Search

It is widely acknowledged that environmental loading, such as changes in temperature and humidity, greatly influences concrete slab movement, causing considerable strain and stress. A field construction test was conducted in order to investigate strain properties of jointed plain concrete pavement (JPCP) placed in a relatively closed section like tunnels. In this study, environmental loading in and outside tunnels was measured, and early age strain properties of concrete pavement were examined with varied slab spacing. To analyze the strains at each component of concrete pavement, Vibration Wire Strain Gauges (VWSGs) and non-stress devices were used in the field test. Base on the data measurement and calculation process, the total strain, shrinkage strain, thermal strain, and elastic strain of the concrete slab could be obtained separately. Observation data for three weeks after concrete placement indicated that the temperature difference between the top and bottom of the slab was smaller than 3°C inside the tunnel, while there was be as high as 10°C temperature difference outside the tunnel. Inside the tunnel, similar strain properties were displayed in the 6 m and 8 m slabs, where strain levels were half those of general road sections. [ABSTRACT FROM AUTHOR]

Spalling, which deteriorates the condition of concrete pavements and reduces riding comfort, is caused by many factors. In this study, as a potential factor for spalling, the relationship between crack closure and the zero-stress temperature (ZST) was investigated based on measurements made on three types of concrete pavement. As a result, the ZST, which is determined by the air and concrete temperatures when the concrete is placed, was found to be correlated with crack behavior in concrete pavement. In particular, continuously reinforced concrete overlay (CRCO) or pavement (CRCP) tended to develop crack closure at temperatures exceeding the ZST due to the effect of rebars embedded in the CRCP in constraining excessive opening of cracks. In contrast, the whitetopping section with joints did not show crack closure irrespective of the ZST. From this, it can be inferred that early-age concrete temperature management can contribute to the performance enhancement and service life extension of concrete pavements. [ABSTRACT FROM AUTHOR]

Tunnel construction in Korea has significantly increased since 2002. This is due to Korean government's eco-friendly strategy to reduce lengthy and inefficient roadways in mountain areas, and to provide direct access to highway networks in congested urban area. Tunnel construction can be largely divided into two major processes; tunneling or removing of earth, and making of concrete wall and slab. For any concrete road construction, curing concrete is highly encouraged as it helps concrete to reach desired maximum strength and durability. However, it is also a tedious and time-consuming process. This paper provides data that support an idea of eliminating the curing of inner portion of the concrete slab in tunnel when the construction is conducted during certain time of the year and at certain geographical locations. It is a well-known fact that curing, which is a process to slow down evaporation of moisture within concrete, depends on environmental factors such as temperature, relative humidity, and wind speed. This paper provides comparative analyses of these environmental data obtained from both outside and inside of ten tunnels around various geographic locations of Korea. Based on these results, this paper suggests that curing is not required for concrete slab inside relatively long tunnels. [ABSTRACT FROM AUTHOR]

Curing compounds are widely used to cure concrete pavement because of their high efficiency and simple usability. Image processing has been proposed to facilitate quality control during construction by including a white-colored pigment in the sprayed compound. However, errors can occur as a result of a number of variables such as camera aperture, shutter speed, and illuminance during the picture-taking process. This paper proposes a method in which the 'mastercurve' concept is applied to standardize the camera aperture and shutter speed. The shift function, y = 0.0067x − 0.2305x + 1.4171, is applied between the aperture and shutter speed, and a brightness value enabled to classify curing compounds under the same illuminance condition. In addition, the correlation between the illuminance and brightness of the images are identified via regression analysis. The results of analysis of sample images under various conditions indicate that the relative application rate of the curing compound can be evaluated. These results demonstrate that the proposed image processing methodology is suitable for curing compound quality control. [ABSTRACT FROM AUTHOR]

This study presents the results of geogrid pullout tests conducted in wet and fine-grained soils. Failures of reinforced soil structures have often involved inadequate drainage due to the use of fine-grained soils, which has led to stringent specifications for backfill material in such structures although there are significant economic reasons for relieving the specifications. One approach to improve the issue is to reinforce fine-grained soils with geosynthetic providing both reinforcement and lateral drainage. Although using reinforcement with in-plane drainage capability is conceptually promising, transmissivity requirements for this application have not been properly evaluated. Pullout tests were conducted on cohesive soils using geogrids with the same tensile strength but with and without in-plane drainage channels. The results indicate that geogrids with in-plane drainage layers show higher pullout resistance than conventional geogrids. The finding contributes to promoting the use of poorly draining soils as backfill material. [ABSTRACT FROM AUTHOR]

In order to make bicycling more popular, which generates no CO emission, the construction and connection of a bike road network are very necessary. Among various bike path pavement construction methods, this study chose a roller compacted concrete method that uses low cement and is environment-friendly. Roller compacted concrete, a durable paving material that can carry heavy traffic loads, has been developed as a fast, economical construction method. This study is to investigate the mechanical performance of the roller compacted concrete as a bike path road pavement. Through an analysis of the experimental results, mechanical performance and compaction rate under different compaction methods were studied for the field application. Based on the observations from compressive strength tests, it is recommended that the mixes for the low cementitious materials-based roller compacted concrete pavement have the cementitious binder content greater than 250 kgf/m. In order to provide appropriate workability the water content should be at least greater than 120 kgf/m when the binder content is greater than 250 kgf/m. When the compaction method suggested herein is applied it is strongly recommended that the low cement based roller compacted concrete pavement has its compaction ratio greater than 93%. [ABSTRACT FROM AUTHOR]

In every city, low-volume roads and parking lots are composed of dense-graded pavements that increase storm-water runoff; however, urban flooding problems can be prevented if an appropriate pavement system is achieved. One preferable solution to this problem for low volume roads and parking lots is to use permeable interlocking block pavement. To determine the storage capacity of this kind of pavement, a series of material property tests were performed such as specific gravity, void ratios, and porosity etc., which was further used to calculate the water storage capacity of the pavement. And rainfall simulation tests were performed to evaluate surface runoff, delay time, storage capacity, and outflows over two hours. A regression analysis showed that the water storage capacity measurement from rain simulation tests agreed with the storage capacity calculation depending on laboratory materials-properties tests, based on their high correlation and coefficient values, each within the 95% confidence interval. [ABSTRACT FROM AUTHOR]

Recycled Concrete Aggregate (RCA) is different from natural aggregate because of RCA's cement paste and contaminants that cause low density and high porosity. In many cases, these properties of RCA that lead to poor engineering qualities are the major reasons that RCA is not recommended as aggregate for Hot Mix Asphalt (HMA). In this research, the performance of HMA mixtures with RCA is quantitatively evaluated using various tests to verify the applicability of RCA as aggregate for HMA material. For this verification, the Indirect Tensile (IDT) strength test, Kim test, wheel tracking test, and tensile strength ratio test accompanied by fundamental material property tests were performed on asphalt mixtures with four types of aggregate blends. In addition, asphalt mixtures with RCA, whose binder contents were determined from the Superpave mix design method, were utilized and evaluated against Marshall design criteria in order to effectively reflect both field specifications and field compaction conditions in South Korea. As a result of this study, it is observed that the study asphalt mixtures with RCA (Mixes II and III) show good performance compared to the asphalt mixture with natural aggregate only (Mix I) in terms of indirect tensile strength ratio, deformation strength, rut depth, and IDT strength, whereas Mix IV, which consists of coarse and fine RCA, does not exhibit good performance. By evaluating the Marshall test properties of each mixture, it is also concluded that the dynamic loading in the Marshall test compaction method possibly causes friction in the RCA of the asphalt mixtures and, therefore, leads to an underestimation of the engineering properties of HMA with RCA. [ABSTRACT FROM AUTHOR]

The performance of a joint in airport rigid pavements can be evaluated using load transfer efficiency (LTE). Various existing methods to calculate LTE using different parameters were reviewed in this paper, illustrating how the performance of a joint that performs well is underestimated. To address this concern, a new parameter obtained from the deflection time history output of HWD (Heavy Weight Deflectometer) is being proposed to calculate LTE. Field measurements and FEM (Finite Element Method) modeling were employed to validate the proposed calculation in comparison with the conventional calculations of LTE. Based on the statistical analysis, the proposed method shows low variance and error compared to the conventional calculation of LTE in airport pavements. Moreover, core samples were collected along the tested joints to verify if the calculated values manifest the internal condition of the joints. The calculated results from the proposed LTE show a good agreement not only with the surface condition of the joints, but also with the collected core samples. [ABSTRACT FROM AUTHOR]