PURPOSES : The exposed aggregate number (EAN) and mean texture depth (MTD) of exposed aggregate concrete pavement (EACP) influence the functional performance of EACP in terms of pavement noise and skid resistance. The selection of the exposure time of EACP is important because the designed EAN and MTD of EACP can be achieved when the exposure process is performed at an appropriate time. On the one hand, too early exposure may cause protrusions and unwanted removal of aggregates and mortar. On the other hand, late exposure may cause difficulty in exposure of the mortar. In this study, a method to determine the optimum exposure time for EACP is suggested using a non-destructive method. METHODS : A set of laboratory tests was performed to investigate the variation in EAN and MTD of EACP according to the elastic modulus obtained by non-destructive equipment. From the results of this investigation, the optimum exposure time using the non-destructive method and the exposure time window (ETW) method was suggested. In addition, the usefulness of ETW suggested by laboratory tests was verified from a field application. RESULTS : From the laboratory tests, it was found that the targets of the surface condition of EACP (EAN: 59 per 25 cm2, MTD: 1.39 mm) can be achieved when the concrete elastic modulus is higher than 20GPa. The proposed guideline using the non-destructive method was applied for the field construction of EACP and achieved similar results. CONCLUSIONS : It was found that the proposed guideline for determining the exposure time window based on non-destructive testing is useful.

PURPOSES : Concrete pavement is excellent in structural performance and durability. However, its functionality – such as noise and skid resistance – is a shortcoming. Functionality such as noise reduction and skid resistance of concrete pavement is affected by the texture surface, and the texture surface is classified according to the length of the wavelength. In recent years, Fine-size exposed aggregate concrete pavement has been applied, which has excellent structural performance and durability, and secures functionalities such as noise reduction and long-term skid resistance by randomly forming texture surface. Fine-size exposed aggregate concrete pavements are constructed by removing the surface cement binder to randomly expose coarse aggregate and their functionality is mainly governed by the surface texture. However, deteriorated concrete by tire-pavement friction and deicing agent may cause abrasion and aggregate loss on the surface texture; thus reducing their functional performances. Abrasion is created by the thin cutoff of aggregate texture under repeated tire-pavement friction. In addition, aggregate loss is defined by the detachment of aggregates from cement binder. This study aims to evaluate the abrasion and aggregate loss of Fine-size exposed aggregate concrete pavement surface texture under tire-pavement friction and scaling tests. METHODS : In the study, abrasion and aggregate loss of tining and exposed aggregate concrete surface treatments were evaluated. Deterioration of each surface treatment was replicated by scaling test under ASTM C 672 test method. Afterward, abrasion test was conducted by ASTM C779 to simulate the tire-pavement friction under traffic. Consequently, abrasion and aggregate loss were measured. RESULTS : Abrasion depth of non-scaling tining, 10-mm EACP, and 8-mm EACP was 1.76, 1.12, and 1.01mm, respectively. Compared to scaling surface treatments, the difference of abrasion depth in tining texture was the largest with value of 0.4mm. For both textures of finesize exposed aggregate concrete, abrasion depth difference was about 0.1mm. Moreover, The 10-mm EACP exhibited a 2.6% of aggregate loss rate caused by tire-pavement friction before conducting concrete deterioration test. After 40-cycle scaling test, aggregate loss increased up to 12.2%. For 8-mm EACP, aggregate loss rate was 1.7% on non-scaling concrete. Further, this rate was magnified up to 7.3% for the 40-cycle scaling concrete. CONCLUSIONS : Under non-scaling or scaling tests, fine-size exposed aggregate concrete pavement showed better abrasion resistance than tining texture since tining was formed by aggregates and cement binder. Additionally, rate of aggregate loss was significant when EACP experienced the deicing agent under numerous cycles of freeze-thaw action.

PURPOSES: The noise problem in concrete pavements has an adverse effect to the road user or nearby residents and is generated by the contact between a tire and the pavement surface. Exposed aggregate concrete pavements have been adopted to solve the tire-pavement noise problem in the United States and Europe. However, the efficiency of the coagulation retarder and exposure equipment used for this kind of pavement has not yet been investigated. Therefore, this study aims to evaluate the ability of the coagulation retarder and exposure equipment in producing the optimum exposed aggregate texture to achieve low pavement noise. A method for the exposure time selection has also been introduced here. METHODS: Sodium gluconate retarders were selected for use in this study. The retarder-water ratios of 1:1, 1:2, and 1:3 were investigated. The retarder was sprayed on a fresh concrete surface with rates of 200 g/m2, 300 g/m2, and 400 g/m2. The aggregates were then exposed to the surface using a steel brush and a water jet. The efficiencies for the low-noise texture, workability, and environmental impact produced by the two exposure devices were estimated. The EAN and the MTD were investigated according to the exposure time. RESULTS : The aggregates were exposed after the retarder was sprayed on the fresh concrete surface; the exposure lasted for 18 h to 26 h each time. The retarder-water ratio of 1:2 and the spraying rate of 300 g/m2 produced an optimum surface texture for low noise. Additionally, the steel brush performed more effectively in exposing aggregate to the surface compared to the water jet. The selected exposure time window (ETW) was 28 h to 35 h. CONCLUSIONS : The optimum retarder was the sodium gluconate retarder with a retarder-water ratio of 1:2 and a spraying rate of 300 g/m2. The steel brush showed a good performance in exposing the aggregates and showing the efficiency of the coagulation retarder in the given environment so as to produce the quality control condition. The ETW was influenced by the construction, mixture design, and construction environment; however, the selected ETW in this study was 26 h~35 h.

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 : 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.