본 연구는 여성 독거노인의 심리적 고독감과 삶의 만족도 의 관계에서 사회적 지지의 매개효과를 검증하고자 하였다. 본 연구는 D시에 거주하는 여성 독거노인을 대상으로 2022 년 7월 1일부터 8월 31일까지 300명의 자료를 수집하였으며, 이 중 290명의 자료를 분석에 활용하였다. 자료분석은 빈도 분석, 기술통계, 상관관계 그리고 구조방정식 분석을 하였다. 분석결과, 첫째, 여성 독거노인의 고독감은 삶의 만족도에 유 의미한 부(-)의 관계의 영향을 확인하고, 사회적 지지와 삶의 만족도는 정(+)의 방향에서 유의미한 영향을 이루는 것을 확 인할 수 있다. 둘째, 여성 독거노인의 고독감과 삶의 만족도 의 관계에서 사회적 지지의 매개효과를 확인할 수 있었으며, 사회인구학적 특성인 경제적 상태의 영향력을 확인하였다. 이를 바탕으로 여성 독거노인의 삶의 만족도를 증진할 수 있 는 방안을 제시하였다는 점에서 의의가 있다.

PURPOSES : The purpose of this study is to suggest a thermal expansion coefficient measurement method using an embedded strain transducer (EST) and vibrating wire gauge (VWG), as well as to evaluate the reliability of the proposed methods by comparing them with the AASHTO T 336-10 standard method. METHODS : To apply the AASHTO 336-10 test method, which is the criterion for reliability evaluation, a reference specimen using stainless steel (sus304) is manufactured, and a thermal expansion coefficient of 17.308με/°C is obtained based on ISO regulations. Using the reference specimen, the correction factor of the thermal expansion coefficient measurement equipment is measured to be 2.93με/°C, and using this value, the thermal expansion coefficient of the mortar specimen containing the embedded gauges is measured accurately. The reliability of the proposed experimental method is evaluated by measuring the thermal expansion coefficient of the embedded gauge with temperature compensation and then comparing it with that of the reference specimen. RESULTS : The coefficient of thermal expansion of the mortar specimen is measured to be 12.423με/°C based on AASHTO 336-10, 11.963με/°C using the EST method, and 12.522με/°C using the VWG method. Based on the results obtained using the AASHTO method, the embedded gauges show a difference of 1%~3% in terms of the average results, as well as a difference in the standard deviation of 0.059~0.186. Therefore, our level of confidence in the thermal expansion coefficient experiment using the embedded gauges is high. CONCLUSIONS : When using the AASHTO 336-10 test method, the thermal expansion coefficient should be obtained by measuring the length change of the specimen; however, some engineering judgment of the experimenter is required when the measurement values fluctuate during the temperature stabilization period. In the thermal expansion coefficient test using embedded gauges (EST and VWG), temperature compensation must be performed. Furthermore, it is assumed that the temperature difference between the water tank and test specimen does not significantly affect the thermal expansion coefficient measurement because the important point is not the actual temperature value but the temperature gradient. For reliability evaluation, a statistical significance review of the strain distribution by measurement method is performed via a T-test comparing with the AASHTO test result (12.423με/°C) and the reliability level for each measurement method remains confidential.

PURPOSES : This study analyzes the service life of the repair methods of jointed plain concrete pavement (JPCP) on expressways in Korea using PMS data. METHODS : The Korea Expressway Corporation PMS data acquired from five major expressways in Korea were used for the analysis. The service lives of the repair methods were considered for two different cases: 1) the previous repair methods had been completely rerepaired by another or the same method due to their damage, and 2) the current repair methods were still in use. RESULTS : The service lives of D/G and section repair were shown to be at least 30 % and 50 % shorter than expected, respectively. Joint sealing and crack sealing exhibited a service life similar to that expected. The Mill-and-Asphalt-overlay method showed an approximately 30 % longer service life; this might be because some damage to the asphalt overlay is typically neglected until subsequent maintenance and repair. When multiple repairs were applied in series for an identical pavement section, the service life of repairs on previously damaged secti ons become even shorter compared to their first application. CONCLUSIONS : It was found that the analyzed service life of most important repair methods did not reach the expected service life, and that the service life of the same repair method becomes shorter as applied to the previously repaired concrete pavement sections. These shorter service lives should be seriously considered in future JPCP repair strategy development.

PURPOSES : The purpose of this study is to propose the certification process of International Roughness Index measuring device, i.e., a method for evaluating riding quality on road surfaces. METHODS : ROMDAS was selected as a reference device for verifying the accuracy of the IRI measuring device and the reliability of ROMDAS was checked through leveling in the laboratory and outdoors. To verify four different IRI measuring devices in Korea, the proper field test section was selected and IRI evaluation was conducted. A distance measuring instrument (DMI) - for verifying the accuracy of mileage - and IRI (as an index of roughness) were selected as the main evaluation parameters. For DMI verification, five repeated experiments were conducted for a 1 km section and, for IRI verification, speed variables of 40 km/h, 60 km/h, and 80 km/h were selected. Each device was tested at each speed 10 times. The accuracy of the measurement device was analyzed by comparing the measurement results with the verification criteria. RESULTS : As a result of the comparative experiment between the leveling and ROMDAS devices, the deviation of each measurement point value was within 1 mm and the R2 value was 0.8, demonstrating an excellent correlation. As a result of DMI verification, the tolerance of the three devices was found to be within 0.1 %; however, one device had a tolerance of 0.8 %, indicating that correction was necessary. For IRI evaluation, the average IRI value of the two reference devices was 2.02 m/km and the Minnesota standard was used as an analysis criterion. After the test, only one of the four devices was found to be effective across all speed ranges. Therefore, it was determined that additional sensor calibration is required to improve accuracy. CONCLUSIONS : In this study, the IRI device accuracy was evaluated through field tests. Hence, a new certification process for the IRI test device was proposed via four steps. To improve the accuracy of the IRI measurement, it is necessary to periodically verify the device. If this proposed certification process is applied, the accuracy of the IRI devices can be improved.

PURPOSES : The purpose of this study is to verify the effectiveness of the developed ultra-thin-continuously reinforced concrete partition (UT-CRCP) overlay method through a comparative analysis of the early-behavior of the UT-CRCP with a 100 mm cutting overlay of the existing JPCP. METHODS : This study aims to minimize the vulnerability of the existing JPCP (joint section behavior) by overlaying the continuous reinforcement form to constrain joint behavior. For this purpose, the early-behavior of the JPCP section was measured and the early-behavior of the UT-CRCP section was compared with that of the cutting overlay of the same section. The testbed was constructed for comparative analysis of the two types of pavements and the early behavior was measured using the pure environmental loads, i.e., situations where there was no traffic load. For the UT-CRCP, which is a comparative test group, UT-CRCP was constructed approximately one year after the JPCP was constructed by milling the top of the existing JPCP by 100 mm. RESULTS : 1) UT-CRCP was shown to effectively reduce the amount of crack width change on the surface by 17 %, compared to JPCP, by placing reinforcement inside the pavement. 2) The restricting effect of the UT-CRCP was analyzed by comparing the strain generated by the cross-section depth for the two pavement types. As a result, the restricting rate by depth (20, 80, 120, and 280 mm) was 68.4 %, 80.2 %, 89.2 %, and 26.7 %, respectively. 3) We reviewed the comprehensive gauge restricting rate at depths of 80 mm and 120 mm (80.2 % and 89.2 %, respectively) and the absolute value of behavior that is located at the ±20 mm of the interface of JPCP and UT-CRCP. Thus, it was possible to estimate that both layers of pavements exhibit the same behavior (tied) at the interface between the two pavement layers. CONCLUSIONS : In this study, the early behavior of the BCO concept UT-CRCP overlay technique was analyzed and quantitatively presented to overcome the limitations of JPCP with relatively weak point behavior and to increase the commonality of aged concrete pavement to the performance of the new pavement.

PURPOSES: This study determines the life of asphalt overlay over old concrete pavements for various times of overlay, using the actual 30- year performance history of the Jungbu Expressway. The results from this study can be used as the basis for decisions on the proper time for overlay, and can also provide information for life cycle cost analysis. METHODS : The maintenance history of the Jungbu Expressway and traffic database 30 years after construction were analyzed. The durations between the first overlay and subsequent overlay for each section of the pavement were analyzed for the entire Jungbu Expressway. The durations were analyzed in terms of both years and the ESAL traffic volumes. RESULTS : 1. The life of the asphalt overlay over the old concrete pavements depended on the time of overlay in terms of both age and cumulative ESALs. A strong correlation was observed between the overlay life and the cumulative ESALs at the time of overlay. 2. The life of the second overlay at the same section was significantly shorter than the first overlay. For JCP, the average lives of the first and second overlays were 6.1 and 2.4 years, respectively. For CRCP, they were 4.8 and 2.7 years, respectively. The main reason for the shorter life of the overlay for CRCP may be that the overlay time was generally later than that for the JCP. 3. The life of the overlay was analyzed according to its materials. SMA exhibited the best performance, followed by CRM. CONCLUSIONS: Life of the overlay reduced with the time of overlay especially in terms of cumulative ESALs, and the life of the second overlay at the same section was significantly shorter than the first overlay. The results can be used in the decision making of the time of overlay and in the life cycle cost analysis.

PURPOSES: The purpose of this study is to determine the effective maintenance method for a deteriorated jointed plain concrete pavement by evaluating the long-term performance of the repaired concrete overlay sections. METHODS: Long-term performance evaluation was conducted for the test section at the intersection between SeoPa and IlDong in National Road No. 37. Firstly, the distress conditions of the concrete pavement, which was constructed in December 2003, were evaluated by referring to the existing report. Secondly, the results of pretreatment, material properties, and initial performance evaluation were analyzed for the overlay test conducted in 2011. Finally, a field survey was carried out using visual inspection and nondestructive testing with a FWD in August 2018, and long-term performance evaluation was conducted for about seven years after maintenance. RESULTS: Visual inspection of the old concrete pavement showed severe damage such as joint spalling and asphalt patching. The cores taken from the old concrete had indirect tensile strength of 2.6-3.8 MPa. It is difficult to determine the freeze-thaw resistance because the average amount of air was only 1.6-2.2%, and spacing factor values were over 400㎛ regardless of location. During maintenance, overlay and partial depth repair were performed by applying three types of overlay materials which are typical in Korea. On the material side, high compressive strength (over 40 MPa) and chlorine ion penetration resistance (less than 1,000 coulomb) at 56 days were achieved. In August 2018, seven years after maintenance, visual inspection and nondestructive testing using FWD were conducted for long-term performance evaluation. Regardless of the maintenance materials, surface deficiencies such as spalling and map cracking occurred extensively near the joint. CONCLUSIONS: In conclusion, if the strength and durability index of aged concrete pavement is low, then it was determined that partial depth repair at the joint is not an effective maintenance alternative. In the case of overlay, the durability of the overlay material is considered the most important factor. In the absence of adequate reinforcement at the joint of the distressed concrete pavement, freeze-thaw damage caused by moisture penetration through the joint and failure of the old concrete are repeated, making it difficult to ensure long-term durability.

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 : 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/m3, 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/m2 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.