• Cement
• /
• s.196
• /
• pp.6-12
• /
• 2012

2012년 국내 경제는 민간소비의 위축이 지속되는 가운데 민간부문에서의 건설경기 침체와 공공부문 투자 위축으로 건설 및 설비투자의 부진이 이어졌다. 이러한 가운데 2013년에는 세계경제가 선진국과 개도국의 저성장 기조 속에서도 소폭 회복될 것으로 예상됨에 따라 2012년에 비해 다소 회복된 3%대 중반의 성장세를 기록할 것으로 전망된다. 여기서는 현대경제연구원의 '2013년 국내 경제 전망과 정책 과제' 보고서를 통해 최근 국내외 경제 여건 및 2013년도 경제 전망과 함께 정책 과제에 대해 살펴본다.

• Cement
• /
• s.196
• /
• pp.13-19
• /
• 2012

2013년에도 국내 건설경기는 본격적인 회복국면 진입이 어려울 것으로 보인다. 따라서 시멘트업계는 2013년에도 지속해 경영합리화의 기조를 유지해야 할 것으로 판단된다. 다만, 2013년 하반기에 대내외 거시경제 여건이 개선되어 국내 거시경제가 상저하고의 패턴을 보인다면 건설경기도 2013년 하반기에는 완만하게나마 회복세를 보일 것으로 기대된다. 이 글에서는 먼저 2013년 건설경기에 영향을 미칠 주용 쟁점요인을 살펴본 뒤 2013년 국내 건설수주 및 건설투자를 전망하고 시사점을 도출해 본다.

• Cement
• /
• s.200
• /
• pp.6-11
• /
• 2013

2013년 한국 경제는 1분기를 저점으로 회복세로 돌아섰으나 연간으로 잠재성장률 3.8%에 크게 못 미치는 2%대 중후반의 성장률을 기록할 것으로 보인다. 2014년 국내 경제는 수출 증가가 설비투자 증가로 이어지면서 경기 회복을 견인해 3%대 후반의 성장률을 기록할 전망이나, 잠재성장률의 하락 추세는 지속될 것으로 전망된다. 여기서는 현대경제연구원의 '2014년 국내 경제 전망' 보고서를 통해 2013년 경제의 특징, 2014년도 대외여건 및 경제 전망과 함께 정책 과제에 대해 살펴본다.

• Journal of the Korea Institute of Building Construction
• /
• v.8 no.4
• /
• pp.79-85
• /
• 2008

The purpose of this study is to evaluate the mix design of pH reducing cement concrete which can be used for environment-friendly concrete. Cement pastes and concretes are prepared with water-binder ratios and various admixtures such as blast-furnace slag, fly ash and recycled cement, and tested for compressive strength and pH. pH is measured through pore solution expressed from hydrated cement paste by special apparatus. From the test results, regardless of water-binder ratio, The pH of expressed pore solution from hydrated cement paste which is made of ordinary portland cement with blast-furnace slag, fly ash is decreased with increasing of admixtures content, and compressive strength is also slightly improved. The compressive strength of cement paste made of recycled cement which is burnt at $1000^{\circ}C$, for 2 hours is considerably increased compared with that of none-burnt recycled cement due to restoration of hydraulic property, but pH is a little higher. Porous concrete with ordinary portland cement has high pH in the range of 12.22 to 12.59, however, that is reduced to the range of 8.95 to 10.39 by carbonation at the surface of porous concrete. The pH reduction of porous concrete is possible by various admixture addition, however their degrees are very slight. Therefore, to reduce the pH considerably, carbonation method of porous concrete is better in pH reduction methods for plant survival condition of pH of 9.0 or less. In this study, it is apparent that pH for the environment-friendly porous concrete products used in the construction field can be suppressed by this carbonation method and various admixtures addition.

• Environmental Engineering Research
• /
• v.23 no.2
• /
• pp.189-194
• /
• 2018

The traditional gold mining in Kulon Progo district, Special Region of Yogyakarta Province produced tailings containing mercury (Hg) from the gold amalgamation process. Mercury accumulated in tailings has 164.19 mg/kg - 383.21 mg/kg in total concentration. Stabilization/solidification (S/S) is one of the remediation technologies to reduce waste pollution. Portland cement is one of the additive materials in S/S that effective encapsulates heavy metal waste. The aim of this research is to know the optimum composition of tailings mixture with Portland cement in S/S process. This research used variation of tailings composition. Variation of Portland cement composition with tailing are 100:0, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80 and 10:90. The result of this study found that the optimum composition of Portland cement: tailings was 10:90, with compression test of $257ton/m^2$ and TCLP test was 0.0069 mg/L. The compression test results were in accordance to US EPA Standard quality of $35ton/m^2$. TCLP test results meet the standard of Indonesian Government Regulation No. 101 Year 2014 of 0.05 mg/L.

• Journal of the Korea Institute of Building Construction
• /
• v.12 no.3
• /
• pp.284-290
• /
• 2012

Cement Fineness Modulus (CFM) is a method of expressing the distribution of particle sizes of cement in numeric form. If CFM is controlled through crush process of cement without modifying the chemical components or mineral composition of cement, it is judged to be able to produce a cement satisfying various requirements because it is estimated to enable various approaches to cement such as high early strength, moderate heat, low heat cement and so on. Therefore, in this study, as basic research for manufacturing special cement utilizing the controls of CFM, the intention was to review the impacts of CFM on the fundamental properties of concrete. To summarize the result, as mixture characteristics of fresh concrete, ratio of small aggregate and unit quantity were gradually increased, securing greater fluidity, with an increase in CFM, while the amount of AE and SP were reduced gradually. In addition, setting time was delayed as CFM increased. Furthermore, compression strength was relatively high during initial aging as CFM became smaller, but as time passed, compression strength became smaller, and it showed the same level of strength as aging time passed about three years.

• Journal of the Korean Institute of Educational Facilities
• /
• v.20 no.4
• /
• pp.35-43
• /
• 2013

Some results of experimental investigation conducted to assess the effect of cement composite strength and ductility on the shear behavior and crack-damage mitigation of stud connections between existing reinforced concrete frame in school buildings and seismic strengthening elements from cyclically direct shear tests are described. The cement composite strengths include 50 for medium strength and 70 MPa for high strength. Two types of cement composites, strain-hardening cement composite (SHCC) and non-shrinkage mortar, are used for stud shear connection specimens. The special SHCCs are reinforced with hybrid 0.2% polyethylene (PE) and 1.3% polyvinyl alcohol (PVA) fibers at the volume fraction and exhibits tensile strain capacity ranging from 0.2 to 0.5%. Test result indicates that SHCC improves the seismic performance and crack-damage mitigation of stud shear connections compared with stud connections with non-shrinkage mortar. However, the performance enhancement in SHCC stud connections with transverse and longitudinal reinforcements is less notable for those without additional reinforcement.

• Journal of the Korea Institute of Building Construction
• /
• v.7 no.4
• /
• pp.109-116
• /
• 2007

Building structures are generally large in size and have a long life, and the construction of such structures requires the investment of a huge amount of money and social infrastructure. Furthermore, building structures are closely related to people's life. Recently, however, the rapid development of society has been worsening air pollution, which is in turn accelerating the degradation of building structures. Thus, the safety of building structure is emerging as a critical issue. To cope with this problem, the government enacted "The Special Act on Safety Control for Infrastructure" but we need engineers' higher concern over the maintenance and reinforcement of existing structures. Recently researches are being made actively on repair mortar using ultra rapid hardening cement for recovering the performance of structures. The present study conducted an experiment on the basic physical properties of ultra rapid hardening mortar for repairing and reinforcing building structures using magnesia cement and mono-ammonium phosphate. In the experiment, we changed the water-cement ratio and carried out replacement at different ratio of MAP/MgO(%). We used retarder to have working life, and made comparative analysis through evaluating working life and fluidity and measuring strength by age.

• Journal of the Korean Geotechnical Society
• /
• v.33 no.1
• /
• pp.5-15
• /
• 2017

Skin friction may be one of the most critical factors in designing the prebored and precast pile. Special attention was given to the interface behavior of cement milk-surrounding soil during the installation of prebored and precast pile. Small-scale field model pile test was conducted for the case of single pile. The size and geometry of the small-scale field model piles were designed with pile length 1.3m, boring diameter 0.067 m. Quick maintain-load test was conducted for the cases of boring diameter 150, 125, 90, 86, 74 mm and water-cement ratio 90, 70, 60%. It was shown that the bearing capacity of the pile increased as the cement-water ratio and cement milk thickness increased. Considering the scale effect between the small-scale model test and the actual construction site, it was found that cement milk thickness of 0.1~0.4D (50~200 mm) was reasonable for the stability of the structure. Also, the proper cement paste water / cement ratio was about 70% when considering the results of this study and quality control.

• Advances in concrete construction
• /
• v.2 no.4
• /
• pp.249-259
• /
• 2014

Mortar is a masonry product which is matrix of concrete. It consists of binder and fine aggregate and moreover, it is an essential associate in any reinforced structural construction. The strength of mortar is a special concern to the engineer because mortar is responsible to give protection in the outer part of the structure as well as at a brick joint in masonry wall system. The purpose of this research is to investigate the compressive strength and tensile strength of mortar, which are important mechanical properties, by replacing the cement and sand by stone dust. Moreover, to minimize the increasing demand of cement and sand, checking of appropriateness of stone dust as a construction material is necessary to ensure both solid waste minimization and recovery by exchanging stone dust with cement and sand. Stone dust passing by No. 200 sieve, is used as cement replacing material and retained by No. 100 sieve is used for sand replacement. Sand was replaced by stone dust of 15%, 20%, 25%, 30%, 35%, 40%, 45% and 50% by weight of sand while cement was replaced by stone dust of 3%, 5%, and 7% by weight of cement. Test result indicates that, compressive strength of specimen mix with 35% of sand replacing stone dust and 3% of cement replacing stone dust increases 21.33% and 22.76% respectively than the normal mortar specimen at 7 and 28 days while for tensile it increases up to 13.47%. At the end, optimum dose was selected and crack analysis as well as discussion also included.