PURPOSES : The purpose of this study is to verify the effect of improving the retroreflectivity of pavement marking by increasing the refractive index of glass bead. METHODS : Pavement marking test-beds has been installed in National Highway 19, 42 and KICT Yeoncheon SOC Center. In testbeds several marking sections were installed for each type of marking materials and glass beads. In this test-beds initial dry and wet retroreflectivity were measured and analyzed. RESULTS : When the refractive index of glass bead was adjusted upward in water based paint(glass bead No.1→ No.2), dry retroreflectivity increased by about 30 to 70%, and wet retroreflectivity slightly increased by about 10 to 40%. When using glass bead No. 2 in water based paint, it was found to meet the standards of the Road Traffic Act. However, since wet retroreflectivity of water based paint slightly exceeds the standard value, a follow-up investigation is needed to determine how long this performance can be maintained. When using glass bead No.1 in MMA(methyl methacrylate), the average wet retroreflectivity was evaluated to be 128 to 150 mcd/lx/m2, and when using glass bead No.2, the average wet retroreflectivity was evaluated to be about 200 to 270 mcd/lx/m2. Accordingly, MMA showed the best performance compared to other paints. CONCLUSIONS : When using glass bead No.1 in water-soluble paints and thermoplastic, it did not meet the wet retroreflectivity standards of the Road Traffic Act. But when using glass bead No.2, it met the wet retroreflectivity standards. As a result of analyzing the road marking budget according to the upward adjustment of the refractive index of glass bead, it was analyzed that if only the material class was adjusted upward, the cost would increase by more than twice the current budget. In order to decrease this budget increase rate(to increase service life), it is necessary to strengthen quality control standards for pavement marking and develop scientific-systematic quality control techniques.

PURPOSES : In this paper, problems and improvements in pavement marking standards are proposed as a result of the analysis of domestic/foreign standards and field data. METHODS : In this study, the US FHWA and all state standards were analyzed and domestic pavement marking standards were compared and analyzed. In addition, national highway marking test data, namely the Yeoncheon Test-Bed data, and data from Hawkins et al. (2015) were analyzed. Based on this, problems and improvements in the Korean pavement marking standards are proposed. RESULTS : As a result of literature and field data analysis, various problems were found in the Road Traffic Act and National Police Agency manual. In this standard, there is no definition of Qd; the RD reference value is set too low; and the RW and RR reference values are difficult to be considered reasonable values. CONCLUSIONS : There is an aspect in which the standard items and values of pavement markings are set under some policy judgment. Therefore, it is necessary to properly revise the standards, considering technical and economic aspects.

PURPOSES : Recently, interest in maintaining aged concrete pavements has been increasing. An asphalt overlay is generally used for pavement maintenance, and a tack coat is used to secure interlayer adhesion. Particularly, aged concrete pavements are required for higher adhesion performance of tack coats for attaching interlayers to materials with different properties. Insufficient interlayer adhesion could cause pavement damage, such as slippage, rutting, shoving, corrugation, and pothole. In this study, we examined the performance of interface adhesion by applying a tack coat material developed for maintaining aged concrete pavement. METHODS : In this study, we examined the effect of adhesion performance at the pavement interface, using a tack coat material developed for the maintenance of aged concrete pavement. RESULTS : The developed tack coat not only accomplished the performance objectives but also improved the results by more than 12 to 43%, compared to commonly used materials. CONCLUSIONS : The use of developed tack coat is expected to improve the interlayer adhesion and reduce the delay of the maintenance process in aged concrete pavement.

PURPOSES : The purpose of this study is to analyze the effect of ions in emulsion asphalt on recycling cold asphalt concrete and suggest the possibility of using anionic and nonionic emulsion asphalt. METHODS : In this study, indirect tensile strength, toughness, tensile strength ratio, and dynamic immersion tests were conducted to determine the effects of cation, anion, and non-ion emulsified asphalt on the cold recycled asphalt mixture. Crack resistance was evaluated through indirect tensile strength and toughness tests and the tensile strength ratio and dynamic immersion test were evaluated through tensile strength ratio and dynamic water immersion test. RESULTS : Indirect tensile strength and toughness measurement results demonstrated that the mixture using anion and non-ion emulsified asphalt tended to be higher than that using cation emulsified asphalt; this is due to the high content of reclaimed asphalt pavement with a cationic or ionic surface, which is related to the use of cation-emulsified asphalt in the mixture and has shown a low strength tendency. The tensile strength ratio measurement demonstrated that the mixture using non-ion emulsified asphalt tended to be approximately 15 % higher than that of the anion mixture. This demonstrated that the chemical additive used in the mixture showed a complete hydration reaction with the distribution to the mixture. The dynamic immersion test indicates that the aggregate film rate of asphalt is highly influenced by the surface electric charge of the new aggregate while the ionicity effect appears to be insignificant, at 75 - 85 %, when circular aggregates are used. CONCLUSIONS : High reclaimed asphalt pavement content in cold recycled asphalt mixture, as well as non-ion and anionic emulsified asphalt, is advantageous, reducing cracking and improving moisture resistance. It is believed that anions and non-ions may be better utilized than applying the existing criteria to the cold temperature recycled asphalt mixture with high reclaimed asphalt pavement content. In addition, if the scope of the emulsified asphalt is expanded, various additives can be used, which will require analysis of materials, such as fertilizers and additives.

PURPOSES: This study developed a new backfill method for mini trenching. The purpose of this study is to evaluate the performance of the new backfill method in the field. METHODS: In this study, asphalt pavement was created to verify mini trenching. Trenching test sections were then made in various trench widths in the asphalt pavement. The trench widths were 10 cm, 15 cm, 20 cm, and 25 cm. For the trenching test section, a general backfill method and new backfill method (2-layer SCB) were devised and applied. To evaluate the test section, a vehicle loading test and FWD (falling weight deflectometer) test were performed. RESULTS : In the vehicle loading test, the duct vertical strain of the general section was up to 22 times larger than that of the 2-layer SCB section. According to the results of the FWD test, the D0 deflection of the 2-layer SCB section was smaller than that of the general section. These results indicate that 2-layer SCB has a good structural performance. With the use of FWD data, BLI (base layer index) and MLI (middle layer index) were analyzed. BLI is an indirect index for evaluating base layer. The BLI of the 2-layer SCB section was smaller than that of the general section, because the bottom layer (cellular mortar) of the 2-layer SCB is superior to that of the general section. MLI, on the other hand, is an indirect index for evaluating subbase layer. As the trench width increases, MLI increases. The MLI of the 2-layer SCB section was smaller than that of the general section. These results indicate that the damage is relatively greater when the trench width increases and that the 2-layer SCB strengthens a relatively weakened subbase. CONCLUSIONS: In this study, the performance of the 2-layer SCB was analyzed. The results of the study showed that good performance was obtained when 2-layer SCB was applied to a mini trenching section.

PURPOSES: In this study, the effects of adding a superabsorbent polymer (SAP) to the concrete mixture on the strength of the concrete and abrasion resistance were analyzed, and whether the property of concrete can be improved by the internal curing effect of SAP was evaluated. METHODS: In this study, a total of eight different mixes were tested. The amounts of SAP added were 0%, 0.6%, 1.2% while that of silica fume were 0% and 6% based on the weight of the binder. The compressive test, rapid chloride penetration resistance test, and abrasion test were performed to verify the internal curing effects of SAP. RESULTS : The compressive test showed that SAP concrete had greater compressive strength than ordinary concrete. Comparison of the compressive strengths of dry and wet cured specimens of each mixture showed that SAP concrete had a smaller difference compared with ordinary concrete. The rapid chloride resistance test showed that SAP did not increase chloride penetration resistance. However, since this experiment only considered wet curing, further investigation of dry curing is necessary. The abrasion resistance test showed that for the case of concrete cured under dry conditions without spraying the curing compound, the abrasion resistance of the SAP concrete improved by approximately 49% at 14 days and 27% at 28 days of curing compared with ordinary concrete. CONCLUSIONS : The effect of SAP on the strength and abrasion resistance of concrete was analyzed. The results showed that the internal curing effect of SAP improved concrete strength and abrasion resistance. The internal curing effect maintains the overall internal humidity in concrete by supplying water held by the SAP to the dried cement paste.

PURPOSES : It is necessary to clarify the rheological properties of cement paste as a basic research in the development of mechanistic concrete mix design. The rheological properties of cement paste with different binder types, mix propositions, and with/without high range water reducers have been analyzed. METHODS: In this study, ordinary Portland cement, fly-ash, blast furnace slag, silica fume, and limestone powder were used as binders. The range of water-binder ratio was 0.3-0.5, and a total of 30 different mixes have been tested. The slump flow test, V-funnel test, and Dynamic Shear Rheometer (DSR) test were performed to analyze the rheological properties of cement paste. RESULTS : As a result of the slump flow test, it was found that the composition ratio of the binder contents greatly affected the paste flow when the high range water reducers were added. The results of V-funnel test showed that when the water-binder ratio was decreased without high range water reducers, the binder composition ratio had a large effect on the passing time of the V-funnel tester, but with high range water reducers the impact of the binder composition ratio was decreased. The slump flow and V-funnel have a certain relationship with the rheological factors (yield stress and plastic viscosity), but the correlation was not significant. Finally, we proposed the M-value considering the density and specific surface area of the binder. The correlation between rheological factors and M-value were better demonstrated than experimental values, but there is still a limit to predict the rheological factor in general mix design. CONCLUSIONS: In this study, the rheological properties of cement paste were analyzed. The binder type, composition ratio of binder, and with/without high range water reducers have combined to provide the complex effects on the rheological properties of cement paste. The correlation between the proposed M-value and rheological factor was found to be better than experimental results, but needs to be improved in the future.