摘要：
In order to further improve the performance of bio-asphalt, because of its poor high-temperature performance, another biomass material, diatomaceous earth, was employed as a composite modifier, and a composite-modified asphalt was made to increase the high-temperature performance of bio-asphalt. The optimal preparation parameters of a rapeseed heavy oil-diatomaceous earth composite-modified asphalt were identified by employing an orthogonal test design. Based on the laboratory test, the physical properties, rheological properties, and microscopic properties of the asphalt were evaluated correspondingly by utilising matrix asphalt, rapeseed heavy oil-modified asphalt, and diatomaceous earth-modified asphalt as the control group. The results of the orthogonal test analysis showed that the optimum preparation parameters of the rapeseed heavy oil-diatomaceous earth composite-modified asphalt were 8% rapeseed heavy oil, 5% diatomaceous earth, a shear period of 35 min, and a shear rate of 2500 r/min. The addition of rapeseed heavy oil improved the fatigue resistance and low-temperature performance of the asphalt, but, at the same time, the asphalt penetration increased, the softening point and viscosity decreased, and the high-temperature rutting resistance decreased. Compared with the matrix asphalt, the viscosity of the rapeseed heavy oil-diatomaceous earth composite-modified asphalt at 135 degrees C rose by 23.2%. The rutting factor G*/sin delta increased by 45.5%, 15.6%, 17.6%, 29.8%, and 22.0%, while the fatigue factor G*center dot sin delta increased by 41.9%, 14.2%, 16.7%, 19.4%, and 23.1%, respectively, in the high-temperature rheological properties test temperature interval from 52 degrees C to 76 degrees C. The creep stiffness S fell by 16.2%, 36.1%, and 25.2%, while the creep rate m rose by 25.8%, 52.9%, and 13.4%, respectively, in the low-temperature rheological performance test temperature interval from -24 degrees C to -12 degrees C. Therefore, diatomaceous earth may effectively counteract the softening effect of the rapeseed heavy oil on the matrix asphalt and may raise the strength level and permanent deformation resistance of the composite-modified asphalt with only partial loss of fatigue resistance. The matrix asphalt, rapeseed oil, and diatomaceous earth exhibited high compatibility. The integration of rapeseed oil and diatomaceous earth largely did not modify the chemical properties of asphalt, and it was able to maintain the qualities of asphalt itself. Rapeseed heavy oil and diatomaceous earth on the thermal stability of the matrix asphalt has the opposite effect. The reorganisation component of diatomaceous earth on the colloidal structure of asphalt is conducive to the stabilisation of the nature of the asphalt, which can significantly improve the temperature stability of asphalt.
通讯机构：
[Liang, Chenghao] C;Cent South Univ Forestry & Technol, Sch Civil Engn, Changsha 410004, Peoples R China.
摘要：
<jats:p>Using recycled aggregate from construction and demolition (C&D) wastes as a construction material is a potential method for solving the disposal of C&D wastes, which can reduce the exploitation of natural aggregate. In this study, extensive laboratory tests were carried out to investigate the reliability of the C&D wastes used as road base material. Meanwhile, the gradation design and the dominant aggregate size range were considered, and a physical disposal method was proposed to enhance the structural performance of the recycled material by replacing the skeleton of the recycled aggregate (RA) with high-quality limestone. The test results showed that (1) given the high absorbency and fragility of C&D wastes, its RA was not enough to provide the strength and stability required by the base; (2) the compaction characteristics of the RA are quite different from that of the limestone aggregate, but the final compaction effect is basically the same; (3) the replacement treatment proposed in this study is an effective approach to improve the performance of the recycled granular base because the breakage rate decreased by at least 28.2% and the mechanical properties increased by approximately 50% compared with that of the untreated specimen; and (4) when the limestone content reached 75%, the California bearing ratio and the resilient modulus of the graded B specimen exceeded 120% and 200 MPa, respectively, satisfying the pavement requirement in medium traffic.</jats:p>
摘要：
Based on the loading features of reinforced timber-concrete composite (TCC) beams, a calculation model of their ultimate flexural capacity is established. To verify calculation results, four TCC beams with different degrees of reinforcement were prepared and tested, and a good agreement between test data and calculations was found to exist.
关键词：
Concrete box-girder bridge;The overall heating and cooling;Temperature gradient;Thermal stress;Sensitivity
摘要：
Setting in the youshui Bridge Project and referring to the stipulation on the temperature gradient in current code, this aims to investigate the effects on the stress condition of concrete box-girder bridges caused by the overall heating, cooling or standard temperature changes. The process was carried out by virtue of the general finite element analysis software-MIDAS/CIVIL. The result showed that temperature would greatly affect the structural behavior of a bridge, in particular that the stress condition of the top plate is sensitive to temperature changes. It was therefore suggested that climate conditions should be taken into consideration when determining the temperature gradient values in the code.
