In this paper, a sensitivity of ultrasonic wave transmission method to detect the presence of different superplasticizers and hiperplasticizers in cement pastes is discussed. A completely new ultrasonic apparatus Pundit Lab+ of Proceq company was used and analysis of variance was performed in order to analyze the reproducibility of the method and apparatus itself. Different admixtures of TKK Srpenica and different dosages of the admixtures were used within this project. It was found that the ultrasonic wave transmission method can be used very effectively to detect the presence of different superplasticizers (SP) and hiperplasticizers (HP) in cement pastes. Moreover, using this nondestructive method, one is able to analyze the influence of these admixtures on the formation of structure of different cement pastes at early ages.
COBISS.SI-ID: 955998
In this paper, a possibility of using a frequency spectrum of ultrasonic P-waves to monitor the hydration process and formation of structure of different cement pastes at early ages is studied. A new parameter, labeled as a TG factor, is introduced, which is defined as a dimensionless ratio between maximum amplitudes of two dominant frequency ranges that appear in a frequency spectrum of received ultrasound signals. The evolutions of the TG factor with time of various cement pastes show, that four stages and three characteristic points can be identified on the TG-vs.-time graphs, indicating that the development of the frequency spectrum is closely related to the setting phenomena. By comparing the TG factor and the P-wave velocity evolutions in time, some important milestones in the setting process were identified. The time when the higher frequencies in the frequency spectrum begin to develop was found to be correlated to the reduced workability of the cement pastes while the initial setting seems to correspond to the time when the amplitudes of lower and higher frequencies become equal. Since the P-wave velocity and the TG factor were found to detect some different phenomena that appear during the hydration process, the combined use of these two parameters results in a more comprehensive ultrasonic method that gives a more complete picture of the setting.
COBISS.SI-ID: V reviziji
In this paper, some basic types of different chemical admixtures in cement based materials are briefly described. Since superplasticizers are the most frequently used chemical admixtures in cement based materials, the paper demonstrates the influence of these chemical admixtures on the setting process of the materials. The possibility of using a new, nondestructive ultrasonic method to analyze the influence of this type of chemical admixtures on the formation of structure of the materials is also presented. The combined use of chemical admixtures and this ultrasonic nondestructive method results to a more economical building construction, reduces the material consuption and consequently contributes to the responsible environmental management.
COBISS.SI-ID: Sprejeto v