Browsing by Author "Tobbala D.E."

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Effect of using wastewater from the ready-mixed concrete plant on the performance of one-part alkali-activated GBFS/FA composites: Fresh, mechanical and durability properties
(2023-10-01) Bodur B.; Bayraktar O.Y.; Benli A.; Kaplan G.; Tobbala D.E.; Tayeh B.
Water scarcity is the world's most pressing issue, as concrete batching facilities and concrete mixer trucks produce massive amounts of wash water every day. Recycling waste water from ready-mix concrete factories' concrete washing water is critical for conserving hundreds of millions of tons of water and preventing water and soil contamination. This study examined the impact of waste washing water on the microstructural, durability, fresh, and mechanical characteristics of one-part alkali-activated ground blast furnace slag (GBFS)/fly as (FA) composites (AAC) containing partial and complete replacement of tap water under ambient conditions. GBFS was used as the main binder in the production of AAC. FA was also used as a binder at 0%, 25%, and 50% instead of GBFS. Sodium metasilicate (MS) was used as a one-part activator at two dosages 7.5% and 15% of the total binder. The fresh properties (setting time and flowability), physical properties, compressive and flexural strength (3, 7, 28, 90, and 180 days) and durability (high-temperature resistance, freeze, and thaw resistance, drying shrinkage, sorptivity, HCl and MgSO4 resistances, NaCl effect and alkali-silica reaction) and microstructure analysis were investigated. The findings showed that the use of wastewater (WW) instead of tap water (TW) contributed positively or had no serious negative effect on the mechanical and durability properties of AAC. Compressive strength of 72.37 MPa and 81.67 MPa was gained with the inclusion of 50%WW at 7.5 and 15 %MS content respectively. The findings showed that WW improved the workability of fresh ACC containing FA, reduced dry shrinkage and sorptivity of ACC with 15%MS content, and refined the pores of hardened ACC. The results also supported that WW contributed to the decrease in expansion due to ASR and sulfate expansion. Using WW improved the high temperature and F-T resistance of ACC mixtures containing 15%MS content.
Hemp fiber reinforced one-part alkali-activated composites with expanded perlite: Mechanical properties, microstructure analysis and high-temperature resistance
(2023-01-11) Bayraktar O.Y.; Tobbala D.E.; Turkoglu M.; Kaplan G.; Tayeh B.A.
The objective of the current research is to find out what impacts hemp fibers (HF) lengths and percentages have on the fresh, physical, mechanical, sorptivity, dry shrinkage, and thermal properties of HF-reinforced alkali-activated composite (AAC) reinforced with ground blast furnace slag (GBFS). Two groups of AAC mixes with 10 and 20 mm HF lengths were produced. Each group contained different percentages of HF with varying fiber lengths added to mixes at 0.5 %, 1 %, 2 %, and 3.0 % by weight of cement, respectively. Flow diameters were measured to determine the fresh-state properties of the AACs. Water absorption and apparent porosity were determined as physical properties. The unit weights of AAC mixtures are between 1045–1672 kg/m3. Measurements were made on compression and flexural characteristics at 7 and 28 days. The 28-day compressive strengths of AAC mixtures vary between 1.28 and 2.73 MPa, and the bending strengths vary between 0.48 and 1.65 MPa. AAC was also tested for water absorption, drying shrinkage, thermal conductivity, fresh and dry unit weight and porosity. The resistance of high temperatures at 250, 500, and 750 °C was determined. There is a significant improvement in compressive and flexural strength and thermal conductivity when HF is added at a 20 mm length. This improvement was confirmed and emphasized through scanning electron microscopy (SEM). According to study results, high-temperature alkali cooking treatments up to 250 °C may improve the thermal stability of HF cellulose. The best HF mix, M2-2 %, increased the 28-day compressive strength by 28.8 % and produced the best results at temperatures as high as 750 °C. The compressive strength of the mixtures exposed to 750 °C was obtained as approximately 2 MPa.