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    Development of alkali-activated binders from recycled mixed masonry-originated waste
    (ELSEVIER, 2021) Yildirim, Gürkan; Kul, Anil; Ozcelikci, Emircan; Sahmaran, Mustafa; Aldemir, Alper; Figueira, Diogo; Ashour, Ashraf
    In this study, the main emphasis is placed on the development and characterization of alkali-activated binders completely produced by the use of mixed construction and demolition waste (CDW)-based masonry units as aluminosilicate precursors. Combined usage of precursors was aimed to better simulate the real-life cases since in the incident of construction and demolition, these wastes are anticipated to be generated collectively. As different masonry units, red clay brick (RCB), hollow brick (HB) and roof tile (RT) were used in binary combinations by 75-25%, 50-50% and 25-75% of the total weight of the binder. Mixtures were produced with different curing temperature/periods and molarities of NaOH solution as the alkaline activator. Characterization was made by the compressive strength measurements supported by microstructural investigations which included the analyses of X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX). Results clearly showed that completely CDW-based masonry units can be effectively used collectively in producing alkali-activated binders having up to 80 MPa compressive strength provided that the mixture design parameters are optimized. Among different precursors utilized, HB seems to contribute more to the compressive strength. Irrespective of their composition, main reaction products of alkali-activated binders from CDW-based masonry units are sodium aluminosilicate hydrate (N-A-S-H) gels containing different zeolitic polytypes with structure ranging from amorphous to polycrystalline.
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    Öğe
    Eco-hybrid cement-based building insulation materials as a circular economy solution to construction and demolition waste
    (Elsevier Sci Ltd, 2023) Ozcelikci, Emircan; Oskay, Atakan; Bayer, Ismail Raci; Sahmaran, Mustafa
    The primary focus of this study is to develop non-structural ultra-lightweight circular building insulation ma-terials by utilizing a substantial amount of construction and demolition waste (CDW). A unique type of Eco-hybrid cement was formulated as the binder phase, while fine recycled concrete aggregates (FRCA) were used in the aggregate phase. The physical, mechanical, and thermal conductivity properties of the mixtures were assessed by altering the content of Eco-hybrid cement, FRCA, foaming agent, silica-aerogel and water-to-binder ratio. The findings indicated that the fresh properties are primarily influenced by the FRCA and foaming agent ratio, whereas the mechanical properties are predominantly associated with the Eco-hybrid cement and foaming agent content. Microstructural analysis revealed that thermal performance is greatly affected by the pore size distribution and their interconnectivity. Consequently, an ultra-lightweight green foam concrete was successfully developed with a dry density of 0.514 g/cm3 and a thermal conductivity of 0.049 W/mK.
  • [ X ]
    Öğe
    Evaluation of Mechanical and Microstructural Properties of Engineered Geopolymer Composites with Construction and Demolition Waste-Based Matrices
    (Asce-Amer Soc Civil Engineers, 2024) Kul, Anil; Ozcelikci, Emircan; Ozel, Behlul Furkan; Gunal, Muhammed Faruk; Yildirim, Gurkan; Bayer, Ismail Raci; Demir, Ilhami
    The main purpose of this work was to combine the advantages of increased material greenness, waste upcycling, reduced raw material demand, and the superior characteristics of traditional engineered cementitious composites (ECCs). To this end, engineered geopolymer composites (EGCs) with matrices based entirely on components from construction and demolition waste (CDW) as precursors and aggregates were developed. The CDW-based precursors included roof tiles, red clay bricks, hollow bricks, glass, and concrete. Different combinations of sodium hydroxide, sodium silicate, and calcium hydroxide were used as alkaline activators. Hybridized polyethylene and nylon fibers were used as fibers. To investigate the influences of the additional calcium source, slag-substituted versions of the same mixtures were produced. At the fresh state, Marsh cone and mini-slump tests were performed. At the hardened state, mechanical property tests (compressive strength and four-point bending) and microstructural characterization tests (X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy) were conducted. The findings revealed that, regardless of the mixture composition, all EGCs exhibited a deflection-hardening response coupled with multiple microcracking behavior. The 28-day average ranges for compressive strength, flexural strength, and midspan deflection results were 25.2-42.1 MPa, 6.2-9.5 MPa, and 14.1-28.3 mm, respectively. Slag substitution mostly improved the mechanical performance of EGCs. The main geopolymerization products were sodium aluminosilicate hydrate (NASH), calcium aluminosilicate hydrate (CASH), and C-(N)-ASH gels, the formation of which varied depending on the type of precursor and activator.