Pozzolanic Efficiency of Calcined Clays in Blended Cements with Focus on the Early Hydration

2021 ◽  
pp. 1-32
Author(s):  
Nancy Beuntner ◽  
Karl-Christian Thienel
Keyword(s):  
Reaction Mechanism ◽  
Pore Solution ◽  
Isothermal Calorimetry ◽  
Mineralogical Composition ◽  
Early Hydration ◽  
Supplementary Cementitious Material ◽  
Calcined Clay ◽  
Blended Cements ◽  
Combination Of Methods ◽  
The Impact

The fundamental knowledge about the reaction mechanism of calcined clays in cement and the mutual interaction is important for their assessment as supplementary cementitious material and the resulting concrete properties. In this study, the hydration of two cements differing in alkali content and with the addition of a highly reactive, aluminum-rich metakaolin and one calcined common clay with low kaolinite content was investigated during the first 48 hours. For this purpose, four established methods that describe the early hydration were used: isothermal calorimetry, thermogravimetry, in-situ X-ray diffraction and chemical analysis of pore solution. This so far unique combination of methods enabled the understanding of the complex binder (cement-calcined clay) hydration behavior. The results showed considerable differences depending on type of calcined clay, its chemical-mineralogical composition, fineness and especially towards its reaction mechanism with aluminate clinker phases controlled by the composition of pore solution. The impact of calcined clay on the early clinker hydration exceeds significantly physical effects only.

Early hydration of SCM-blended Portland cements: A pore solution and isothermal calorimetry study

2017 ◽  
Vol 93 ◽  
pp. 71-82 ◽  
Author(s):  
Axel Schöler ◽  
Barbara Lothenbach ◽  
Frank Winnefeld ◽  
Mohsen Ben Haha ◽  
Maciej Zajac ◽  
...  
Keyword(s):  
Pore Solution ◽  
Isothermal Calorimetry ◽  
Early Hydration ◽  
Portland Cements

Investigation on the Effect of Hydroxyapatite Nanorod on Cement Hydration and Strength Development

2021 ◽  
Vol 21 (3) ◽  
pp. 1578-1589
Author(s):  
Han Yan ◽  
Qianping Ran ◽  
Yong Yang ◽  
Xin Shu ◽  
Qian Zhang ◽  
...  
Keyword(s):  
Isothermal Calorimetry ◽  
Superior Performance ◽  
Strength Development ◽  
Hydration Reaction ◽  
X Ray Diffraction ◽  
Early Hydration ◽  
Cement Pastes ◽  
Supplementary Cementitious Material ◽  
Acceleration Period

This work investigated the effect of hydroxyapatite (HA) nanorods on the strength development and hydration of cement. Undispersed HA nanorods (HA-UD) and dispersed HA nanorods (HA-DN) were prepared by atom-efficient neutralization. The strength of mortars modified by HA nanorods was tested, as well as their compatibility with supplementary cementitious material. The hydration of HA-modified cement pastes was characterized via in situ X-ray diffraction, isothermal calorimetry and scanning electron microscopy. As the results suggest, the undispersed HA-DN caused a considerable increase in superplasticizer demand to achieve the same level of flow. Both HA nanorods showed a significant accelerating effect on early hydration, with approximately 100% strength enhancement at 12 h at 2.0% dosage. The effect on early strength of the nanorods is retained in systems with up to 30% fly ash in the binder mass. According to the characterizations, the rate of the hydration reaction in the acceleration period was enhanced by HA nanorods, and C3S consumption was also increased. In all of the testing situations, HA-DN showed superior performance, likely due to improved spatial distribution of the hydroxyapatites. The results suggest that proper dispersion of the nanorods is necessary to optimize its performance.

scholarly journals The impact of lithium nitrate on the physical and mechanical properties of Portland cement)

2018 ◽  
Vol 163 ◽  
pp. 04002
Author(s):  
Justyna Zapała-Sławeta ◽  
Zdzisława Owsiak
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Portland Cement ◽  
Isothermal Calorimetry ◽  
Setting Time ◽  
Physical And Mechanical Properties ◽  
Strength Development ◽  
Lithium Nitrate ◽  
Early Hydration ◽  
The Impact

The effectiveness of lithium nitrate as a chemical additive which reduces the negative effects of alkali aggregate reaction was subject to research by scientists in many centres around the world. The literature data on the impact of lithium nitrate on the physical and mechanical properties of cements are rare. Without a precise definition of the impact of lithium nitrate on the cement properties, it is extremely hard to determine its real advantages in practical usage. In this paper, studies were undertaken to assess the impact of LiNO3 on the properties of pastes and mortars with Portland cement. The rate of hydration of the cement with lithium additive was examined by isothermal calorimetry, measurements of setting time and phase composition of cement pastes in the initial stages of hydration. The influence of the admixture on the compressive strength development of mortars after 2, 7 and 28 days of hardening was also researched. Results indicate that lithium nitrate accelerates the early hydration of Portland cement, affecting the precipitation of hydration products. The compressive strength of mortars with lithium admixture decrease after 28 days, although 2 an 7-day strength were greater than the control mortars.

scholarly journals Calcined Clay as Supplementary Cementitious Material

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4734
Author(s):  
Roman Jaskulski ◽  
Daria Jóźwiak-Niedźwiedzka ◽  
Yaroslav Yakymechko
Keyword(s):  
Cement Content ◽  
Cementitious Material ◽  
Testing Methods ◽  
Concrete Technology ◽  
Research Papers ◽  
Supplementary Cementitious Material ◽  
Calcined Clay ◽  
Blended Cements ◽  
Activity Assessment ◽  
Fundamental Information

Calcined clays are the only potential materials available in large quantities to meet the requirements of eco-efficient cement-based materials by reducing the clinker content in blended cements or reducing the cement content in concrete. More than 200 recent research papers on the idea of replacing Portland cement with large amounts of calcined clay are presented and discussed in detail. First, the fundamental information about the properties and structure of clay minerals is described. Then, the process of activation and hydration of clays is discussed, including the methods of pozzolanic activity assessment. Additionally, various testing methods of clays from different worldwide deposits are presented. The application of calcined clay in cement and concrete technology is then introduced. A separate chapter is devoted to lime calcined clay cement. Then an influence of calcined clay on durability of concrete is summarized. Finally, conclusions are formulated.

Scanning Electron Microscopy and x-ray analysis of microparticles and early hydration effects

1995 ◽  
Vol 53 ◽  
pp. 692-693
Author(s):  
Yun Lu ◽  
David C. Joy
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Morphological Development ◽  
Early Hydration ◽  
X Ray ◽  
Blended Cements ◽  
Powder Particles ◽  
Chemical Wastes ◽  
Scanning Electron

High resolution scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDXA) were performed to investigate microparticles in blended cements and their hydration products containing sodium-rich chemical wastes. The physical appearance of powder particles and the morphological development at different hydration stages were characterized by using high resolution SEM Hitachi S-900 and by SEM S-800 with a EDX spectrometer. Microparticles were dispersed on the sample holder and glued by 1% palomino solution. Hydrated bulk samples were dehydrated by acetone and mounted on the holder by silver paste. Both fracture surfaces and flat cutting sections of hydrating samples were prepared and examined. Some specimens were coated with an 3 nm thick Au-Pd or Cr layer to provide good conducting surfaces. For high resolution SEM S-900 observations the accelerating voltage of electrons was 1-2 KeV to protect the electron charging. Microchemical analyses were carried out by S800/EDS equipped with a LINK detector of take-off angle =40°.

Effectiveness of PCE superplasticizers in calcined clay blended cements

2021 ◽  
Vol 141 ◽  
pp. 106334
Author(s):  
Ran Li ◽  
Lei Lei ◽  
Tongbo Sui ◽  
Johann Plank
Keyword(s):  
Calcined Clay ◽  
Blended Cements

Conversion of Red Muds into Pozzolans

1991 ◽  
Vol 245 ◽  
Author(s):  
Jean Pera
Keyword(s):  
Red Mud ◽  
Mineralogical Composition ◽  
Waste Materials ◽  
Strength Development ◽  
Blended Cements ◽  
Temperature Range ◽  
Lime Consumption ◽  
Red Muds ◽  
Mineralogical Compositions

ABSTRACTRed muds are waste materials obtained from the aluminium extraction industry. They consist mainly of clays, aluminium and iron hydrated oxides. Three muds were studied; they differed in chemical and mineralogical compositions. They were converted into reactive pozzolans by calcination in the temperature range 600–800°C for five hours. Pozzolanicity was investigated on calcined red mud-OPC mixes studying strength development and lime consumption as evaluated by DTA. The nature of hydrates formed during hardening was also identified.The mineralogical composition of the mud is the most important factor affecting its pozzolanicity. Blended cements containing 30% calcined red mud develop significant strengths.

scholarly journals The role of graphene/graphene oxide in cement hydration

2021 ◽  
Vol 10 (1) ◽  
pp. 768-778
Author(s):  
Shaoqiang Meng ◽  
Xiaowei Ouyang ◽  
Jiyang Fu ◽  
Yanfei Niu ◽  
Yuwei Ma
Keyword(s):  
Graphene Oxide ◽  
Cement Paste ◽  
Cement Hydration ◽  
Isothermal Calorimetry ◽  
High Mobility ◽  
Nucleation And Growth ◽  
Early Hydration ◽  
Mobility Of Ions ◽  
Cement Surface

Abstract Graphene (G) and graphene oxide (GO) have been shown to significantly improve the mechanical properties of cement-based materials. In this study, the effect of the G/GO on cement hydration was investigated. First, the zeta potential of G/GO in simulated solutions was tested, and the interaction between G/GO’s surface and Ca2+ was explored. Subsequently, scanning electron microscopy was used to observe the morphology of C–S–H nucleation and growth on the cement surface in the cement paste containing G/GO. Furthermore, XRD and TGA analyses were carried out on the hydration products of the sample. At last, isothermal calorimetry was applied to investigate the influence of G/GO on the early hydration of cement. The results showed that the addition of G/GO significantly accelerates C–S–H nucleation and growth on the cement surface. It is indicated that the high mobility ions derived by G/GO in the cement paste dominate the reason for the accelerated hydration of cement. The presence of G, especially GO, facilitates the mobility of ions, especially Ca2+, thus enhances the interaction between the cement surface and the ions. This strong interaction promotes the C–S–H nucleation and growth, and therefore, the hydration of the cement.

Research Progress on the Hydration of Portland Cement with Calcined Clay and Limestone

2021 ◽  
Vol 1036 ◽  
pp. 240-246
Author(s):  
Jin Tang ◽  
Su Hua Ma ◽  
Wei Feng Li ◽  
Hui Yang ◽  
Xiao Dong Shen
Keyword(s):  
Mechanical Properties ◽  
Portland Cement ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Research Progress ◽  
Hydration Reaction ◽  
Hydration Products ◽  
Early Hydration ◽  
Calcined Clay ◽  
Dense Microstructure

The use of calcined clay and limestone as supplementary cementitious materials, can have a certain influence on the hydration of Portland cement. This paper reviewed the influence of limestone and calcined clay and the mixture of limestone and calcined clay on the hydration of cement. Both limestone and calcined clay accelerate the hydration reaction in the early hydration age and enhance the properties of cement. Limestone reacts with C3A to form carboaluminate, which indirectly stabilized the presence of ettringite, while calcined clay consumed portlandite to form C-(A)-S-H gel, additional hydration products promote the densification of pore structure and increase the mechanical properties. The synergistic effect of calcined clay and limestone stabilize the existence of ettringite and stimulate the further formation of carboaluminate, as well as the C-(A)-S-H gel, contributed to a dense microstructure.

scholarly journals Physico-chemical variability and heavy metal pollution of surface sediment in a non-channeled section of Dilúvio Stream (Southern Brazil) and the influence of channeled section in sediment pollution

2019 ◽  
Vol 14 (1) ◽  
pp. 1 ◽  
Author(s):  
Pedro Alexandre Sodrzeieski ◽  
Leonardo Capeleto de Andrade ◽  
Tales Tiecher ◽  
Flávio Anastácio de Oliveira Camargo
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Total Concentration ◽  
Mineralogical Composition ◽  
Sediment Pollution ◽  
Anthropogenic Influence ◽  
Southern Brazil ◽  
Physico Chemical ◽  
Chemical Variability ◽  
The Impact

Dilúvio Stream flows through an area with a great population density in Porto Alegre, Southern Brazil. The anthropogenic influence in the surroundings impacted negatively the quality of the sediments of Dilúvio Stream and Lake Guaíba. This study evaluated the physico-chemical variability of surface sediments in a non-channeled section of Dilúvio Stream. Additionally, we compared the concentration of several heavy metals in this section with data from previous studies in the margins of Lake Guaíba near the outflow of Dilúvio Stream in order to evaluate the impact of urbanization on sediment pollution. The pH, bulk density, particle-size distribution, electrical conductivity, organic carbon, assimilable phosphorus, total nitrogen, mineralogical composition (X-ray diffractogram) and pseudo total concentration of several metals (Fe, Al, Ca, Mg, Na, K, Mn, Ba, Zn, V, As, Pb, Cu, Cr, Co, Ni, Cd, Mo, and Se) were evaluated. The results showed that the sediments in the non-channeled section of Dilúvio Stream are predominantly sandy, with heavy metal contents below the quality reference values. Quartz and feldspar predominated in all sites. The concentration of Zn, Pb, Cu, Cr, and Ni were lower than that observed in the margins of Lake Guaíba near the outflow of Dilúvio Stream, possibly due to pollution input throughout the channeled section. The Dilúvio Stream shows indications of an anthropogenic influence in the heavy metals concentration through the channeled area.

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