Browsing by Author "Nodehi M."

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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.
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.
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.
The effect of limestone and bottom ash sand with recycled fine aggregate in foam concrete
(2022-08-15) Gencel O.; Balci B.; Bayraktar O.Y.; Nodehi M.; Sarı A.; Kaplan G.; Hekimoğlu G.; Gholampour A.; Benli A.; Ozbakkaloglu T.
To follow resource conservation, the production of optimized and sustainable structures through the use of insulating materials, such as foam concrete, has become a trend in construction industry. Although foam concrete has numerous benefits, the larger use of Portland cement in its mixture and its relatively low thermo-durability properties because of the low quantity of solid materials are of major concerns, challenging its large-scale applications. In that respect, this research evaluates the use of recycled fine concrete aggregate, limestone and bottom ash sand as the main aggregate materials to evaluate the physico-mechanical and thermo-durability properties of foam concrete. To that end, 25 mixes have been produced and a comprehensive series of tests including flowability, compressive and flexural strengths, water absorption, apparent porosity, drying shrinkage, sorptivity, abrasion resistance, thermal conductivity, along with the effect of elevated temperature and its respective cooling regime on foam concretes have been conducted in this study. The results show that foam concretes manufactured with bottom ash and recycled fine aggregates develop a considerably lower thermal conductivity values despite being outperformed in physico-mechanical properties by those mixes produced with limestone sand. Nonetheless, the inclusion of bottom ash sand is found to produce foam concretes with a comparable physico-mechanical and thermo-durability properties to mixes with limestone. The results of this study point to the suitability of utilizing alternative fine-sized aggregates, such as recycled fine aggregates along with bottom ash sand, in the production of foam concrete without compromising the insulating properties of the produced 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.