Aggregate type and mineralogy are critical factors that influence the engineering properties of concrete. Temperature variations result in internal volume changes could potentially cause a network of micro-cracks leading to a reduction in the concrete’s compressive strength. The study specifically studied the effect of the type and mineralogy of fine and coarse aggregates in the normal strength concrete properties. As performance measures, the coefficient of thermal expansion (CTE) and compressive strength were tested with concrete specimens containing different types of fine aggregates (manufactured and natural sands) and coarse aggregates (dolomite and granite). Petrographic examinations were then performed to determine the mineralogical characteristics of the aggregate and to examine the aggregate and concrete microstructure. The test results indicate the concrete CTE increases with the silicon (Si) volume content in the aggregate. For the concrete specimens with higher CTE, the micro-crack density in the interfacial transition zone (ITZ) tended to be higher. The width of ITZ in one of the concrete specimens with a high CTE displayed the widest core ITZ (approx. 11 µm) while the concrete specimens with a low CTE showed the narrowest core ITZ (approx. 3.5 µm). This was attributed to early-age thermal cracking. Specimens with higher CTE are more susceptible to thermal stress.

Effect of Aggregate Mineralogy and Concrete Microstructure on Thermal Expansion and Strength Properties of Concrete

In order to investigate the actual health condition of asphalt concrete pavements on widened road embankments, a full-scale model test study was conducted. A fiber Bragg grating–based sensor networ...

Experimental investigation of pavement behavior after embankment widening using a fiber optic sensor network

A new dynamic finite-element computer program, DYNA-SLAB, for the analysis of jointed concrete pavements subjected to moving transient loads is presented. The dynamic solution is formulated in both the time and the frequency domains. The structural model for the slab system is the one used in the static computer program ILLI-SLAB. The foundation support is represented by either a damped Winkler model with uniformly distributed frequency-dependent springs and dashpots or a system of semi-infinite horizontal layers resting on a rigid base or a semi-infinite half-space. An important contribution from the study is a new analytical method for determining the stiffness and damping coefficients to be used in the Winkler foundation model. The accuracy of DYNA-SLAB has been verified by comparing the results produced by the program with those from theoretical closed-form solutions and from a powerful dynamic soil-structure interaction computer program called SASSI as well as with field data. The analytical results indicate that dynamic analysis is generally not needed for the design of rigid pavements and that it usually leads to decreased pavement response. Thus, it appears that a quasistatic analysis is sufficient and that the results from this type of analysis will generally be conservative, provided that the wheel loads used in the analysis have been adjusted for the effects of vehicle velocity, truck suspension characteristics, and pavement roughness.

Dynamic Finite-Element Analysis of Jointed Concrete Pavements

Temperature in pavement and subgrade and its effect on moisture

Negative temperature gradient and the moisture gradient through the thickness of a concrete slab result in curling and warping of the slab edges to a concave configuration. The tendency of the slab pavement to separate from the subbase layer, called lift-off, is mainly controlled by such environmental effects and the weight of the slab itself. Because of such effects, cracks may propagate at the interface of the concrete slab and the subgrade. The induced stress and displacement fields around the interface crack tip are characterized by the stress intensity factors. The stress intensity factors can then be used in assessment of the cracked bond strength by employing any fracture criteria; therefore, it is necessary that the stress intensity factors be obtained. This paper proposes a new approach for determination of slab lift-off that uses concepts from interfacial fracture mechanics. A two-dimensional finite element analysis was performed to simulate lift-off in concrete slab pavements, and the effect of...

New Approach to Determining Concrete Slab Lift-Off by Use of Interfacial Fracture Mechanics Concepts

The effect of slab curling on the development of cracking at saw-cut notches and long-term joint movement in the concrete pavement sections of the Korea Highway Corporation test road was investigated in addition to joint deflections and load transfer efficiency (LTE) at the joints. During paving operations, 50 joints were saw-cut immediately after the occurrence of a random crack in the concrete pavement. The location and the time of the uncontrolled cracking were observed by a comparison of the tensile strength of the concrete with the tensile stress developed by the slab curling because of the temperature difference between the top and bottom of the slab. The development of cracking and movement of the saw-cut joints and random cracks were observed over a 2-year period after construction. The relationship between the initial and long-term joint movements is presented. The deflections and LTE at the joints and random cracks were measured by using the falling weight deflectometer 2 years after concrete placement. The effect of slab curling due to a permanent built-in temperature difference on the deflection at the joint is described. In addition, the effect of dowel locking due to the upward slab curling on the load transfer capacity of the joint is presented.

Effect of slab curling on movement and load transfer capacity of saw-cut joints

Structures underneath pavements commonly reduce the bearing capacity of the ground because of poor compaction and long-term settlement at sites around these structures. When a load is applied at these sites, the stress on the concrete slab increases and may exceed the design strength, inducing distress and shortening the lifespan of the pavement. In this study, we investigated the transverse cracking of concrete pavement slabs above box culverts in a test road of the Korea Expressway Corporation. Transverse cracking in the slabs was surveyed in both the north- and southbound lanes with different cover depths over the box culverts. To examine the transverse cracking, the jointed concrete pavement of the test road containing the culvert was modeled and analyzed by the finite-element method. Wheel loading was applied after taking into account the self-weight of the pavement and the temperature gradient within the concrete slab. The positions and magnitudes of the maximum tensile stress and the corresponding positions of wheel loading were investigated for each loading combination. In this manner, we identified the optimal joint positions for which the maximum tensile stress in the pavement slab is minimized. We also analyzed the behavior of the pavement in relation to the cover depth and reinforced concrete transition slab length. Accordingly, we proposed an appropriate length for the reinforced concrete transition slab to ensure minimized tensile stress in the pavement slab.

Influence of Box Culverts on Behavior of Jointed Concrete Pavements

Jointed Concrete Pavement (JCP) has been constructed in over half of the total expressway system in Korea due to its long service life and low maintenance costs. The JCP on a box culvert is susceptible to failure brought by the freezing and heaving phenomenon during winter. This contributes to the shortening of pavement service life and deterioration of road quality. In order to address this problem, several alternatives have been suggested. The results of temperature variation of the soil layer on a box culvert and the profile measurements show that the water in the soil freezes during winter. Furthermore, it is impossible to prevent this by a dummy ditch, however, a waterproof mat, a tent, and an elastic-asphalt mat can be effective. Based on measurements of moisture contents in the soil, a method to combine a waterproof mat and crack or joint sealing showed good performance. For a soil material and a crown at the top of a culvert, when 1% crown for anti-freezing material or 4% crown for subgrade was applied to the surface, the risk of freezing and heaving decreased.

Evaluation of methods to prevent soil on a box culvert from freezing-heaving

In the present study, three strain gauge installation methods (mound, trench-cut, and block-out) are evaluated to propose a set of methods that are appropriate for different layers of hot mix asphalt (HMA) pavements. The block-out method is also improved to minimize strain gauge mislocations (i.e., installation offsets). Field tests show that the improved block-out method is suitable for most layers, except for a thin surface, for which the mound should be used. To validate the proposed methods, 374 strain gauges are installed at different layers of thirty-three HMA pavement sections (48 in surface, 157 in intermediate, and 169 in base) at the Korea Highway Corporation Test Road (KHCTR) and their initial and long-term performances are monitored at different times. In addition, the failure rates of the embedded strain gauges are correlated with the evolution of the overall pavement conditions and key distresses at selected sections from 2003 to 2007.

Short- and Long-Term Evaluation of Asphalt Concrete Strain Gauge Installation Methods Applied to the KHCTR

PURPOSES: This study aims to evaluate the runoff reduction with permeable pavements using the SWMM analysis. METHODS: In this study, simulations were carried out using two different models, simple and complex, to evaluate the runoff reduction when an impermeable pavement is replaced with a permeable pavement. In the simple model, the target area for the analysis was grouped into four areas by the land use characteristics, using the statistical database. In the complex model, simulation was performed based on the data on the sewer and road network configuration of Yongsan-Gu Bogwang-Dong in Seoul, using the ArcGIS software. A scenario was created to investigate the hydro-performance of the permeable pavement based on the return period, runoff coefficient, and the area of permeable pavement that could be laid within one hour after rainfall. RESULTS : The simple modeling analysis results showed that, when an impervious pavement is replaced with a permeable pavement, the peak discharge reduced from to . This represents a reduction of approximately 37.6%. The peak discharge from the whole basin showed a reduction of approximately 11.0%, and the quantity decreased from to . The total flowoff reduced from to , i.e., by approximately 10.9%. In the complex model, performed using the ArcGIS interpretation with fewer permeable pavements applicable, the return period and the runoff coefficient increased, and the total flowoff and peak discharge also increased. When the return period was set to 20 years, and a runoff coefficient of 0.05 was applied to all the roads, the total outflow reduced by , and the ratio reduced to 11.7%. When the return period was increased from 20 years to 30 and 100 years, the total outflow reduction decreased from 11.7% to 8.0% and 5.1%, respectively. When a runoff coefficient of 0.5 was applied to all the roads under the return period of 20 years, the total outflow reduction was 10.8%; when the return period was increased to 30 and 100 years, the total outflow reduction decreased to 6.5% and 2.9%, respectively. However, unlike in the simple model, for all the cases in the complex model, the peak discharge reductions were less than 1%. CONCLUSIONS : Being one of the techniques for water circulation and runoff reduction, a high reduction for the small return period rainfall event of penetration was obtained by applying permeable pavements instead of impermeable pavement. With the SWMM analysis results, it was proved that changing to permeable pavement is one of the ways to effectively provide water circulation to various green infrastructure projects, and for stormwater management in urban watersheds.

http://www.koreascience.or.kr:80/article/JAKO201525550548530.pdf

Jaehoon Lee

Papers

Effect of slab curling on movement and load transfer capacity of saw-cut joints

Influence of Box Culverts on Behavior of Jointed Concrete Pavements

Evaluation of methods to prevent soil on a box culvert from freezing-heaving

Short- and Long-Term Evaluation of Asphalt Concrete Strain Gauge Installation Methods Applied to the KHCTR

Performance Evaluation of the Runoff Reduction with Permeable Pavements using the SWMM Model