Meteorological Observations of the Vento Norte Phenomenon in the Central Region of Rio Grande do Sul

During the cold season, episodes of a windstorm known as Vento Norte (VNOR) are frequently observed in the city of Santa Maria, situated in the central region of Rio Grande do Sul (RS). The onset of this windstorm is characterized by strong gusts with northerly component which are accompanied by a sharp increase in temperature and abrupt drying. A methodology based on the observed behavior of the standard deviation of temperature during VNOR was successful in identifying the onset and demise of the windstorm. Additionally, the research shows the results of different micrometeorological variables during the event. Early morning and evening atmospheric profiles exhibit an elevated mixed layer over central RS in association with the strong VNOR winds, indicating the presence of mechanically-forced mixing during nighttime hours.

Coupling of mechanical deformation and reaction in mechanochemical transformations

Co-deformation and forced mixing contribute to the rate of chemical reaction between molecular solids subjected to mechanical processing.

Experimental study on the influence of mixing time on concrete performance under different mixing modes

To study the influence of different mixing times on the performance of concrete under vibration mixing and conventional mixing, C40 and C60 are selected in this paper to verify the influence of mixing time of 60, 75, 90, 105, and 120 s on the compressive strength and durability of concrete comparing vibration mixing and common forced mixing. The results show that the early strength of concrete is more significantly improved in 3 and 7 day; the strength with vibration mixing for mixing 105 s in each age is higher than that of conventional mixing at 120 s; under the condition of guaranteed strength, the mixing time of at least 15 s can be reduced. The strength of C40 concrete with vibration mixing has a peak value with the corresponding mixing time of 105 s, and the rapid growth stage of compressive strength is 15 s earlier than that of conventional mixing. For all mixing time, the electric flux of vibrated concrete is significantly smaller than that of forced concrete, and the change rate is generally above 10%; compared with conventional mixing for 120 s, the durability of C40 and C60 concrete increases by 11.8 and 11.1%, respectively, at the time of vibration mixing for 105 s. It was found that under the same mixing time, the compressive strength of concrete with vibration mixing method is higher than that of conventional mixing. In a certain range, the durability of concrete can be improved by prolonging the mixing time.

Anti-cracking Technology and Application of Fiber Reinforced Concrete on Bridge Deck Pavement

In order to make the bridge deck pavement not easy cracking, the anti-cracking technology is put into effect on a certain bridge. The cementing material is selected after analyzing the theory that how fiber can enhance the concrete anti-cracking performance. The proper fiber is selected by testing and comparing the dispersibility and hydroscopicity of three kinds of fibers. The proper content of fiber is found by test and comparing different fiber contents in the same mix proportion concrete. The fiber is sent into the in forced-mixing concrete plant by spreading the fiber on the crawler belt. The construction technology including slab treatment, transport, pave, vibrate and curing is put forward. After 1 year observing, there is no any cracking on the bridge deck pavement. The life of bridge is increased. The cost of maintain is decreased. The goal of anti-cracking has been achieved.

Influence of Ultrafine Addition Obtained from Pre-Hydrated Cement on Cement Paste

This article focuses to influence of a pre-hydrated cement suspensions on hardening cement paste properties investigation. The pre-hydration was occurred by 2-th, 4-th 6-th hours during forced mixing. Changes of particle dispersion caused by hydration were determined. It is shown that by hydrolysis increase particles dispersion and subsequently increases quantity of new hydrate formations. Influence of the pre-hydrated cement suspensions on hardening cement paste properties is determined. It is shown that application pre-hydrated addition leads to increasing a cement paste water demand by 12, 17 and 14% for duration of hydration by 2, 4 and 6 hours consequently and to decreasing setting time. It caused by generating supplementary new formations of crystalline hydrate with subsequently increasing rate cement paste structuration. Rate of hardening was increased with increasing duration of the pre-hydration for 10% pre-hydrated cement addition. Obtained results may recommended the addition of pre-hydrated cement in form of cement suspension as cement gel for concrete nanomodification

Features of vibration mixers design

The article presents the results of the analysis of vibration mixers designs, presents their classification. The classification is based on the principle of action and the method of mixing. Practice has shown that mixing by vibration produces a significant effect. With vibrational mixing, all the expected components are evenly distributed throughout the volume of the mixture. The main disadvantage of the vibration method is the negative impact on the design of the mixer, as well as on the environment and humans. The problems that complicate the design of vibration mixers include a wide range of physicomechanical properties of the mixed components, a significant difference in the concentration of the components of the mixtures. The advantages are the intensification of the mixing process, the possibility of more efficient mixing of materials with different physicochemical properties compared with other mixing methods, significant time savings on the process, and energy efficiency of vibration technologies. Three main categories of vibration mixers are distinguished by design features and the mixing method: vibration mixers with self-circulation of the mixture, vibration mixers with forced mixing with vibration effects on the components of the mixer, vibration mixers with free mixing with vibration effects on the components of the mixer. Based on the analysis, one can consider a perspective direction the design of vibration mixers of the first and second groups, increasing the efficiency of vibration mixers is possible through the introduction of the latest technologies and the use of modern materials. The creation of effective vibration exciters is one of the main tasks of improving the design of vibration mixers. A comparative analysis of vibration mixers with mechanical inertial, eccentric, electromagnetic, pneumatic, hydraulic and other types of vibration exciter is carried out. One of the promising directions for the design of vibration mixers is associated with the creation of effective vibration exciters with an amplitude controlled during operation.