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Reuse or recycling of construction and demolition waste (CDW) has become an inevitable trend in the world. Currently, the amount of CDW generated in Hanoi is estimated at more than 4,000 tons per day, of which only about 30% has been controlled and recycled. The CDW comes from many different sources such as construction, repair, renovation, demolition of houses, residential buildings, public buildings, transportation infrastructure works, etc... The CDW commonly comprises soil, bricks, mortar and concrete, and has been reused in many applications around the world. In Vietnam, there are also some research programs set up for reutilizing the material, however, has not been concretely applied in practice. In order to consider the applicability of CDW in road construction, an experimental program was conducted using CDW as the aggregate for the cement treated grain material base layer in road pavement structure. The weight ratios of cement used in the mixture were 4%, 5%, 6%, 7% and 8%. The test results showed that the main mechanical properties of compressive strength, split tensile strength and elastic modulus of the mixture, increased proportionally with the cement content in the mixture.

The solution of using organic and inorganic chemical agents to strengthen loading capacity of soil for base, subbase or surface layers in unpaved road pavement has been applied for a long time in the world. In Vietnam, the method has been applied with conventional such as lime, cement, fly ash, or bitumen. Since the years of 2000s, the new soil stabilizers have been introduced to Vietnam. However, the price of the imported admixtures is still the barrier for practical applications. DBS-06 is a domestic lignosulfonate soil stabilizer synthesized from the paper industry waste, which was collected from the HoaBinh paper factory located in Ky Son District, HoaBinh Province. The study program was conducted to investigate the main mechanical properties of the soil specimens stabilized by DBS-06intending for used in road construction. The test results showed that the soil treated with DBS-06 was significantly improved the strength of compression, split tensile and elastic modulus, the three critical indicators representing forload bearing capacity of the material, in both normal and water saturated conditions.

Dolomite is commonly used in the construction of highway pavement in the world. However, there are still no concrete specifications or regulations on the use of dolomite for highway construction. Dolomite is available in huge quantities in NinhBinh Province. This is a high potential material for grain bases of highway pavement structure. The alternative material could be a considerable contribution to diversify the supply of aggregate resources for highway pavement construction in the province, and thus contribute to the conservation of natural landscape heritages and limestone resources for related building materials manufacturing industries. In order to evaluate the use of dolomite in highway pavement construction, a research program is conducted to test the working capacity of the cement treated dolomite aggregate, which is intended to use as upper base material in pavement structure. The experimental results showed that the mechanical indicators of the mixture satisfy the requirements for the base layers of highway pavement structure.

Polymer concrete (PC) is a popular construction material used for repair, thin over-lays for floors and bridge decks, and other specialized fields such as precast components, machine construction. The material has many desirable properties such as fast curing, high compressive and flexural strength, high bonding to substrate, resistance to chemical agents. This study focuses on investigation properties of polymer concrete applying in repairing works of Portland cement concrete (PCC) pavement of airport by experiments. The research results in both laboratory and field tests showed that the material has advanced properties and meet very well the requirements from practice. This result has been proposed to apply polymer concrete for treatment of surface distresses of Portland cement concrete pavement of airports in Vietnam.

Assessing and predicting machine reliability and failure risks is an essential requirement of international standards for machine safety. The existing methods for determining reliability indicators and risk assessment are based on statistical information about failures and faults that occur during machine operation. Collecting, accumulation and processing of statistical data about failures of machines by traditional methods does not provide the necessary efficiency and reliability of the received information. In this connection forecasting of reliability, estimation, and risk management in production and operation of machines with necessary reliability is not a simple task. Modern diagnostic systems offer unlimited possibilities for the timely acquisition and transmission of information concerning the technical condition of machines, which can be used for the solution of problems. Depending on the structure and location of the transmission, storage and processing of the information, a distinction is made between stationary or remote diagnostics systems. With the modern development of communication and data transmission, remote systems are improved versions of stationary diagnostic systems. In the article the questions of formation of a recognition system and monitoring of a technical condition of building machines by means of the diagnostic information are considered. The main purpose of the development and implementation of the system is to ensure the reliability and safety of operation of construction machines. In order to solve this problem, it is necessary to recognize and promptly prevent the occurrence of failure, which requires the allocation of a special class of intermediate states, called pre-emergency. The results of the implementation of the recognition and monitoring system of construction machines with the help of diagnostic information are presented.

Foehn wind or foehn effect is a hot dry wind type blowing down from the mountains. It appears in the middle of Vietnam from early April to mid-September every year. The foehn effect has characteristic humidity drops deeply while the temperature rises. This has affected the concrete shrinkage deformation in the work construction. This paper presented an experimental study to evaluate the concrete shrinkage deformation under the influence of the Foehn wind in Vietnam. The experiment was performed in a simulated environment with temperatures high and humidity down, which is intended to simulate the phenomenon of foehn wind and climate change in the middle of Vietnam. The datasets obtained from this experiment were tested with previous results, it was highly accurate and reliable. The research obtained results have reflected that the concrete shrinkage deformation in foehn wind conditions has a significant effect compared to normal conditions in both the value and speed. In addition, this test also shows that the concrete shrinkage deformation with Ca(OH)2 added to in the mixture is smaller than concrete without Ca(OH)2.

Hydro-mechanical power-split transmissions (HPSTs) are a kind of continuously variable transmission; HPSTs integrated with the hydraulic energy recovery and accumulation function are the most coherent selection to im-prove the energy efficiency of the garbage truck. With an accumulator located in the speed-increasing hydraulic converter of the HPSTs, it is possible to recover and accumulate energy during braking and reuse energy when starting, accelerating or using other technologies in the process of garbage collection and transportation. Some results of simulation research and analysis of the energy recovery and accumulation process introduced in this paper can be used as a scientific basis for the complete design of energy saving powertrain systems, quality, and environmental friendliness for garbage trucks. In this study, the results of the simulation and analysis of the energy recovery and accumulation process were reported. Our findings can be used as a scientific basis for the complete design of energy saving powertrain systems, quality, and environmental friendliness for garbage trucks.

During the construction of massive concrete structures, the main factor that affects the structure is temperature. The resulting temperature is the result of hydration of the cement and some other factors, which leads to the formation of thermal cracks at an early age. So, the prediction of temperature history in massive concrete structures has been a very important problem. In this study, with the help of numerical methods, a temperature nomogram was built to quickly determine the maximum temperature in concrete structures with different parameters such as size, cement content, and the initial temperature of the concrete mixture. The obtained temperature nomogram has been compared with the results of the finite element method and the model experiment gives reliable results. It can be used to predict maximum temperature in mass concrete structures to prevent the formation of thermal cracks.

This article proposes a formula to determine the required amount of ice to partially replace the water in the concrete mix to control the initial temperature of the concrete mix and reduce possible cracking. The formula was created based on the principle of energy balance in the heat transfer process. At the same time, the obtained results were compared with the other methods. Besides, an example of the calculation for a concrete block during the construction was performed. The maximum temperature and temperature difference in mass concrete obtained depend significantly on the initial temperature of the concrete mixture. The research results and the proposed techniques can be used in the practical design of mass concrete structures.

This study presents a solution to contextualized span bridges constructed with composite steel girders with reinforced concrete slabs by reinforced concrete. This kind of structure, in comparison with a simple span, has many advantages as overcoming internal forces, reducing large displacements and cutting the number of expansion joints. Also, numerical simulations were conducted to evaluate the effectiveness of continuous composite beams for steel-concrete bridges and control of cracking of concrete at the supports at an early age. The models and conclusions in this paper can provide safety guidance for construct composite steel girder bridge in Vietnam.

In the last few decades, fires caused serious damage in civil engineering, especially in the high-rise building, factories, offices, etc. Usually the structures are built with fireproof materials such as concrete. It is a complex material, and its properties can change dramatically when exposed to high temperatures. This problem requires engineers to study and evaluate the effect of the fire in the structure. This paper studies the effect of the fire on the temperature distribution in concrete structure using Finite Element Ansys software. The results will be used to provide reference data for concrete structures under the action of fire. The research is an intermediate task to convert the fire activity in a structural model into the real impact in calculating model. It plays significant role in calculating structural model for counteracting the action of fire.

In construction practice of concrete mass needs a large amount of concrete. Due to the small surface area to volume ratio, the concrete mass is often happening thermal cracking caused by the release of heat during the hydration of the cement. The causes of thermal cracking in concrete mass are complex but the main reason is the increase in temperature in the concrete structure. Provide measures to control the maximum temperature concrete mass is very absolutely necessary. A finite element model of the concrete mass was established by the software Midas civil, the temperature field in the concrete mass has been determined and a mathematical model was created that adequately describes the influence factors on the temperature field in a concrete mass such as unit cement content, cement maximum heat released, the placing temperature of concrete and the water temperature in order to determine the optimal parameters.

In Vietnam, nano technology began to be interested in research and development, typically the seminar program of production research, silicon nano applications from waste materials and investment projects to build silicon nano manufacturing in Ho Chi Minh City. Researching the properties and applications of nano concrete in Vietnam with the desire to apply to some types of bridge and road structures today and step by step research on nano concrete application in designing some structure of bridges, roads, and other special works. With new materials used to determine the mechanical properties of materials and the characteristics of destruction at the limit of failure is essential. Moreover, high strength concrete materials are often brittle, so it is necessary to study measures to increase the plasticity to obtain the structure to ensure the requirements of the bearing and nano concrete with steel fibers. Steel fibers will make nano concrete increase tensile resistance in concrete.

This paper analyses and compares the performance of L*A*B* and HSV color spaces and applies them to calculate the injury rate on fish. To do these issues, the following steps are done. An original image is transformed into L*A*B and HSV color spaces. A channel “a” is separated from L*A*B* color space. In channel a, a formula to adjust “channel a value” is proposed to realize the shapes of injury on fish clearly and a new channel a is obtained by adjusting the channel a. The new channel “a” is converted into injury binary image by manual threshold. Otsu’s method is applied converted the original channel a image of fish shape into binary image. Finally, by calculating the number of pixels of areas of shape and total injury of fish, the injury rate is calculated. The steps of image processing of HSV color space is similar to L*A*B* color space. The proposed process are tested on fish.

Cracking is an important problem in the process of building a concrete massive structure. The overwhelming majority of cracks occurring in the concrete are usually caused by temperature effects. Because of this, it is essential to control and regulate temperature, it is necessary to prevent cracking. The formation of the temperature regime of a massive structure is affected by a large number of factors: its size; cement consumption and its maximum heat release; temperature of the concrete to be laid; ambient temperature, etc. In this paper, we consider the influence of the size and construction schedule of a massive concrete structure on its temperature regime. Using the computer program Midas civil 2011, the temperature regime was calculated, maximum temperatures were obtained in massive concrete and massive concrete columns with different sizes. The analysis of possible fracture for different values of the factors are considered.

During the construction of concrete dams from rolled-compacted concrete, the main effect on the structure are the temperature effects. As a result of heat generation during hydration of cement and the influence of many other factors, significant temperature gradients and cracks may occur. In this paper, the optimal maximum temperatures arising in the body of the concrete dam under construction are determined by the method of experiment planning and the method of numerical simulation - the finite element method. The analysis of the influence of the acting factors on the temperature regime and the thermal stressed state at the rock-built concrete dam from rolled concrete is carried out. The dependences are obtained and nomograms are constructed to determine the optimal parameters. With the help of the computer program Midas Civil 2011, calculations of the temperature regime of the constructed dam were carried out and the maximum temperatures were determined. The calculations of thermal stress state of the structure along with an analysis of the possible cracking are conducted.

The benefits of using mineral additive as a partial replacement for cement in heavyweight concrete are discussed. This paper presents the strength development and temperature distribution of concrete using Class F of natural pozzolan (PU) sourced from Northern part of Vietnam. Based on the results of conducted studies, strengths of the natural pozzolan concrete at different ages were generally lower than those of control concrete. The 7-day compressive strengths of concrete with 20% PU decreases mostly by 30.1% and least by 12.3% at the age of 28 days in comparison with control concrete. However, natural pozzolan increases the workability of fresh concrete up to 16.67% in comparison with control concrete. By using the computer program Midas Civil, the maximum temperatures at the center of concrete block with 100% cement and of concrete block with 80% cement + 20% PU are 65.7600C and 52.4400C, respectively, after 48 hours from the beginning of pouring. In addition, temperature difference between the central point and the environmental temperature of the control concrete are higher than heavyweight concrete using 20% PU. Meaningfully, the risk of through thermal cracking of heavyweight concrete without pozzolan are higher than heavyweight concrete PU to replace 20% of mass cement.

The paper focuses on problems of the engineering implementation of 3-axis gyrostabilizer of the camera for orthophotography performed from light and ultralight aircrafts. The functional diagram of gyrostabilizer is characterized by a lighter ball-bearing having a large inner diameter used for the platform suspension on its internal (vertical) axis. The problem is to transfer the supply voltage to the platform and the electric signals to and from the platform. Design solutions concerning the power supply and information transfer are supported by the experimental techniques suggested in this paper, namely: the use of the rolling contact; three-phase gyro motor power supply replaced by that from the single-phase network; signal transmission from the precession angle sensor using the air transformer; current and voltage frequency division; DC mode selection for the torquer. The results obtained prove the efficiency of the suggested design solutions.