Browsing by Author "Kaplan, Gokhan"

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Microstructure and durability properties of lightweight and high-performance sustainable cement-based composites with rice husk ash.
(2021-10-01T00:00:00Z) Kaplan, Gokhan; Salem Elmekahal, Mohamed A
Sustainable solutions are investigated to reduce the environmental damage caused by greenhouse gases and CO emissions. Cement is a construction material responsible for greenhouse gases and CO emissions. Thus, CO emissions are reduced by using replacement materials such as rice husk ash instead of cement. This study investigated the durability and mechanical properties of lightweight and high-performance, sustainable cement-based composites. A foaming agent was used to reduce the unit weight of the mixtures. Also, pumice powder (PP) and rice husk ash (RHA) were used to improve cement-based composites' durability and mechanical properties. The density of mixtures varies between 1666 and 2205 kg/m. The early age strength of the mixes using 12.5% RHA has increased. The mixtures' compressive strength (91 days) with 25% RHA and 50% PP was 46.6 MPa. As the PP content of mixes increased, drying shrinkage values increased. Expansions decrease as the initial compressive strength increases in mixtures exposed to sulfate. As RHA and PP's ratio increased, weight loss decreased in mixes exposed to HCl, while weight loss increased in mixes exposed to HSO. It was determined that the content of CH(OH) is important in mixes exposed to HCl and impermeability is important in mixes exposed to HSO. It has been observed that the initial compressive strength is also important in mixes exposed to the freeze-thaw effect. As the foam content of the mixes increased, the compressive strength decreased, while the drying shrinkage increased. As a result, using up to 25% RHA has increased the performance of cement-based composites.
The impact of recycled coarse aggregates obtained from waste concretes on lightweight pervious concrete properties.
(2021-04-01T00:00:00Z) Kaplan, Gokhan; Gulcan, Aslinur; Cagdas, Betul; Bayraktar, Oguzhan Yavuz
Significant environmental damage can result from the use of natural resources such as cement, aggregate, and water in concrete production. Thus, more sustainable alternatives for concrete production are needed to protect the environment and natural resources. In this study, lightweight pervious concrete production involving recycled coarse aggregates (RCAs) with potential to cause environmental pollution was investigated. First, RCAs were produced from concretes possessing low compressive strength and were classified. Second, pervious concretes were produced from these RCAs. Third, the mechanical properties, permeability, and abrasion strength of the pervious concretes were determined. The water/cement (w/c) ratios of the mixtures were determined to be 0.32, 0.34, and 0.36, and the aggregate/cement (a/c) ratios were selected to be 3.5 and 4. Twelve different pervious concretes were produced and tested in total. The bulk densities (BD) of the mortars varied over an interval of 1160-1080 kg/m. The aim was to design pervious concretes with lightweight bulk densities. When the w/c ratio was 0.34, the compressive, splitting tensile and abrasion strengths were high. The compressive strength of the pervious concretes varied over an interval of 1.50-2.00 MPa. It was determined that for optimal permeability, the most appropriate w/c ratio was 0.36, and the best a/c ratio was 4. When the a/c ratio was 4, the strength values were high, and as a result, the mechanical properties were poor. With respect to aggregate gradation, it was determined that a grain size distribution of 9.50-12.50 mm was most suitable for this pervious concrete. Recycled aggregates with low strength produced low strength concrete. Therefore, the pervious concrete produced in this study is most suitable for pedestrian roads where heavy vehicle traffic does not exist.