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The pH of Cement-based Materials:A Review

Journal of Wuhan University of Technology(Materials Science) 2020年第5期35卷 908-924页

作者： Sumra Yousuf Payam Shafigh Zainah Ibrahim Department of Civil Engineering Faculty of EngineeringUniversity of Malaya50603 Kuala LumpurMalaysia Department of Building and Architectural Engineering Faculty of Engineering&TechnologyBahauddin Zakariya UniversityMultan 60000Pakistan Department of Building Surveying Faculty of Built EnvironmentUniversity of Malaya.50603 Kuala LumpurMalaysia Center for Building Construction&Tropical Architecture(BuCTA)Faculty of Built EnvironmentUniversity of Malaya50603 Kuala LumpurMalaysia

Cement-based materials (CBMs),such as paste,mortar and concrete,are highly alkaline with an initial high pH of approximately 12.0 to *** have a high pH due to the existing oxide mineral portlandite and alkali metal contents in Portland *** high pH of concrete provides excellent protection and reinforces the steel bars against *** pH of concrete does not remain constant due to ageing and other defect-causing factors,such as chloride ingress,alkali leaching,carbonation,corrosion,acid attack,moisture and biodegradation *** the concrete pH has negative impact on the strength,durability and service life of concrete ***,the high pH of concrete may also cause concrete structure deterioration,such as alkali silica reaction,porosity and moisture related damages in concrete *** pH of CBMs can be influenced by high *** instance,the extremely high volume (85%-100%) of slag-blended cement pastes shows considerable pH reduction from 12.80 to 11.34 at 800 ℃.As many concrete structure deterioration are related to concrete pH,using an accurate and reliable method to measure pH and analyse the durability of reinforced concrete structure based on pH values is extremely *** study is a comprehensive review of the pH of CBM in terms of measurement,limitations and varying values for different CBM types.

关键词： pH cementitious materials concrete portlandite durability corrosion alkali

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THE STUDY OF MINERAL COMPONENTS IN KAOLINE FROM HUNAN JIEPAI

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Journal of Wuhan University of Technology(Materials Science) 1995年第3期10卷 24-28页

作者：彭长琪彭华崔崇 WUHAN UNIV TECHNOL DEPT RESOURCES & ENVIRONM ENGNWUHAN 430070PEOPLES R CHINA

This paper finds out distributive pattern of principal minerals in Jiepai kaoline and demonstrates the black matter to be not organic matter but fine scaly mica-hematite aggregate in black vein mud, the nanometer mine... 详细信息

关键词： Jiepai kaoline black vein mud micahematite portlandite

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Hydration and Mechanical Properties of Portland Cement Blended with Low-CaO Steel Slag

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Journal of Physical Science and Application 2014年第7期4卷 444-449页

作者： Eugene Atiemo Kwabena Appiah Boakye James Sarfo-Ansah CSIR-Building and Road Research Institute Box UP40 Kumasi Ghana

The hydration and mechanical properties of Portland cement blended with low-CaO steel slag were studied and reported. The steel slag was used to replace cement up to 30% and then blended cement powder, paste and mortar samples prepared for the experiment. The quantitative analysis of XRD shows that ettringite formation is greatly reduced by incorporation of steel slag but there was a relatively low reduction of portlandite. Thermal analysis by TG shows that slag injection reduced portlandite content in the cement by at least 50%. Generally, the slag cement pastes required less water to form a workable paste compared to the reference cement, reducing as the slag content was increased. However, the setting times were higher than the reference. The permeability of the blended cement samples were lower than the control. The incorporation of 5% slag could not have an effect on the compressive strength of the concrete. The results confirmed that whilst cements with up to 15% slag content satisfied the strength requirements of class 42.5 N and those containing 20%-30% produce Class 32.5R cement.

关键词： Hydration cement low-CaO steel slag ettringite portlandite permeability.

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Effect of High Temperatures on the Microstructure of Cement Paste

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Journal of Materials Science and Chemical Engineering 2017年第11期5卷 33-48页

作者： M. A. Tantawy Chemistry Department Faculty of Science Minia University Minya Egypt

The microstructural and compositional changes within the cement paste exposed to high temperatures were monitored by XRD, FTIR, TGA/DTA and SEM techniques to understand the nature of decomposition of C-S-H gel and the associated physicomechanical properties of thermally damaged cement paste. OPC paste (w/c ratio 0.27) was hydrated for 28 days then fired up to 750°C for 2 hours (heating rate 10°C/min). The relative mass percent of calcium hydrates and portlandite was estimated by calculations derived from TGA results. Beyond 450°C, the percentage of portlandite sharply diminishes and C-S-H progressively decomposes into C2S and C3S until complete loss of calcium hydrates content occurs at 750°C. An increase of the total porosity, severe loss in mechanical strength and propagation of harmful cracks occurs. The thermal shock as a result of cooling of the heated cement paste and the rehydration of lime enhance the propagation of harmful cracks.

关键词： Cement paste C-S-H portlandite Dehydration Microstructure

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Hydration Properties of Calcined Clay Pozzolan and Limestone Mineral Admixtures in Binary and Ternary Cements

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Journal of Physical Science and Application 2014年第5期4卷 323-327页

作者： Eugene Atiemo Charles Kwame Kankam Francis Momade Kwabena Appiah Boakye CSIR-Building and Road Research Institute UST Box 40 Kumasi Ghana Kwame Nkrumah University of Science and Technology College of Engineering Kumasi Ghana

This paper investigates the properties of hydrated binary and ternary blended cements using limestone and calcined clay pozzolan as supplementary cementitious materials. The blended cements were hydrated and their phase compositions were evaluated by thermogravimetric and powder X-ray diffraction at 28 days. The morphology of the samples was also determined. The water demand, setting time, compressive and flexural strengths of mortar and concrete samples were determined up to 365 days. The study concluded that the portlandite [Ca（OH）2] content was considerably reduced whilst ettfingite formation were enhanced as a result of admixture reactions. The water demand and setting times of blended cements were lower than OPC with 5% admixture content but higher with increasing content. The mechanical test results also showed that Class 42.5N and 32.5R cements can be produced from the binary and ternary blends containing up to 10% and 20% admixtures, respectively.

关键词： limestone calcined clay pozzolan supplementary cementitious materials admixtures portlandite ettringite strength.

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Influence of Mineral Admixtures on Essential Properties of Ternary Cement Blends

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Journal of Civil Engineering and Architecture 2014年第10期8卷 1221-1225页

作者： Eugene Atiemo Charles Kwaku Kankam Francis Momade Council for Scientific and Industrial Research Building and Road Research Institute Kumasi Ghana Department of Civil Engineering Kwame Nkrumah University of Science and Technology Kumasi Ghana Department of Materials Engineering Kwame Nkrumah University of Science and Technology Kumasi Ghana

Two CaCO3-based materials （limestone and clamshells） and steel slag were used as mineral admixtures in cement to produce ternary blends and their influences on hydration and portlandite formation were analyzed. Additionally, mechanical properties were determined. These properties were determined using X-ray diffraction and scanning electron microscopic/energy dispersive X-ray analytical techniques as well as applying methods specified by EN （European Standards） and ASTM （American Standards for Testing and Materials）. The portlandite （Ca（OH）E） content was considerably reduced from 36.9% of reference cement to between 13.79% and 15.5%. With the water demand and setting times of the cements containing up to 10%, admixtures did not change significantly. The mechanical tests results showed that ternary blends produced 2-day strengths higher than that specified by EN 197-1 and that blends containing up to 20% admixtures can be used to produce both Class 32.5N and 42.5N cements.

关键词： Limestone clamshells steel slag temary cement portlandite compressive strength.

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