Bo Tian

Reduction of Tire-Pavement Noise by Porous Concrete Pavement

AbstractThis study investigates the effect of Portland cement porous concrete on tire-pavement noise reduction. The acoustical absorption coefficients were measured in the laboratory for porous concrete materials representing combinations of various maximum aggregate sizes, gradation, layer thickness, and composition layers. The laboratory results indicated that porous concrete with a maximum aggregate size of 9.5xa0mm had the highest acoustical absorption coefficient. They also showed that the peak absorption coefficient depends on the mixture characteristics and the thickness of the specimen. A thickness of 80xa0mm had optimum absorption. The results from the laboratory study were used to design and build a test road in the field with two test cells. The wet-on-wet construction method was successfully used to build the porous cement friction course over conventional concrete pavement. Tire-pavement noise was measured on the test cells using the close-proximity method under various vehicle speeds and differe...

Effect of methylene blue (MB)-value of manufactured sand on the durability of concretes

The relation between the methylene blue (MB) value of MS and its limestone powder content and clay content was investigated. The effects of MB values ranging from 0.35 to 2.5 on the workability of fresh concrete, the mechanical properties, the resistance to freezing as well as the resistance to chlorine ion permeation of the hardened concrete were all investigated. The experimental results showed that the MB value had no correlation with the limestone powder content of MS, while it was directly related to the clay content. With an increase of MB value, concrete workability decreased, as did the flexural and 7-day compressive strengths, however, the 28-day compressive strength was not affected. Furthermore, influence of MB value on concretes of different strength levels was different. For low-strength concretes, an increase of MB value could improve its impermeability, but this was not the case for high-strength concretes. Instead, their resistance to chloride ion permeability decreased slightly. However, even a slight increase in MB value remarkably accelerated freeze-thaw damage of MS concrete. It was thus concluded that the critical MB value of 1.4 would not cause significant deterioration in the performance of MS concretes.

Precast Pavement Smoothness Control Method

In the course of road maintenance, importance has been gradually attached by administrative authorities to precast pavement for its advantages like quickness, endurance and eco-friendliness. To ensure the smoothness of precast pavement, analyses and researches were done in terms of, say, precast pavement slab precision control, base course treatment, fabricated pavement slab leveling and treatment of joint faulting, and a control measure to ensure and improve the smoothness of precast pavement is suggested with consideration given to its service effectiveness in actual projects.

Research on skid resistance and noise reduction properties of cement concrete pavements with different surface textures

AbstractThe present study discusses the use of the new windscreen pavement/tire noise testing method and the lateral friction coefficient test vehicle to test the skid resistance and noise reduction properties of cement concrete pavements with different surface textures and to analyze the skid resistance and noise reduction mechanisms of pavements with different surface textures. The tests show that the improved noise testing equipment can effectively check the interference of outside noise and ensure the accuracy of test data. In addition, by improving the common surface texture of cement concrete pavements, the pavement noise can be reduced and skid resistance is increased. The noise of porous, exposed aggregate, and longitudinally grooved cement concrete pavements is equal to that of asphalt pavements and all of them display good skid-resistant effect.

Cement Mortar Liquidity Testing Method by Rheological Properties

AbstractA cement mortar mixer that can test torque is designed to realize online observation of working performance of the cement mortar and to predict cement mortar slump. The influence of different rotating speeds and mixing times on cement mortar quality is analyzed using factors of slump and torque. The best stirring speed is determined to be 180u2009u2009r/min and the best mixing time 60–180xa0s. The relation between cement mortar slump and torque at different shear rates is studied, and different power functions for different shear rates are found. At a given shear rate, i.e.,xa0a rotation speed of 180u2009u2009r/min, the relation between slump and torque is set up, which could provide a test method and theoretical basis for cement mortar online quality control and slump forecast.

Research on Roller Compacted Concrete Graduation with Vibration Liquefaction

In the rolling process, reasonable way of grading and rolling can improve the compactness and anti-permeability of roller compacted concrete (RCC), as well can make its strength meet the design requirements. Vibration liquefaction is the key step for RCC in the rolling process. Therefore, this paper first puts forward the more suitable method, Modified Vebe Vibration Liquefaction Test, to account for the characteristics of vibration liquefaction in RCC, and then, studies the coarse aggregate gradation scope using aggregate gradually filling theory. Though Modified Vebe Vibration Liquefaction Test, the research show that the aggregate VCA and the characteristics of vibration liquefaction of RCC have a good correlation. Finally, by studying the sand ratio and fineness modulus of sand how to affect the performance of liquefied RCC, the optimum value range of sand ratio and fineness modulus of sand was determined.

Test and Study on the Long-Age Performance of Cement Concrete Pavement Material

Experimental research is conducted to determine the long-age statistical parameters of road pavement properties such as flexural strength, flexural elastic modulus, compressive strength, and splitting strength after 18 months. Changes in regularity are analyzed, and the functional equations of the performance indices with the age of pavement concrete material are fitted. The differences in performance under the conditions of standard indoor curing and outdoor natural curing are then compared. The regularity of concrete strength varying with age, the relationship between flexural strength and splitting strength, and relationship between compressive strength and flexural strength are discussed. A comprehensive summary of the development rule of the long-age performance of road pavement concrete materials is performed. Finally, by analyzing the data of the ratio of compressive strength to flexural strength, it is recommended that controlling the flexural strength and water-cement ratio can reduce the brittleness of the concrete slab.

Characteristics of Base Friction for Concrete Pavement Structure in China: Experimental Study

The restraint between the slab and the base of a concrete pavement structure is an important factor in the design of a concrete pavement. Excessive restraint can lead to unexpected distresses because of the daily cycle of ambient thermal influence and the changing moisture conditions that are ultimately detrimental to the performance of a pavement. Evaluation of base friction is needed for configuring joint sealing, slab thickness, and reinforced steel. The semirigid base, made mostly of cement-stabilized crushed stone, is widely used as the typical base for cement concrete pavement in China. Usually, a polythene sheet is placed between the concrete slab and the base to smooth the interface. In some cases, geotextiles and an asphalt bond breaker may be used to reduce friction. A series of push-off tests was performed under various conditions to study the characteristics of base friction for a typical concrete pavement in China. A polythene sheet, a geotextile, emulsified asphalt, and asphalt bond breakers of three thicknesses (2, 4, and 6 cm) were placed between concrete slabs and semirigid bases. Concrete slabs were also cast directly on the base with no bond breaker to determine the influence of these factors on the characteristics of base friction. Factors that could affect the behavior of a concrete slab under frictional drag, including rate of movements, slab thickness, and number of movement cycles, were investigated.

Research on Application of Precast-Assemble Technology to Road Maintenance Engineering

Through research on precast assembling structural design and construction technology in cement concrete pavement maintenance engineering, this paper brings forward reasonable size for precast assembling slab in cement concrete pavement maintenance engineering to improve original precast assembling construction technology and brings forward effective improvement measures for original construction technical difficulties. And simultaneously, through making a comparison of socioeconomic benefits among precast assembling maintenance mode, cast-in-place ordinary concrete maintenance mode , cast-in-place early-strength concrete maintenance mode and cast-in-place reinforced concrete, uses that precast assembling maintenance technology is a cement concrete pavement quick maintenance technology with extremely high performance price ratio.

Study on Techniques for Rapidly Testing the Composition of Concrete Mixture

With regards to the quality problem of concrete that cant be found out earlier in the quality control, this paper discussed the principle to rapidly detect composition of concrete mixture and analyzed the measurement accuracy of water checker for fresh concrete through laboratory test. Experiments showed that the error in unit cement and unit water measured by instruments is relatively small and able to meet the accuracy requirements. And, the application of rapid detection techniques to the concrete quality control in practical engineering has achieved good results.