples of 40 × 40 × 160 mm size were obtained with the grouts/mortars produced, and the samples were exposed to five temperature effects, namely, 20, 150, 300, 700, and 1000 ° C. Samples kept at 20 ° C are accepted as baseline. A total of 429 samples were studied, including the cooling process in the air (spontaneously in the laboratory, 20 ° C ± 2). After the samples achieved room temperature, flexural and compressive strength tests were carried out at 28 and 90 days. Test results demonstrate that SF, WGP, and SFWGP, which are environmental wastes, can be disposed both as a pozzolanic additive material both alone and together in cement mortars, can be utilized in buildings with high fire hazard, and the sample with the highest linear absorption coefficient is the sample obtained with SFWGP, and also, the expansion values that occur in SF and WGP are less than the control sample.