• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.138-144
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• 2017

In order to reduce carbon dioxide emission in construction industry, less amount of cement use can be one of the alternatives to manufacture concrete. One of the non-sintered construction materials are limestone, which is the raw material to manufacture ordinary Portland cement(OPC). A large amount of limestone have already been used as binders such as blended cement in Europe and US. Even European countries were already established the standard of blended cement, where the limestone can be used up to 35 percent. In this study, experimental researches were conducted to investigate the effects of limestone replacement on the mechanical properties and durability of concrete with 15%, 25% and 35% of limestone substitution to use limestone in blended cement. 15 percent use of limestone in blended cement developed equivalent or even higher compressive strengths compared to Plain mixture. Porosity of limestone cement with 15 percent substitution was much lower than Plain mixture. Most durability tests such as concrete carbonation, freeze-thaw cycle and drying shrinkage strains were conducted to evaluate long-term performance, and the test results indicated that 15 percent of limestone use did not significantly influence on the concrete durability compared with plain concrete.

• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.411-418
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• 2013

Recently, in order to reduce a damage of chloride attack and hydration heat in marine concrete structures, blended cement in mixing the marine concrete is widely used. Long term strength development is distinct in concrete with blended cement and it also has excellent resistance to chloride attack and reduction of hydration heat. However, blended cement has a characteristic of relatively low compressive strength in early age of 28 days. On the other hand, a high level of compressive strength is required in the Standard Specification for marine concrete mix design. Such concrete mix design satisfying Standard Specification is effective to chloride attack but disadvantageous for hydration heat reduction due to large quantity of binder. In this study, the material properties of marine concrete considering water-binder ratio and binder type are experimentally investigated. Through the research results, compressive strength in blended cement at the age of 56 days is similar although it has smaller compressive strength at the age of 28 days compared with result of OPC (ordinary portland cement). Even though blended cement has a large water-binder ratio and small unit of binder content, chloride ion diffusion coefficient is still small and hydration heat is also found to be reduced. For meeting the required compressive strength in Standard Specification for marine concrete at 28 days, the increased unit content of binder is needed but the increased hydration heat is also expected.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.58-63
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• 1999

Almost all concrete structures have many inevitable cracks for various reasons such as drying shrinkage, heat liberation of cement, fatigues or repeating loads and movements. Conventionally, they are repaired with epoxy materials. The Epoxy resins used by repair materials are different from properties of the base concrete materials such as thermal and mechanical properties - thermal expansion coefficients, bending strength. And the epoxy resin cannot release the water inside the concrete structure and cause corrosion of the steel bars. In this study, before the experiment got launched, we had analyzed cement and slag. Then We blended the two grades of ultra fine cement using high blaine cement and slag. And the cement slurry was produced by water and suprplasticizer to each blended ultra fine cement in various conditions. The slurry produced by each conditions was evaluated with flow properties such as viscosity, dropping time, segregation and observation of dry surface after injection.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.19-20
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• 2022

Portland Limestone Cement (PLC) is a blended cement using limestone powder as SCMs (Supplementary Cementitious Materials), and is currently regarded as an essential means for achieving carbon neutral in the cement industry. This study was performed to investigate the fresh and hardened properties of cement mortar according to the fineness and replacement ratio of limestone powder. As a result, the compressive strength of mortar used high blaine limestone powder were equivalent level of that of OPC.

• Cement Symposium
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• no.1
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• pp.31-40
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• 1973

Cement industry in Korea, has made a remarkable progress in recent years and now annual production capacity is about 9,000,000 tons. However, this large amount of cement is only one kind of general portland cement type I, and it is urgent problem for ceme

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.375-380
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• 2010

In this study, physical properties of cement blended with Finex-slag powder(OPC-FS) were investigated by the measurement of flowability, compressive strength, hydration heat, and $Ca(OH)_2$ content. In addition, those properties of the cement blended with blast furnace slag(OPC-BFS) were also measured for comparison. It was found that OPC-FS and OPC-BFS showed similar trend in the rheological properties. In the blended cement pastes with the $4,000\;cm^2/g$ Blaine value the flowability of OPCFS was better than that of OPC-BFS. The initial 3 day mortar compressive strength and the hydration heat of paste of OPC-FS was a bit higher, compared with OPC-BFS. Accordingly $Ca(OH)_2$ produced in the cement hydration was decreased very rapidly.

• Advances in concrete construction
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• v.11 no.3
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• pp.183-192
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• 2021

Due to economic and environmental benefits, increasing the substitution ratio of ordinary cement by industry by-products like fly ash (FA) is one of the best approaches to reduce the impact of the concrete industry on the environment. However, as the substitution rate of FA increases, it will have an adverse impact on the performance of cement-based materials, so the actual substitution rate of FA is limited to around 10-30%. Therefore, in order to increase the early-age strength of high replacement (30-70%) low-calcium ultrafine FA blended cement paste, sodium sulfate and calcium sulfate dihydrate were used to improve the reactivity of FA. The results show that sodium sulfate has a significant enhancement effect on the strength of the composite pastes in the early and late ages, while calcium sulfate dihydrate has only a slight effect in the late ages. The addition of sodium sulfate in the cement-FA blended system can enhance the gain rate of non-evaporation water, and can decrease the Ca(OH)2 content. In addition, when the sulfate chemical activators are added, the ettringite content increases, and the surface of the FA is dissolved and hydrated.

• Computers and Concrete
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• v.6 no.5
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• pp.391-401
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• 2009

This paper presents a study of the strength and chloride penetration of blended Portland cement mortar containing ground palm oil fuel ash (POA) and ground river sand (GS). Ordinary Portland cement (OPC) was partially replaced with POA and GS. Compressive strength, rapid chloride penetration test (RCPT) and chloride penetration depth of mortars were determined. The GS only asserted the packing effect and its incorporation reduced the strength and the resistance to chloride penetration of mortar. The POA asserted both packing and pozzolanic effects. The use of the blend of equal portion of POA and GS also produced high strength mortars, save cost and excellent resistance to chloride penetration owing to the synergic effect of the blend of POA and GS. For chloride depth, the mathematical model correlates well with the experimental results. The computer graphics of chloride depth of the ternary blended mortars are also constructed and can be used to aid the understanding and the proportioning of the blended system.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.343-344
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• 2009

Compressive strength and chloride ions permeability measurements of ternary blended cement concretes incorporating ground granulated blast-furnace slag and fly ash were performed From a result of this study, it was found that there may be not a linear relationship between compressive strength and durability of ternary blended cement concretes.

• Corrosion Science and Technology
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• v.6 no.1
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• pp.12-17
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• 2007

Portland cement incorporating supplementary cementing material develops excellent mechanical properties and long term durability characteristics. India is a leading rice producing country and rice husk is considered as waste in the rice milling industries. In this present work, the rice husk ash (RHA) was added to concrete as cement replacement from 0 to 30%. Corrosion performance of reinforcing steel embedded in RHA blended concretes was studied using linear polarization, AC impedance and gravimetric methods. The corrosion rate of steel bars embedded in RHA concretes were compared with control concrete. The results clearly indicate that the corrosion rate of reinforcing steel embedded in concrete is significantly reduced with the incorporation of RHA. A good correlation among gravimetric method and electrochemical methods was observed. Electrochemical impedance study showed 98 percentage reduction in corrosion rate to the RHA blended concrete with 15% replacement than control concrete.