SHE : Self-healing concrete – Its efficiency and evaluation
Technical Committee SHE
Deputy Chair: Prof. Dr. Erik SCHLANGEN
Activity ending in: 2020
Concrete is used world-widely in construction because of its low cost, high compressive strength, good compatibility with steel, and the ease of which it can be designed. However, crack formation is prone to present in concrete structures owing to its low tensile strength, which may lead to a durability problem and may also affect its serviceability. To prevent such deterioration, inspection of cracks and subsequent repair are usually carried out for concrete structures, thus various techniques and methods have been developed. However, continuous inspection and maintenance can be difficult to implement when cracks are not visible or accessible—for example, for underground structures or in the case of infrastructure in continuous service such as highways. Moreover, a considerable amount of labour is required and costs related to repair work may amount to half of the annual construction budget (Cailleux, E, et al., 2009). In contrast, in nature, damage can usually be self-healed. Thus, structures that mimic nature and self-healing could be of great interest and has attracted more and more researchers’ attention. In 2015, a total over 200 papers were presented in 5th international conference on self-healing materials (Proceedings ICSHM 2015) which was normally biannually opened. Also, there have been several review papers published in recent years. de Rooij et al (2013), Wu et al. (2012), Tittelboom & Belie (2013), and Mihashi and Nishiwaki (2012) presented reviews on self-healing in cementitious materials and engineered cementitious composite as a self-healing material.
There have been serval routes developed to achieve self-healing functionality for concrete materials. JCI Technical Committee on Autogenous Healing in Cementitious Materials (Igarashi et al. 2009) proposed a kind of classification of phenomena and definitions of terms on self-healing/repairing concrete, which included (1) natural healing; (2) autonomic healing; and (3) activated repairing. RILEM Technical Committee 221-SHC (de Rooij et al. 2013) proposed a set of evolved definitions by using the terms “autogenic” and “autonomic”. While, there is a lack of a universal healing efficiency and evaluation methods for comparison, which is indispensable for the possible application in practice. Also, these methods mainly belong to healing to some damage occurred in the materials. Few methods are for deterioration of concrete due to reduction of pH value or ion intrusion.
The TC will deal with efficiency and evaluation of self-healing concrete from two points of view, one is self-healing due to damage; the other is self-recovery of protection functionality. The work of the TC should give a recommendation of testing methods for efficiency and evaluation of self-healing concrete. Various methods have been and are being developed in recent years. For the possible application in practice, it is essential to present normal efficiency and evaluation methods.
The scope of the TC will be located in the following three areas:
1. Literature Review
- Investigation of current efficiency and evaluation methods for self-healing concrete mainly due to damage.
- Investigation of current efficiency and evaluation methods for protection functionality self-recovery concrete due to reduction of pH value or ion intrusion.
- Determination of several methods possibly applying to most self-healing approaches as well as to protection functionality self-recovery concrete
2. Efficiency and evaluation for self-healing concrete due to damage
- Laboratory Experimentation for performance in both macro scope and micro scope.
- Numerical Analyse in meso-scope level for evaluation of the testing results.
- Determination of the most appropriate efficiency and evaluation method by evaluating different test methods in different participant laboratories.
3. Efficiency and evaluation for the concrete with protection functionality recovery
- Similar to item 2. Laboratory Experimentation in both macro scope and micro scope; Numerical Analyse and Determination of the most appropriate method.
Terms of reference
An estimation of time necessary should be approximately 4-5 years. The principal tasks of the TC will be divided into 3 task groups (TG) based on the 1. Literature review, 2. Efficiency and evaluation for self-healing concrete due to damage and 3. Efficiency and evaluation for the concrete with protection functionality recovery. More groups could be possibly organized in future based on the necessity and interest.
TG1 –TG1 will carry out literature review mainly on efficiency and evaluation methods for self-healing and protection functionality recovery concrete. State of the art reports will be produced. The reports will serve as the basis for the two groups TG2 and TG3.
TG2 – TG2 will be responsible for the efficiency and evaluation for self-healing concrete due to damage. The laboratory experimentation will focus on for performance evaluation in both macro scope and micro scope. There will also be numerical analyse in meso-scope level for evaluation of the testing results. Through investigation of various methods, several most possibly appropriate ones will be selected for a round-Robin testing in different participant laboratories, then a series of universal methods should be determined.
TG3 –TG3 will be responsible for efficiency and evaluation for the concrete with protection functionality recovery. Similar to TG2, The laboratory experimentation will be carried out in both macro scope and micro scope. Numerical analyse in mesoscope level will also be implemented. And for determination of universal methods, a round-Robin testing will be carried out.
The scope of the membership of the TC includes academics, post graduate students, and researchers around the world. (Europe, USA, Japan, Korea, Singapore, China et al.)
Detailed working programme
General TC: A kick-off meeting will be organized in October 2016 in Shenzhen, China. The meeting will be among the committee members and other interested parties to determine the available expertise, competencies and abilities of the committee. The leading members for the TGs will be decided with one chair for each group. The TGs will also be assigned secretaries from the midst of the committee with TG1 being assigned two (responsible to each subgroup) and TG2 along with TG3 being assigned one each. These assignments will be subject to change based on change in availability or priority.
TG1 Literature Review – The literature review will be the first task of the committee and will be along with other TGs research work in approximately 2 to 3 year. The state-of-the-art reports will cover current and future efficiency and evaluation methods for self-healing and protection functionality recovery concrete.
TG2 Efficiency and evaluation for self-healing concrete due to damage. This group will be divided into two subsidiary groups: 1. One is for experimentation. 2. The other is for numerical analysis. This group will begin with a meeting to discuss the possible work by different participate laboratories. The preliminary work of this group is expected to begin several months after the first TC meeting and continue for the length of the project.
TG3 Efficiency and evaluation for the concrete with protection functionality recovery. Similar to TG3, This group will also be divided into two subsidiary groups:
1. one is for experimentation.
2. The other is for numerical analysis. This group will also begin with a meeting several months after the first TC meeting and continue for the length of the project.
The intermediate goal is to obtain a number of methods for round-robin testing based on literature surveying. The final goal is to give a recommendation of a series of the most suitable evaluation method for self-healing and protection functionality recovery concrete based on experimentation and numerical analysis.
The TC is a successor of RILEM TC 221-SHC chaired by Prof. Erik Schlangen , which studied “Self-healing phenomena in cement-based materials”, completing their work in 2013. Some members of this committee will be solicited to participate in the current one, or to provide their expertise.
The TC will be parallel to RILEM TC “Self-Healing of Asphalt Pavement Materials (SHAPM)”, chaired by Hassan Baaj, which will mainly focus on Asphalt Pavement Materials. Also Prof. Erik Schlangen will serve as Secretary in the TC.
The proposed TC will mainly focus on efficiency and evaluation for self-healing concrete due to damage and for the concrete with protection functionality recovery.
The proposed TC coincides well with the mission of RILEM in terms of:
- “The mission of the association is to advance scientific knowledge related to construction materials, systems and structures” since self-healing concrete should be a sustainable construction material, and would provide superior performance in service-life from durability point of view. It is new and the relevant research will largely advance development of science and technology.
- “and to encourage transfer and application of this knowledge world-wide.” The members of this RILEM TC are from worldwide, such as Europe, USA, Japan, Korea, Singapore, China et al. It will promote international cooperation on the development of self-healing concrete. A universal evaluation method will be recommended, which will largely advance the application of self-healing concrete technology in practice.
The TC will deliver state of the art reports on the subjects of efficiency and evaluation methods for self-healing and protection functionality recovery concrete which includes experimentation and numerical analysis.
The TC will recommend an efficiency and evaluation method based on the experimental study using round-robin testing and numerical analysis. The method could be universally used to appraise the self-healing efficiency of concrete.
A workshop will be organized in the intermediate stage and an international symposium will be organized close to the end of this project.
Group of users
Academics, postgraduate students, and researchers on concrete, and standardization committees, testing laboratories, concrete manufacture companies and government will be targeted by the outcomes of the TC.
Specific use of the results
The biggest challenge of human-beings in 21th century is the sustainable development (i.e. economy in harmony with social and ecological development). The shortage of resources, energy consumption and harmful emission form the key issues to be urgently solved by global people. On the other hand, environmental actions make the civil works prematurely unserviceable, as a result, being repaired and strengthened in order to fulfil their safety and serviceability functionalities. It is desired to have a structure with a service life as long as possible to compensate the negative consequences from sustainability and durability issues. The self-resilience system for concrete (including self-healing and self-recovery) is regarded as an advanced and efficient way to deal with the above-mentioned global problem. With the outcome of the Rilem TC, it will be helpful to promote this wonderful method being able to apply in practice in a more efficient way.