scholarly journals Effects of Curing Conditions and Supplementary Cementitious Materials on Autogenous Self-Healing of Early Age Cracks in Cement Mortar

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 752
Author(s):  
Mian Luo ◽  
Kang Jing ◽  
Jingquan Bai ◽  
Ziqi Ding ◽  
Dingyi Yang ◽  
...  
Keyword(s):  
Cement Mortar ◽  
Cementitious Materials ◽  
Visual Observation ◽  
Healing Time ◽  
Supplementary Cementitious Materials ◽  
Early Age ◽  
Self Healing ◽  
Replacement Ratio ◽  
Curing Conditions ◽  
Healing Efficiency

The autogenous healing potential of cement-based materials is affected by multiple factors, such as mix composition, crack width, pre-cracking age and external environmental conditions. In this study, the effects of curing conditions and supplementary cementitious materials (SCMs) on autogenous self-healing of early age cracks in cement mortar were investigated. Three curing conditions, i.e., standard curing, wet–dry cycles and incubated in water, and two SCMs, i.e., fly ash (FA) and blast furnace slag (BFS) with various contents (cement replacement ratio at 0%, 20%, and 40%) were examined. A single early age crack (pre-cracking age of 3 days) with a width of 200~300 μm was generated in cylindrical mortar specimens. Autogenous crack self-healing efficiency of mortar specimens was evaluated by performing a visual observation and a water permeability test. Moreover, microstructure analysis (XRD, SEM and TG/DTG) was utilized to characterize the healing products. The results indicated that the presence of water was essential for the autogenous self-healing of early age cracks in cement mortar. The efficiency of self-healing cracks was highest in specimens incubated in water. However, no significant self-healing occurred in specimens exposed to standard curing. For wet–dry cycles, a longer healing time was needed to obtain good self-healing compared to samples incubated in water. SCMs type and content significantly affected the autogenous self-healing ability of early age cracks. The self-healing efficiency of early age cracks decreased with increases in FA and BFS content. BFS mortars exhibited greater recovery in relation to water penetration resistance compared to the reference and FA mortars. Almost the same regain of water tightness and a lower crack-healing ratio after healing of 28 days in FA mortars were observed compared to the reference. The major healing product in the surface cracks of specimens with and without SCMs was micron-sized calcite crystals with a typical rhombohedral morphology.

scholarly journals Meta-Analysis and Machine Learning Models to Optimize the Efficiency of Self-Healing Capacity of Cementitious Material

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4437
Author(s):  
Shashank Gupta ◽  
Salam Al-Obaidi ◽  
Liberato Ferrara
Keyword(s):  
Meta Analysis ◽  
Cementitious Materials ◽  
Initial Crack ◽  
Supplementary Cementitious Materials ◽  
Structural Performance ◽  
Self Healing ◽  
Design Strategies ◽  
Healing Efficiency ◽  
Cement Based Materials ◽  
Artificial Neural Network Ann

Concrete and cement-based materials inherently possess an autogenous self-healing capacity. Despite the huge amount of literature on the topic, self-healing concepts still fail to consistently enter design strategies able to effectively quantify their benefits on structural performance. This study aims to develop quantitative relationships through statistical models and artificial neural network (ANN) by establishing a correlation between the mix proportions, exposure type and time, and width of the initial crack against suitably defined self-healing indices (SHI), quantifying the recovery of material performance. Furthermore, it is intended to pave the way towards consistent incorporation of self-healing concepts into durability-based design approaches for reinforced concrete structures, aimed at quantifying, with reliable confidence, the benefits in terms of slower degradation of the structural performance and extension of the service lifespan. It has been observed that the exposure type, crack width and presence of healing stimulators such as crystalline admixtures has the most significant effect on enhancing SHI and hence self-healing efficiency. However, other parameters, such as the amount of fibers and Supplementary Cementitious Materials have less impact on the autogenous self-healing. The study proposes, through suitably built design charts and ANN analysis, a straightforward input–output model to quickly predict and evaluate, and hence “design”, the self-healing efficiency of cement-based materials.

scholarly journals Numerical Studies of the Effects of Water Capsules on Self-Healing Efficiency and Mechanical Properties in Cementitious Materials

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Haoliang Huang ◽  
Guang Ye
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Elastic Modulus ◽  
Cementitious Materials ◽  
Self Healing ◽  
Negative Effects ◽  
Numerical Studies ◽  
Healing Efficiency ◽  
The Impact ◽  
Positive Effect

In this research, self-healing due to further hydration of unhydrated cement particles is taken as an example for investigating the effects of capsules on the self-healing efficiency and mechanical properties of cementitious materials. The efficiency of supply of water by using capsules as a function of capsule dosages and sizes was determined numerically. By knowing the amount of water supplied via capsules, the efficiency of self-healing due to further hydration of unhydrated cement was quantified. In addition, the impact of capsules on mechanical properties was investigated numerically. The amount of released water increases with the dosage of capsules at different slops as the size of capsules varies. Concerning the best efficiency of self-healing, the optimizing size of capsules is 6.5 mm for capsule dosages of 3%, 5%, and 7%, respectively. Both elastic modulus and tensile strength of cementitious materials decrease with the increase of capsule. The decreasing tendency of tensile strength is larger than that of elastic modulus. However, it was found that the increase of positive effect (the capacity of inducing self-healing) of capsules is larger than that of negative effects (decreasing mechanical properties) when the dosage of capsules increases.

Effect of Various Supplementary Cementitious Materials on Early-Age Concrete Cracking

2020 ◽  
Vol 32 (4) ◽  
pp. 04020049
Author(s):  
Inamullah Khan ◽  
Tengfei Xu ◽  
Mohammad Shakhaout Hossain Khan ◽  
Arnaud Castel ◽  
Raymond Ian Gilbert
Keyword(s):  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Early Age ◽  
Concrete Cracking ◽  
Early Age Concrete

scholarly journals Self-Healable Supramolecular Vanadium Pentoxide Reinforced Polydimethylsiloxane-Graft-Polyurethane Composites

Polymers ◽  
2018 ◽  
Vol 11 (1) ◽  
pp. 41 ◽  
Author(s):  
Ali Berkem ◽  
Ahmet Capoglu ◽  
Turgut Nugay ◽  
Erol Sancaktar ◽  
Ilke Anac
Keyword(s):  
Tensile Strength ◽  
Vanadium Pentoxide ◽  
Coupling Reaction ◽  
Optical Microscope ◽  
Mechanical Tests ◽  
Healing Time ◽  
The Self ◽  
Supramolecular Polymer ◽  
Self Healing ◽  
Healing Efficiency

The self-healing ability can be imparted to the polymers by different mechanisms. In this study, self-healing polydimethylsiloxane-graft-polyurethane (PDMS-g-PUR)/Vanadium pentoxide (V2O5) nanofiber supramolecular polymer composites based on a reversible hydrogen bonding mechanism are prepared. V2O5 nanofibers are synthesized via colloidal route and characterized by XRD, SEM, EDX, and TEM techniques. In order to prepare PDMS-g-PUR, linear aliphatic PUR having one –COOH functional group (PUR-COOH) is synthesized and grafted onto aminopropyl functionalized PDMS by EDC/HCl coupling reaction. PUR-COOH and PDMS-g-PUR are characterized by 1H NMR, FTIR. PDMS-g-PUR/V2O5 nanofiber composites are prepared and characterized by DSC/TGA, FTIR, and tensile tests. The self-healing ability of PDMS-graft-PUR and composites are determined by mechanical tests and optical microscope. Tensile strength data obtained from mechanical tests show that healing efficiencies of PDMS-g-PUR increase with healing time and reach 85.4 ± 1.2 % after waiting 120 min at 50 °C. The addition of V2O5 nanofibers enhances the mechanical properties and healing efficiency of the PDMS-g-PUR. An increase of healing efficiency and max tensile strength from 85.4 ± 1.2% to 95.3 ± 0.4% and 113.08 ± 5.24 kPa to 1443.40 ± 8.96 kPa is observed after the addition of 10 wt % V2O5 nanofiber into the polymer.

Influences of Initial Curing Conditions on the Microstructure of Fly Ash Cement System

2010 ◽  
Vol 168-170 ◽  
pp. 532-536 ◽  
Author(s):  
Guo Li ◽  
En Li Lu ◽  
Peng Wang ◽  
Ou Geng ◽  
Yong Sheng Ji
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Cement Mortar ◽  
Early Age ◽  
Concrete Durability ◽  
Cement Concrete ◽  
Hydration Degree ◽  
Curing Conditions ◽  
Cement System ◽  
C 30

In order to study the influences of initial curing conditions on fly ash (FA) cement concrete durability, fly ash cement samples with 30% replacement ratio were fabricated and cured in water at 10°C, 20°C, 30°Cand 40°C for 3d, 7d, 14d and 28d respectively. Hydration degrees of fly ash at early age were measured using the selective dissolve method. Correspondingly the pore structure and morphology of FA-cement mortar and compared cement mortar were studied by using MIP and SEM methods. Then early age compressive strengths of FA-cement concrete and compared normal cement concrete were tested. Experimental results show that initial curing temperatures and ages are important factors to fly ash early age hydration degree, FA-cement system microstructure, morphology and early age compressive strength etc. High curing temperatures and longer curing time can lead higher fly ash hydration degree, and then higher compressive strength of FA-cement concrete, and make the micro-structures of fly ash-cement system denser.

scholarly journals Encapsulation Techniques and Test Methods of Evaluating the Bacteria-Based Self-Healing Efficiency of Concrete: A Literature Review

2020 ◽  
Vol 62 (1) ◽  
pp. 63-85
Author(s):  
Rahul Roy ◽  
Emanuele Rossi ◽  
Johan Silfwerbrand ◽  
Henk Jonkers
Keyword(s):  
Service Life ◽  
Polymeric Materials ◽  
Cementitious Materials ◽  
Test Methods ◽  
Self Healing ◽  
Load Factors ◽  
Healing Efficiency ◽  
Healing Agent ◽  
Maximum Crack ◽  
Encapsulated Bacteria

AbstractCrack formation in concrete structures due to various load and non-load factors leading to degradation of service life is very common. Repair and maintenance operations are, therefore, necessary to prevent cracks propagating and reducing the service life of the structures. Accessibility to affected areas can, however, be difficult as the reconstruction and maintenance of concrete buildings are expensive in labour and capital. Autonomous healing by encapsulated bacteria-based self-healing agents is a possible solution. During this process, the bacteria are released from a broken capsule or triggered by water and oxygen access. However, its performance and reliability depend on continuous water supply, protection against the harsh environment, and densification of the cementitious matrix for the bacteria to act. There are vast methods of encapsulating bacteria and the most common carriers used are: encapsulation in polymeric materials, lightweight aggregates, cementitious materials, special minerals, nanomaterials, and waste-derived biomass. Self-healing efficiency of these encapsulated technologies can be assessed through many experimental methodologies according to the literature. These experimental evaluations are performed in terms of quantification of crackhealing, recovery of durability and mechanical properties (macro-level test) and characterization of precipitated crystals by healing agent (micro-level test). Until now, quantification of crack-healing by light microscopy revealed maximum crack width of 1.80mm healed. All research methods available for assesing self-healing efficiency of bacteria-based healing agents are worth reviewing in order to include a coherent, if not standardized framework testing system and a comparative evaluation for a novel incorporated bacteria-based healing agent.

Effect of Polyurethane Viscosity on Self-Healing Efficiency of Cementitious Materials Exposed to High Temperatures from Sun Radiation

2018 ◽  
Vol 30 (7) ◽  
pp. 04018145 ◽  
Author(s):  
B. Van Belleghem ◽  
E. Gruyaert ◽  
K. Van Tittelboom ◽  
W. Moerman ◽  
B. Dekeyser ◽  
...  
Keyword(s):  
High Temperatures ◽  
Cementitious Materials ◽  
Self Healing ◽  
Healing Efficiency
Sign in / Sign up

Export Citation Format

Share Document