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    Engineering properties and thermal conductivity of lightweight concrete with polyester-coated pumice aggregates
    (De Gruyter Poland Sp Z O O, 2025) Tuncer, Metin; Bideci, Alper; Bideci, Ozlem Salli; Comak, Bekir; Durmus, Gokhan
    Pumice aggregates stand out with their low density and high porosity. However, their high water retention capacity and low mechanical strength are the primary disadvantages limiting their use in lightweight concrete production. In this study, pumice aggregates with particle sizes ranging from 4 to 16 mm were coated with polyester, known for its superior adhesion and insulation properties, to produce polyester-coated pumice aggregates. Subsequently, five different lightweight concrete mixtures were prepared using 450 kg/m(3) cement, incorporating coated and non-coated pumice aggregates as coarse aggregates at replacement ratios of 0, 25, 50, 75, and 100%. Aggregate tests included specific gravity and water absorption, while fresh concretes were evaluated for unit weight and slump. Hardened concretes were tested for dry unit weight, water absorption, ultrasonic pulse velocity (UPV), compressive strength, freeze-thaw resistance, and thermal conductivity. The results revealed that the polyester coating increased the specific gravity of pumice aggregates by up to 45% and reduced water absorption by 85%. The use of coated aggregates increased the unit weight of the concrete but resulted in a reduction in compressive strength and UPV. Despite a compressive strength reduction of up to 58% depending on the coated aggregate content, concrete specimens produced with polyester-coated aggregates exhibited the highest performance in terms of freeze-thaw resistance and thermal conductivity.
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    Experimental Investigation of Durability Properties of Polymer Coated Pumice Aggregate Lightweight Concretes
    (Mdpi, 2025) Tuncer, Metin; Bideci, Alper; Comak, Bekir; Durmus, Goekhan; Bideci, Ozlem Salli
    Pumice aggregates with low density and high porosity are widely used in lightweight concrete. The high water retention ability of pumice aggregates adversely affects the properties of fresh concrete. Additionally, pumice aggregates' inadequate mechanical strength and durability hinder concrete performance. In recent years, research on coated aggregates has gained traction to improve the physical properties, mechanical strength, and durability characteristics of concrete. In this study, coarse pumice aggregates were coated with polyester and partially substituted with uncoated aggregates at ratios of 0%, 25%, 50%, 75%, and 100% in lightweight concrete formulations. Specific weight and water absorption tests were performed on the aggregates, while slump and unit weight tests were performed on fresh concrete mixtures. SEM-EDX analyses, unit weight, water absorbing capacity, sorptivity, compressive strength, freeze-thaw resistance, and sulfate resistance tests were performed on concrete specimens. The results indicated that the polyester coating significantly increased the specific weight of the aggregates and decreased the water absorption rates by up to 85%. Despite the coated aggregates resulting in decreased compressive strength of concrete specimens, they demonstrated reduced water absorbing capacity and sorptivity characteristics relative to reference concrete. Moreover, concrete made with coated aggregates exhibited better results in freeze-thaw and sulphate resistance tests.
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    Fiber-Reinforced Lightweight Calcium Aluminate Cement-Based Concrete: Effect of Exposure to Elevated Temperatures
    (Mdpi, 2023) Bideci, Ozlem Salli; Yilmaz, Hakan; Gencel, Osman; Bideci, Alper; Comak, Bekir; Nodehi, Mehrab; Ozbakkaloglu, Togay
    Calcium aluminate cements (CACs) are a group of rapid-hardening hydraulic binders with a higher aluminum composition and lower ecological footprint compared to their ordinary Portland cement (CEM) counterparts. CACs are commonly known to have higher thermo-durability properties but have previously been observed to experience a major strength loss over time when exposed to thermal and humidity conditions due to the chemical conversion of their natural hydrated products. To address this, in this study, silica fume is added to induce a different hydration phase path suggested by previous studies and utilized in conjunction with fiber-reinforced lightweight pumice to produce lightweight concrete. To closely evaluate the performance of the produced samples with CAC compared to CEM, two different types of cement (CEM and CAC) with different proportions of pumice and crushed stone aggregate at temperatures between 200 and 1000 degrees C were tested. In this context, sieve analysis, bulk density, flowability, compressive and flexural strength, ultrasonic pulse velocity and weight loss of the different mixes were determined. The results of this study point to the better mechanical properties of CAC samples produced with pumice aggregates (compared to crushed stone) when samples are exposed to high temperatures. As a result, it is found that CACs perform better than CEM samples with lightweight pumice at elevated temperatures, showing the suitability of producing lightweight thermal-resistant CAC-based concretes.
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    A MIXTURE DESIGN GUIDE TO PRODUCE PERVIOUS CONCRETES BY BASALT AGGREGATES WITH DIFFERENT GRADATIONS AND DETERMINATION OF ENGINEERING CHARACTERISTICS OF PRODUCED CONCRETES
    (Serban Solacolu Foundation, 2023) Karaalioglu, Emre; Comak, Bekir; Aykanat, Batuhan
    As a result of rapid urbanization, impermeable surfaces used in* roads, pavements, parks, and gardens cause a rapid increase in the number of urban floods and overflows. As they infiltrate rainwater into the subsurface and decrease the surface water flow, protect the underground water sources, support sustainability, and offer solutions to relieve the environmental concerns, pervious concretes gain importance with each passing day. In this study, to enhance the mechanical characteristics of them without compromising on their permeability characteristics it was aimed to make the optimum mixture design of pervious concretes which are prepared with basalt aggregates. 3 different paste volumes (15%, 20%, 25%) and 3 different aggregate gradations (10-15 mm, 5-10 mm, 10-15 mm (50%) + 5-10 mm (50%)) were used. Density, consistency, void rate, permeability, compressive strength, and splitting tensile strength tests were performed on produced pervious concrete samples. As a conclusion, it was determined that aggregate size has been directly proportional to void rate, while void rate has been inversely proportional to compressive strength in pervious concretes. It was determined that optimum design mixture was the (P25-F100-C0) mixture which was produced with 5-10 mm basalt aggregates that had 25% cement paste volume.