Advanced Materials Research Vols. 255-260

Abstract: Multiple Head Breaker (MHB) is an innovative cement concrete pavement breaking machine with high impact energy. The impact energy of multiple head propagates in vertical and horizontal direction simultaneously which results the environmental vibration effect consequently. The slope and structures beside the highway are influenced by vibration in rubblizing of cement concrete pavement. But there is a lack of research on environmental vibration effect, such as the influence range, whether there exists destructive effect or not. The characteristics and influence range of ground vibration are analyzed on the base of vibration data acquired by seismograph. The vibration attenuates fast and takes on some traits of concussion and instantaneous vibration. The safe influence range of MHB is associated with characteristic of slope soil. Relationship between vibrancy distance and vertical & horizontal vibration acceleration is established. And the influence range and safe distance are put forward which can provide reasonable parameters for design and construction in rehabilitation of cement concrete pavement.

Abstract: Impacting and compacting technology is widely applied for re-built old PCC pavement. However, underground pipe would be influenced by impacting machine to possibly occur fracture. A 3D finite element model was established by ADINA software to analyze distribution of additional stress and displacement upon pipe when machine traveled across different positions of slab. The results indicated that longitudinal compressive stress and vertical displacements at the corner of the slab were larger than those at the longitudinal middle fringe of the slab; the influenced depth of additional stress caused by impacting force was about 2.5m and additional stress decayed quickly with the increasing depth; the maximum soil pressure measured in field was smaller than that in numerical simulation.

Abstract: The quality of compaction is important to Hot Mixed Asphalt (HMA) pavement. Most premature failures of asphalt pavement are concerned with poor compaction. Characteristics of cooling curve of asphalt mixture were studied in this paper. Through on site measurement, it was found that air temperature, solar radiation, wind velocity and layer thickness had great influence on cooling time. Then, with ABAQUS finite element software, the rule of HMA mixture cooling curves during paving was simulated. A simple multi-factors regression equation was given which can be used to estimate the effective compactible time.

Abstract: With the theory of M.W.Sayers, the pavement surface roughness was simulated by the sine curve. Through the Mat lab and VC + + program, the dynamic vehicle load caused by pavement surface roughness was analyzed and calculated. Given the dynamic road and environment factors and combined the test results of highway surface roughness, the deterioration law of pavement roughness were studied by amendment Shell permanent deformation theory. A new prediction method was put forward to predict the remaining life of asphalt concrete pavement, which was proved to be reasonable and reliable and can provide a valuable basis for the scientific decision-making of asphalt pavement management.

Abstract: Additives on low temperature compaction and performances of compacted mixtures, the author devised low temperature environment compaction test, and then, comparison tests of volume parameters, high temperature stability, low temperature crack resistance and water sensitivity were conducted. Tests results showed that the wax additives and the surface-active additive can significantly contribute to mixtures low-temperature compactibility. The wax additive helps to improve high temperature stability obviously, and has no significant contribution to low temperature crack resistance and water sensitivity. The surface-active additive directly reduces water sensitivity, the wax additive indirectly plays the role of reducing water sensitivity by increasing the density of mixture, and the foam additive has no obvious effect on the water sensitivity.

Abstract: The moisture content of subgrade soil increase will lead to soil strength and modulus decrease, the thesis proposes geotextile - graded gravel - geomembrane composite drainage layer solution, for raw materials in different areas, proposes different composite drainage layer layout scheme, and the technical specifications requirements of raw materials. Test section is constructed, analyses the composite drainage layer construction technology carefully, and humidity sensors are planted in the drainage layer, in which the test data show that: after setting the composite drainage layer, subgrade moisture is less affected by seasonal rainfall, humidity change is always in a lesser extent, water stability of the subgrade is increased significantly.

Abstract: Pavement bonding associates with shear strength which depends on different tack coat materials and temperature. The higher temperature has, the lower shear strength is; and increasing the application rate does not significantly improve the shear strength. The test results show that the shear strength decreases with an increase in temperatures has the maximum value at optimum application rate (OAR) and emulsion asphalt used has higher shear strength than that of cutback asphalt. The tack materials and temperature are significantly effective the shear strength, in accordance with the statistic of two-way analysis of variance (ANOVA) test.

Abstract: Temperature grows up and climate changes year by year as result of global warming. One of the main reasons is the carbon dioxide emission. How to overcome global warming effect by means of energy conservation and carbon reduction is one of the important subjects and one of government's important administrative policies. Nowadays, the price of the international crude oil raised causes the price of the asphalt and ignition oil going up. Warm mix asphalt (WMA), a new-type mix asphalt technology, which has the characteristics of environmental protection, energy conservation and good workability is from Europe. Compared with Hot mix asphalt (HMA), the properties of the WMA is same as the HMA. Thus, the technology of WMA with emulsion asphalt mixture under energy conservation, carbon reduction, and cost reducing by way of temperature control, is introduced by this study in order to change the traditional HMA. The study used dense-graded aggregate with three nominal maximum aggregate sizes (NMAS) of 9.5mm, 12.5mm and 19mm is tested by indirect tensile strength, moisture sensitivity and permanent deformation test for evaluation and the results will be for reference of the HMA mix plant factories.

Abstract: A laboratory investigation was carried out on the volumetric properties of WMA fabricated using the Superpave gyratory compactor (SGC) and the Marshall compactor as a function of compaction temperature. The volumetric properties were obtained and analyzed at the six compaction temperatures 170°C,150°C,130°C,110°C,100°C,90°C. The results show that: Evotherm® can improved the compatibility of the mixtures; Warm Mix Asphalt is sensitivity to the temperature when the compaction method is Marshall; the method of SGC is conducive to dense asphalt pavement for WMA; the best compaction temperature of WMA is not lower than 125°C; the compaction temperature can decreased more than 20°C for WMA comparison with the HMA.

Abstract: Weathered red sandstone soil has weak water stability, unsatisfactory mechanical and poor engineering properties, which limits its utilization. When the proposing expressway through the soil, a large number of abandoned would be generated, which would burden construction costs and bring about many adverse effects to the local environment. To turn waste into treasure, the improving experiment with EN-1 soil stabilizer was conducted. Through the unconfined compressive strength test, the optimal mixing ratio of EN-1 soil stabilizer was identified as 0.014%. Series of tests on the road performance indexes were carried out under the condition of the optimal ratio of EN-1. The test results showed that 28d strength of the improved soil achieved 2.98MPa, 7d water stability coefficient achieved 0.75, the improved soil possessed good engineering properties, which can meet the requirements of expressway pavement materials.