scholarly journals Resistivity Measurements to Study the Early Chemical and Autogenous Shrinkage of a Binary Alkali-activated Slag-metakaolin System

2021 ◽  
Vol 791 (1) ◽  
pp. 012146
Author(s):  
Chunyan Zhu ◽  
Yu Zhou ◽  
Yaoxiang Guo ◽  
Zhiwen Wen ◽  
Liangwei Zhang ◽  
...  
Keyword(s):  
Autogenous Shrinkage ◽  
Alkali Activated Slag ◽  
Resistivity Measurements ◽  
Activated Slag ◽  
Alkali Activated

scholarly journals Mitigating the Drying Shrinkage and Autogenous Shrinkage of Alkali-Activated Slag by NaAlO2

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3499
Author(s):  
Bin Chen ◽  
Jun Wang ◽  
Jinyou Zhao
Keyword(s):  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Nitrogen Adsorption ◽  
Partial Substitution ◽  
Hydration Reaction ◽  
X Ray Diffraction ◽  
Na2o Content ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Alkali Activated

The shrinkage of alkali-activated slag (AAS) is obviously higher than ordinary Portland cement, which limited its application in engineering. In this study, the effects of NaAlO2 in mitigating drying shrinkage and autogenous shrinkage of AAS were studied. To further understand the shrinkage mechanism, the hydration products and microstructures were studied by X-ray diffraction, scanning electron microscopy and nitrogen adsorption approaches. As the partial substitution rate of NaAlO2 for Na2SiO3 increased, the drying shrinkage and autogenous shrinkage reduced significantly. The addition of NaAlO2 could slow down the rate of hydration reaction and reduce the porosity, change the pore diameter and the composition of generated paste and cause more hydrotalcite and tetranatrolite generated—which contributed to reduced shrinkage. Additionally, raising the Na2O content rate caused obvious differences in drying shrinkage and autogenous shrinkage. As the Na2O content elevated, the drying shrinkage decreased and autogenous shrinkage increased. A high Na2O content would cause complete hydration reactions and provoke high autogenous shrinkage. However, incomplete hydration reactions left more water in the paste, and the evaporated water dramatically influenced drying shrinkage. The results indicate that addition of NaAlO2 could greatly mitigate the drying shrinkage and autogenous shrinkage of AAS.

scholarly journals A Low-Autogenous-Shrinkage Alkali-Activated Slag and Fly Ash Concrete

2020 ◽  
Vol 10 (17) ◽  
pp. 6092
Author(s):  
Zhenming Li ◽  
Xingliang Yao ◽  
Yun Chen ◽  
Tianshi Lu ◽  
Guang Ye
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
High Performance ◽  
Structural Engineering ◽  
Autogenous Shrinkage ◽  
Portland Cement Concrete ◽  
Alkali Activated Slag ◽  
Cracking Potential ◽  
Activated Slag ◽  
Alkali Activated

Alkali-activated slag and fly ash (AASF) materials are emerging as promising alternatives to conventional Portland cement. Despite the superior mechanical properties of AASF materials, they are known to show large autogenous shrinkage, which hinders the wide application of these eco-friendly materials in infrastructure. To mitigate the autogenous shrinkage of AASF, two innovative autogenous-shrinkage-mitigating admixtures, superabsorbent polymers (SAPs) and metakaolin (MK), are applied in this study. The results show that the incorporation of SAPs and MK significantly mitigates autogenous shrinkage and cracking potential of AASF paste and concrete. Moreover, the AASF concrete with SAPs and MK shows enhanced workability and tensile strength-to-compressive strength ratios. These results indicate that SAPs and MK are promising admixtures to make AASF concrete a high-performance alternative to Portland cement concrete in structural engineering.

Experimental Determination of Early Shrinkage of Alkali-Activated Slag

2019 ◽  
Vol 292 ◽  
pp. 114-119
Author(s):  
Martin Alexa ◽  
Dalibor Kocáb ◽  
Barbara Kucharczyková ◽  
Jan Kotrla
Keyword(s):  
Autogenous Shrinkage ◽  
Volume Changes ◽  
Alkali Activated Slag ◽  
Detailed Evaluation ◽  
The Difference ◽  
Organic Admixture ◽  
Activated Slag ◽  
The Relationship ◽  
Alkali Activated

This paper deals with the relationship between chemical processes in the early stages of hydration of alkali-activated slag, volume changes and the development of the microstructure of this material. Two test pastes were produced for the purpose of the experiment - one with and the other without an organic admixture (isopropyl alcohol). The pastes were used to monitor autogenous shrinkage by measuring volume changes and at the same time the changes in the material during setting and early hardening using a modern ultrasonic instrument Vikasonic. The output of the described experiment is a detailed evaluation of the difference in the behaviour of the used alkali-activated paste with and without the addition of an organic admixture.

Shrinkage Behavior of Alkali-Activated Slag Cement Pastes

2018 ◽  
Vol 761 ◽  
pp. 45-48 ◽  
Author(s):  
Vladyslav Omelchuk ◽  
Guang Ye ◽  
Rayisa Runova ◽  
Igor I. Rudenko
Keyword(s):  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Chemical Shrinkage ◽  
Slag Cement ◽  
Cement Pastes ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Mineral Additives ◽  
Alkali Activated ◽  
Shrinkage Behavior

Nowadays, alkali-activated cements (AACs) are the most promising alternatives to ordinary portland cement (OPC). Such cements characterized by better strength and corrosion resistance that determine improved durability of materials based on them. However, the shrinkage of AAC systems is noticeably higher compared with OPC. The purpose of this work was to study the shrinkage behavior of alkali-activated slag cement (AASC) pastes. To improve early age performance of AASCs – OPC and Ca(OH)2, as mineral additives, were added to the designed cement mixtures. The properties, like, flexural and compressive strength of cement mortars, chemical shrinkage, autogenous shrinkage and drying shrinkage of cement pastes were studied. The results showed that the chemical shrinkage, autogenous shrinkage and drying shrinkage at 28 days were between 0.064 – 0.074 ml/g, 4.5 – 7.9 mm/m and 3.3 – 4.9 mm/m, respectively. The relationship between the nature of alkaline components, the type of mineral additives and the shrinkage behavior of cements were discussed.

scholarly journals The Effect of Biochar on the Properties of Alkali-Activated Slag Pastes

2021 ◽  
Vol 2 (1) ◽  
pp. 1-14
Author(s):  
Joshua Prabahar ◽  
Babak Vafaei ◽  
Elvis Baffoe ◽  
Ali Ghahremaninezhad
Keyword(s):  
Computed Tomography ◽  
Autogenous Shrinkage ◽  
Absorption Kinetics ◽  
Effective Solution ◽  
Micro Computed Tomography ◽  
Alkali Activated Slag ◽  
X Ray ◽  
Void Structure ◽  
Activated Slag ◽  
Alkali Activated

This paper examines the influence of biochar on the properties of alkali-activated slag pastes using two activator solutions, namely NaOH and Na2CO3. The biochar demonstrated different absorption kinetics in the mixture of slag and the two activator solutions. The pastes with biochar showed a delay in the heat flow peak, compared to the pastes without biochar, but the cumulative heat release in these pastes at later hours was increased, compared to the pastes without biochar. It was found that the use of biochar reduced autogenous shrinkage in the pastes and the reduction in autogenous shrinkage was more pronounced in the alkali-activated slag with NaOH, compared to Na2CO3. The void structure of the pastes was investigated using x-ray micro-computed tomography. It was found that refined pore structure due to reduced effective solution/slag in the pastes with biochar was able to compensate for the decreasing effect of biochar voids on compressive strength. The electrical resistivity was shown to be lower in the pastes with biochar.

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