scholarly journals Elastic Wave Monitoring of Cementitious Mixtures Including Internal Curing Mechanisms

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2463
Author(s):  
Gerlinde Lefever ◽  
Didier Snoeck ◽  
Nele De Belie ◽  
Danny Van Hemelrijck ◽  
Dimitrios G. Aggelis
Keyword(s):  
Acoustic Emission ◽  
Autogenous Shrinkage ◽  
Cementitious Materials ◽  
Internal Curing ◽  
Water Evaporation ◽  
Curing Process ◽  
Hydration Kinetics ◽  
Water Release ◽  
Additional Water ◽  
Non Destructive

The mitigation of autogenous shrinkage in cementitious materials by internal curing has been widely studied. By the inclusion of water reservoirs, in form of saturated lightweight aggregates or superabsorbent polymers, additional water is provided to the hydrating matrix. The onset of water release is of high importance and determines the efficiency of the internal curing mechanism. However, the monitoring of it poses problems as it is a process that takes place in the microstructure. Using acoustic emission (AE) sensors, the internal curing process is monitored, revealing its initiation and intensity, as well as the duration. In addition, AE is able to capture the water evaporation from saturated specimens. By ultrasonic testing, differences in the hydration kinetics are observed imposed by the different methods of internal curing. The results presented in this paper show the sensitivity of combined AE and ultrasound experiments to various fundamental mechanisms taking place inside cementitious materials and demonstrate the ability of acoustic emission to evaluate internal curing in a non-destructive and easily implementable way.

scholarly journals Novel microcapsules for internal curing of high-performance cementitious system

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Xiaoyu Shang ◽  
Baojian Zhan ◽  
Jiangshan Li ◽  
Rui Zhong
Keyword(s):  
High Performance ◽  
Autogenous Shrinkage ◽  
Double Emulsion ◽  
Internal Curing ◽  
The Novel ◽  
Polymer Shell ◽  
Water Release ◽  
Cement Based Materials ◽  
Alkaline Environments ◽  
Cementitious System

Abstract Conventional internal curing materials for high-performance cementitious system cannot easily have artificial modifications, such that the curing effect is difficult to control during the process. In this study, a novel microcapsule is proposed for controlled internal curing of cement-based materials. The microcapsules are synthesized by a double emulsion method to form a polymer shell-water core structure. The sensitivity of polymer shell to alkaline environments is used to trigger the release of core water. Thus, water release can be controlled by tailoring the shell thickness and microcapsules sizes by changing the polymer dosage and stirring rate during synthesis. The experimental results indicate that the novel microcapsules can effectively release water for internal curing of a cementitious matrix, which exhibits a high curing efficiency in terms of nearly autogenous shrinkage and increases the compressive strength. The novel microcapsules could be promising internal curing agents to enhance high-performance cement-based materials.

scholarly journals Efficiency of Sodium Polyacrylate to Improve Durability of Concrete under Adverse Curing Condition

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Tanvir Manzur ◽  
Shohana Iffat ◽  
Munaz Ahmed Noor
Keyword(s):  
Internal Curing ◽  
Curing Agent ◽  
Sodium Polyacrylate ◽  
Curing Process ◽  
Super Absorbent Polymer ◽  
Curing Conditions ◽  
Naturally Occurring ◽  
Additional Water ◽  
Strength And Durability ◽  
Absorbent Polymer

The conventional external curing process requires supply of large amount of water in addition to mixing water as well as strict quality control protocol. However, in a developing country like Bangladesh, many local contractors do not have awareness and required knowledge on importance of curing which often results in weaker concrete with durability issues. Moreover, at times it is difficult to maintain proper external curing process due to nonavailability of water and skilled laborer. Internal curing can be adopted under such scenario since this method is simple and less quality intensive. Usually, naturally occurring porous light weight aggregates (LWA) are used as internal curing agent. However, naturally occurring LWA are not available in many countries like Bangladesh. Under these circumstances, Super Absorbent Polymer (SAP) can be utilized as an alternative internal curing agent. In this study, sodium polyacrylate (SP) as SAP has been used to produce internally cured concrete. Desorption isotherm of SP has been developed to investigate its effectiveness as internal curing agent. Test results showed that internally cured concrete with SP performed better in terms of both strength and durability as compared to control samples when subjected to adverse curing conditions where supply of additional water for external curing was absent.

scholarly journals Discussing Different Approaches for the Time-Zero as Start for Autogenous Shrinkage in Cement Pastes Containing Superabsorbent Polymers

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2962 ◽  
Author(s):  
José Roberto Tenório Filho ◽  
Maria Adelaide Pereira Gomes de Araújo ◽  
Didier Snoeck ◽  
Nele De Belie
Keyword(s):  
Transition Point ◽  
Setting Time ◽  
Autogenous Shrinkage ◽  
Strain Curve ◽  
Cementitious Materials ◽  
Internal Curing ◽  
Superabsorbent Polymers ◽  
Time Zero ◽  
Autogenous Strain ◽  
Curing Agents

Many studies have already been published concerning autogenous shrinkage in cementitious materials. Still, no consensus can be found in the literature regarding the determination of the time-zero to initiate the recording of autogenous shrinkage. With internal curing agents, a correct evaluation of their efficiency depends on an appropriate choice of the time-zero. This study investigates different approaches to estimate the time-zero for cement paste mixtures with and without superabsorbent polymers as internal curing agents. The initial and final setting times were determined by an electronic Vicat and ultrasonic pulse velocity measurements (UPV); the transition point between the fluid and solid state was determined from the autogenous strain curve; the development of the capillary pressure was also studied. The choice of time-zero before the transition point led to higher values of shrinkage strain that should not be taken into account for autogenous shrinkage. A negligible difference was found between the strains when the final setting time and the transition point were taken as time-zero. Considering the artefacts and practical issues involving the different methods, the use of the transition point from the autogenous strain curve is the most suitable technique for determining the time-zero.

scholarly journals The Contribution of Elastic Wave NDT to the Characterization of Modern Cementitious Media

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2959 ◽  
Author(s):  
Gerlinde Lefever ◽  
Didier Snoeck ◽  
Nele De Belie ◽  
Sandra Van Vlierberghe ◽  
Danny Van Hemelrijck ◽  
...  
Keyword(s):  
Mechanical Performance ◽  
Autogenous Shrinkage ◽  
Measuring Method ◽  
Cementitious Materials ◽  
Mechanical Tests ◽  
Self Healing ◽  
Destructive Testing ◽  
Superabsorbent Polymers ◽  
Non Destructive

To mitigate autogenous shrinkage in cementitious materials and simultaneously preserve the material’s mechanical performance, superabsorbent polymers and nanosilica are included in the mixture design. The use of the specific additives influences both the hydration process and the hardened microstructure, while autogenous healing of cracks can be stimulated. These three stages are monitored by means of non-destructive testing, showing the sensitivity of elastic waves to the occurring phenomena. Whereas the action of the superabsorbent polymers was evidenced by acoustic emission, the use of ultrasound revealed the differences in the developed microstructure and the self-healing of cracks by a comparison with more commonly performed mechanical tests. The ability of NDT to determine these various features renders it a promising measuring method for future characterization of innovative cementitious materials.

Evaluation of Water Evaporation in Cementitious Materials by Low Field NMR

2011 ◽  
Vol 492 ◽  
pp. 437-440 ◽  
Author(s):  
An Ming She ◽  
Wu Yao ◽  
Wan Cheng Yuan
Keyword(s):  
Quantitative Research ◽  
Bound Water ◽  
Cementitious Materials ◽  
Water Evaporation ◽  
Basic Process ◽  
Low Field ◽  
Water Filling ◽  
Low Field Nmr ◽  
Selective Sensitivity ◽  
Non Destructive

The water evaporation is a basic process occurring during the service life of cementitious materials. In this paper, the evaporation process of water from heated cement specimens with different composites were studied by low field nuclear magnetic resonance. The results show that there is a linear relationship between the signals intensity and water filling index. The non-evaporable water in the specimen contributes little to signal intensity. In addition, the relaxation signals have selective sensitivity. It could be used as a non-destructive method to the quantitative research of physically bound water in the cementitious materials.

scholarly journals Chloride Diffusion in Concrete Modified with Polyacrylic Superabsorbent Polymer (SAP) Hydrogel—The Influence of the Water-to-Cement Ratio and SAP-Entrained Water

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4064
Author(s):  
Maciej Kalinowski ◽  
Piotr Woyciechowski
Keyword(s):  
Reference Value ◽  
Chloride Ion ◽  
Cementitious Materials ◽  
Negative Influence ◽  
Chloride Diffusion ◽  
Water Release ◽  
Dry Conditions ◽  
Saturated Form ◽  
Additional Water ◽  
The Impact

This paper examines the influence of polyacrylic superabsorbent polymers (SAP) on the properties concerning chloride diffusion in cementitious materials. The conducted study investigated the influence of SAP on chloride diffusion in concretes of the initial w/c = 0.4 (for which the changes in compressive strength due to the SAP presence were negligible). The impact on the diffusivity of concrete of several variables was analyzed: the material characteristics of SAP, additional water added to the concrete to make up for the amount of water stored in the SAP structure, and the method of SAP dosing to the mix (either in a non-saturated form or in a hydrogel form). We found that, in the case of modifying concrete with polyacrylic SAP of a median particle size in dry conditions of 330 µm and without additional water, the coefficient of chloride ion diffusion was reduced to 65% of the reference value. The negative influence (increase) of increasing w/ctot by the amount of water initially entrained by SAP on the chloride diffusivity of concrete was identified. The conducted study indicates the premise of the mechanism of the water release from SAP in cementitious composites.

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