From composition to the microstructure and durability of limestone ternary blended cements: A Systematic review

2021 ◽  
pp. 1-44
Author(s):  
Samuel Adu-Amankwah ◽  
Suraj Rahmon ◽  
Leon Black
Keyword(s):  
Large Scale ◽  
Air Entrainment ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Chloride Ingress ◽  
Blended Cements ◽  
Freeze Thaw ◽  
Significant Research ◽  
Large Scale Field

Limestone ternary cements have attracted significant research and commercial attention recently, for technical and environmental reasons. Standardization of these cements is imminent under BS EN197-5. Presently, detailed understanding of the hydration and microstructure evolution of limestone ternary cements from different alumina-rich supplementary cementitious materials (SCMs) exists in the scientific literature; improved reaction kinetics and additional phase assemblages refine the pore structure. However, understanding of the performance of these cements under exposure conditions is less prevalent. In this contribution, we review these data in a way that allows stakeholders to appreciate the capabilities of the different compositions and their performance. We focus our discussion on critically examining the interplay between the cement composition and the microstructure on durability. It is demonstrated that limestone ternary cements offer a pathway for reducing the embodied CO2 of concrete without compromising their performance. The resistance to chloride ingress, sulphate attack and ASR are significantly improved in a manner similar to binary cements. Carbonation and freeze-thaw resistance is generally lower than OPC but adequate air entrainment can offer improvement in freeze-thaw resistance. The challenge to widespread adoption of these cements is evidence of durability under field conditions. To this end, we recommend large-scale field trialling of these cements and understanding of the role of combined exposures on durability and mechanical properties.

scholarly journals Sustainable low-carbon binders and concretes

2020 ◽  
Vol 166 ◽  
pp. 06007
Author(s):  
Myroslav Sanytsky ◽  
Tetiana Kropyvnytska ◽  
Stanislav Fic ◽  
Hanna Ivashchyshyn
Keyword(s):  
Activity Index ◽  
Chemical Properties ◽  
High Volume ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Cement Matrix ◽  
Low Carbon ◽  
Blended Cements ◽  
Physical And Chemical

Sustainable development depends on a consistency of interests, social, ecological and economic, and that the interests are evaluated in a balanced manner. In order to reduce CO2 emissions, the conception of decreasing clinker factor and increasing the role of supplementary cementitious materials (SCMs) in the cementitious materials has high economical and environmental efficiency. The performance of clinkerefficient blended cements with supplementary cementitious materials were examined. The influence of superfine zeolite with increased surface energy on the physical and chemical properties of low-carbon blended cements is shown. Increasing the dispersion of cementitious materials contributes to the growth of their strength activity index due to compaction of cement matrix and pozzolanic reactions in unclincker part. In consequence of the early structure formation and the directed formation of the microstructure of the cement matrix is solving the problem of obtaining clinker-efficient concretes. Shown that low-carbon blended cements with high volume of SCMs are suitable, in principle, for producing structural concretes.

scholarly journals Field Validation of Concrete Transport Property Measurement Methods

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1166 ◽  
Author(s):  
Ahmed Abd El Fattah ◽  
Ibrahim Al-Duais ◽  
Kyle Riding ◽  
Michael Thomas ◽  
Salah Al-Dulaijan ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Effective Diffusion Coefficient ◽  
Corrosion Inhibitors ◽  
Effective Diffusion ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Chloride Diffusion ◽  
Chloride Ingress ◽  
Exposure Site

Reinforcing steel corrosion, caused by chloride ingress into concrete, is the leading cause of reinforced concrete deterioration. One of the main findings in the literature for reducing chloride ingress is the improvement of the durability characteristics of concrete by the addition of supplementary cementitious materials (SCMs) and/or chemical agents to concrete mixtures. In this study, standard ASTM tests—such as rapid chloride permeability (RCPT), bulk diffusion and sorptivity tests—were used to measure concrete properties such as porosity, sorptivity, salt diffusion, and permeability. Eight different mixtures, prepared with different SCMs and corrosion inhibitors, were tested. Apparent and effective chloride diffusion coefficients were calculated using bound chloride isotherms and time-dependent decrease in diffusion. Diffusion coefficients decreased with time, especially with the addition of SCMs and corrosion inhibitors. The apparent diffusion coefficient calculated using the error function was slightly lower than the effective diffusion coefficient; however, there was a linear trend between the two. The formation factor was found to correlate with the effective diffusion coefficient. The results of the laboratory tests were compared and benchmarked to their counterparts in the marine exposure site in the Arabian Gulf in order to identify laboratory key tests to predict concrete durability. The overall performance of concrete containing SCMs, especially fly ash, were the best among the other mixtures in the laboratory and the field.

scholarly journals The Role of Mindset in Education : A Large-Scale Field Experiment in Disadvantaged Schools

2021 ◽  
Author(s):  
Elise Huillery ◽  
Adrien Bouguen ◽  
Axelle Charpentier ◽  
Yann Algan ◽  
Coralie Chevallier
Keyword(s):  
Field Experiment ◽  
Experimental Evidence ◽  
Large Scale ◽  
Cost Effective ◽  
Growth Mindset ◽  
Disadvantaged Schools ◽  
Scale Field ◽  
Large Scale Field ◽  
The Impact

This article provides experimental evidence of the impact of a four-year inter-vention aimed at developing students’ growth mindset and internal locus ofcontrol in disadvantaged middle schools. We find a 0.07 standard deviationincrease in GPA, associated with a change in students’ mindset, improved be-havior as reported by teachers and school registers, and higher educational andprofessional aspirations. International empirical benchmarks reveal that theintervention is at least ten times more cost-effective than the typical educa-tional intervention. However, while reducing between-school inequality whentargeted to disadvantaged schools, the program benefits less to more fragilestudents, therefore increasing within-school inequality.

scholarly journals Role of Aluminum and Lithium in Mitigating Alkali-Silica Reaction—A Review

2022 ◽  
Vol 8 ◽  
Author(s):  
Zhenguo Shi ◽  
Barbara Lothenbach
Keyword(s):  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Lithium Salts ◽  
Alkali Silica Reaction ◽  
Reaction Products ◽  
Ambient Conditions ◽  
Slow Kinetics ◽  
Zeolite Formation ◽  
Available Information

Effective mitigation of alkali-silica reaction (ASR) is critical for producing durable concrete. The use of alumina-rich supplementary cementitious materials (SCMs) and chemical admixtures such as lithium salts to prevent expansion caused by ASR was first reported 70 years ago, shortly after the discovery of ASR in 1940s. Despite numerous investigations, the understanding of the mechanisms of Al and Li for mitigating ASR remain partially inexplicit in the case of Al, and hardly understood in the case of Li. This paper reviews the available information on the effect of Al and Li on ASR expansion, the influencing factors, possible mechanisms and limitations. The role of Al in mitigating ASR is likely related to the reduction of dissolution rate of reactive silica. Moreover, the presence of Al may alter the structure of crystalline ASR products to zeolite or its precursor, but such effect seems to be not that significant at ambient conditions due to the slow kinetics of zeolite formation. Several mechanisms for the lithium salts in mitigating ASR have been proposed, but most of them are not conclusive primarily due to the lack of knowledge about the formed reaction products. Combination of Al-rich SCMs and lithium salts may be used as an economic solution for ASR mitigation, although systematic studies are necessary prior to the applications.

scholarly journals Portland Cements with High Content of Calcined Clay: Mechanical Strength Behaviour and Sulfate Durability

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4206 ◽  
Author(s):  
Carlos H. Aramburo ◽  
César Pedrajas ◽  
Rafael Talero
Keyword(s):  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Chemical Effect ◽  
Portland Cements ◽  
Calcined Clay ◽  
Blended Cements ◽  
Sulfate Resistance ◽  
Type Iv ◽  
Mechanical Strengths ◽  
Mineralogical Compositions

Calcined clay has become the supplementary cementitious materials with the greatest potential to reduce the clinker/cement. In this research, the mechanical strengths and sulphate resistance of blended cements with a high content of calcined clay as a pozzolanic addition were evaluated to demonstrate that these cements could be designed as CEM (cement) type IV/A-SR and IV/B-SR cements by the current European standard UNE-EN 197-1: 2011. The blended cements were prepared by two Portland cements (P1 and PY6) with different mineralogical compositions and a calcined clay. The level of replacement was greater than 40% by weight. The results obtained confirm the decrease in the mechanical strengths and the increase in the sulfate resistance of the two Portland cements when they are replaced by calcined clay at a level of replacement greater than 40%. These results are a consequence of the chemical effect from the pozzolanic activity of the calcined clay. Therefore, there is an important decrease in portlandite levels of paste liquid phase that causes the increase in sulfate resistance and the decrease of the mechanical strengths.

scholarly journals The Influence of Chemical Activators on the Hydration Behavior and Technical Properties of Calcium Sulfoaluminate Cements Blended with Ground Granulated Blast Furnace Slags

Buildings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 268
Author(s):  
Milena Marroccoli ◽  
Antonio Telesca
Keyword(s):  
Blast Furnace ◽  
Co2 Emissions ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
X Ray Diffraction ◽  
Cement Production ◽  
Blended Cements ◽  
Calcium Sulfoaluminate ◽  
Technical Performance ◽  
Technical Properties

The manufacture of Ordinary Portland cement (OPC) generates around 8% of the global CO2 emissions related to human activities. The last 20 years have seen considerable efforts in the research and development of methods to lower the carbon footprint associated with cement production. Specific focus has been on limiting the use of OPC and employing alternative binders, such as calcium sulfoaluminate (CSA) cements, namely special hydraulic binders obtained from non-Portland clinkers. CSA cements could be considered a valuable OPC alternative thanks to their distinctive composition and technical performance and the reduced environmental impact of their manufacturing process. To additionally reduce CO2 emissions, CSA cements can also be blended with supplementary cementitious materials. This paper investigates the influence of two separately added chemical activators (NaOH or Na2CO3) on the technical properties and hydration behavior of four CSA blended cements obtained by adding to a plain CSA cement two different ground granulated blast furnace slags. Differential thermal-thermogravimetric, X-ray diffraction and mercury intrusion porosimetry analyses were done, along with shrinkage/expansion and compressive strength measurements.

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