Advanced Materials Research Vol. 723

Abstract: South Gobi road of 240-km flexible pavement was constructed from UKHAA KHUDAG to GASHUUN SUKHAIT in South Gobi, Mongolia in 2011. However, due to the heavy traffic and severe weather condition, early distresses have occurred from a length of 100-km flexible pavements in South Gobi road after one year service life. In order to enhance crack and rutting resistances and to improve paving quality control in South Gobi road, polymer modifier is selected to reduce rutting at high temperature and cracking at low temperature and warm-mix asphalt (WMA) additive is selected to reduce the mixing and compacting temperatures and provide better compaction on the road and the ability to haul paving mix for longer distances. This paper adopted comprehensive asphalt tests to evaluate physical and rheological characteristics, and crack potential at low temperature for use in a South Gobi road. Laboratory tests were performed on asphalt binder with a polymer modifier and warm-mix asphalt additive by conducting the following tests: softening test, ductility test, Superpave^TM test and cold bending test. These test results of asphalt binder with SBS polymer modifier and warm-mix asphalt additive were significantly more positive than those of typical asphalt binder. On the basis of test results, it can be concluded that the asphalt binder with SBS polymer modifier and WMA additive is stronger and less susceptible to rutting and crack than typical asphalt binder used in South Gobi.

Abstract: This paper discusses the use of tailings for road pavement, especially for Asphalt Concrete Wearing Course (AC-WC) based on laboratory test results. The benefits of this study are: (1) diversification of road pavement materials, (2) the use of tailings optimally as road pavement material, (3) reduce the potential for environmental contamination. Tests on the characteristics of the tailings conducted to evaluate the properties related to its performance as a blending component. In this study, the percentage of tailings by 15%, 20% and 25% is added to the AC-WC mixture. Mix design performed by the method of Marshall. In the optimum asphalt content (OAC) the influence of water resistance and resistance to permanent deformation of sample are evaluated. The best performance is use of tailings by 20%. This mixture is not a mixture of the sensitive to inaccuracies in the asphalt mixture compared with the mixture using tailing by 15% and 25%. Wheel tracking test showed that the mixture has the smallest permanent deformation that is 2 mm.While resistance to water and temperature same for all all mixtures. This study shows that the tailings could be used as a road pavement material, which replaces the sand-sized aggregates.

Abstract: The use of modifiers or additives in the asphalt mixtures is a suitable and common method for improving their mechanical properties especially under high temperature service conditions. However, for cold climates which the pavement of roads usually experience subzero temperatures, the overall failure mechanism of asphalt layers may be occurred mainly due to elastic brittle fracture and growth of initiated cracks inside the pavements. Fracture toughness is the most important parameter for characterizing the crack growth and failure of cracked materials and structures such as the asphalt pavements. Hence, the main aim of this research is to study the effect of different additives including Poly phosphoric acid (PPA), Styrene butadiene styrene (SBS), Anti striping agent (ANTI), Crumb rubber (CR) and FT-paraffin wax (Sasobit) on the low temperature mode I fracture resistance of asphalt mixtures. A series of asphalt samples with different percentages of the mentioned additives were manufactured in the shape of semi circular specimens containing vertical edge cracks. The test samples were then loaded monotonically using a symmetric three-point bend fixture at a constant subzero temperature of-15°C. The value of mode I fracture toughness (K_Ic) were determined by recording the critical fracture loads of tested specimens. It is shown that all the investigated additives increase the low temperature fracture toughness of the asphalt mixture and the maximum increase in the value of K_Ic occurs when the sasobit and CR additives are used.

Abstract: To meet demand of highperformance pavement concrete in highway, differentproportional concretes incorporating 30%—40% ground granulatedblast furnace slag and (or) fly ash were investigated on engineering properties in laboratory. Workability offresh concrete was evaluated by result of testing slump, mechanical property ofconcrete by flexural strength, abrasion resistance of concrete by index ofabrasion resistance and durability of concrete by chloride diffusioncoefficient and value of charge passed. The results indicate that measuredcharacteristics of concretes are superior to the relevant requisitions in specificationof highway. It was revealed that partial substitution ofmineral admixtures increased workability of fresh concrete, abrasion resistanceand durability of concrete. Addition of groundgranulated blast furnace slag is more favorable to flexural strength ofconcrete than that of fly ash, in particular for early-term to avoid delaying construction time with lower strength caused in use of greatvolume admixture.

Abstract: This paper has studied the mechanical properties (freeze-thaw splitting strength, and dynamic modulus) and road performance (dynamic creep and fatigue life) of the asphalt mixture under the freeze-thaw circle test, and made the quantitative analysis of the influence on the material performance under freeze-thaw circle test.

Abstract: A study to achieve high-strength, high porosity and permeability pervious concrete pavement was carried out. First, the mix proportion in terms of cement content and coarse aggregate-cement ratio (CA/C) and water-cement (W/C) ratio were varied. Next, a mix proportion providing the optimal combination of strength and porosity was chosen, and polymer superplasticizers and short discrete fibers were added to examine their effect on the strength and porosity. Results showed that a water-cement ratio of 0.2 resulted in a dry and brittle mix that led to compressive strength less than 15 MPa but a high permeability rate of approximately 20mm/s. A mix with CA/C ratio of 4.25 resulted in compressive strength of 13.9 MPa, flexural strength of 3MPa and high porosity of more than 20%. Using comb polymer superplasticier and 2% steel fibers resulted in compressive strength of 25.1 MPa and flexural strength of 3.6 MPa at 28 days without compromising on the porosity.

Abstract: Concrete mixes containing Reclaimed Asphalt Pavement (RAP) were evaluated by the Superpave^® Indirect Tensile (IDT) strength test using a constant force-control and a displacement-control rate. The IDT strength of concrete without RAP at early age was seen to increase as the temperature decreased. The effect of temperature was not seen among the concrete at later ages. In addition, the IDT strength of concrete containing RAP was seen to decrease as the percentage of RAP and temperature increased. The IDT strength computed from the maximum load at 28 days curing time was found to correlate well with the splitting tensile strength.

Abstract: To reuse waste rubber tires is a global issue. One method of reusing tires is to process them into crumb-sized particles and produce crumb rubber modified asphalt (CRMA), which is a an effective way of reducing the pollution and resource utilization. Rotary viscosities of CRMA prepared under different conditions were measured to analyze the effects of treating methods, treating temperature, crumb rubber size, treating time and rubber dosage on the viscosity of CRMA. And a prediction model of viscosity of CRMA was developed. Test results indicate that, using the high-speed stirring method, viscosity of CRMA (η) appears quadratic function relationship with processing temperature (T) and crumb rubber mesh (D), exponential relation with the dosage of crumb rubber (R), but has no significant rule with the stirring time. By regression analysis, prediction model of viscosity of CRMA has a high viscosity fitting accuracy, which can provide a reference for production process of CRMA.

Abstract: This research aims to investigate the influence of the normal load on the shear behavior of double-layer asphalt specimens. The LCB shear test device proposed by Miro has been chosen as model for the design and the development of two new shear tests in the laboratories of the Sapienza University of Rome; under both shear tests, it possible to apply a normal load so as to reproduce the composed state of stress carried out by the vehicular loading. Several compression levels are investigated, paying attention especially to the load application modes and to the effect of the normal stress on the interlocking properties. The study parameters chosen for the analysis are the maximum shear stress and the slope of the final branch of the response curve or the residual shear stress, in relation to the failure behavior due to the devices. The results of tests performed on the first machine, when the normal load is applied, show a direct proportionality with the normal load and the slope of the response curves after the peak remain constant because it is related to the friction features. With the second machine, which was adjusted to evaluate the shear behaviour for high interface displacements, the peak shear stress and the residual one were also evaluated, showing the increasing in relation to the compression applied during the test. The two machines provide different but comparable results.

Abstract: Raveling, mainly caused by interfacial failure between binder and aggregate or cohesive failure of asphalt mortar, is one of the major causes of premature failure in asphalt pavements, and it also accelerates the severity of other distresses. The experiential adhesive experiment named Vialit Test under low temperature was chosen to investigate the adhesion behavior between binder and aggregate in this paper. The influence of aggregate size, aggregate types, binder types and impact energy were discussed. Quantity of ravelling aggregates and weight loss of aggregate and binders were used to evaluate the adhesive performance. Test results demonstrate that aggregate types have limited effects on the adhesion at low temperature, while aggregate size, binder types and impact energy have significant effects on adhesive performance between binder and aggregate. Binders with fine fillers exhibit better adhesion to aggregate when compares with pure asphalt.