Browsing by Author "Kaplan G."

Now showing 1 - 20 of 48

A study of some durability properties of mortars with white cement and Portland cement
(2017-01-01) Öztürk A.; Kaplan G.
Workability, strength and durability are among the most important properties when working with concrete. Increased compressive strength of concrete has favorable impact on durability along with on its several other features. To ensure a high degree of durability, it is essential that clean, sound materials and the lowest possible water content are used in the concrete, together with thorough mixing. Good consolidation during placement of the concrete is important, as are proper curing and protection of the concrete during the early hardening period, which assure favorable conditions of temperature and moisture. Cure concrete properly for a minimum of three days in order to develop good durability. In this study mortars with white cement and Portland cement and different w/c ratios were produced and investigated. The mortars produced were then tested for the impacts of alkali silica reaction (ASR), high temperatures, abrasion and acid effect. Results show that less expansion was measured on the mortars using portland cement while the white cement gave the largest expansions (approximate 0.60%).However, there was no significant difference between cements in terms of their acid resistance. The impact of higher temperatures on mortars produced using white cement was less in comparison with normal Portland cement. Durability tests showed that w/c ratio plays an important role.
A study on the use of advanced nondestructive testing methods on histroric structures
(2018-01-01) Tuğla R.; Demircan R.K.; Kaplan G.
Historic structures are social and cultural heritage for the land they are built on. To protect this heritage and to preserve it for the generations to come are among the most important responsibilities of nations. However numerous historical structures are found in Turkey, the awareness around nondestructive maintenance processes which will keep the identity of the structure intact is not developed as required. Historical structures require preservation, and necessary maintenance and reinforcement measures to be taken in order to survive damages arising from several reasons. Such work must be designed by multidisciplinary professionals and must be applied adhering to the original form of the structure. Among the limiting factors involved in an intervention to a structure is the knowledge on the strength and material properties of the structural elements used. Structural elements of a historical building must be subjected to measurements based on a number of assumptions made for parameters such as compressive strength, shear strength and elasticity modules. As a result of practices based on such assumptions, historical structures may face unnecessary repair and reinforcement processes. With the advancement made in technology now it is possible to obtain the necessary data from historical buildings without causing damage or causing minimal damage using nondestructive or semi-destructive test methods. Therefore, it is important and necessary to use and popularize the use of nondestructive testing methods for historical structures. This study investigates the following nondestructive testing methods and reports on the results obtained in a comparative manner: concrete rebound hammer method; flat-jack method; penetration resistance method; ultrasonic method; impact-echo method; and magnetic and electrical methods.
Artificial neural network estimation of the effect of varying curing conditions and cement type on hardened concrete properties
(2019-01-03) Kaplan G.; Yaprak H.; Memiş S.; Alnkaa A.
The use of mineral admixtures and industrial waste as a replacement for Portland cement is recognized widely for its energy efficiency along with reduced CO2 emissions. The use of materials such as fly ash, blast-furnace slag or limestone powder in concrete production makes this process a sustainable one. This study explored a number of hardened concrete properties, such as compressive strength, ultrasonic pulse velocity, dynamic elasticity modulus, water absorption and depth of penetration under varying curing conditions having produced concrete samples using Portland cement (PC), slag cement (SC) and limestone cement (LC). The samples were produced at 0.63 and 0.70 w/c (water/cement) ratios. Hardened concrete samples were then cured under three conditions, namely standard (W), open air (A) and sealed plastic bag (B). Although it was found that the early-age strength of slag cement was lower, it was improved significantly on 90th day. In terms of the effect of curing conditions on compressive strength, cure W offered the highest compressive strength, as expected, while cure A offered slightly lower compressive strength levels. An increase in the w/c ratio was found to have a negative impact on pozzolanic reactions, which resulted in poor hardened concrete properties. Furthermore, carbonation effect was found to have positive effects on some of the concrete properties, and it was observed to have improved the depth of water penetration. Moreover, it was possible to estimate the compressive strength with high precision using artificial neural networks (ANN). The values of the slopes of the regression lines for training, validating and testing datasets were 0.9881, 0.9885 and 0.9776, respectively. This indicates the high accuracy of the developed model as well as a good correlation between the predicted compressive strength values and the experimental (measured) ones.
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.
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.
Behavior of mortar samples with waste brick and ceramic under freeze-thaw effect
(2018-01-01) Memiş S.; Özkan I.G.M.; Yılmazoğlu M.U.; Kaplan G.; Yaprak H.
Increasing number of industrial facilities and population concentration in particular regions along with overconsumption are main reasons of the increased environmental pollution. It is a necessity to preserve available resources and to keep the waste in control in order to achieve a sustainable development goal. In recent years, concepts of waste management, recycling and sustainability have gained importance with regards to the construction industry. Today, approximately 35 billion tons of concrete is produced worldwide and 80% of this amount consists of aggregated manufactured using natural resources. A significant environmental impact is the case even for the production of cement, a binding agent for concrete, which accounts for 1 ton CO2 emission in order to produce 1 ton of cement. The main subject of this study is the production of a sustainable construction material with the use of ceramic instead of both aggregate and cement. Clay is defined as a common natural material with fine-grains, with layers and a high water absorption capacity. Ceramic products are construction materials which can replace cement generally in the form of artificial puzzolana. The main subject of this study is the use of the waste obtained from ceramic plants which produces ceramic products in mortars. Taguchi L9 array design was used as part of this experimental study. Water-binder ratio was set to 0.50 in the preparation of the mixes and natural aggregates were used. Aggregates were then replaced by pieces ceramic and brick at a percentage between 20 and 60% while cement was replaced by ceramic and brick powder at a percentage between 10 and 30%. The mixes were then subjected to freeze and thaw tests at 30, 60 and 90 cycles in accordance with ASTM C 666 standard. Dynamic modulus and mechanical properties of the mortars subjected to f-t effect were then identified. When the results of the tests were examined, it was found that the compressive strength at 7th and 28th days were decreased with the increase of the volume of ceramic and brick powder used while it was found that the use of ceramic and brick powder did not have a significant effect on the compressive strength at the 90th day. The use of ceramic and brick aggregate led to favorable results in terms of freeze-thaw resistance. Especially the use of 10% ceramic [(whiteware) CA] and 20% other ceramic [(brick) BA] aggregate in mortars subjected to 90 f-t cycles increased the dynamic modulus while similar results were found for the use of 5% ceramic powder and 10% brick powder in mortars subjected to 90 days of f-t cycles. This study shows that waste material obtained from ceramic and bricks industry can be repurposed in the construction industry.
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.
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.
Cost optimization of mortars containing different pigments and their freeze-thaw resistance properties
(2016-01-01) Yildizel S.; Kaplan G.; Öztürk A.
Nowadays, it is common to use colored concrete or mortar in prefabricated concrete and reinforced concrete construction elements. Within the scope of this study, colored mortars were obtained with the addition of brown, yellow, black, and red pigments into the white cement. Those mixtures are examined for their compressive strength, unit weight, water absorption, and freeze-thaw resistance. Subsequent to comparison of these properties, a cost optimization has been conducted in order to compare pigment costs. The outcomes showed that the pore structure in architectural mortar applications plays an important role in terms of durability. And cost optimization results show that light colored minerals can be used instead of white cements.
Determination of the Physical and Mechanical Properties of the Materials Used in the Northern City Walls of Historical Sinop Castle
(2019-02-24) Demircan R.K.; Kaplan G.; Unay A.I.
Turkey is a country that has hosted many civilizations due to its geographical location. The artefacts of these civilizations constitute important historical heritages of the country. The preservation, restoration and strengthening of historical artefacts and their transfer to future generations are the responsibilities of every country. Historical Sinop Castle that investigated in this study locates in the Sinop city where takes place northernmost of Turkey. Sinop province is a half island due to its geographical position and it is known that the castle walls were built due to the protection of this city. It is not known exactly when the historic Sinop Castle was built. It is estimated the time period of built could be 8th century B.C based on excavations. It is known that to hosted the Milets, the Cimmerians, the Persians, the Romans, the Byzantines, the Seljuks and the Ottoman Empire. Sinop Castle, which could survive until today, has a length of 880 m in the North, 500 m in the east, 400 m in the south and 273 m in the west, and it defines the old borders of the city. It is observed that northern city walls of castle (Kumkapi Site) have been subjected to natural influences due to the its location and it is in danger of collapse. The purpose of scientific research on materials used in historical buildings; to obtain more information about visual, physical, mechanical and mineralogical properties of materials used in these structures. Using this information, suggestions on material selection to be used in the restoration of structures will be presented. In this study, stone and mortar samples were taken from the northern city walls of castle (Kumkapi Site) under the necessary laws and regulations. It was paid attention for the stone and mortar samples taken from the area at the sea level of the castle were intact. Samples of stone and mortar are masonry samples on the front surface, filler part and back surface of the castle. As physical analyzes on the samples; water absorption rates (bulk/weight), real density, apparent density, porosity, and pressure resistance tests as mechanical analysis were applied. In accordance with the results obtained, the suitability of the material with the material values used in the literature was emphasized. In addition, it was aimed to suggest restoration proposals that compare the mortar samples taken from the castle walls with the mortar samples of some researchers in the literature.
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.
Glass fibre reinforced concrete rebound optimization
(2017-01-01) Yildizel S.; Yiǧit M.; Kaplan G.
Glass fibre reinforced concrete placement technique generates losses due to rebound effects of the already sprayed concrete particles. Rebounded concrete amount cause a significant difference between the initial mix design and emplaced mix compositions. Apart from the structural differences, it comes with a cost increase which was resulted by the splashed concrete amount. Many factors such as viscosity and quantity of mixes dominate this rebound amount in sprayed glass fibre reinforced concrete applications depending on production technologies and processes; however, this research focuses on the spray distance and the angle of the spray gun which mainly effects the rebound amount in glass fibre reinforced concrete production. This paper aims to understand the required angle and distance for glass fibre reinforced concrete mixes having on-site plastic viscosity values. Glass fibre reinforced mixtures were also modelled with a finite element method based software and, the analysis results were compared with production line results. Results of the analysis and on-site studies showed a decisive correlation between, discharge distance, discharge angle and the viscosity of the 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.
Holomental: Improving Mental Rotation Ability with Mixed Reality
(2024-06-03) Piri Z.; Kaplan G.; Cagiltay B.; Cagiltay K.