• Title/Summary/Keyword: water cement ratio

Search Result 1,135, Processing Time 0.038 seconds

An Experimental Study on Estimate of the Optimal Grout Injection Ratio for Stabilization of Mudstone fill (이암 성토지반의 안정화를 위한 최적주입률 산정에 관한 실험적 연구)

  • Lee, Jungsang;Lee, Seungjun;Kim, Yunjoong;Kim, Taesoo;Do, Jongnam;Chun, Byungsik
    • Journal of the Korean GEO-environmental Society
    • /
    • v.13 no.7
    • /
    • pp.31-38
    • /
    • 2012
  • Water glass chemical grouts are primarily used in ground injection projects. Natural and Durable Stabilizer (NDS), Space Grout Rocket (SGR), and other similar materials composing of inorganic accelerating agents with ultra fine cement have been gaining popularity as ground improvement material in South Korea. However, there are questions as to grouting results and environmental issues caused by NDS grout. This study uses the injection method in mudstone embarkment to evaluate the differences in strength, permeability, and optimum injection volume through the use of uniaxial and triaxial compression tests and fish poison tests for NDS and SGR materials. After 28 days, results showed SGR and NDS to have a 50% increase in strength and 50% decrease in permeability with the proper injection rate at 50%.

An Experimental Study on the Durability Evaluation of Polymer Cement Restoration Materials for Deteriorated Reinforced Concrete Structures (성능저하된 철근콘크리트구조물 폴리머시멘트계 보수용 단면복구재의 내구성 평가에 관한 실험적 연구)

  • Kim, Moo-Han;Kim, Jae-Hwan;Cho, Bong-Suk;Park, Jong-Ho
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.10 no.1
    • /
    • pp.123-130
    • /
    • 2006
  • The duties of the restorative materials are to bear up against stress and to protect reinforcement corrosion. So the restorative materials are estimated by various kinds of strength, permeability and etc, But, in case of existing performance evaluation of restorative materials, because various deterioration factors are separately acted, the system of performance evaluation is different from that of combined deterioration of real structure and it is difficult to evaluate the exact performance of restorative materials. In this study, to evaluate Performance of restorative materials, we compare their korea standard properties in terms of compressive and bending strength and permeability of water and air with real durability for carbonation, salt damage and actual reinforcement corrosion like ratio of corrosion area. weight reduction and corrosion velocity of steel bar under environment of combined deterioration. The results showed that strength and permeability of restorative materials are similar but their resistance to carbonation, salt damage and actual reinforcement corrosion are very different.

An Experimental Study on the Time-Dependent Deformation of the Alkali Activated Slag Concrete (알칼리 활성 슬래그 콘크리트의 시간의존적 변형에 관한 실험적 연구)

  • Lee, Young-Jun;Kwon, Eun-Hee;Park, Dong-Cheon
    • Journal of the Korea Institute of Building Construction
    • /
    • v.15 no.5
    • /
    • pp.457-464
    • /
    • 2015
  • The alternative material for cement has been attracting attention in construction projects. Especially, the alkali activated slag(hereafter, AAS) concrete is able to use for a structural vertical member because of 40MPa of compressive strength, However, the research about time-dependent deformation such as creep which is important to strength member is insufficient. Therefore, in this study, experiments were performed with respect to time-dependent deformation including the drying shrinkage and creep deformation of AAS concrete. The creep deformed ratio of AAS concrete was more than OPC concrete by approximately 4.3% and the dry shrinkage deformation of AAS concrete was more than OPC concrete by approximately 69%. The large amount of sodium silicate, alkali activator, is added causing temperature crack than promoted drying and drying creep which is confirmed by water ration test and SEM.

THE USE OF MULTINUTRIENT BLOCK SUPPLEMENTED TO UREA TREATED RICE STRAW BASE DIET FOR DAIRY HEIFERS

  • Cheva-Isarakul, B.;Promma, S.
    • Asian-Australasian Journal of Animal Sciences
    • /
    • v.8 no.2
    • /
    • pp.113-118
    • /
    • 1995
  • Eighteen Holstein Friesian ${\times}$ Native heifers with an average live weight of $175.4{\pm}27.8kg$ were allotted to 3 dietary groups. All animals were kept individually in a stanchion barn with free access to water and urea-treated rice straw (UTS). The supplemented feeds were as follows: Group (Gr) 1 - concentrate mixture (15% CP) at 1% body weight (BW), Gr 2 - concentrate mixture at 0.7% BW + free licking of multinutrient block (MNB), Gr 3 - as Gr 2 + 0.3% BW ground com. Multinutrient block composed of 20% mineral mixture, 10% urea, 18% molasses, 20% soybean meal, 22% sesame meal, 10% cement, 0.15 million IU and 50 IU/kg MNB of vitamin A and E. The experimental period lasted 12 weeks. The result revealed that MNB enhanced intake of UTS and total dry matter intake. Animals in Gr 3 consumed a higher amount of feed than the other 2 groups, thus resulting in the highest live weight gain and tended to possess the best feed conversion ratio. Heifers in Gr 2 also performed better than Gr 1 although the difference was not significant. Average MNB intake found to be 0.65 kg/day. Feed cost per kg gain was not significantly different amon groups. However if the cost of MNB could be lower, it would benefit the production cost of animals. The advantage of MNB is the safety of using a high level of urea. Although it was supplemented to UTS which also contained non-protein nitrogen (NPN), no toxic sign was shown. The results indicated that MNB could be partially substituted to concentrate mixture and it was even better when used incombination with soluble carbohydrate feed.

Investigation and Evaluation on Performance of Durability for Freeway Concrete Viaducts in Seoul Metropolitan Area (서울시내 위치한 콘크리트 고가차도의 내구성능 조사 및 평가)

  • Lee, Chang-Soo;Yoon, In-Seok
    • Journal of the Korean Society of Hazard Mitigation
    • /
    • v.2 no.1 s.4
    • /
    • pp.143-152
    • /
    • 2002
  • The objectives of this paper were to obtain the fundamental data to analyze the causes of deterioration of 39 freeway concrete viaducts in Seoul metropolitan area. To investigate the degree of concrete deterioration, carbonation depth, soluble chloride concentration in hardened concrete and half-cell potentials of reinforcement were measured. The number of structures which carbonation depth penetrates to reinforcement was 25% of total. The model of carbonation .ate was induced to 3.92 $\sqrt{t}$, which was 5% faster than 3.727 $\sqrt{t}$ assumed 60% water-cement ratio, R=1 in that of kishitani. After measuring chloride concentration in concrete, it was concluded that about 24% of all readings on samples from concrete exceed the critical content to minimize the risk of chloride-induced corrosion. About 31% of the freeway viaducts structures had a value lower than -350mV(vs. CSE), so it could conclude that the excessive chloride concentration was the major cause of reinforcement corrosion. Among the structures which measured half-cell potentials less than -350mV, about 50% exceeds the maximum acceptable limit of chloride concentration.

Comparison of rheological properties containing natural and crushed sands in self-compacting concretes (잔골재 종류에 따른 고유동 콘크리트의 유동 특성)

  • Lee, Keun-Su;Choi, Yeol;Jung, Woong;Lee, Jae-Ik
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2008.11a
    • /
    • pp.365-368
    • /
    • 2008
  • In recent, the crushed sand as a fine aggregate has increasingly used for concrete industry due to the shortage of natural sand from river and the growing demand for protection of natural environments. Aggregates may have a significant influence on the properties of self-compacting concrete (SCC) including self-compacting mortar (SCM). The rheological properties of SCC and SCM using crushed sand as a fine aggregate has been compared to that of SCC and SCM using natural sand and mixed sand of both. Test results indicate that the yield stress of SCM containing 50% of mixed sand present higher than those prepared with natural sand and crushed sand according to SP content. the slump values of SCC with natural sand have approximately 5-15% higher than those of SCC with crushed sand. Also the L-box test values ($H_2/H_1$) of SCC with natural sand have approximately 20-30 higher than those of SCC with crushed sand under same water/cement ratio and viscosity enhancing admixture.

  • PDF

A Study on Properties of Ultra High Strength Concrete of above 100MPa (100MPa급 이상의 초고강도 콘크리트의 자기수축 특성에 관한 연구)

  • Lee, Sang-Ho;Kim, U-Jae;No, Hyeon-Seung;Lee, Jae-Sam;Lee, Han-Seung
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2008.11a
    • /
    • pp.677-680
    • /
    • 2008
  • The autogenous shrinkage of HPC is important in that it can lead the early cracks in concrete structures. The purpose of the present study is to explore the autogenous shrinkage of HPC with cellulose fiber and expansive additive and to derive a realistic equation to estimate the autogenous shrinkage model of that. For this purpose, comprehensive experimental program has been set up to observe the autogenous shrinkage for various test series. Major test variables were the quantity of expansive additive and cellulose fiber. Water-cement ratio is fixed with 13%. The autogenous shrinkage of HPC is found to decrease with increasing expansive additive and cellulose fiber. A prediction equation to estimate the autogenous shrinkage of HPC was derived and proposed in this study. The proposed equation shows reasonably good correlation with test data on autogenous shrinkage of HPC.

  • PDF

The Study on High Performance of Offshore Concrete Using Crushed Stone Fines (쇄석미분말을 사용한 해양콘크리트의 고성능화에 관한 연구)

  • Chang, Chun-Ho;Jung, Yong-Wook
    • Journal of the Korean Society of Marine Environment & Safety
    • /
    • v.15 no.2
    • /
    • pp.135-142
    • /
    • 2009
  • This study investigates the characteristic properties of strength, flowability, durability and drying shrinkage to control strength and to reduce heat of hydration of high performance concrete using crushed stone fines. According to the experimental results, when crushed stone fines are increased every 10%, $10{\sim}15%$ of compressive strength is decreased and flowability of high performance concrete is effectively improved due to the decrease of modulus of deformation and confined water ratio. When crushed stone fines are replaced every 10%, $4^{\circ}C$ of the highest adiabatic temperature rise is decreased by reducing the unit cement. However, 5% of drying shrinkage is increased in the same condition In the meantime, durability of high performance concrete is excellent, having over 100% of good relative dynamic modulus of elasticity due to fineness of formation mused by the increase of the unit powder content and the improvement of flowability, without regard to the replacement of crushed stone fines. Therefore, It can be said that the usage of crushed stone fines can control the strength of high performance concrete by replacement and reduce heat of hydration.

  • PDF

A study on mechanical properties of concrete including activated recycled plastic waste

  • Ashok, M.;Jayabalan, P.;Saraswathy, V.;Muralidharan, S.
    • Advances in concrete construction
    • /
    • v.9 no.2
    • /
    • pp.207-215
    • /
    • 2020
  • This paper describes the experimental studies carried out to determine the properties of fresh and hardened concrete with Recycled Plastic Waste (RPW) as a partial replacement material for fine aggregates. In the experimental study, RPW was used for replacing river sand and manufactured sand (M sand) aggregates in concrete. The replacement level of fine aggregates was ranging from 5% to 20% by volume with an increment of 5%. M40 grade of concrete with water cement ratio of 0.40 was used in this study. Two different types of RPW were used, and they are (i) un-activated RPW and (ii) activated RPW. The activated RPW was obtained by alkali activation of un-activated RPW using NaOH solution. The hardened properties of the concrete determined were dry density, compressive strength, split tensile strength, flexural strength and ultrasonic pulse velocity (UPV). The properties of the concrete with river sand, M sand, activated RPW and un-activated RPW were compared and inferences were drawn. The effect of activation using NaOH solution was investigated using FT-IR study. The micro structural examination of hardened concrete was carried out using Scanning Electron Microscopy (SEM). The test results show that the strength of concrete with activated RPW was more than that of un-activated RPW. From the results, it is evident that it is feasible to use 5% un-activated RPW and 15% activated RPW as fine aggregates for making concrete without affecting the strength properties.

Simulation of Particle Behaviors within a Multi-stage Impact Crusher using Discrete Element Method (이산요소법을 이용한 다단 임팩트 파쇄기 내 입자 거동 모사)

  • Yu, Myoungyuol;Lee, Hoon
    • Resources Recycling
    • /
    • v.27 no.3
    • /
    • pp.86-92
    • /
    • 2018
  • The amount of construction waste generated is steadily increasing every year, and the Law for Promotion of Recycling is enacted. However, it is difficult to use it as a recycled aggregate for concrete, which is presented in the quality standard of recycled aggregate with high water uptake and low density due to low separation of aggregate between concrete and cement paste. Therefore, in this study, a multi-stage impact crusher was used to remove mortar, which is essential for improving the quality of recycled aggregate. In analyzing the characteristics of the equipment, the spectrum of energy generated in each part between the particle and the equipment was calculated by using DEM. In order to generate an effective separation phenomenon, it was confirmed that the operation condition of 900 RPM was appropriate based on the ratio of the number of collisions (L/H) of the low energy group (L) to the number of collisions of the high energy group (H).