PURPOSES : Exposed aggregate concrete pavements have been adopted in several countries because of their advantages of pavement texture characteristics, which can produce low tire-pavement noise and higher load-carrying capacities. The magnitude of tire-pavement noise greatly depends on the wavelength of pavement texture. The wavelength of exposed aggregate concrete pavement can be controlled with maximum sizing and by controlling the amount of coarse aggregates in the concrete mixture. In this study, the maximum size and the amount of coarse aggregate in the exposed aggregate concrete pavement are investigated to produce equal levels of wavelength in the asphalt pavement. METHODS: A simple method to measure the average wavelength of pavement texture is introduced. Subsequently, the average wavelength of typical asphalt pavement is investigated. A set of mixture designs of exposed aggregate concrete with three maximum-sized coarse aggregates, and three amounts of coarse aggregate are used. The average wavelengths are measured to find the mixture design needed to produce equal levels of wavelength as typical asphalt pavement. RESULTS : With a cement content of 420 kg/m3 and fine aggregate modulus of 30%, the number of exposed aggregates was 48, and the shortest texture depth provided a wavelength of 4.2 mm. According to the number of exposed aggregates, the exposed aggregate concrete pavement could be rendered low-noise, because its wavelength was similar to that of asphalt pavement ranging from 3.9 to 4.4 mm. CONCLUSIONS : Selection of appropriate maximum sizes and the amount of coarse aggregates for exposed aggregate concrete pavement can produce a wavelength texture closely resembling that of asphalt pavement. Therefore, the noise level of exposed aggregate concrete pavement can be reduced with an appropriate maximum size and the amount of coarse aggregates are employed.

PURPOSES : The performance of pavements is decreased by reduced bearing capacity, deterioration, and distress due to complex loading conditions such as traffic and environmental loads. Therefore, the proper maintenance of pavements must be performed, and accurate evaluation of pavement conditions is essential. In order to improve the accuracy of the heavy weight deflectometer (HWD), which is a nondestructive evaluation method, the correlation between HWD test results and temperature factors were analyzed in this study. METHODS : The HWD test was conducted five times for one day on airport concrete pavement, and the ambient temperature, surface temperature, and slab internal temperature were collected. Since the slab internal temperature was nonlinear, it was replaced by the equivalent linear temperature difference (ELTD). The correlation between the HWD test results and each temperature factor was analyzed by the coefficient of correlation and coefficient of determination. RESULTSAND: The deflection of the slab center, mid edge, and corner, and impulse stiffness modulus (ISM) showed significantly high correlation with each temperature factor, especially the ELTD. However, the load transfer Efficiency (LTE) had very low correlation with the temperature factors. CONCLUSIONS : It is necessary to analyze the effect of aggregate interlocking on LTE according to the overall temperature changes in slabs by conducting seasonal HWD tests. It is also necessary to confirm the effect of seasonal temperature changes on deflection and ISM.

PURPOSES: The purpose of this study is to determine the effective maintenance method for a deteriorated jointed plain concrete pavement by evaluating the long-term performance of the repaired concrete overlay sections. METHODS: Long-term performance evaluation was conducted for the test section at the intersection between SeoPa and IlDong in National Road No. 37. Firstly, the distress conditions of the concrete pavement, which was constructed in December 2003, were evaluated by referring to the existing report. Secondly, the results of pretreatment, material properties, and initial performance evaluation were analyzed for the overlay test conducted in 2011. Finally, a field survey was carried out using visual inspection and nondestructive testing with a FWD in August 2018, and long-term performance evaluation was conducted for about seven years after maintenance. RESULTS: Visual inspection of the old concrete pavement showed severe damage such as joint spalling and asphalt patching. The cores taken from the old concrete had indirect tensile strength of 2.6-3.8 MPa. It is difficult to determine the freeze-thaw resistance because the average amount of air was only 1.6-2.2%, and spacing factor values were over 400㎛ regardless of location. During maintenance, overlay and partial depth repair were performed by applying three types of overlay materials which are typical in Korea. On the material side, high compressive strength (over 40 MPa) and chlorine ion penetration resistance (less than 1,000 coulomb) at 56 days were achieved. In August 2018, seven years after maintenance, visual inspection and nondestructive testing using FWD were conducted for long-term performance evaluation. Regardless of the maintenance materials, surface deficiencies such as spalling and map cracking occurred extensively near the joint. CONCLUSIONS: In conclusion, if the strength and durability index of aged concrete pavement is low, then it was determined that partial depth repair at the joint is not an effective maintenance alternative. In the case of overlay, the durability of the overlay material is considered the most important factor. In the absence of adequate reinforcement at the joint of the distressed concrete pavement, freeze-thaw damage caused by moisture penetration through the joint and failure of the old concrete are repeated, making it difficult to ensure long-term durability.

PURPOSES : In Korea, concrete pavements with transverse tining, which have excellent skid resistance, have been mainly constructed to secure road bearing capacity and safety. However, transverse tining has higher noise level of approximately 4-5 dB(A) compared with asphalt pavement. As a method to determine low-noise characteristics of concrete pavements, the fine-size exposed aggregate concrete pavement (EACP) has been studied in Korea and abroad. The surface of EACPs consists of exposed coarse aggregates and 2-3 mm removal surface mortar. EACPs have the advantages of maintaining low-noise and adequate skid-resistance levels during the performance period. Although EACPs have been widely studied to reduce noise, quantitative noise analysis with various paving methods has not been performed owing to differences in mixture proportioning, construction conditions, environmental conditions, and measurement methods. Therefore, the purpose of this study is to investigate the low-noise characteristics of fine-size EACPs by comparing noise with various paving methods, including concrete and asphalt pavements. METHODS: In this study, noise data were collected to quantitatively analyze the low-noise characteristics of EACPs compared with various paving methods such as transverse tining, longitudinal tining, SMA, and HMA. RESULTS: The evaluation of the low-noise characteristics of EACPs compared with transverse tining showed that the relative noise of 13 mm EACP with transverse tining was reduced by approximately 2% at 60 km/h, 4% at 80 km/h, and 5% at 100 km/h. The relative noise of 10 mm EACP with transverse tining was reduced to 3%, 7%, and 8% at 50 km/h, 80 km/h, and 100 km/h, respectively. In addition, it was confirmed that the noise of 10 mm EACP was similar to that of asphalt pavement. CONCLUSIONS : It was confirmed that EACP using 10 mm coarse aggregates generates lower noise than that using 13 mm coarse aggregates. Therefore, the use of coarse aggregates smaller than 10 mm needs to be considered to improve the low-noise effect of EACP.

PURPOSES : Previously, airport concrete pavement was designed using only aircraft gear loading without consideration of environmental loading. In this study, a multiple-regression model was developed to predict maximum tensile stress of airport concrete pavement based on finite element analysis using both environmental and B777 aircraft gear loadings. METHODS: A finite element model of airport concrete pavement and B777 aircraft main gears were fabricated to perform finite element analysis. The geometric shape of the pavement, material properties of the layers, and the loading conditions were used as input parameters for the finite element model. The sensitivity of maximum tensile stress of a concrete slab according to the variation in each input parameter was investigated by setting the ranges of the input parameters and performing finite element analysis. Based on the sensitivity analysis results, influential factors affecting the maximum tensile stress were found to be used as independent variables of the multi regression model. The maximum tensile stresses predicted by both the multiple regression model and finite element model were compared to verify the validity of the model developed in this study. RESULTS: As a result of the finite element analysis, it was determined that the maximum tensile stress developed at the bottom of the slab edge where gear loading was applied in the case that environmental loading was small. In contrast, the maximum tensile stress developed at the top of the slab center situated between the main gears in the case that the environmental loading got larger. As a result of the sensitivity analysis and multiple regression analysis, a maximum tensile stress prediction model was developed. The independent variables used included the joint spacing, slab thickness, the equivalent linear temperature difference between the top and bottom of the slab, the maximum take-off weight of a B777 aircraft, and the composite modulus of the subgrade reaction. The model was validated by comparing the predicted maximum tensile stress to the result of the finite element analysis. CONCLUSIONS : The research shown in this paper can be utilized as a precedent study for airport concrete pavement design using environmental and aircraft gear loadings simultaneously.

PURPOSES : The purpose of this study was to suggest a quantitative trend of the daily and seasonal cyclic movement of transverse crackwidth based on measurements in CRCP(Continuously Reinforced Concrete Pavement) within the first year of construction. METHODS : Crack gauges were installed in eight normal cracks, two induced cracks, and two construction joints of newly constructed CRCP. Crack width movements were continuously collected for about a year to investigate the cyclic behavior after construction. The daily and seasonal crack width movements were quantitatively analyzed and compared. RESULTS: Crack width movement in hot weather was relatively less than in cold weather. As a result of frequency analysis of the daily cyclic behavior, it was revealed by measurement that the minimum crack width from 2 p.m. to 4 p.m. was caused by expansion of the concrete; and that the maximum width from 6 a.m. to 8 a.m. was caused by contraction. Average crack width movements were calculated for every month and showed seasonal cyclic behavior. Maximum crack width was measured from December to January. Average crack width was investigated from March to April. Daily crack width movement in relation to concrete temperature was calculated from -0.00017 to -0.03844 mm/℃ and showed gradual decrease in absolute value with time caused by change in the crack spacing. It was found that the relationships between the monthly average crack width and concrete temperature are from -0.004 to -0.012 mm/℃. CONCLUSIONS : Crack-width movement shows a daily and seasonal cyclic behavior. Crack-width measurement in any time or season will have variance caused by daily and seasonal cyclic movement. Variances and trends were obtained in this study based on measurements for various cracks. The long-term behavior of cracks should be surveyed and compared with these measurements to investigate trends of convergence with time, caused by convergence of crack spacing.

PURPOSES : The purpose of this study is to analyze the magnitude of shoving of asphalt pavement by junction type between airport concrete and asphalt pavements, and to suggest a junction type to reduce shoving. METHODS : The actual pavement junction of a domestic airport, which is called airport “A”was modified by placing the bottom of the buried slab on the top surface of the subbase. A finite element model was developed that simulated three junction types: a standard section of junction proposed by the FAA (Federal Aviation Administration), an actual section of junction from airport “A”and a modified section of junction from airport“ A”. The vertical displacement of the asphalt surface caused by the horizontal displacement of the concrete pavement was investigated in the three types of junction. RESULTS: A vertical displacement of approximately 13 mm occurred for the FAA standard section under horizontal pushing of 100 mm, and a vertical displacement of approximately 55 mm occurred for the actual section of airport “A”under the same level of pushing. On the other hand, for the modified section from airport“ A”a vertical displacement of approximately 17 mm occurred under the same level of pushing, which is slightly larger than the vertical displacement of the FAA standard section. CONCLUSIONS: It was confirmed that shoving of the asphalt pavement at the junction could be reduced by placing the bottom of the buried slab on the top surface of the subbase. It was also determined that the junction type suggested in this study was more advantageous than the FAA standard section because it resists faulting by the buried slab that is connected to the concrete pavement. Faulting of the junctions caused by aircraft loading will be compared by performing finite element analysis in the following study.

PURPOSES : In this study, the propriety of expansion joint spacing of airport concrete pavement was examined by using weather and material characteristics. METHODS: A finite element model for simulating airport concrete pavement was developed and blowup occurrence due to temperature increase was analyzed. The critical temperature causing the expansion of concrete slab and blow up at the expansion joint was calculated according to the initial vertical displacement at the joint. The amount of expansion that can occur in the concrete slab for 20 years of design life was calculated by summing the expansion and contraction by temperature, alkali-silica reaction, and drying shrinkage. The effective expansion of pavement section between adjacent expansion joints was calculated by subtracting the effective width of expansion joint from the summation of the expansion of the pavement section. The temperature change causing the effective expansion of pavement section was also calculated. The effective expansion equivalent temperature change was compared to the critical temperature, which causes the blowup, according to expansion joint spacing to verify the propriety of expansion joint applied to the airport concrete pavement. RESULTS: When an initial vertical displacement of the expansion joint was 3mm or less, the blowup never occurred for 300m of joint spacing which is used in Korean airports currently. But, there was a risk of blow-up when an initial vertical displacement of the expansion joint was 5mm or more due to the weather or material characteristics. CONCLUSIONS: It was confirmed that the intial vertical displacement at the expansion joint could be managed below 3mm from the previous research results. Accordingly it was concluded that the 300m of current expansion joint spacing of Korean airports could be used without blowup by controling the alkali-silica reaction below its allowable limit.