PURPOSES: This paper presents the noise reduction effect of asphalt concrete pavement using steel slag aggregate. METHODS: Steel slag aggregates induce various mechanical effects because of their high stiffness and specific gravity. It is also known that the noise reduction effect is due to its high specific gravity and porous nature. In this study, the noise reduction in a steel slag asphalt concrete pavement section was measured and analyzed. RESULTS : On average, an asphalt concrete pavement with steel slag reduces road traffic noise by about 2 dB(A). In addition, the analysis of sound pressure levels by frequency showed lower sound pressure levels in steel slag asphalt concrete pavement than general HMA in all frequency ranges (from low to high frequencies). An analysis of the benefits with regard to noise, by assuming a road-traffic noise reduction of 2 dB(A) with asphalt concrete pavement using steel slag, shows that the noise abatement cost approach can save 1.6 million won a year over soundproof wall costs. In addition, the noise damage cost approach results in cost savings (with regard to noise) of between 19 and 60 million won per year depending on the population density. CONCLUSIONS: The use of steel slag aggregate as an asphalt concrete mixture material not only improves the mechanical performance but also has a noise reduction effect. It is expected that the steel slag asphalt concrete pavement can reduce the environmental burden by utilizing resources and provide a safer and more comfortable pavement condition to the road users.

PURPOSES: This study was conducted to investigate the causes of damage and to suggest proper repair methods for the sections in which a number of transverse cracks and faulting occurred in JCP (Jointed Concrete Pavement) slabs during the early-age performance period. METHODS: Field crack survey, FWD (Falling Weight Deflectometer) investigation, dowel bar installation condition survey, longitudinal profile survey, and in-situ core specimen inspection were conducted. . RESULTS : As a result of the analysis, it was found that there was no decline in the composite modulus of the subgrade reaction (k-value). The dowel bars were properly installed, but the LTE (Load Transfer Efficiency) of the joint and transverse cracks were analyzed to be very low. In addition, it was found that there are voids in the bottom of the slab at the joints and corners. Due to the excessive built-in curling in the early age of concrete pavement construction, upward curling displacement occurred at the joints and corners, resulting in voids at the bottom of the slab. As a result, it was found that transverse cracks occurred due to the defective joint LTE. CONCLUSIONS: Excessive built-in curling can cause early age cracks in the JCP slabs. In order to minimize the occurrence of reflection cracks after the application of the asphalt overlay in the future, concepts of alternative repair methods were proposed.

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 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 : 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.

The world-wide need to reduce the energy used and the greenhouse gases emitted during cement manufacture has led to the pursuit of more eco-efficient materials, such as ground granulated blastfurnace slag(GGBS) and fly ash. Especially, GGBS is a by-product generated during the manufacture of pig ions. GGBS can be divided into water-cooled slag(WS) and air-cooled slag(AS). With comparison of WS, the AS is formed by allowing the molten slag to cool relatively slowly under ambient conditions. This study presents experimental findings on the mechanical and durability performance of cement concrete pavement with replacement of cement by WS and/or AS. In order to produce concrete specimens, total replacement of cement by GGBS(WS+AS) was fixed at 40% by mass. Concrete specimens were regularly monitored for the variation of mechanical properties such as flexural strength, compressive strength and initial surface absorption. In addition, in order to assess durability of concrete pavement with WS and/or AS, the chloride ion penetration resistance and scaling resistance tests were adopted, and the corresponding results were compared to those of plain concrete pavement. The test results indicated that the performance of concrete pavement was significantly dependent on the replacement level of WS by AS. Concrete specimens incorporating 20% replacement level of AS showed a poor mechanical performance, while 5% replacement of AS showed a beneficial effect both mechanical and durability performance. Especially, the 5% AS replacement led to the higher resistance of concrete pavement against frost-salt action. Based on the experimental results, the present study would be helpful to design high-performance cement concrete pavement.

Asphalt pavement overlay method is one of widely chosen construction methods for remodelling existing aged concrete pavement layer. However, in this case reflective cracking is a challenging issue due to movement of transverse joints: built in existing concrete pavement layer with constant interval length. In this paper, collecting field data: collection of displacement and temperature data on existing concrete pavement layer for further complicated pavement performance analysis, was performed. To fulfil this objective, various types of thermometer were embedded into concrete layer with different depth level. Then, movement of existing concrete layer was measured numerically. Each Displacement Measuring Gauge (DMG) along with thermometer was embedded with depth of 3cm and 15cm, respectively. Additional thermometers were embedded at the middle depth of overlaid asphalt pavement layer for further extensive analysis and data collection. Total four testing sites were considered based on different asphalt mixture type and construction method. The 1st site was constructed with conventional construction approach, the 2nd site was constructed with a new pavement equipment contains simultaneous tack-coating function, the 3rd site was similar to 1st site but Guss-asphalt was constructed as a binder course, and in 4th site Noise-Reduction Porous Asphalt (NRPA) was constructed as a surface course and regular Dense Grade Asphalt (DGA) was constructed as a binder course. A field asphalt pavement layer sample coring works: along with basic material property tests, were also performed to acquire not only overlaid asphalt but also existing concrete pavement materials. This gauge measuring work in this study is an initial step therefore, long-term movement data of each pavement layer was not able to be collected, unfortunately. However through collecting and analysing initial data on each test site, two crucial findings were acquired. First, in all four tested site highest temperature variations were observed at the upper asphalt pavement layer and the variation trends decreased with increase of pavement depth (in case of concrete pavement layer, temperature and movement variations also decreased with increase of pavement depth). Secondly, when Guss-asphalt was applied as a binder course temperature variations of existing concrete pavement layer was crucially smaller than those of other comparison cases. These current findings and collected data set can provide successful input information for further pavement structure analysis such as 2D (and/or 3D) Finite Element Method (FEM) analysis as a future study.

Roller Compacted Concrete Pavement (RCCP) is placed by roller compaction of a mixture of less cement and unit water content and more aggregates and provides excellent early strength development with the help of interlocking of aggregates and hydration. The unit cement content of RCC pavements accounts for 85% of conventional pavements, with low drying shrinkage. As low drying shrinkage leads to smaller crack widths than ordinary concrete, RCC pavements can help elevate reflecting crack resistance if applied to a base layer of a composite pavement system. In a composite pavement with an asphalt surface laid over a concrete base, pavement temperature change is important in predicting pavement performance. As movement of the lower concrete layer is determined by temperature depending on pavement depth, temperature data of the pavement structure serves as an important parameter to prevent and control reflecting crack. Among the causes of reflecting crack, horizontal behavior of the lower concrete layer and curling-caused vertical behavior of joints/cracks are considered closely related to temperature change characteristics of the lower concrete course (Baek, 2010). Previous studies at home and abroad about reflecting crack have focused on pavement behavior depending on daily and yearly in-service temperature changes of a composite pavement (Manuel, 2005). Until now, however, studies have not been conducted on initial temperature characteristics of concrete in composite pavements where asphalt surface is placed over an RCC base. Annual temperature changes of in-service concrete pavements go up to 60 ℃, and those of asphalt overlays become around the twice at 110 ℃. This study evaluated initial crack behavior of composite pavement by investigating pavement temperature by depth of an RCC base and analyzing joint movement depending on change to temperatures of continuously jointed pavements. Findings from the study suggest that in composite pavements and asphalt overlays, time of laying asphalt has an important impact on crack behavior and reflecting crack.

Roller Compacted Concrete Pavement (RCCP) is a pavement placed and compacted using an asphalt paver and a compaction roller by applying a small amount of concrete mixture and shows excellent structural performance as a result of hydration reaction of cement and interlocking of aggregates by roller compaction. It also provides economic advantages over conventional concrete pavements by reducing unit cement content and construction period, simplifying construction process, and decreasing traffic closure time (Wayne, 2006). However, given that it tends to show lower IRI levels than common concrete pavements since its low unit water content and binder weight ratios make uniform quality control difficult and roller compaction after paving makes the surface irregular and rough, with rough profile at the bottom of the pavement being reflected on the surface, RCCP is used mainly in port and industrial roads for low speed (60km/h or less) traffic (Dale Harringtion, 2010; Gregory, 2009). In order to apply RCCP to high-speed roadways, diamond grinding (DG) or asphalt overlay that is highly effective in improving roughness is needed (Fares Abdo, 2014; Gregory, 2009). Applying DG over RCCP leads to excellent skid resistance and noise reduction effects as a great percentage of aggregates makes the pavement surface rough, enhancing durability of concrete and the life of DG functionality. In addition, RCCP can be used as a high performance base layer of composite pavements, as it can reduce reflecting cracking at joints and cracked sections thanks to early strength development and low drying shrinkage of concrete. In this study, we assessed longitudinal roughness improvement effects by roughness-affecting factor by applying DG methods and asphalt overlays to three RCCP sites with a variety of sub-structural conditions and analyzed the effects on roughness of existing RCC pavements depending on surfacing method (DG, APOverlay).

This paper presents a method to deice concrete pavement with carbon nanotube (CNT) so as to avoid the adverse effects of conventional deicing method such as salt on the structure, function and environment. To meet the research objective, laboratory tests were incorporated with finite element method. Laboratory tests conducted with CNT embedded inside the slab to investigate how far the heat transfers on the surface temperature of above 0oC when CNT generates the target temperature of 60oC in the freezer temperature of -10oC. Also, the cases of three different spacing of 15, 20 and 30 cm between CNTs were conducted to determine the maximum allowable spacing of CNT. Along with these experimental tests, heat transferring analysis conducted to validate the test results.

The objective of this study was to evaluate the effectiveness of various crack inducers to be used in the advanced reinforced concrete pavement (ARCP) by conducting yard tests. Some of cracks are induced in ARCP to reduce the stresses in steel bars and to form more uniformly spaced cracks so that the required steel bar amount can be decreased and at the same time the pavement performance can be improved. In this study, an experimental ARCP was constructed for the length of 22.4 m, width of 1.12 m, and thickness of 0.26 m. The anchor lugs were placed at both ends of ARCP to pretend continuities of the system. 8 crack inducers with a uniform spacing of 2.8 m were installed in different manners when placing concrete, so the test length of the experimental ARCP was 19.6 m. The variables of crack inducers included the shape, material, installed depth, and installing method. The basic shape of the crack inducer represented a round face and a flat opposite face with a height of 50 mm and a width of 10 mm. The slightly different shaped crack inducers were installed for inducing cracks at both ends of ARCP. The crack inducers were primarily made of glass fiber reinforced plastic (GFRP) but a crack was induced using a polyethylene sheet inducer. The installed depths of the crack inducers were 30, 40 and 70 mm to the top of the crack inducer from the pavement surface. Most crack inducers were preinstalled on the transverse steel bar locations before concrete pouring, but 2 crack inducers were installed just after concrete placement when concrete was still fresh. The temperature measurement sensors of i-Buttons and thermocouples were installed at the top, middle and bottom of slab to measure the temperature variations of slab. The displacement transducers were also installed at the crack locations to measure the crack width movements. The experimental results showed that the cracks were induced at all the locations where the crack inducers were placed. In addition to the induced cracks, just one crack was formed naturally. The crack patterns on the surface of pavement were all comparable. The crack width measurement data showed that there were slight differences in the crack width movements among the cracks but all the cracks including both the induced and naturally formed cracks moved little within a 0.1 mm range. Therefore, any type of the crack inducers employed in this study can be used to initiate cracks in ARCP.

Airport concrete pavement slabs show contraction and expansion behavior due to environmental factors such as temperature and humidity. Among the various environmental factors, temperature is the most influential factor in the concrete slab. However, it is inadequate to consider air temperature or surface temperature as influential factors especially for airport concrete slabs with very large thicknesses. Therefore, this study intends to utilize the equivalent linear temperature difference calculated from the data of the thermometer embedded in 5 depths(50mm, 150mm, 250mm, 350mm, 450mm) on the airport concrete slab. Equivalent linear temperature difference is the temperature difference between the uppermost and lowermost part of the concrete slab, which shows the same behavior due to actual temperature. Since the upper part of the concrete slab is more affected by air temperature than the lower part, the daily temperature range is large. Therefore, the equivalent linear temperature difference increases during the day and decreases at night, and concrete slabs show curl-down during the day and curl-up at night. This daily variation of curling behavior causes a difference in HWD experimental results. The HWD(Heavy Weight Deflectometer) test is mainly performed to investigate the condition of the pavement. And the calculated values are deflection, ISM(Impact Stiffness Modulus), LTE(Load Transfer Efficiency). The equivalent linear temperature difference represents the behavior of the concrete slab by the environmental load, and the calculated values by the HWD test represent the behavior. Therefore, the purpose of this study is to investigate the behavior of concrete slab by combined load including environmental load and traffic load through correlation analysis between these values. This study was supported by Incheon International Airport Corporation(BEX00625) and Korea Airports Corporation.

Tensile stress occurs and random crack develops in concrete pavement slab when it contracts by variation of temperature and humidity. The tensile stress decreases and the random cracks are minimized by saw cutting the slab and inducing the crack with regular spacing. The sawn or formed joint depth must extend to between 1/4 and 1/3 of the pavement depth to ensure the formation of a clean crack. The ‘Crack inducers (Triangular timber)’ have been installed at bottom of concrete slab to minimize concrete disturbance during initial age. In particular, it is often used to relatively thick airfield pavement compared to road. There are slabs of various thicknesses at the airfield, but the crack inducers are often designed to be installed uniformly without analyzed the joint behaviour to slab thickness. In this paper, the installation of crack inducer considering thickness variation is analyzed and applied. As a result, random cracks or joint freezing wasn’t occurred anywhere on the runway.

As a surface treatment method of concrete pavement in Korea, transverse tinning has initially been applied to improve drainage and friction at first. Since 2003, in order to reduce the noise of concrete pavement, longitudinal tinning have been studied and proved its superiority. Therefore, Korea Expressway Corporation (KEC) has applied this as surface texturing method in concrete pavement from 2008 to the present. However, the lateral vibration during vehicle running has been continuously raised in the longitudinal tinning section, and lots of efforts have been made to solve this problem. Nonetheless, complaints still occur intermittently in some sections. In this research, three sections in which complaints occur and three test sections were chosen to evaluate characteristics of lateral vibration between tire and longitudinal texturing. Based on the literature survey on the correlation between longitudinal texturing and tire, evaluation of the site and FEM analysis of each road surface were carried out. As a result of the analysis, the lateral vibration occurred most frequently in the random tinning section compared to other sections, and it was relatively few at the other improved tinning of the test section. Further studies on various tire types and timing intervals in the future will provide a standard of longitudinal texturing, which will reduce lateral vibration.

As of 2016, Texas Department of Transportation (TxDOT) manages a total of 16,327 lane miles of Portland cement concrete (PCC) pavement, which represents an important asset to TxDOT. As PCC pavements in Texas built in the 1960s through 1980s have already exceeded or are approaching the end of their design lives, many of these projects will require rehabilitations of some form. Considering the expected steady increase in truck traffic in the future, PCC overlays represent one of the best options for that rehabilitation. Currently, guidelines on PCC pavement overlays on PCC pavement focus on overlay slab thickness determination, but do not provide clear directions on whether existing PCC pavement is a good candidate for concrete overlay, or if the pavement is a good candidate, which overlay type –bonded concrete overlay (BCO) or unbonded concrete overlay (UBCO) –is appropriate. Sound guidelines are needed for the selection of an optimum overlay type, especially for continuously reinforced concrete pavement (CRCP) overlays, which could extend the performance period of structurally deficient PCC pavements in Texas at a reasonable cost. In the present study, the evaluations of PCC overlay performance of various BCO and UBCO projects built in Texas were conducted to develop the BCO design procedures based on mechanistic-empirical principles, and the development of design guidelines for the selection of an optimum overlay type.

Fly ash is used as alumina-silicate resource material to reaction processing on geopolymer materials. The strength of material is belonging to alkaline liquid, fly ash, activity reaction of fly ash. Geopolymer concrete as non-toxic, bleed free and high strength material can be used for construction on rigid pavement. Study on influence of polypropylene fiber on performance characteristic of geopolymer concrete is considered. In this research, the mix proportion with fly ash and alkaline liquid is used to react on geopolymer concrete. The poly-propylene fiber in range from 0 to 0.5% by volume is added in mixture of geopolymer concrete. The ratio between length and diameter in range of 100-500 is investigated. The results are indicated that workability of fresh concrete is reduced by using poly-propylene fiber. The adding of poly-propylene fiber is significantly affected on characteristic of geopolymer concrete. Poly-propylene fiber can be distributed in fly ash matrix and reduced shrinkage of concrete during activation. After geopolymerization, compressive and the flexural strength of concrete produced with fibers are enhanced up to 10% and 20%, respectively. However, when the length to diameter ratio increases, compressive strength is tended to decrease with mixture using polypropylene fiber.

A number of roller-compacted concrete pavements (RCCP) have been constructed without saw-cut joints in order to save construction cost. Then it will allow natural cracks to randomly occur at the early age after concrete placement. Crack spacing of unjointed RCCP is crucial to ensure an adequate crack width and load transfer across the cracks since large crack spacing will result in excessive crack width and reduce load transfer efficiency that may be cause faulting, excessive deflection, and further cracking in RCCP slab. Due to pavement thickness, climatic condition, and material properties, unjointed RCCP may have different natural crack spacing. In this study, an analytical approach to predict natural crack spacing of an unjointed RCCP was developed. An analytical method based on elastic theory to calculate axial restraint stress using a bilinear slab-subbase interfacial constraint assumption was conducted. Curling stress induced by temperature gradient through the depth of the slab was also considered. The analytical model incorporates the environmental effect, strength gain and modulus of elasticity, coefficient of thermal expansion, drying shrinkage, base type materials, and slab geometries. The predicted crack spacing results obtained from the predictive model were validated through field measured data. The results showed a good agreement compared with crack spacing measured in the field. Furthermore, the result from a sensitive analysis using proposed predictive model showed that crack spacing increased when thickness of RCCP increased. The predicted crack spacing results may be used as input parameters to estimate crack widths in unjointed RCCP under given climatic condition, and material properties. If estimated crack width is excessive and cannot maintain an adequate load transfer across the cracks, saw-cut joints with an appropriate spacing should be provided in order to minimize crack width, and to prevent future cracking of RCCP leading to better performance.