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    A comparative study of petroleum coke and silica aerogel inclusion on mechanical, pore structure, thermal conductivity and microstructure properties of hybrid mortars
    (Elsevier, 2020) Bostanci, Levent
    Development of cost-effective and energy - efficient materials is an on-going effort in construction sector. For this purpose, researchers have focused on utilizing various industrial by - products and nano thermal insulation materials in cement - based mixtures in recent years. This paper presents a comparative study on mechanical, pore structure, thermal conductivity properties and microstructure morphology of hybrid mortar mixtures containing petroleum coke as a partial replacement of sand (0%, 10% and 15%, by weight) and silica aerogel powder as a cement additive (0.35%, 0.7% and 1.0%, by weight). Results showed that a thermal conductivity reduction of 21.83% was determined at an aerogel content of 0.35% with higher compressive, flexural strengths and toughness capacities. Moreover, there was an insulation enhancement in the petroleum coke-incorporated samples up to 33% at a replacement level of 15%. However, in the case of equivalent thermal conductivity, compressive toughness and post - peak toughness capacities of aerogel-incorporated mixtures were higher up to respectively 20% and 17% in comparison to petroleum coke-incorporated mixtures. This research opens up a new perspective in the design of hybrid cement mortars containing silica aerogel powder and petroleum coke with the optimization of mechanical-thermal insulation properties.
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    Effect of a low content of waste rubber inclusion on pore structure and thermal insulation properties of hybrid slag mortars
    (Springer Heidelberg, 2022) Bostanci, Levent
    The reuse of sustainable waste materials in cement-based mixtures is a key solution for the production of environmentally friendly construction materials. Among the various types of industrial wastes, the utilization of waste rubber (WR) has become a vital topic in the sustainable material design. This study aimed at developing an eco-friendly mortar by enhancing the use of WR as a cement additive in hybrid slag mortar mixtures. For this purpose, five different hybrid slag mixtures were prepared, with three contents (0%, 1.0%, and 2.0%) and two different particle size ranges (0-0.6 mm and 0-1.0 mm) of WR. The experimental results demonstrate that the incorporation of a low content of WR into the mixtures leads to a major pore modification effect, resulting in an increase in the number of pores with lower pore sizes. Based on the pore modification effect, a thermal insulation enhancement of approximate to 17% was measured with limited strength reductions. Besides, strong linear relationships between the strengths and the effective pore contents with R-2 of > 0.80 were detected. With the aim of promoting the sustainable design, the integration of a low content of rubber and slag seems as a good option.
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    Effect of waste glass powder addition on properties of alkali-activated silica fume mortars
    (Elsevier, 2020) Bostanci, Levent
    In cement technology, sustainable-based politics demands the use of industrial by-products and waste - based materials. Glass powder (GP) and silica fume (SF) are excellent solid materials to develop a sustainable cementbased material due to a high content of silicon dioxide (SiO2) in their chemical compositions. This study focuses on the properties of alkali-activated silica fume (AASF) mortars containing waste glass powder (WGP). For this purpose, WGP was utilized as partial replacement of sand in AASF mortar mixtures at four levels: 0%, 15%, 30%, and 45% by weight. Displacement -controlled compressive and flexural strength tests were carried out on prismatic 40 x 40 x 160 mm test samples that had been cured for 2,7 and 28 days. The Mercury Intrusion Porosimetry (MIP) test and the thermal conductivity coefficient measurement were carried out following the compressive strength test on 28-day samples. The microstructure morphology and mineralogical properties of the mortar samples were studied by means of Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), respectively. Experimental studies have shown that at a replacement level of 30%, WGP simultaneously improves the flexural strength of mortars by 12.65% and reduces the thermal conductivity coefficient by 30.88% under stable macro pores and transient capillary-micro pores formation in AASF pore structure. As an alternative to conventional cement mortar, WGP-incorporated AASF mortars attract a great deal of attention.
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    Investigation of mechanical properties of mortars with carbon fiber using multi slice computed tomography
    (Pontificia Univ Catolica Chile, Escuela Construccion Civil, 2017) Sola, Ozlem Celik; Erdem, Savas; Bostanci, Levent; Atis, Cengiz Duran; Sayin, Baris
    Carbon fibers (CFs) in the cement mortars are used in order to improve characteristics properties of the composite materials such as mechanical properties. Moreover, the uniformity of fiber dispersion is significant aspect for improvement of the composites. Computed Tomography (CT) imaging is a fully nondestructive technique to view features in the interior of opaque solid objects to obtain digital information on their properties. In this study, firstly, flexural test was conducted were investigated for 4x4x16 cm samples incorporated with carbon fiber at 2- and 7-days curing. Secondly, the images that were obtained by using multi-slice CT technique. Finally, the compressive strength properties of the mortars mixed with carbon fiber were discussed. According to the test results, the dispersion and orientation of CFs in the samples have a remarkable impact on mechanical properties of the composites.
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    Mechanical Properties and Thermal Conductivity of Aerogel-Incorporated Alkali-Activated Slag Mortars
    (Hindawi, 2018) Bostanci, Levent; Celik Sola, Ozlem
    Compressive strength, thermal conductivity coefficient, and porosimetric properties of alkali-activated slag (AAS) mortars containing silica aerogel were investigated experimentally in this study. For this purpose, slag mortar mixtures at 0.75% and 1.0% aerogel content ratios were prepared, and these mortar mixtures were activated with lithium carbonate (Li2CO3) at 0.03% and 1.50% dosage rates. Mortar samples were exposed to curing process in water for 2, 7, and 28 days, and the samples, which completed the curing stage, were subjected to the compressive strength test. +e porosimetry test and the thermal conductivity coefficient measurement were carried out following the compressive strength test on 28-day samples. +e varying aerogel content rate in the mixtures and the effects of the dosage of Li2CO3 on the gel, capillary, and macropore distributions, and the effect of changing porosimetric properties on compressive strength and thermal conductivity coefficient were analyzed in detail. Experimental studies have shown that AAS mortars including an optimum 0.75% aerogel content rate and 0.03% Li2CO3 activation provided a compressive strength of 34.1 MPa and a thermal conductivity coefficient of 1.32 W/mK. Aerogel addition provides a partial compressive strength increase at 7- and 28- day samples while it also causes maximum strength loss of 5.0% at 2-day samples.
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    Mechanical, Pore Structure, Thermal Insulation and Micro Structure Properties of Alkali-Activated Slag mortars Containing Waste Glass Powder
    (Gazi Univ, 2022) Bostanci, Levent
    The idea of limiting the consumption of energy and natural resources is the focal point of today's sustainability policies. Due to its high energy requirement and natural resource consumption, the studies in order to develop an alternative for conventional cement mortars are increasing day by day. For this purpose; in this study, the effect of the waste glass powder inclusion on the mechanical, pore structure, thermal conductivity and microstructure properties of the alkali-activated slag mortars was investigated. Waste glass powder was utilized as a partial replacement of sand at contents of 15%, 30% and 45% by weight and slag was used in the binder content at a level of 50% as a replacement of cement in mixtures. The results obtained from the study revealed that the thermal insulation properties could be increased by 35% with a limited level of mechanical strength reduction for the replacement of sand with waste glasss powder at the level of 15%. The alkali-activated slag mortars containing waste glass powder indicate a great potential to be used in the future instead of conventional cement mortars with their superior thermal insulation and eco-friendly properties in compliance with sustainability policies.
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    Strength Prediction of Hybrid Slag Mortars Containing Chopped Carbon Fibers Through Pore Features
    (Springer Int Publ Ag, 2022) Bostanci, Levent
    Fiber inclusion has gained great attention in recent years due to the possibility of enhanced mechanical performance in cementitious materials. Fiber distribution, orientation, bundle areas, etc. are proved effective factors on determining the strength properties of fiber-incorporated mortars. In this work, the pore structure-based mechanical behavior of hybrid slag (HS) mortars containing chopped carbon fiber (CCF) was investigated with the aim of building a bridge between the pore structure features and strength properties including all the strength-affecting factors mentioned above. The mechanism of strength gain with the depending changes on pore structure was discussed both at early and later ages of hydration. Results show that a higher amount of 50-100 nm pore proportion resulted in a desirable matrix without fiber bundle areas and a strong correlation between the 50 and 100 nm pore content, and the 28-day compressive strength was detected with R-2 of 0.98. Moreover, measurement of critical pore contents plays a remarkable role for the prediction of both flexural and compressive strengths of mortars after 7 and 28 days of curing. Based on the relations determined, the measurement of the strength- governing pore formation seems as a key factor in order to get a clear understanding of the total influence of the individual strength-affecting factors experienced in fiber inclusive cementitious materials.
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    Synergistic effect of a small amount of silica aerogel powder and scrap rubber addition on properties of alkali-activated slag mortars
    (Elsevier Sci Ltd, 2020) Bostanci, Levent
    The combined use of smart and waste - based materials for energy efficiency in buildings seems as a promising solution. Due to its unmatched insulation properties, silica aerogel is an attractive smart material in cement technology compared to other conventional insulation materials. However, the high manufacturing cost of silica aerogel limits its application in the construction industry. In this study, the combined effect of silica aerogel (0%, 0.3% and 0.6% of binder weight) and scrap rubber (0%, 1.5% and 3.0% of binder weight) addition in alkali-activated slag (AAS) mortars was investigated. A small amount of silica aerogel and scrap rubber addition into mixtures was analyzed with the aim of minimizing reductions in mechanical properties with enhanced thermal insulation. Experimental results demonstrated that in the case of 3.0% scrap rubber loading at 0.3% aerogel content ratio, a remarkable synergistic effect could be observed in terms of thermal insulation up to 33%. Besides, after 2 days of curing, 48.35% and 77.55% increases in compressive toughness and post - peak compressive toughness of samples were detected, respectively. Synergistic effect of a small amount of silica aerogel and scrap rubber in calcium-silicate structure indicates a great potential for energy conservation. (C) 2020 Elsevier Ltd. All rights reserved.