| 1. |
- Çelik, Ali İhsan, et al.
(författare)
-
Mechanical performance of geopolymer concrete with micro silica fume and waste steel lathe scraps
- 2023
-
Ingår i: Case Studies in Construction Materials. - : Elsevier. - 2214-5095. ; 19
-
Tidskriftsartikel (refereegranskat)abstract
- Environmental studies for solutions are among the most important agendas of the scientific world. Most of the new studies are taking into account environmental effects. However, it is interesting for the scientific world to find solutions for accumulated environmental problems, to reduce harmful production, and to turn wastes that cause environmental pollution into useful products. In addition to incorporating fly ash, a recognized environmentally friendly and sustainable material, geopolymer concrete, utilizes micro silica fume (micro silica) as a binding agent. Furthermore, waste lathe scraps are introduced to enhance and safeguard the concrete’s mechanical properties. During the preparation phase, significant enhancements have been identified in the workability and setting time of concrete. A total of 16 test samples were prepared in this study. Micro silica of 0%, 5%, 10%, and 20%, and lathe scraps of 0%, 1%, 2%, and 3% were examined. Experimental findings revealed that incorporating 5% micro silica resulted in notable improvements in the compressive, flexural, and splitting tensile strengths, with the increases of 14.4%, 7.45%, and 6.18%, respectively. However, higher additions of 10% and 20% were found to decrease these strengths. In contrast, the inclusion of 1% lathe scraps led to considerable increases in the compressive, flexural, and splitting tensile strengths by 11.4%, 6.35%, and 8.23%, respectively. However, the addition of 2% and 3% lathe scraps resulted in the reduced capacity. The findings demonstrated that combining 5% micro silica with 1% lathe scraps provided the highest strength, with the improvements of 25.7%, 14.4%, and 12% in the compressive, flexural,and splitting tensile strengths, respectively. Considering the enhancements in the workability, setting time, and strengths observed in all the tests, the recommended optimal geopolymer mixture is 5% micro silica together with 1% lathe scraps.
|
|
| 2. |
- Madenci, Emrah, et al.
(författare)
-
Behavior of functionally graded carbon nanotube reinforced composite sandwich beams with pultruded GFRP core under bending effect
- 2024
-
Ingår i: Frontiers in Materials. - : Frontiers. - 2296-8016. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- A novel generation of composite sandwich beams with laminated carbon fiber-reinforced polymer skins and pultruded glass fiber-reinforced polymer core materials was examined for their flexural behavior. The strength and failure mechanisms of the composite sandwich beams in flatwise and edgewise configurations were investigated using three-point static bending tests. These sophisticated composite structures must be designed and used in a variety of sectors, and our research provides vital insights into their performance and failure patterns. In comparison to the reference specimens (FGM-1), the carbon nanotube-reinforced specimens’ bending capacity was affected and ranged from −2.5% to 7.75%. The amount of the carbon nanotube addition had a substantial impact on the beams’ application level and load-carrying capacity. Particularly, the application of 0.5 wt% additive in the outermost fiber region of the beams, such as in FGM-4, led to an increase in the bending capacity. However, the stiffness values at the maximum load were decreased by 0.3%–18.6% compared to FGM-1, with the minimum level of the decrease in FGM-4. The experimental results were compared with the theoretical calculations based on the high-order shear deformation theory, which yielded an approximation between 11.99% and 12.98% by applying the Navier’s solution.
|
|
| 3. |
- Madenci, Emrah, et al.
(författare)
-
Experimental investigation and analytical verification of buckling of functionally graded carbon nanotube-reinforced sandwich beams
- 2024
-
Ingår i: Heliyon. - : Elsevier. - 2405-8440. ; 10:8
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon nanotube (CNT) reinforcement can lead to a new way to enhance the properties of composites by transforming the reinforcement phases into nanoscale fillers. In this study, the buckling response of functionally graded CNT-reinforced composite (FG-CNTRC) sandwich beams was investigated experimentally and analytically. The top and bottom plates of the sandwich beams were composed of carbon fiber laminated composite layers and hard core. The hard core was made of a pultruded glass fiber-reinforced polymer (GFRP) profile. The layers of FG-CNTRC surfaces were reinforced with different proportions of CNT. The reference sample was made of only a pultruded GFRP profile. In the study, the reference sample and four samples with CNT were tested under compression. The largest buckling load difference between the reference sample and the sample with CNT was 37.7%. The difference between the analytical calculation results and experimental results was obtained with an approximation of 0.49%–4.92%. Finally, the buckling, debonding, interlaminar cracks, and fiber breakage were observed in the samples.
|
|
| 4. |
- Qureshi, Hisham Jahangir, et al.
(författare)
-
Prediction of compressive strength of two-stage (preplaced aggregate) concrete using gene expression programming and random forest
- 2023
-
Ingår i: Case Studies in Construction Materials. - : Elsevier Ltd. - 2214-5095. ; 19
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this research is to predict preplaced-aggregate concrete (PAC) compressive strength (CS) by using machine learning approaches such as gene expression programming (GEP) and random forest (RF). PAC requires injecting a portland cement-sand grout with admixtures into a mold after coarse aggregate has been deposited, making CS prediction complicated and requiring substantial study. Machine learning methods were used to cut down on the time and money needed for extensive experimental testing. The database includes 135 values for CS with eleven input variables. There is an acceptable degree of agreement between predicted and experimental values, as shown by the CS R2 values of 0.94 for GEP and 0.96 for RF. When comparing RF with GEP, RF performed better as measured by R2. The lower values displayed by the statistical error also showed that RF performed better than GEP. To compare, the GEP model's COV, MAE, RSME, and RMSLE were 0.527, 1.569, 2.706, and 0.133, whereas those for RF were 0.450, 1.648, 2.17, and 0.092. The SHAP analysis showed the effects of each input parameter, illuminating the positive effect of increasing the superplasticizer content on strength and the negative effect of raising the water-to-binder ratio. Using machine learning approaches to forecast the CS of PAC, this study has the potential to boost environmental protection and economic advantage.
|
|
| 5. |
- Özkılıç, Yasin Onuralp, et al.
(författare)
-
Optimum usage of waste marble powder to reduce use of cement toward eco-friendly concrete
- 2023
-
Ingår i: Journal of Materials Research and Technology. - : Elsevier. - 2238-7854 .- 2214-0697. ; 25, s. 4799-4819
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, waste marble powder (WMP) was used to replace cement of concrete in specific amounts. To accomplish this aim, WMP was replaced at 10%, 20%, 30%, and 40% of the cement weight, and a reference concrete sample without WMP (REF) was created to compare the compressive strength, splitting tensile strength, and flexural strength. The replacement of WMP at 10%, 20%, 30%, and 40% of the cement weight resulted in 5.7%, 21.7%, 38.1%, and 43.6% decreases in the compressive strength compared with REF. Furthermore, the splitting tensile strength results commonly followed the same trend as the compressive strength. However, WMP at 10%, 20%, 30%, and 40% led to 5.3%, 8.6%, 19.4%, and 26.7% decreases in the flexural strength compared with REF. In addition, three different calculations, ranging from simple to complex, were proposed to compute mechanical resistances of concrete with WMP. These proposed calculations for practical applications were validated using values from the literature and the implications obtained from the current research. While the simple calculations were based on the strength of REF and the WMP percentages, the complex calculations were dependent on the design of the concrete mixture, age of the samples, and the WMP percentages. For the complex calculations, the ANN approach was used with the help of the coefficient of determination (R2) for the K-fold cross validation method. All the proposed methods provided high accurate estimation to predict the properties of concrete with WMP. Based on the studies, utilizing 10% WMP as the replacement of cement is recommended to obtain the optimum benefits considering both mechanical and environmental aspects. Moreover, scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analyses were then conducted to observe the interaction of WMP in concrete. According to the SEM analyses, some pores were detected and the interfacial transition zone was observed in the reaction zone. On the other hand, based on the EDX analyses, the presence of WMP in concrete was manifested by the presence of high levels of calcium.
|
|
