• Title/Summary/Keyword: portland cement mortar

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Effects of NaOH and Na2SiO3·9H2O Addition on Strength Development of Class F Fly Ash-Mortar (F급 플라이 애쉬-모르타르의 강도발현에 대한 NaOH과 Na2SiO3·9H2O 첨가의 영향)

  • Park, Sang-Sook;Kang, Hwa-Young;Han, Sang-Ho;Kang, Hee-Bog
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.9 no.4
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    • pp.261-269
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    • 2005
  • The object of this research is to produce alkali activated fly ash-cement using low calcium fly ash as substitute for portland cement. The experimental program included activation of fly ash by a strong base(NaOH) at different concentration, temperature, and liquid-to-fly ash ratios. To achieve for higher compressive strength of the hardened product, sodium meta silicate is added to the alkaline solution. From the factors considered on strength development, the ratio of liquid/fly ash, the activator concentration and temperature always result to be significative factors. The optimization studied show that the alkaline solution concentration of $NaOH(210g)+Na_2SiO_3{\cdot}9H_2O(30g)+H_2O=1L$ at $50^{\circ}C$ produces the best alkali activation effect for the low calcium fly ash. SEM and XRD patterns showed that the components of alkali-activated fly ash consist mainly of mullite, quartz and amorphous aluminosilicate.

Utilization of Mine failings from the Jeonju-Il Mine (전주일(全州一) 금속광산(金屬鑛山) 폐광미(廢鑛尾)의 활용(活用) 방안(方案) 연구(硏究))

  • Jeong, Soo-Bok;Chae, Yeung-Bae;Hyun, Jong-Yeong;Kim, Hyung-Seok;Yoon, Sung-Moon
    • Resources Recycling
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    • v.16 no.1 s.75
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    • pp.44-53
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    • 2007
  • The Jeonju-Il mine tailings contain large quantities of $SiO_2\;and\;Al_2O_3$ and lesser quantities of metallic components. In this study, we studied about the possibility of using mine tailings as a raw material in various industries. it was found that the sintered mine tailings had a good quality in every respect such as chromaticity, firing shrinkage and water absorption etc. Therefore if can substitute clay mineral in the ceramic industry. Also it can substitute about 2.94% of the raw materials of ordinary portland cement. We can use the coarse tailing as the fine aggregate for the ready-mixed mortar; and the fine tailing, as the filler for the bituminous paving mixture; because both products were not only suitable for Korea industrial standard in quality, but also environmentally harmless.

The Effect of Blaine and SO3 Contents of OPC on Shotcrete Binder with Calcium Aluminate Accelerator (OPC의 분말도 및 SO3 함량이 시멘트 광물계 급결제를 사용한 숏크리트 결합재 물성에 미치는 영향)

  • Kang, Bong-Hee;Kim, Gyu-Yong;Choi, Jae-Won;Koo, Kyung-Mo;Hwang, Bong-Choon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.24 no.2
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    • pp.78-85
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    • 2020
  • Shotcrete concrete is generally used in the form of ready-mixed concrete products using type I ordinary portland cement(hereinafter referred to as OPC) and about 5% of accelerator mixed separately in the field. In this study, we tested the effect of OPC fineness and SO3 content on a penetration resistance, compressive strength of binder for shotcrete using calcium aluminate type accerlerator. And we analysed hydrates and pore structure effects on mortar performance. In the future, it is expected to be useful for manufacturing optimized OPC as a binder for shotcrete.

A Study on the Strength Properties of Green Mortar Using Limestone Powder (석회석(石灰石) 미분말(微粉末)을 이용(利用)한 그린모르타르의 강도(强度) 특성(特性)에 관한 연구(硏究))

  • Jo, Byung-Wan;Choi, Ji-Sun;Kim, Kyung-Tae
    • Resources Recycling
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    • v.22 no.3
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    • pp.36-42
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    • 2013
  • According to the recent community-based structures enlargement, specification, and diversification. It needs appropriate construction materials in terms of intensity and environmental aspects. Thus, in manufacturing the cement using micro limestone powder which is main material. It is also expected to save energies and reduces $CO_2$, by using the blast furnace slag and fly ash which are mitigated environmental load construction materials that emerged. In this research, The durability aspect tries to be grasped considering the chemical property according to the coherence of the hydration product. Consequently, The compressive strength was measured over 30 Mpa on 3rd. In addition, according to the content of the limestone powder, the setting time is promoted. It has the feature expanded in the length change. And it is determined because the possibility of replacing the existing for construction material such as it is measured compared with the time to use the portland cement usually that flexural strength is high with the age 7 days ago, so it is sufficient.

Properties of Portland Cement Clinker Using Polysilicon Sludge (폴리실리콘 슬러지를 원료로 사용한 포틀랜드 시멘트 클링커의 특성)

  • Lee, Seung-Heun;Lee, Se-Jin;Woo, Yang-Yee;Park, Jeoung-Soo
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.2 no.4
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    • pp.328-334
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    • 2014
  • This study reviewed the usability of sludge, a material that is additionally created when polysilicon (a solar light material) is produced, as the raw material for cement clinker. It was evaluated that when cement clinker is produced, the chloric component of polysilicon acted as a mineralizer in the firing process. In addition, the physical features of the produced cement were measured. The setting time of the produced cement was reduced as the amount of content of polysilicon sludge increased. Such results were drawn because the chloric component acted as hydration accelerator and enhanced the dissolution of calcium hydroxide that was formed by hydration of $C_3S$. Furthermore, for such reason, on the day 1, the compression strength of mortar increased as the content of polysilicon sludge increased. In day 3, 7, and 28, the tendency in which the compression strength increasing up to 5% of the amount of added polysilicon sludge was shown. It is because when clinker was produced, the chloric component increased the amount of $C_3S$ mineral created, thus enhancing the compression strength after day 3.

Comparative study on dynamic properties of argillaceous siltstone and its grouting-reinforced body

  • Huang, Ming;Xu, Chao-Shui;Zhan, Jin-Wu;Wang, Jun-Bao
    • Geomechanics and Engineering
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    • v.13 no.2
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    • pp.333-352
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    • 2017
  • A comparison study is made between the dynamic properties of an argillaceous siltstone and its grouting-reinforced body. The purpose is to investigate how grout injection can help repair broken soft rocks. A slightly weathered argillaceous siltstone is selected, and part of the siltstone is mechanically crushed and cemented with Portland cement to simulate the grouting-reinforced body. Core specimens with the size of $50mm{\times}38mm$ are prepared from the original rock and the grouting-reinforced body. Impact tests on these samples are then carried out using a Split Hopkinson Pressure Bar (SHPB) apparatus. Failure patterns are analyzed and geotechnical parameters of the specimens are estimated. Based on the experimental results, for the grouting-reinforced body, its shock resistance is poorer than that of the original rock, and most cracks happen in the cementation boundaries between the cement mortar and the original rock particles. It was observed that the grouting-reinforced body ends up with more fragmented residues, most of them have larger fractal dimensions, and its dynamic strength is generally lower. The mass ratio of broken rocks to cement has a significant effect on its dynamic properties and there is an optimal ratio that the maximum dynamic peak strength can be achieved. The dynamic strain-softening behavior of the grouting-reinforced body is more significant compared with that of the original rock. Both the time dependent damage model and the modified overstress damage model are equally applicable to the original rock, but the former performs much better compared with the latter for the grouting-reinforced body. In addition, it was also shown that water content and impact velocity both have significant effect on dynamic properties of the original rock and its grouting-reinforced body. Higher water content leads to more small broken rock pieces, larger fractal dimensions, lower dynamic peak strength and smaller elastic modulus. However, the water content plays a minor role in fractal dimensions when the impact velocity is beyond a certain value. Higher impact loading rate leads to higher degree of fragmentation and larger fractal dimensions both in argillaceous siltstone and its grouting-reinforced body. These results provide a sound basis for the quantitative evaluation on how cement grouting can contribute to the repair of broken soft rocks.

Durability Characteristics of Ternary Cement Matrix Using Ferronickel Slag According to the Alkali-Activators (알칼리 활성화제 종류별 페로니켈슬래그를 사용한 3성분계 시멘트 경화체의 내구특성)

  • Cho, Won-Jung;Park, Eon-Sang;Jung, Ho-Seop;Ann, Ki-Yong
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.8 no.2
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    • pp.190-197
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    • 2020
  • This paper evaluates the mechanical properties and durability of cement matrix blended with mineral admixtures and ferronickel slag(FNS) powder which is an industrial b y-product during ferronickel smelting process. The hydration heat, pore structure, compressive strength, length change, rapid chloride penetration test(RCPT), and freezing and thawing resistance of ternary blended cement matrix were investigated and compared with ordinary portland cement matrix. The result showed that the compressive strength of ternary blended cement matrix using ferronickel slag powder and mineral mixture was low in strength compared to the reference concrete, but recovered to a certain extent by using alkali activator. Length change of cement mortar using FNS powder have shown less shrinkage occurs than the reference specimen. In addition, irrespective of using the alkali-activators, all ternary mix are indicative of the 'very low' range for chloride ion penetrability according to the ASTM C 1202, and the freeze-thaw resistance also showed excellent results.

Chloride Threshold Value for Steel Corrosion considering Chemical Properties of Concrete (콘크리트의 화학적 특성을 고려한 철근 부식 임계 염소이온 농도)

  • Song, Ha-Won;Jung, Min-Sun;Ann, Ki Yong;Lee, Chang-Hong
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.1A
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    • pp.75-84
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    • 2009
  • The present study assesses the chloride threshold level for corrosion of steel in concrete by examining the properties of four different binders used for blended concrete in terms of chloride binding, buffering of cement matrix to a pH fall and the corrosion behaviour. As binders, ordinary Portland cement (OPC), 30% pulverised fuel ash (PFA), 60% ground granulated blast furnace slag (GGBS) and 10% silica fume (SF) were used in a concrete mix. Testing for chloride binding was carried out using the water extraction method, the buffering of cement matrix was assessed by measuring the resistance to an artificial acidification of nitric acid, and the corrosion rate of steel in mortar with chlorides in cast was measured at 28 days using an anodic polarisation technique. Results show that the chloride binding capacity was much affected by $C_{3}A$ content and physical adsorption, and its order was 60% GGBS>30% PFA>OPC>10% SF. The buffering of cement matrix to a pH fall was varied with binder type and given values of the pH. From the result of corrosion test, it was found that the chloride threshold ranged 1.03, 0.65, 0.45 and 0.98% by weight of cement for OPC, 30% PFA, 60% GGBS and 10% SF respectively, assuming that corrosion starts at the corrosion rate of $0.1-0.2{\mu}A/cm^{2}$. The mole ratio of [$Cl^{-}$]:[$H^{+}$], as a new presentation of the chloride threshold, indicated the value of 0.008-0.009, irrespective of binder, which would be indicative of the inhibitive characteristic of binder.

Corrosion-Inhibition and Durability of Polymer-Modified Mortars Using Bisphenol A and F Type Epoxy Resin with Calumite (비스페놀 A 및 F형 에폭시수지와 칼루마이트를 병용한 폴리머 시멘트 모르타르의 방청성 및 내구성)

  • Kim, Joo-Young;Kim, Wan-Ki
    • Journal of the Korea Concrete Institute
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    • v.26 no.4
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    • pp.517-524
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    • 2014
  • Nitrite-Type hydrocalumite (calumite) is a material that can adsorb chloride ions ($Cl^-$) that cause corrosion of reinforce bars and liberate the nitrite ions ($NO_2{^-}$) that inhibit corrosion in reinforced concrete. In this study, polymer-modified mortars using two types of epoxy resin with calumite are prepared with various polymer binder-ratios of 0, 5, 10, 15, 20% and calumite contents of 0, 5%. The specimens are tested for chloride ion penetration, carbonation, drying shrinkage and corrosion inhibition. As a result, the chloride ion penetration and carbonation depth of PMM using epoxy resin somewhat increases with increasing calumite contents, but those remarkably decreases depending on the polymer-binder ratios. The 28-d drying shrinkage shows a tendency to decrease with increasing polymer-binder ratio and calumite content. Unmodified mortars with calumite content of 5% did not satisfy quality requirement by KS. However, it was satisfied with KS requirement by the modification of epoxy resin in cement mortar. On the whole, the carbonation and chloride ion penetration depth of epoxy-modified mortars with calumite is considerably improved with an increase in the polymer-binder ratio regardless of the calumite content, and is remarkably improved over unmodified mortar. And, the replacement of the portland cement with the calumite has a marked effect in the corrosion-inhibiting property of the epoxy-modified mortars.

Study on Hydration Heat of Blended Belite Binder (벨라이트계 혼합 결합재의 수화열 특성에 관한 연구)

  • Lee, Kewn-Chu;Cho, Jae-Woo;Jung, Sang-Hwa;Kim, Jang-Ho Jay
    • Journal of the Korea Concrete Institute
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    • v.23 no.2
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    • pp.145-150
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    • 2011
  • Presently, mass concrete structures are being built in federal and private projects of civil infrastructures and building structures. The hydration heat of mass concrete structures is the most important factor in the quality of concrete matrix and construction period. Moreover, internal cracks caused by hydration heat degrades durability, water tightness, and strength of concrete. To reduce hydration heat, it is necessary to blend belite cement (${\beta}-C_2S$) with industrial by-products (i.e. granulated slag and fly ash). In this experiment, 14 levels of binary binders and 4 levels of ternary binders were used to understand the effect of different replacement ratio on hydration heat, strength and microstructure (i.e. SEM and XRD) of mortar. Cumulative hydration heat at 28 days for the binary and ternary binders was affected by replacement ratio of fly ash and/or granulated slag. As fly ash content increased, hydration heat decreased. As granulated slag content increased, reduction rate of the hydration heat was lower than when fly ash was used. Especially, the hydration heat of ternary binder blended with 40% flyash and 30% granulated slag showed about 50% of hydration heat from using belite cement (P). The study results showed that the temperature rise of concrete matrix can be decreased by using blended belite binders producing low hydration heat and reasonable strength.