| dc.description.abstract | This research aims to evaluate the characteristic of fine particles containing electric arc furnace slags, by chemical analysis (pH value analysis, Phenolphthalein Test, optical microscope analysis, and XRF analysis) and physical analysis (expansion test, appearance and morphology, and Compressive strength test), to explore the influence of adding electric arc furnace slags on fine aggregates and cement matrix materials, and to initially establish a systematic testing standard based on those results. This research desires to put forward a simpler, faster, more accurate testing method that can be adapted to local conditions, to ensure the safety of the structure.
The results of the chemical analysis show that the pH value of the test results increases with the reduction of particle size. The possibility that the pellets are mixed with slag can be judged by whether the pH value is ≥ 9. The color of phenolphthalein after testing is mainly transparent/white, light red, and dark red, and the color saturation degree increases with the decrease of particle size and the increase of dosage. Optical microscope analysis is more suitable for calculating the maximum proportion of large-area slags in the particle calculation, and the maximum error does not exceed 20%. It can be seen from XRF that the main component of natural pellets is SiO2, followed by Al2O3. Both the oxidized slags and the reduced slags are mainly composed of CaO. The results of the physical analysis show that, for the control group, the test age must be increased to more than 120 days in order to observe differences when using the detection method at room temperature. Using the detection method in high temperature and high alkali environment, the influence of the mortar rod due to the expansion of the slag can be effectively observed when the test age is 5 days. Testing those specimens in high temperature and high-pressure environment, it was found that the expansion amount after autoclaving increased with the increase of the slags mixed, and the compressive strength after autoclaving showed different degrees of strength reduction. The expansion of the mortar bar increases with the increase of the autoclaving time. The expansion of the slags can be observed about 1.0 to 1.4 times at 3 hours, and then increases by about 1.0 to 1.6 times when it increases to 6 hours. After the autoclaved deterioration of the mortar block, preliminary classification was carried out based on the appearance of the specimen, and the grades were A-E from good to bad. The compressive strength test results show that the reduction is about 1.2 to 3.4 times at 3 hours, the compressive strength of oxidized slags is reduced by about 1.1 to 1.5 times when it increases to 6 hours, and the reduced slags are less stable at 6 hours. These results can be explained due to the hydration reaction of cement and reduced slags under high temperature.
According to this research results, the slags detection process is determined as follows: (1) The sample is firstly judged by the phenolphthalein discoloration test, (2) The pH value test is used to verify the proportion of the slags mixed, (3) The optical microscope is used to determine the proportion of the slags. The particle calculation method infers the accurate content of the slag. (4) If the proportion contained is too high, a mortar sample can be made for high temperature and high-pressure environmental testing to verify its safety. | en_US |