Advanced Materials Research Vol. 857

Abstract: The Aircraft Classification Number-Pavement Classification Number method is the main approach for evaluating the structure of the airport pavement. However, the weakness of exiting methods lies in the difficulty of obtaining the exact PCN of the airport from the Airports Authority. This paper investigated the attenuation behaviors of the pavement structure under the envrionment of aircraft operation, and then the improved evaluation method for airport pavement was presented. The improved method could provide the technical support for accurately judging the bearing capacity of the exiting pavement structure and supply the decision-making reference to the Airports Authority.

Abstract: This paper addresses key issues regarding important factors affecting the sustainability and long-term performance of Portland cement concrete (PCC) pavement structures. Key distress types and their associated features are discussed in terms of their effect on performance and sustainability in terms of specific pavement components. Relevant material properties are also identified and discussed as to how they are represented in laboratory and field testing. A process to manage inspection resources is described and illustrated with the aid of a sustainability worksheet. This paper does not represent a guide or a standard for design or analysis.

Abstract: Finite element model analysis was performed with respect to patterns of load transfer relying on the action of aggregate interlocking and on the concurrent action of aggregate interlocking and dowel bars. The best timing for dowel bar retrofit was determined by way of increase in load transfer efficiency and maximum tensile stress borne at joints. The situation of dowel bar retrofit to restore load transfer efficiency was verified by way of onsite tests and economic analysis performed before we came to the conclusion that the way of dowel bar retrofit to restore load transfer efficiency is fairly cost effective. The construction technique of dowel bar retrofit to restore load transfer efficiency is finally summarized in light of engineering practice.

Abstract: 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.

Abstract: This research explored the variation of bond-breaking effect with variety of bond-breaking layers installed between the concrete pavement surface slabs and the lean concrete (LCB) base, in order to offer parameters for structure analysis of pavements with bond-breaking layers and to optimize the selection of bond-breaking layers for the practical road engineering projects. This research tested the bonding stresses and the frictional forces at slab-base interface of pavements under different bond-breaking condition, as well as the anti-erosion performance of base course, via the anti-erosion tests in laboratory and the field tests for mechanical performance of slab-base interface treated with different bond-breaking layers in some highway projects of Hunan and Guangdong Provinces. Bond-breaking media applied in this research include the 3cm asphalt concrete (AC), 1cm emulsified asphalt slurry seal (EASS), geotextile and emulsion wax curing agent (EWCA). The findings from the field tests for bonding stress between slab-base layers indicated that EASS and EWCA did better than geotextile in reducing friction or bonding stress between slab-base layers. And the findings from the anti-erosion tests indicated that: under the same conditions, specimens covered with geotextile did far better than specimens brushed with asphalt on the surface in resisting erosion, and specimens covered with geotextile or brushed with asphalt did far better than no bond-breaking layer in resisting erosion. The mechanical performance of slab-base interface with different bond-breaking media derived from this research offers scientific reference to pavement design and construction control in the practical road engineering projects. Key words: Mechanical performance of slab-base interface; Tests for bonding stress and anti-erosion tests; Bond-breaking layer of cement concrete pavement; Lean concrete base;Cement stabilized macadam base course.

Abstract: With the development of sensor, signal acquiring and processing technologies, amounts of overlay design methods for old cement concrete pavement have been proposed. However, there are difficulties in applying these methods to the real pavement under the long-term operational environments. In this study, the research achievements for resisting the generation and extension of reflection cracks of the old cement concrete pavement, developed over the last couple of decades and their applications, were summarized firstly, and then the primary challenge in applying these methods was discussed.

Abstract: Concrete pavement slabs experience volume change due to the variation of temperature and moisture level. The frictional drag acting on the bottom of slab due to the base friction is in the opposite direction of horizontal slab displacement, and resist against the horizontal slab movements. The magnitude of frictional force and horizontal slab displacement has interdependent relationship. In the present study, the interface friction of typical concrete pavements was evaluated by performing a number of push-off tests. In this paper, reviews of classical friction theory and friction characteristics at the interface of concrete slabs and the underlying subbases are presented.

Abstract: Some horizontal cracks will appear during the strength formation of the semi-rigid base, for the influences of dry shrinkage and temperature shrinkage exist, so the engineers often adopt the manual method of equidistant cutting crack to avoid the irregular cracks. In order to analyse the influences on the axle load stress of the cement-concrete pavement slab which caused by the width and position of the base cracks or cutting cracks, the 3D FEM was used to study them under the different working conditions considering the crack, width and position. By the above research, the results show the existing cracks affect the integrity and continuity of the pavement structure; The crack width has no large influence on the stress of the pavement slab, while the base stress decreases apparently with the increasing width, and it becomes stable finally; The stress of the pavement slab is maximum when the crack or cutting crack is located in the middle, while it's small when the crack or cutting crack is located in the one fourth of the pavement slab.

Abstract: The curling stresses of rigid pavement are the result of in-situ and built-in temperature gradient. A profound investigation on the reasons causing longitudinal cracking (LC) was conducted in this paper. Based on finite element method (FEM) analysis results obtained from ISLAB 2000, the wheel load stress generated by a single axle load that is applied along the transverse joints is considered to be the critical loading condition for longitudinal cracking. Nonlinear environmental stress due to the curling of Portland Cement Concrete (PCC) was analyzed using the numerical program developed in this study; the paving time within a day has a significant influence on the curling stresses at the top portion of PCC slab at the critical loading position for longitudinal cracking. Research in this paper proposed an analytical method to determine the influence of the paving condition (day time and night time) on the built-in setting gradient and its effect on the in-situ effective equivalent temperature differential.

Abstract: This paper studies the freezing-and-thawing durability of cement concrete on the basis of experimental investigation of air-void parameters, which has a significant influence on the durability of concrete. More specifically, this research firstly discusses the effect of air-entraining agent types on the air-void parameters feature, and then a rapid freezing-and-thawing test is conducted to assess the durability of the concrete specimens, so as to observe the relationship between the frost resistance performance evaluation index, which is applied as durability factors in this study, and the air-void parameters of concrete, such as the air void spacing factor and the air content of cement concrete.