PURPOSES : This study deals with the working life of polymer concrete, which is typically used as a repair or overlay material for portland cement concrete pavements. METHODS : In the scope of this study, laboratory testing was conducted on fresh MMA modified UP polymer concrete, which uses an MMA monomer for viscosity adjustment and strength improvement of UP resin. The experimental variables were temperature (-20 to +20℃) and binder components (MMA, MEKPO, and DMA). RESULTS : The result showed that the optimum binder ratios for polymer concrete production were 12, 11, and 10 wt.% when the MMA contents were 20, 30, and 40 wt.%, respectively. The working life of polymer concrete depending on temperature and binder components could be expressed by a logarithmic functional formula. The coefficient of variation for each binder component was the highest for DMA content while the lowest for MEKPO content. Also, the contents of each binder component for ensuring the working life of 60 minutes were proposed. CONCLUSIONS : Ultimately, the present study derived a linear regression equation estimating 60 minutes working life based on the setting times of each binder component.

In this study, the conventional model for the yield stress with the volume fraction of aggregate, where the volume fraction of aggregate was considered separately into the volume fraction of fine and coarse aggregate. The modified model equation can be applied to relate the yield stress of the wet sieved mortar and that of the concrete. Based on the model equation and the mix proportion of concrete, the yield stress of concrete is well predicted, which contributes the simplification of the performance evaluation process of concrete.

In this paper, the mechanical properties of fresh concrete were evaluated by using electric arc furnace oxidizing slag(EOS) aggregate. Water-Cement(W/C) ratio was selected as 0.45 and 0.30, and the mixing amount of EOS aggregate as 0%, 50%, 100%. Experimental items of fresh concrete were slump, flow, air content, unit volume weight. As a results, As the mixing amount of EOS aggregate increased, the slump and flow increased but the air content decreased.

The objective of this paper is to provide the feasibility of premixed type ternary blended aggregates using raw fly ash(Ra), crushed sand(CS) and sea sand(SS) by studying fresh properties of the concrete. Ra is varied from 2.5% to 10% with interval of 2.5% by weight of mixed aggregates. Test results indicates that the replacement of Ra by mixed aggregates with low quality crushed sand and sea sand resulted in decrease of slump and air contents due to increased viscosity.

The objective of this paper is to offer the feasibility of premixed type ternary blended aggregates using reject ash(RA), crushed sand(CS) and sea sand(SS) by studying fresh properties of the concrete. RA is varied from 2.5% to 10% with interval of 2.5% by weight of mixed aggregates. Test results indicates that the replacement of RA by mixed aggregates with low quality crushed sand and sea sand resulted in decrease of slump and air contents.

The purpose of this study is to evaluate the factor of determining chloride content in fresh concrete. Usually, in construction field, ion electrode method is used as a test for chloride content. As a result of this study, Ion electrode has a problem of interfering ion effect and requires special care in handling.

In this study, the inhibitive effect of electrochemical treatment subjected to fresh and hardened concrete and literature reviews in terms of the treatment were performed. In hardened concrete, chloride ions are mixed during casting to destroy the passivity of steel, and then the current was provided for 2 weeks with 250, 500 and 750 mA/m2. After completion of electrochemical treatment, the extraction of chloride ions was quantified and repassivation of steel was observed. Simultaneously, the equated levels of current density for 2 weeks were applied to fresh concrete. Steel-concrete interface in concrete was observed by BSE image analysis and the concrete properties in terms of the diffusivity of chloride ions and the resistance of steel corrosion was measured. As the result, electrochemical treatment is very effectiveness to rehabilitate the passive film on the steel surface and 63-73% of chloride ions in concrete were extracted by the treatment. As the treatment was applied to fresh concrete, the resistance of steel corrosion was improved due to the densification of Ca(OH)2 layers in the vicinity of steel. However, an increase in the current density resulted in an increase in surface chloride content of concrete.

콘크리트 믹서트럭의 덮개는 레미콘 플랜트에서 공사 현장까지의 운반 도중 굳지 않은 콘크리트의 유동성이 저하하지 않도록 사용하는데, 설문 결과 일반시민들에게 더러운 이미지를 주고 있다. 이러한 이미지로 인해 건설 산업 전체의 이미지에도 영향을 미칠 것으로 예상하여 덮개의 효용성 여부를 밝히기 위해 레미콘을 현장에 대기시켜 둔 채 유동성을 비롯한 공기량, 콘크리트 온도변화 등의 현장 실험을 실시하였다. 또한 이와 비교를 위해 동일한 조건으로 실내 실험을 병행하여 결과를 도출하였다. 실험 결과, 믹서트럭의 덮개는 슬럼프 저하에 미치는 영향이 적은 것으로 나타났다. 공기량 변화는 덮개 유무에 관계없이 60분까지는 적정한 수준으로 품질에 큰 영향을 미치지 않는 것으로 나타났다. 또한 콘크리트 압축강도는 덮개 유무에 관계없이 90분까지의 시료의 경우에 목표설계기준강도에 모두 적합한 것으로 나타났다.