Superior photocatalytic NOx removal of cementitious materials prepared with white cement over ordinary Portland cement and the underlying mechanisms

2018 ◽  
Vol 90 ◽  
pp. 42-49 ◽  
Author(s):  
Ming-Zhi Guo ◽  
Chi Sun Poon
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Cementitious Materials ◽  
Nox Removal ◽  
White Cement ◽  
Underlying Mechanisms

scholarly journals A Review of the Mechanical Properties and Durability of Ecological Concretes in a Cold Climate in Comparison to Standard Ordinary Portland Cement-Based Concrete

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3467
Author(s):  
Ankit Kothari ◽  
Karin Habermehl-Cwirzen ◽  
Hans Hedlund ◽  
Andrzej Cwirzen
Keyword(s):  
Carbon Dioxide ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Cementitious Materials ◽  
Cold Climate ◽  
Supplementary Cementitious Materials ◽  
Short Exposure ◽  
Chemical Admixtures ◽  
Composite Cements ◽  
Alkali Activated

Most of the currently used concretes are based on ordinary Portland cement (OPC) which results in a high carbon dioxide footprint and thus has a negative environmental impact. Replacing OPCs, partially or fully by ecological binders, i.e., supplementary cementitious materials (SCMs) or alternative binders, aims to decrease the carbon dioxide footprint. Both solutions introduced a number of technological problems, including their performance, when exposed to low, subfreezing temperatures during casting operations and the hardening stage. This review indicates that the present knowledge enables the production of OPC-based concretes at temperatures as low as −10 °C, without the need of any additional measures such as, e.g., heating. Conversely, composite cements containing SCMs or alkali-activated binders (AACs) showed mixed performances, ranging from inferior to superior in comparison with OPC. Most concretes based on composite cements require pre/post heat curing or only a short exposure to sub-zero temperatures. At the same time, certain alkali-activated systems performed very well even at −20 °C without the need for additional curing. Chemical admixtures developed for OPC do not always perform well in other binder systems. This review showed that there is only a limited knowledge on how chemical admixtures work in ecological concretes at low temperatures and how to accelerate the hydration rate of composite cements containing high amounts of SCMs or AACs, when these are cured at subfreezing temperatures.

scholarly journals Alteration of Bentonite Reacted with Cementitious Materials for 5 and 10 Years in the Mont Terri Rock Laboratory (CI Experiment)

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 251
Author(s):  
Shingo Yokoyama ◽  
Misato Shimbashi ◽  
Daisuke Minato ◽  
Yasutaka Watanabe ◽  
Andreas Jenni ◽  
...  
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Current Knowledge ◽  
Cementitious Materials ◽  
Opalinus Clay ◽  
Secondary Products ◽  
Rock Laboratory ◽  
Mineral Compositions ◽  
Mont Terri ◽  
Mont Terri Rock Laboratory

The cement–clay interaction (CI) experiment was carried out at the Mont Terri rock laboratory to complement the current knowledge on the influence that cementitious materials have on Opalinus Clay (OPA) and bentonite (MX). Drill cores including the interface of OPA, concrete (LAC = low-alkali binder, and OPC = ordinary Portland cement), and MX, which interacted for 4.9 and 10 years, were successfully retrieved after drilling, and detailed analyses were performed to evaluate potential mineralogical changes. The saturated compacted bentonites in core samples were divided into ten slices, profiling bentonite in the direction towards the interface, to evaluate the extent and spatial variation of the mineralogical alteration of bentonite. Regarding the mineral compositions of bentonite, cristobalite was dissolved within a range of 10 mm from the interface in both LAC-MX and OPC-MX, while calcite precipitated near the interface for OPC-MX. In LAC-MX and OPC-MX, secondary products containing Mg (e.g., M-S-H) also precipitated within 20 mm of the interface. These alterations of bentonite developed during the first 4.9 years, with very limited progress observed for the subsequent 5 years. Detectable changes in the mineralogical nature of montmorillonite (i.e., the formation of illite or beidellite, increase in layer charge) did not occur during the 10 years of interaction.

scholarly journals A Review and Comparative Study of Existing Shrinkage Prediction Models for Portland and Non-Portland Cementitious Materials

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Hailong Ye ◽  
Aleksandra Radlińska
Keyword(s):  
Experimental Data ◽  
Portland Cement ◽  
Theoretical Basis ◽  
Ordinary Portland Cement ◽  
Prediction Models ◽  
High Water ◽  
Cementitious Materials ◽  
Published Data ◽  
Activated Slag ◽  
Specific Comparison

This paper reviews shrinkage prediction models for cementitious materials and presents analysis of selected published data utilizing the aforementioned models. The main objective of this review is to revisit and reexamine the primary shrinkage mechanisms, that is, capillary pressure theory, Gibbs-Bangham shrinkage, and withdrawal of disjoining pressure in Portland and non-Portland cement. In particular, the theoretical basis for current shrinkage models is elaborated on and its soundness and applicability to explain the published experimental data are discussed. Additionally, a specific comparison was made among high water-to-cement (w/c) ratio ordinary Portland cement (OPC), low w/c OPC, and alkaline activated slag.

scholarly journals Leaching Behavior of Cesium, Strontium, Cobalt, and Europium from Immobilized Cement Matrix

2021 ◽  
Vol 11 (18) ◽  
pp. 8418
Author(s):  
Ja-Young Goo ◽  
Bong-Ju Kim ◽  
Myunggoo Kang ◽  
Jongtae Jeong ◽  
Ho Young Jo ◽  
...  
Keyword(s):  
Portland Cement ◽  
Nuclear Power ◽  
Power Plants ◽  
Ordinary Portland Cement ◽  
Cementitious Materials ◽  
The Other ◽  
Cement Matrix ◽  
Leaching Behavior ◽  
Binding Material ◽  
Over Time

Numerous low-level and intermediate-level radioactive wastes are generated from the decommissioning processes of nuclear power plants; these wastes are immobilized to prevent the release of radionuclides under disposal conditions. In this study, we investigated the leaching behavior of Cs, Sr, Co, and Eu, which are common in immobilized decommissioning wastes. Ordinary Portland cement (OPC) was used as an immobilization agent. During the test, leaching of the nuclides occurred in the order of Cs, Sr, Co, and Eu and decreased over time. The results showed that 41.4% of the total Cs leached over 90 days, although the other elements leached in quantities less than 1.5%. CaCO3 was precipitated by the release of cementitious materials, indicating carbonation of the leachate. The leachability indexes in all cases exceeded the acceptable criteria (>6). The results of the present study suggest that OPC can be effectively used as a binding material to immobilize nuclides (Cs, Sr, Co, and Eu) contained in decommissioning wastes.

scholarly journals Synthesis and Characterization of a Hybrid Cement Based on Fly Ash, Metakaolin and Portland Cement Clinker

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1084 ◽  
Author(s):  
Adriagni C. Barboza-Chavez ◽  
Lauren Y. Gómez-Zamorano ◽  
Jorge L. Acevedo-Dávila
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Cementitious Materials ◽  
Cement Industry ◽  
Supplementary Cementitious Materials ◽  
Cement Clinker ◽  
Dense Matrix ◽  
X Ray ◽  
Reduction Of Co2

Hybrid cement has become one of the most viable options in the reduction of CO2 emissions to the environment that are generated by the cement industry. This could be explained by the reduction of the content of clinker in the final mixture and substitution of the remaining percentage with supplementary cementitious materials with the help of an alkaline activation. Following that, properties that are provided by an Ordinary Portland Cement and of a geopolymer are mixed in this type of hybrid material and could be achieved at room temperature. Thereafter, the main objective of this research was to synthesize hybrid cements reducing the clinker content of Portland Cement up to 20% and use metakaolin and fly ash as supplementary cementitious materials in different proportions. The mixtures were alkaline activated with a mixture of sodium silicate and sodium hydroxide, calculating the amounts according to the percentage of Na2O that is present in each of the activators. The samples were then characterized using Compressive strength, X-ray diffraction, Fourier Transform Infrared Spectroscopy, and Scanning Electron Microscopy with energy-dispersive X-ray spectroscopy. The results indicated that the hybrid cements have similar mechanical properties than an Ordinary Portland Cement, and they resulted in a dense matrix of hydration products similar to those that are generated by cements and geopolymers.

Study on Sulphate Resistance of Often-Used Cementitious Material of High Performance Concrete for Marine

2012 ◽  
Vol 450-451 ◽  
pp. 94-101
Author(s):  
Kun Peng Gu ◽  
Cheng Qi Wang
Keyword(s):  
Corrosion Resistance ◽  
Portland Cement ◽  
High Performance ◽  
Ordinary Portland Cement ◽  
High Performance Concrete ◽  
Cementitious Materials ◽  
Resistance Coefficient ◽  
Cementitious Material ◽  
Corrosion Mechanism ◽  
Better Than

Corrosion resistance coefficient and expansion ratio of different cementitious materials are tested under the sulphate corrosion experimental condition, sulphate resistance of often-used cementitious material of high performance concrete for marine is studied and evaluated. The results show that sulphate resistance of portland cement is better than ordinary portland cement, and both of them are low, often-used cementitious material of high performance concrete for marine have certain sulphate resistance, which are better than ordinary portland cement and portland cement, and some of them have strong or very strong sulphate resistance. The evaluation results of the sulphate resistance of often-used cementitious material of high performance concrete for marine are not unanimous completely by corrosion resistance coefficient method and expansion rate method. Sulphate corrosion mechanism of different kinds of cementitious material is analyzed.

Development of an Alternative Cementitious Materials Based on Calcium Carbide Residue and Silica Fume

2021 ◽  
Vol 904 ◽  
pp. 435-440
Author(s):  
Thunthanut Inyai ◽  
Phongthorn Julphunthong ◽  
Panuwat Joyklad
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Silica Fume ◽  
Ordinary Portland Cement ◽  
Raw Materials ◽  
Calcium Carbide ◽  
Cementitious Materials ◽  
Pozzolanic Reaction ◽  
Engineering Properties ◽  
Calcium Carbide Residue

The present study evaluated the engineering properties and microstructure of an alternative binder composed of calcium carbide residue and silica fume. The cementitious mechanisms of this alternative binder based on the pozzolanic reaction in raw materials. The ratio of calcium carbide residue and silica fume was decided based on the chemical composition of raw materials and their chemical reaction. The calcium carbide residue-silica fume mortar was prepared and tested for its compressive strength at several curing periods, with results then compared to conventional mortar made with ordinary Portland cement. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to investigate the microstructure of hardened mortars. The test results suggest that the compressive strength of calcium carbide residue-silica fume mortar continuously developed throughout the curing period. The relative compressive strength of calcium carbide residue-silica fume mortar reached 72.78% of the ordinary Portland cement mortar strength at 28 days curing age.

scholarly journals High-Performance Photocatalytic Cementitious Materials Containing Synthetic Fibers and Shrinkage-Reducing Admixture

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1828 ◽  
Author(s):  
Jung-Jun Park ◽  
Soonho Kim ◽  
Wonsik Shin ◽  
Hong-Joon Choi ◽  
Gi-Joon Park ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Portland Cement ◽  
Cement Mortar ◽  
Glass Fibers ◽  
Cementitious Materials ◽  
Synthetic Fibers ◽  
Total Shrinkage ◽  
White Cement ◽  
Shrinkage Reducing Admixture ◽  
White Portland Cement

This study aims to examine the mechanical, shrinkage and chemical properties of photocatalytic cementitious materials containing synthetic fibers and a shrinkage-reducing admixture (SRA). Two types of titanium dioxide (TiO2) powders and white Portland cement were considered along with ordinary Portland cement (OPC) as a control. Two types of synthetic fibers, i.e., glass and polyethylene (PE), and an SRA with contents varying from 0% to 3% were also considered. Using the TiO2 powders and the white Portland cement was effective in reducing the nitrogen oxides (NOx) concentration in cement composites. The use of PE fibers was more effective than glass fibers in terms of the mechanical properties, i.e., the compressive strength and tensile performance. With the addition of TiO2 powders and SRA or the replacement of OPC with white cement, the mechanical properties of the cement mortar generally deteriorated. The total shrinkage of the mortar could be reduced by incorporating the fibers at volume fractions greater than 1%, and the glass fiber was more effective than the PE fiber in this regard. The TiO2 powders had no significant impact on the shrinkage reduction of the cement mortar, whereas the SRA and the white Portland cement effectively reduced shrinkage. The addition of 3% SRA decreased the total shrinkage by 43%, while the replacement of the OPC with white cement resulted in a 20% reduction in the shrinkage.

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