Tayfun Uygunoğlu

Physical and Mechanical Properties of Polymer Composites with High Content of Wastes Including Boron

In this study, we studied the physical and mechanical properties of polymer composite with wastes that incorporating boron. The polymer composites were produced with epoxy based resin and wastes as mineral additive. The wastes were added to mixtures in different ratio by replacing the resin from 0 to 66% by weight. Slump-flow and viscosity tests are carried out on fresh samples after mixing. Composites were cured in air condition and they were de-molded after 24 hours. They gain ultimate strength after 7 days. Therefore, tests for characteristics were performed on 7 aged specimens. On the polymer composite samples, compressive strength, flexural strength, wear resistance, water absorption and density tests were performed. As a result, addition of the wastes that including boron increased the compressive strength of polymer composites; however, it made the composites more brittle material with low flexural strength.

Effect of mixing water types on the time-dependent zeta potential of Portland cement paste

Abstract The measurement of zeta potential (ZP) has important applications in a wide range of industries including ceramics, pharmaceuticals, medicine, mineral processing, electronics, cement industry and water treatment. It provides new information on cement hydration, gel structure formation and the effects of chemical and mineral admixtures. In this study, ZP and pH measurements of Portland cement suspension prepared at wt% 1 cement/water ratio in the presence of four different types of waters, i.e., pure water, tap water, and salted (NaCl and CaCl2) water, were carried out depending on the time. Also, vicat tests of Portland cement pastes prepared at a water-to-cement ratio of 0.34 were performed. After the vicat tests, X-ray diffraction analysis and scanning electron microscopy investigations were performed on the samples. The most important result obtained from this study is that setting time and time-dependent ZP values of Portland cement paste have different values depending on the used mixing water type. Among the water types, water with CaCl2 gives the lowest ZP as absolute value, so this leads to minimum initial and final setting times for the cement paste prepared with this type of water.

Wear and friction of composites of an epoxy with boron containing wastes

Polymer surface coatings provide superior adhesion to substrates, some flexibility and corrosion resistance. On the other hand, 400,000 ton of boron wastes are generated each year. We have developed polymer composites based on epoxy resins containing up to 50 wt. % of boron wastes and determined their pin-on-disk dynamic friction, wear, Shore D hardness and surface roughness. The hardness and wear resistance increase with increasing boron waste concentration. An equation, with parameters dependent on the load, relating wear rate to hardness is provided. Dynamic friction increases with increasing surface roughness, as represented by the equation. Further, dynamic friction is an increasing function of the wear rate. Micrographs of pure epoxy without fillers shows traces after pin-on-disk testing, with tears, breaks and cracks. For the composites, we observe simpler and relatively homogeneous surfaces.

Effect of aggregate type on linear thermal expansion of self-consolidating concrete at elevated temperatures

Abstract In this study, the effects of aggregate type on the coefficient of thermal expansion of self-consolidating concrete (SCC) produced with normal and lightweight (porous) aggregate (SCLC) were investigated. In experiments, three aggregate types, gravel, volcanic tuff, and diatomite, were used. Different combinations of water/cement ratio and superplasticizer dosage levels were prepared for the SCC and SCLC mixtures. Thermal tests were performed to accurately characterize the coefficient of thermal expansion (CTE) of SCC and SCLC aged 28 days using the dilatometer. The CTEs of SCC and SCLC were defined by measuring the linear change in length of concrete specimens subjected to a range of temperatures from 20°C to 1000°C. The results, in general, showed that SCLC has a lower CTE than that of SCC above 100°C. Moreover, CTE values of SCC and SCLC were decreased with increase in porous structure. The aggregate type has significant influence on the thermal properties of SCC.

Electrical Curing Application on Cement-based Mortar with Different Stress Intensity

In this study, the effects of different stress intensity on the electrical resistivity of hardening (setting) cement-based mortar were investigated. In experiments, four different mould (5 × 5 × 10 cm, 5 × 5 × 15 cm, 5 × 5 × 20 cm and 5 × 5 × 25 cm) were used. Different combinations of stress intensity (7.5, 15, 22.5 and 30 V) were used on mixtures. The measurements were done at room temperature. Electrical resistivity and setting time of the specimens with and without electric current application were also investigated. Moreover, specific setting hydration temperature was measured by using thermocouple. As a result, electric current application can be used for obtaining to rapid setting time on the mortar with high volume stress intensity.

Comparison of properties of prefabricated interlocking pavement blocks cured at different conditions

In this study, influence of curing condition and fly ash content on properties of pre-fabricated concrete interlocking blocks (PCIBs) were investigated. The blocks were produced with crushed sand stone (fine) and crushed stone (coarse) as aggregate. Also, fly ash was added to mixtures in different ratio by replacing the cement from 0 to 30%. PCIBs were cured in three different types as steam cure, water-pool cure and wet cure. Compressive strength, tensile splitting strength, density, apparent porosity, water absorption by weight and abrasion resistance of PCIBs was determined. When comparing the PCIBs, the use of wet cure results in lower physical and mechanical properties after 28 days. By contrast, water-pool and steam cure gives better result on mechanical and physical properties. Also, replacement of cement with fly ash (from 10% to 20%) has a significant effect in increasing important properties of PCIBs.