• International Journal of Highway Engineering
• /
• v.13 no.1
• /
• pp.157-168
• /
• 2011

Recently, the cases of freeze-thaw distress on concrete pavement in domestic have been reported periodically. Hereupon, the necessity to establish the standard of spacing factor came to the fore. The test method for analyzing spacing factor is provided in the standard of ASTM C 457. Since researchers tend to judge study results subjectively, the results should be revised throughly. Image analysis program for determining the characteristics of air-void system on hardened concrete identify air void through the difference of a color. The pixel intensity values used in this program have a significant effect on the analysis results. This study compared the automated void count by varying pixel intensity values with the manual void count in order to determine the optimum range of pixel intensity values. Also, this study analyzed the air-void characteristics on eight kinds of concrete mixtures. In this study, it was confirmed that the variation of void counted manually was around 10% from the results of round robin test, and that the optimum range of pixel intensity values is around 80~90. And it was also confirmed that air content (as a whole) was increased generally and spacing factor was decreased by increasing air-entrainer content. But some concrete mixtures showed a tendency that air content was constant and spacing factor was decreased by increasing air-entrainer content. This causes the air entrained by air-entrainer has more influence on spacing factor than air content. Also, the deviation of spacing factor by cutting position of concrete specimen was about 30~100${\mu}m$ because of the limit of 2-D image analysis. The additional study about variation of spacing factor by cutting position of concrete specimen will be performed later.

• International Journal of Highway Engineering
• /
• v.13 no.3
• /
• pp.51-63
• /
• 2011

Surface of fine-size exposed aggregate portland cement concrete pavements(FS-EAPCC) is consist by exposed coarse aggregate to remove upper 2~3mm mortar of concrete slabs. Advantages of FS-EAPCC are maintaining low-noise and adequate skid-resistance level during the performance period. However, FS-EAPCC is required rational management criteria for field application, since it is early stage for application. Design construction and quality control criteria of FS-EAPCC was temporary laboratory tests which including optimum mix and exposing method, selection of adequate aggregate, resistance against, environmental loading and etc. However, these criteria need to be validated base on field application. In this study, experimental constructions were performed and construction procedure and quality control criteria were suggested based on the performance of the FS-EAPCC.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.1
• /
• pp.109-116
• /
• 2021

In order to replace mineral aggregate used as road pavement materials with steel slag aggregate, this present study evaluated mechanical properties of SMA Concrete mixtures using steel slag aggregate as oxidized slag from electric furnace in iron works. The variables of this experiment are the aggregate type of mineral and steel slag and the sieve sized of 10mm and 13mm. The physical properties inclu ding the specific gravity and absorption rate etc. of the slag aggregate mixtu res satisfied the KS standard as asphalt mixtu re. As a resu lt of evalu ating the mechanical properties of the asphalt mixtures, the optimum asphalt content of the slag aggregate mixtures were lower than that of the mineral aggregate mixtures, but other quality standards were all satisfied. In the deformation strength evaluation, the slag aggregate mixtures were measu red slightly higher than that of the mineral aggregate mixtu res, and the dynamic stability test satisfied the 2,000pass/mm standard value in all specimens. And, the moduli of resilient of the slag aggregate mixtures showed an improved value compared with the mineral aggregate mixtures. Therefore, as the resilient rate of the slag aggregate mixtures improved, it is speculated that there will be an effect of improving public performance according to the repeated traffic load of the vehicle.

• International Journal of Highway Engineering
• /
• v.6 no.3 s.21
• /
• pp.17-26
• /
• 2004

The in-situ California Bearing Ratio (CBR) test has been widely used for evaluating the subgrade condition in asphalt concrete pavements. However, because the in-situ CBR test is expensive and takes plenty of time for operation, it is very difficult to figure out the in-situ characteristics of subgrade strength in detail. For faster and economical operation, the Dynamic Cone Penetrometer (DCP) has been often utilized for estimating the subgrade strength in the field. The relationship between the CBR value and DCP index obtained from the DCP testing has been studied using the laboratory and in-situ testing by other foreign researchers. The objective of this study is to determine the relationship between in-situ CBR value and DCP index of the subgrade materials used in Korea. The DCP index for evaluating the strength of subgrade materials produced in Korea is presented in this paper. Research results propose the regression equation to explain the relationship between the CBR and DCP tests. The in-situ CBR values of subgrade materials range from 20 to 45% indicating the good and sound subgrade condition.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.4 no.4
• /
• pp.388-395
• /
• 2016

This paper explores the photocatalytic sensitivity of cement mortar incorporated with recycled $TiO_2$ from waste water sludge. Basically, $TiO_2$ cluster sank down slowly to the bottom of cement mortar specimen before setting and hardening process. This leads the mismatch of $TiO_2$ concentration on the top and the bottom faces of a specimen. This poorly dispersed $TiO_2$-cement mortar naturally exhibits poor NOx removal efficiency especially on the top of cementitious structure. In architectural engineering application such as building or housing structures, one can simply filp over from the bottom so that more $TiO_2$ concentrated surface can be placed outward into the air. However, in highway pavement case, this could not be applicable due to in-situ installation of concrete pavement. Hence, the dispersion of $TiO_2$ cluster inside the cementitous material is getting important issue onto road construction application. To elaborate this issue, according to our results, silica fume, high-ranged water reducer, viscosity agent, blast furnace slag were not enhanced much of dispersion characteristics of $TiO_2$ cluster. The combination of foaming agent and accelerator of hardening with viscosity agent and small grain size of fine aggregate may help the dispersion of $TiO_2$ inside cementitious materials. Even though the enhanced dispersion were applied to the specimen, NOx removal efficiency doest not change much for the top surface of the specimen. This concurrently affected by the presence of tiny air voids and the dispersion of $TiO_2$ in that these voids could easily adsorbed NOx gas with the aid of large surface area.