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In order to verify the interlayer bonding effect of double-layer continuous paving technology of the thick cement-stabilized base and solve the construction quality control problem of the double-layer continuous paving, based on the interlayer bonding mechanism and the evenness passing mechanism, the laboratory interlayer adhesion test, field test of evenness disturbance, and compaction test were conducted to verify the continuous paving interlayer bonding state. The effect of interval time on interlayer bonding state, evenness, and compactness was analyzed, and construction quality control measures were proposed. The test results show that the double-layer continuous paving process could significantly improve the interlayer bonding state, but there is still a gap from the ideal state (completely continuous). The pull-off strength of continuous paving specimens was 2.1 times that of the discontinuous paving specimens; the shear strength was 2.4 times that of discontinuous paving specimens. At different paving intervals, the longitudinal evenness of the upper and lower layers has little difference. The 140 kN axle load controls the transverse evenness disturbance within 3 mm, which met the requirements of the specification. Based on the evenness passing mechanism, the evenness control standard of double-layer continuous paving base was proposed. The compaction process of double-layer continuous paving base was proposed, and the feasibility was verified through the field test of compaction. The best interval time for double-layer continuous paving was also proposed; it is recommended that the best time for paving the upper layer is after the lower layer is laid for 6 hours (the final setting time of the cement). The construction quality control measures proposed in this study provide a theoretical basis for the construction of double-layer continuous paving technology with thick cement-stabilized base.

The arch expansion of cement stabilised base materials has become increasingly serious due to the current design guideline, typical climate and geological environment in the west of China. This res...

In this paper, by designing the UV irradiance, the compositions and the initial concentrations of automobile exhaust, an asphalt mixture test system – photocatalytic decomposition of automobile exhaust performance (AMTS-PDEP) was developed based on the photocatalytic mechanism of titanium dioxide (TiO2). Testing method and calibration method of test data were also proposed in this paper. Accumulative decomposition ratio (ADr) was used as the evaluation indicator of photocatalytic decomposition of automobile exhaust performance (PDEP) and the influencing factors of PDEP were proposed. Based on the mechanical behavior and PDEP, the design method of asphalt mixture material composition was developed and the attenuation law of PDEP was also demonstrated. The results show that the PDEP of anatase TiO2 is much better than Rutile TiO2. The PDEP of asphalt mixture with 0.3 μm TiO2 is better than other particle sizes. Affected by particle adhesion, the PDEP of asphalt mixtures with 3.5% content of TiO2 reaches the maximum value. The PDEP has positive correlations with volume (VV) of asphalt mixtures, irradiance and temperature. It is recommended that anatase TiO2 (0.3 μm) is used as the photocatalyst, the optimum TiO2 content is 3.1%, TPS modified bitumen is used as the binder, and porous asphalt concrete with a nominal maximum aggregate size of 13 mm (PAC-13) is used as the optimal structural carrier. The PDEP of asphalt mixture decreased with the increase of test times, but it returns to its original level immediately after simply rinse, and repeated rinse does not reduce the PDEP. The PDEP of asphalt mixture decreases with the increase of the pollution index or the decrease of VV caused by compacting.

Thermo-oxidative ageing is one of the main factors affecting bitumen performance. At present, the research on bitumen ageing has entered the micro stage. The purpose of this paper was to study the relationship between nano-morphology parameters and properties of bitumen of bitumen during the ageing process. To this end, bitumen with different ageing degrees was prepared in this paper, and Atomic force microscopy samples with different cooling rates were prepared. The relationship between ageing degree of bitumen and nano-morphology parameters was analyzed. A functional relationship model between nano-morphology parameters and properties of bitumen was established. The results show that the percentage of bee-like structure area ( P bee &minus, like ), maximum amplitude ( H max ) and roughness ( R q ) increased with the increase of ageing degree. the percentage of bee-like structure area, the maximum amplitude and the roughness increase with the increase of cooling rate. With the increase of the percentage of bee-like structure area, the maximum amplitude and the roughness, the viscosity of bitumen at 60 &deg, C increases, penetration decreases, and softening point increases. There is a nonlinear relationship between the nano-morphology parameters and properties of bitumen.

At present, the geogrid is commonly used to treat the differential settlement of the subgrade at the joint of the filling and excavation effectively. In order to further improve the utilization rate of geogrid in the treatment of subgrade, the driving comfort index was proposed innovatively to control the subgrade differential settlement. Based on the human-vehicle-road coupling system model, the influence of subgrade differential settlement area, subsidence value, and vehicle speed on the maximum vertical acceleration of the human body was analyzed. The correlation between the vertical acceleration of the human body under different vehicle speeds and the differential settlement value was obtained through multiple regression calculations, and the subgrade differential settlement control standard based on driving comfort was proposed. By establishing the finite element model of the cut to fill subgrade, the characteristics of differential settlement at the top surface of the subgrade under different geogrid laying positions, densities, and lengths were calculated and analyzed. In addition, the differential settlement layout scheme of the geogrid disposal subgrade based on driving comfort was proposed, and the effectiveness of the scheme was verified by experiments. The results show that the position and length of the grid are the main factors affecting the treatment effect of the vertical and horizontal cut to fill subgrade. The proposed layout scheme can effectively control the differential settlement of the subgrade and raise the utilization rate of the geogrid. The research results can provide theoretical value and reference for the laying of geogrid in mountainous roads.

Pavement performance prediction is a crucial issue in big data maintenance. This paper develops a hybrid grey relation analysis (GRA) and support vector machine regression (SVR) technique to predict pavement performance. The prediction model can solve the shortcomings of the traditional model including a single consideration factor, a short prediction period, and easy overfitting. GAR is employed in selecting the main factors affecting the performance of asphalt pavement. The SVR is performed to predict the performance. Finally, the data collected from the weather station installed on Guangyun Expressway were adopted to verify the validity of the GRA-SVR model. Meanwhile, the contrast with the grey model (GM (1, 1)), genetic algorithm optimization BP[[parms resize(1),pos(50,50),size(200,200),bgcol(156)]]081%, −0.823%, 1.270%, and −4.569%, respectively. The study concluded that the nonlinear and multivariate prediction model established by GRA-SVR has higher precision and operability, which can be used in long-period pavement performance prediction.

The aging of asphalt seriously affects the pavement performance of asphalt mixtures. In this study, we investigated the changes in virgin and aged asphalt during the regeneration process of aging asphalt using atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectrometer, and dynamic shear rheometry (DSR). Dynamic modulus tests were carried out for asphalt mixtures containing 30% and 50% reclaimed asphalt pavement. Comparatively DSR tests were performed to determine the complex shear modulus for asphalt binder blends containing 30.6% and 51% aged asphalt. Based on the Hirsch model, the predicted and measured values of the dynamic modulus were compared to obtain a macroscopic evaluation of the degree of virgin and aged asphalt fusion. The results show that the virgin and aged asphalt are fused with high uniformity. From AFM scans, with increase in virgin asphalt content, the size of the bee-like structure decreased and the number increased. This was reflected in roughness indexes (Rq, Ra, Pbee-like, and Rmax) exhibiting gradually decrease, tending more to the microstructure of virgin asphalt with increasing virgin asphalt content. FTIR results showed that the carbonyl index and sulfoxide index decreased as the virgin asphalt content increased, which was consistent with the AFM test results. With addition of an optimal amount of regenerant the microstructure and high-temperature rheological properties of aged asphalt were positively altered. The improvement in the microstructure and rheological properties of rejuvenated aged asphalt was found to be similar to that of blends altered with 49% of virgin asphalt. With the increase in the content of virgin asphalt, the complex shear modulus of the asphalt G*, the rutting resistance of asphalt G*/sinδ was found to decrease as δ increased. The comparison between the predicted and measured dynamic modulus value confirms the successful fusion of the virgin and aged asphalt from a macro perspective. The macroscopic and microscopic analysis results of the change law of virgin and aged asphalt fusion are consistent.

Five types of material, styrene-butadiene-styrene block copolymer (SBS), ethyl-vinyl-acetate (EVA), naphthenic oil, maleic anhydride grafted ethylene-vinyl acetate copolymer (EVA-g-MAH) and butylated hydroxytoluene (BHT) were used as the raw ingredients for manufacturing direct-to-plant SBS in this paper. Thirteen kinds of direct-to-plant SBS with different EVA/SBS and naphthenic oil/SBS were prepared as well as the processes diagrammatic sketch of dispersion and swelling of direct-to-plant SBS modifier in bitumen were discussed. Microscopic images of direct-to-plant SBS modified bitumen with different components were obtained using fluorescence microscopy. The micro-images were analysed and quantified with MATLAB software. The influence of key components on the micro-morphology of direct-to-plant SBS-modified bitumen is discussed, followed with the tests on melting points and the melting indexes of direct-to-plant SBS with different EVA/SBS and naphthenic oil/SBS. The performances test of bitumen and bituminous mixture modified by these direct-to-plant SBS were also conducted. Results show that, with the ratio improvement of EVA/SBS or naphthenic oil/SBS, the number of the pixel dot number of area (SBS) in microscopic images increased. Enlargement of the pixel dot number of centre line elongate and the structure fineness was observed, indicating that the dispersion and swelling effect of the SBS modifier in bitumen had been improved. Meanwhile, the macro index, such as the melting point and melting index of direct-to-plant SBS, was also improved corresponding to the increase of EVA/SBS ratio or naphthenic oil/SBS ratio. With the addition of EVA or naphthene oil content, penetration and ductility of direct-to-plant SBS modified bitumen received gradual enhancement, but the softening point and viscosity were found out to be decreased. The high-temperature and low-temperature performances of direct-to-plant SBS modified bituminous mixture can be effectively improved by adding EVA or naphthenic oil. By meeting the required performances of direct-to-plant SBS, modified bitumen and bituminous mixture, the component of direct-to-plant SBS is recommended as, SBS:EVA:naphthenic oil:EVA-g-MAH:BHT is 1:0.1&ndash, 0.5:0.05&ndash, 0.2:0.03:0.05. For the compatibleness of SBS with different bitumen are different, necessary tests verification is recommended to be carried out prior to usage.

Compared with traditional deicing method, microwave deicing method has advantages of high energy utilization rate, good deicing effect, environmental protection and economy. In order to improve the microwave deicing efficiency of iced pavement, a microwave heating test of asphalt mixture is designed based on microwave pavement mechanism, which proves the theoretical feasibility of microwave deicing technology. Based on the microwave heating test of the type and content of absorbing materials, the superiority of the absorbing material ferric aluminum mixture (mixing Al2O3 and Fe3O4 with 1:1) and hydroxy iron powder RW as microwave deicing sensitive materials is determined, and the optimal blending mass ratios are 1% and 5%. Then the optimal materials at different microwave frequencies are obtained. When the microwave frequency is 2.45 GHz, the ferric aluminum mixture with a mass ratio of 1% is preferably added. When the microwave frequency is 5.8 GHz, the hydroxy iron powder RW with a mass ratio of 5% is preferably added. Finally, the reliability of road performance is verified, which indicates that the development of the new microwave sensitive material can improve the efficiency of microwave deicing and provide theoretical guidance for the application of microwave deicing technology.

In order to improve the problem of the bad thermal storage stability of Styrene-Butadiene-Styrene Block Copolymer Modified Bitumen (SBS-modified bitumen), the vulcanization reaction was selected as the basic mechanism for the research and development of the stabilizer. Sulfur, tetramethylthiuram disulfide (TMTD), zinc oxide, butylated hydroxytoluene (BHT), kaolin (Al2O3·2SiO2·2H2O) and carbon-white (SiO2) were used as raw materials, and 32 kinds of components with different contents of raw materials were designed. The 48-h segregation softening point and other modified bitumen technical indicators, such as ductility, penetration, penetration index, viscosity, and so on, were tested and analyzed. The fluorescence microscope test was also conducted to explore the crosslinking situation based on the vulcanization reaction. The results show that the component with good performance of the SBS-modified bitumen stabilizer powder was S:TMTD:ZnO:BHT: Al2O3·2SiO2·2H2O = 60:16:4:20:1250 or S:TMTD:ZnO:BHT:SiO2 = 60:16:4:20:625. The optimum content of stabilizer powder was 0.9% (S/modified bitumen). The stabilizer was dry powder and can be directly put into bitumen. It can cross-link SBS and especially has an effect on preventing SBS segregation. The technical performance of SBS-modified bitumen with stabilizer powder, such as hot temperature performance, low temperature performance, anti-aging performance and thermal storage stability, all meet the relevant specifications.