Jeong-Hee Nam

Threshold Values of Performance Indicators for Asphalt Concrete Pavement to Apply to Pavement Performance Warranty

The performance warranty system is quite innovative in requiring a contractor’s warranty for pavement performance over a certain period of time. European countries adopted performance warranty systems about 40 years ago. The United States adopted this system in the early 1990s to improve construction quality and performance, as well as to reduce life cycle cost. In Korea, for the purpose of resolving construction management and quality control problems and poor construction, the performance warranty system is considered as part of the solution. The appropriate performance indicators, reasonable threshold values, and warranty periods have to be selected in order to adopt a performance warranty system that requires keeping the pavement performance above a certain level of satisfaction for the warranty period. For this reason, structural, functional, and safety performance were defined first, and then rut depth, roughness, and crack ratio were selected as performance warranty indicators. For the purpose of suggesting performance warranty threshold values that reflect domestic circumstances, pavement management system data were surveyed, a special project was conducted, and a total of 888 sample sections were analyzed. A threshold level at 95 % of each indicator’s distress was determined for the threshold value; this prevents the worst 5 % of poor performance cases. A 14-mm rut depth, 3.6 m/km International Roughness Index, and 20 % crack ratio for five years were selected as threshold values. To avoid early deterioration of pavement, three- to five-year warranty periods are suggested.

Development of Performance Criteria for Korean Pavement Warranty Specification

Existing road pavement specifications require that contractors meet only certain material and construction conditions regardless of pavement life. However, performance-based warranty specifications guarantee preservation of the product and designate responsibility for repair of defects to contractors. The warranty contracts and specifications for pavements used since the 1960s in Europe have been adopted in several states of the United States based on state-specific needs, and they have also been used in construction projects. In this study, the performance criteria of warranty specifications in Europe and the United States were investigated to develop performance criteria appropriate for Korea. Automated pavement survey equipment was used to inspect and evaluate indicators of pavement performance with regard to certain performance criteria. Each area of pavement was divided into 2-km sections, which were then subdivided into four 500-m segments. Among the numerous possible indicators, cracking, rutting, international roughness index (IRI), and surface defects (e.g., raveling, bleeding, and microcracking) were selected as performance indicators of asphalt pavement, whereas cracking, IRI, spalling, and D-cracking were selected for concrete pavement. Pavement management system (PMS) data from expressways and national highways were collected and analyzed at a 95th percentile confidence level to determine threshold values of the performance indicators. Warranty periods were also determined for newly constructed asphalt and concrete pavements, as well as asphalt overlay pavement. Remedial actions for the performance indicators were also suggested. Performance indicators and threshold values were evaluated by examining the asphalt overlay sections of national highways constructed between 2005 and 2007. As a result, conclusions were drawn about reasonable performance criteria appropriate for Korea.

Physical Properties of Rapid-Setting Concrete Using Ultra Fine Fly Ash

Generally, Ultra Fine Fly Ash (UFFA) has the advantage that it advances greater concrete workability and that it activates a greater pozzolanic reaction than common fly ash due to its ultra fine particle size. These properties enhance concrete durability by reducing permeability and increasing resistance to alkali silica reaction (ASR) and sulfate attack, etc. For these reasons, UFFA can be used in rapid setting concrete. The purpose of this study is to develop and evaluate the rapid setting concrete with UFFA as a repair material for early-opening-to-traffic. In previous studies, if only UFFA is added to the rapid setting concrete mixture, the pozzolanic reaction does not happen actively. In this study, the chemical and physical tests were performed for rapid setting concrete with a combination of UFFA and calcium hydroxide. This enabled the activity of pozzolanic reaction to be evaluated as well as the effectiveness of this mixture on enhancing concrete durability was investigated. This study found that adding UFFA decreased the water/cement ratio of concrete and compensated the reduced portion of the early strength of concrete. Additionally, rapid setting concrete with UFFA and calcium hydroxide activated a greater pozzolanic reaction than normal-UFFA concrete. As the calcium hydroxide increased, the electrical indication of the concrete’s ability to resist chloride ion penetration was promoted significantly.

Estimation of the Compressive Strength of Concrete Using Shear Wave Velocity

Compressive strength of concrete is a very important parameter in the quality control of both new and existing concrete pavement. It has been widely used to evaluate the concrete strength both in the laboratory and in the construction field regardless of whether numerous mix designs or identical mixtures are used. Errors usually happen in the compressive strength test even if the mixture is evenly mixed and compacted into test specimens. This is caused by either by the hand-operated testing machine or by the eccentricity between the specimen and the testing machine. If concrete specimens with identical mix design need to be tested at various curing ages every time concrete is used in the construction field, the result is significant waste of time, money and efforts are required. Consequently, there is a real need to replace the repeated compressive strength tests with the introduction of nondestructive tests to estimate compressive strength of concrete. In this study, a nondestructive test method using elastic waves was used because shear wave velocity is not affected by restraint conditions. The compressive strength of concrete was estimated according to various curing ages as well. In the results, shear wave velocity was very closely related to the compressive strength. The results further showed that the estimation of compressive strength of concrete using shear wave velocity is very effective and reliable.

Performance Evaluation of Bridge Deck Materials based on Ordinary Portland Cement Concrete

PURPOSES : The purpose of this study is to develop bridge deck concrete materials based on ordinary Portland cement concrete, and to evaluate the applicability of the developed materials through material properties tests. METHODS : For field implementation, raw material (cement, fine aggregate, and coarse aggregate) properties, fresh concrete properties (slump and air content), strength (compressive, flexural and bond strength) gain, and durability (freeze-thaw resistance, scaling resistance, and rapid chloride penetrating resistance) performance were evaluated in the laboratory. RESULTS : For the selected binder content of 410 kg/m, W/B = 0.42, and S/a = 0.48, the following material performance results were obtained. Considering the capacity of the deck finisher, a minimum slump of 150 mm was required. At least 6 % of air content was obtained to resist freezethaw damage. In terms of strength, 51.28 MPa of compressive strength, 7.41 MPa of flexural strength, and 2.56 MPa of bond strength at 28 days after construction were obtained. A total of 94.9 % of the relative dynamic modulus of elasticity after 300 cycles of freeze-thaw resistance testing and 0.0056 kg/m of weight loss in a scaling resistance test were measured. However, in a chloride ion penetration resistance test, the result of 3,356 Coulomb, which exceeds the threshold value of the standard specification (1000 Coulomb at 56 days) was observed. CONCLUSIONS : Instead of using high-performance modified bridge deck materials such as latex or silica fume, we developed an optimum mix design based on ordinary Portland cement concrete. A test construction was carried out at ramp bridge B (bridge length = 111 m) in Gim Jai City. Immediately after the concrete was poured, the curing compound was applied, and then wet mat curing was applied for 28 days. Considering the fact that cracks did not occur during the monitoring period, the applicability of the developed material is considered to be high.

ASR Resistance of Ternary Blended Binder Adding Ultra Fine Mineral Admixture

PURPOSES : This study is to evaluate ASR(alkali silica reactivity) resistance of ternary blended binder adding ultra fine mineral admixture. METHODS : This study analyzes ASR expansion using ASTM C 1260 and 1567. RESULTS : This study showed that the fineness of mineral admixture had no effect on ASR expansion. The expansion of ternary blended binder(UFFA 20%+FGGBS 10%) were below 0.1%, and this binder met the ASR standard. Also when adding the CSA expansion agent, ASR expansion slightly decreased. The expansion of latex modified mixture increased by 80% comparing plain mixture. CONCLUSIONS : Ternary blended binder met the ASR standard, and this binder is available in concrete bridge deck overlay.

Durability Evaluation of Ternary Blend Concrete Mixtures adding Ultra Fine Admixture

PURPOSES : The purpose of this study is to evaluate the durability of ternary blended concrete mixtures adding ultra fine admixture. METHODS : From the literature review, crack was considered as the main distress failure criterion on concrete bridge deck pavement. To reduce the initial crack development due to drying shrinkage, CSA expansion agent and shrink reduction agent were used to ternary blended concrete mixtures as a admixture. Laboratory tests including chloride ion penetration test, surface scaling test, rapid freeze & thaw resistance test, non restrained drying shrinkage and restrained drying shrinkage test were conducted to verify the durability of ternary blended concrete mixtures. RESULTS : Based on the test results, proposed mixtures were verified as high qualified durable materials. Expecially initial drying shrinkage crack was not occurred in ternary blended concrete mixtures with CSA expansion agent. CONCLUSIONS : It is concluded that the durability of proposed ternary blend concrete mixture was acceptable to apply for the concrete bridge deck pavement.

An Experimental Study on Relation between compressive strength and Shear Wave velocity for characteristics of coarse aggregate size and type of cement

Strength is one of the very important factors to evaluate the physical properties of concrete. Aggregate forms the most parts in concrete. Cement as a binder in concrete is also closely related to strength. This experiment was tested to understand the effect of the characteristics of aggregate and cement on the relationship between concrete compressive strength and Shear Wave velocity. It was experimented by the different types of cement and maximum coarse aggregate sizes. Type I cement and rapid setting cement was used. Aggregates from three different regions were used. Aggregate of 19mm and 13mm maximum coarse aggregate sizes was used for grading. The relationship between compressive strength and Shear Wave velocity was tested under the condition of same mixture. LA wear test was used to quantify the characteristics of aggregate. As a result, the relationship between concrete compressive strength and Shear Wave velocity was affected by the types of cement, but regular relationship was appeared regardless of types of aggregate, grading and abrasion ratio.

Calibration of Roughness Measuring Instrument for Adopting the Performance Warranty System

Most pavement construction in Korea today is conducted by following prescriptive specifications. The construction must be done according to the standard specifications and the contractor is responsible for any defects where the pavement quality does not meet the minimum requirements written in the specification. Adopting new materials and innovative construction technologies is limited under the current system. Many European countries have adopted the performance warranty systems to improve long-term pavement performance since the 1960’s. In the performance warranty system, a specification defines a certain level of pavement performance as the minimum requirement. Examples of performance indices might include: rutting, roughness, cracking, skid resistance, etc. The prescriptive specification is no longer used in the performance warranty system. Instead, the contractor must satisfy the performance specifications of each index. One of the most important performance indices is the roughness of pavement. The method for evaluating the pavement roughness is essential in order to prevent conflict where there is a disagreement for evaluating results between the contractor and the client. The primary objective of this paper is to present a guideline for the calibration of the roughness measuring instrument of pavement by semi-manual and automatic methods in the performance warranty system.