• International Journal of Highway Engineering
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• v.15 no.1
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• pp.11-21
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• 2013

PURPOSES: As pavement generally provides service shorter than an expected life cycle, maintenance cost increases gradually. In order to help extending the service life and reduce maintenance cost, a new multi-functional composite pavement system is being developed in Korea. METHODS: This study is a part to develop the multi-functional composite pavement and is to investigate the mechanical performances of fiber-reinforced lean concrete for pavement subbase. The inherent problem of fiber reinforced concrete is dispersion of fibers in concrete mix. This study additionally evaluated fiber dispersion characteristics with respect to different fiber types. RESULTS: From the test results, the compressive strengths of the concretes satisfied the required limit of 5MPa at 7days. The standard deviation of the measured number of fibers were lower in the order of nylon, steel fiber and polypropylene. CONCLUSIONS: Reject ash was shown to be satisfactory as a replacement material to Portland cement in lean concrete base. The fiber volume fraction is suggested to be 0.4% even though the fracture toughness did not vary significantly with respect to fiber types. However, fracture energy absorbed up to complete failure increased with the increased fiber volume fraction increment.

• International Journal of Highway Engineering
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• v.14 no.5
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• pp.21-29
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• 2012

PURPOSES: This study is to investigate the mechanical performance of the fiber reinforced lean concrete with respect to different types of fibers. METHODS: Increased vehicle weight and other causes from the exposed conditions have accelerated the deteriorations of road pavement. A new multi-functional composite pavement system is being developed recently in order to extend service life and upgrade the pavement. A variety of tests were conducted before and after hardening of the concrete. RESULTS: From the test results, it was found that the use of different types of fibers did not affect the compressive strength development. This might be due to the inherent property of the lean concrete. When steel fibers were used relatively greater flexural strength and flexural fracture toughness were developed. Also addition of fly ash by replacing a part of Portland cement the fracture toughness was slightly increased. CONCLUSIONS: It has been known that the addition of fibers and use of mineral admixture can be positively considered in the development of multi-functional composite pavement system as its required mechanical performance is obtained.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.265-266
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• 2010

In this study, reduction of the crack in the lean concrete for pavements by combining different types of fibers is discussed to compare and verify its validities. Experimental result using NY fibers is depending on excellent aspect ratio and hydrophilic. Vebe time has shown good results. In addition, the addition of PP fiber had most favorable flexural strength.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.543-551
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• 2012

Road pavements in Korea generally show shorter service life than the predicted one. There are many reasons for this phenomenon including increased traffic load and other attacks from exposure conditions. In order to extend a service life and upgrade the pavement, a new multi-functional composite pavement system is being developed in Korea. This study is to investigate the performances of fiber-reinforced lean concrete for pavement base. This study considered mineral admixtures of fly ash and reject ash. The reject ash is defined as ash that does not meet the specifications for fly ash so that it cannot be used as a supplemental material for cement replacement. Due to the inherent property of lean concrete, compaction during the fabrication of specimens is a key factor. Therefore, this study suggests an appropriate compaction method. From the test results, the compressive strengths of the concrete satisfied the required limit of 5 MPa at 7 days. When a compaction roller was used to mimic actual field conditions, the strength development seemed to be influenced by the compaction energy rather than hydration of cement itself.

• 한국도로학회:학술대회논문집
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• 2011.03a
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• pp.153-158
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• 2011

• International Journal of Highway Engineering
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• v.18 no.1
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• pp.13-21
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• 2016

PURPOSES : In this study, we analyzed the compressive strength characteristics of lean base concrete in relation to changes in the outdoor temperature after analyzing the cold and hot weather temperature standards and calculated the minimum and maximum temperatures when pouring concrete. We examined the rate of strength development of lean base concrete in relation to the temperature change and derived an appropriate analysis formula for FRC base structures by assigning the accumulated strength data and existing maturity formula. METHODS : We measured the strength changes at three curing temperatures (5, 20, and $35^{\circ}C$) by curing the concrete in a temperature range that covered the lowest temperature of the cold period, $5^{\circ}C$, to the highest temperature of the hot period, $35^{\circ}C$. We assigned the general lean concrete and FRC as test variables. A strength test was planned to measure the strength after 3, 5, 7, 14, and 28 days. RESULTS : According to the results of compressive strength tests of plain concrete and FRC in relation to curing temperature, the plain concrete had a compressive strength greater than 5 MPa at all curing temperatures on day 5 and satisfied the lean concrete standard. In the case of FRC, because the initial strength was substantially reduced as a result of a 30% substitution of fly ash, it did not satisfy the strength standard of 5 MPa when it was cured at $5^{\circ}C$ on day 7. In addition, because the fly ash in the FRC caused a Pozzolanic reaction with the progress into late age, the amount of strength development increased. In the case of a curing temperature of $20^{\circ}C$, the FRC strength was about 66% on day 3 compared with the plain concrete, but it is increased to about 77% on day 28. In the case of a curing temperature of $35^{\circ}C$, the FRC strength development rate was about 63% on day 3 compared with the plain concrete, but it increased to about 88% on day 28. CONCLUSIONS : We derived a strength analysis formula using the maturity temperatures with all the strength data and presented the point in time when it reached the base concrete standard, which was 5 MPa for each air temperature. We believe that our findings could be utilized as a reference in the construction of base concrete for a site during a cold or hot weather period.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.21-30
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• 2011

As well known, dowel bars are used to transfer traffic load acting on one edge to another edge of concrete slab in concrete pavement system. The dowel bars widely used in South Korea are round shape steel bar and they shows satisfactory performance under bending stress which is developed by repetitive traffic loading and environment loading. However, they are not invulnerable to erosion that may be caused by moisture from masonry joint or bottom of the pavement system. Especially, the erosion could rapidly progress with saline to prevent frost of snow in winter time. The problem under this circumstance is that the erosion not only drops strength of the steel dower bar but also comes with volume expansion of the steel dowel bar which can reduce load transferring efficiency of the steel dowel bar. To avoid this erosion problem in reasonable expenses, dowers bars with various materials are being developed. Fiber reinforced plastic(FRP) dower that is presented in this paper is suggested as an alternative of the steel dowel bar and it shows competitive resistance against erosion and tensile stress. The FRP dowel bar is developed in tube shape and is filled with high strength no shrinkage. Several slab thickness designs with the FRP dowel bars are performed by evaluating bearing stress between the dowel bar and concrete slab. To calculated the bearing stresses, theoretical formulation and finite element method(FEM) are utilized with material properties measured from laboratory tests. The results show that both FRP tube dowel bars with diameters of 32mm and 40mm satisfy bearing stress requirement for dowel bars. Also, with consideration that lean concrete is typical material to support concrete slab in South Korea, which means low load transfer efficiency and, therefore, low bearing stress, the FRP tube dowel bar can be used as a replacement of round shape steel bar.