A Novel Method for Assessing Cracking Tendency of Concrete at Early Ages

Lead Research Organisation: Brunel University
Department Name: Mech. Engineering, Aerospace & Civil Eng

Abstract

Concrete is the most widely used construction materials in the world with more than 1 m3 of concrete being produced every year for every person on the planet. However, concrete has much lower tensile strength than compression strength and, therefore, is easy to crack under normal service conditions. Cracking in concrete can reduce load carrying capacity and may lead to premature deterioration. In the case of reinforced concrete, cracks reduce overall durability of structures by allowing the penetration of water and aggressive agents, thereby accelerating the deterioration of reinforcing steel. Corrosion of the reinforcing steel in concrete structures such as motorway bridges, buildings and marine installations costs the UK an estimated 550m per year according to Building Research Establishment. Most of these structures continue to require extensive maintenance or replacement. Over the years, engineers have sought to develop simple tests to assess how susceptible a given concrete mixture may be to cracking. Currently, there are three main test methods for assessing cracking potential of concrete mixtures: the ring, the beam and the plate tests. Though the circular ring test has become a standard method, it has very low cracking sensitivity, making it very time-consuming and not cost effective. Besides, cracking can appear anywhere along the circumference of a circular ring specimen, making it very difficult to be located. On the other hand, it has been found difficult to provide a constant restraint and end condition for the beam and plate tests, making their applications very limited.In this project, we will develop a new test method by using elliptical ring specimens to assess cracking tendency of concrete mixtures. Compared to circular ring specimens, the elliptical ring specimen can lead to a higher stress concentration and increased cracking sensitivity, making the elliptical ring test method less time-consuming and more efficient. Besides, due to stress concentration, the location of cracking will concentrate on predictable positions along the circumference of an elliptical ring specimen, thus making it much easier to be detected. The elliptical ring test is therefore helpful for determining the relative likelihood of cracking of concrete mixtures in a much shorter period and for aiding in the selection of concrete mixtures that are less likely to crack before they are used for construction projects. We will also establish a theoretical model to provide design engineers with a tool to predict cracking potential of various concrete mixtures. The theoretical model will be able to predict when and where crack will occur in a concrete elliptical ring specimen. We will also explore the effects of specimen size/geometry and the degree of restraint on shrinkage cracking of concrete to provide the guidance on choosing the geometries of both the elliptical concrete ring specimen and the restraining steel ring for estimating cracking tendency of concrete in the field.Dissemination of the findings to the academic community will be made by quality journal papers and presentations at prestigious conferences. The technique explored in this research will be transferred to the construction industry through technical seminars organized by the project partners through their network, articles published in magazines of the concrete industry, the project website and consultancy service. We will also present our findings obtained from this project to relevant standard organisations, particularly the European Committee for Standardization (CEN), for possible recommendation as a standard test method for estimating cracking tendency of concrete mixtures.

Planned Impact

The economic and societal beneficiaries of this project can be classified into three broad categories: (1) the construction sector including concrete producers and users; (2) the public sector bodies such as the UK Highways Agency (UKHA) and Department for Transport (DfT); and (3) the standards organisations such as the European Committee for Standardization (CEN). Impact on the construction sector: more efficient use of materials, reduced project cost and increased project sustainability credential. The premature deterioration of concrete structures caused by cracking is a major and growing world-wide problem. Cracking in concrete may be of significant concern with regard to durability, watertightness or hazardous waste containment. This project will provide the construction sector with a fast and reliable test method for determining the relative likelihood of cracking of concrete mixtures and help the construction industry to make the right decision in the selection of concrete mixtures that are less likely to crack in service. A consequence of these will be reduced project life costs, longer service life of structures, more efficient use of resources for construction, potentially shorter construction periods, less construction waste generated, reduced negative environment impact from construction and increased project sustainability credential. Impact on the public sector bodies: enhanced infrastructure safety and effectiveness of public transport services. Many of our infrastructures are made of concrete and cracking is one of the main reasons that cause deterioration of concrete infrastructures. Repairing cracking of concrete could bring a big burden to our economy. In most developed countries, including the UK, around 50% of the construction budget is devoted to repair and maintenance of structures with over 30% of this expenditure on concrete structures. Traffic delay costs due to inspection and maintenance programmes are already estimated to be between 15%-40% of the construction costs. Moreover, the efficiency of the public transport service will be reduced and the service may have to be temporarily shut down during the repairing and maintenance periods. In a sustainable society we want to use many of our infrastructures effectively for a long time. It is therefore evident that test procedures and predictive models are required such that cracking potential of concrete which ensures long-term durability can be determined before it is used for an infrastructure. The findings of this project will enable the public sector bodies, such as the UKHA and DfT, to be able to assess quality of concrete used for public projects, such as highway bridges, so that to enhance the safety of our infrastructures, to reduce project life cost and possible traffic delay caused by repairing and maintenance. Hence the findings of this research will help to improve infrastructure health and safety and to enhance the efficiency of public transport service to the general publics. Impact on standards organisation, i.e., CEN: filling in the gap in technical service to better meet industry needs. Currently there is no existing European or British standard for estimating cracking potential of concrete. Our economy is now knowledge-based in which technical standards are becoming very important components. The new test method has great advantages over those standard methods recommended by ASTM and AASHTO. Incorporating this method into European standards can fill in the technical gap so that to facilitate the CEN to provide better technical service to meet industry needs. Thus it will place the European and the UK consultant firms and contractors at the fore front of technology and help them to win contracts in global markets. Therefore, this research will help to foster the economic competitiveness of the Europe and the UK.

Publications

10 25 50

 
Description We have discovered the ASTM/AASHTO circular ring test does not necessarily serve the purpose as they claim. We propose to use the elliptical ring test developed by this award from EPSRC to replace ASTM/AASHTO circular ring test for assessing cracking tendency of concrete and other cement-based materials. We have also developed damage and fracture models for simulating the behaviour of concrete in restrained elliptical ring test. We have deduced equations for calculating degree of restraint by elliptical ring geometry for assessing cracking potential of concrete. Through our research we summarize guides to select ring geometry to mapping concrete in the field for assessing cracking tendency of concrete in a real structure. Our recent research has revealed that the restraining effect to the ring specimens consists of two parts: (1) external restraining effect which comes from the internal steel ring; and (2) the self-restraining effect which comes from concrete ring itself due to its closed shape. We have discovered that it is necessary to differentiate these two types of restraining effects in order to interpret ring test results as the test was designed to be. The purpose of the ring test is to assess cracking tendency of concrete under external restraining effect. There is a need to take the self-restraining effect from the overall restraining effect so that the external restraining effect is explicitly figured out. The current interpretation of ring test results in AASHTO and ASTM mix the two types of restraining effects which should be corrected. Cracking in concrete rings may not be caused by external restraining effect rather in some cases self-restraining effect. Our further studies and publications in 2018/19 have revealed that the effect of moisture and drying condition on the cracking behavior of concrete in a restrained ring test. Crack initiates at the outer circumferential surface and propagates towards the inner surface when dried from the outer circumferential surface. In comparison, crack initiates at the inner circumferential surface and propagates towards the outer circumferential surface when dried from the top and bottom surfaces. This was not taken into account in ASTM/AASHTO standards.
Exploitation Route Our findings have already been used by some researcher as a new and improved experimental method for assessing cracking behaviour of concrete and other cement-based materials as well as effects of individual ingredients on cracking tendency of concrete and other cement-based materials to replace the AASHTO/ASTM ring test method. There are a few groups who are following our research on elliptical ring test. We are now trying to engage technical standard organisation for the possibility to develop a standard test method for assessing cracking tendency of concrete based on the elliptical ring test method developed by us through this project. We have been discussing this with Institute of Concrete Technology (the PI is a member of the Tech & Edu Committee of the Institute of Concrete Technology). Besides, further studies on elliptical ring test is being followed at Dalian University of Technology that is led by Dr Wei Dong and funded by National Natural Science Foundation of China in which the PI is a Co-I of the project. It is the intention of the research team at Dalian University of Technology that they will propose the elliptical ring test as a standard test method for assessing concrete cracking potential to relevant Chinese standard organisations.
Sectors Construction,Education,Transport

 
Description The new and improved method, i.e. elliptical ring test method, has been adopted by industry for assessing cracking tendency of concrete and other cement-based materials. This new test methods has been presented to Institute of Concrete Technology for possible recommendation as a CEN standard. In addition, this new test method has been further explored in a research grant awarded by National Natural Science Foundation of China to the team member Dr Wei Dong at Dalian University of Technology, China, in which I act as an advisor member. It is one of the goals of the research team in China led by Prof Wei Dong that they will present the elliptical ring test method to the relevant Chinese standard organization for possible acceptance as a national standard test method for assessing concrete potential of concrete and other cement-based materials.
First Year Of Impact 2014
Sector Construction,Education,Transport
Impact Types Economic,Policy & public services

 
Description member of Technical & Education Committee of Institute of Concrete Technology
Geographic Reach National 
Policy Influence Type Membership of a guideline committee
Impact The new test method will help contractors to select concrete with less potential to crack. Therefore it helps to enhance the efficiency of using concrete, the secondly used materials just after water, and to reduce waste. Ultimately it will help to enhance the sustainability credential of construction industry.
 
Description A New Framework of High-value Added Zero-waste Recycling of Concrete from Construction and Demolition Waste
Amount £119,527 (GBP)
Funding ID IND/CONT/GA/18-19/24 
Organisation British Council 
Sector Charity/Non Profit
Country United Kingdom
Start 03/2019 
End 02/2021
 
Description Horizon 2020, MARIE Sklodowska-CURIE Actions, Research and Innovation Staff Exchange
Amount € 567,000 (EUR)
Funding ID 645696 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 01/2015 
End 12/2018
 
Description Horizon 2020, NMBP - Energy Efficient Buildings
Amount € 4,996,626 (EUR)
Funding ID 723825 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 09/2016 
End 03/2020
 
Description Royal Academy of Engineering Distinguished Visiting Fellow
Amount £6,000 (GBP)
Funding ID May13DVF023 
Organisation Royal Academy of Engineering 
Sector Charity/Non Profit
Country United Kingdom
Start 05/2014 
End 07/2014
 
Description Royal Academy of Engineering Distinguished Visiting Fellowship
Amount £6,000 (GBP)
Organisation Royal Academy of Engineering 
Sector Charity/Non Profit
Country United Kingdom
Start 08/2016 
End 10/2016
 
Title Comprehensive parametric studies on ring geometry to assist practicing engineers to select the appropriate ring test for assessing concrete cracking in the field 
Description We have conducted a comprehensive parametric studies on ring geometry to assist practicing engineers to select the appropriate ring geometry for assessing cracking of concrete to map their restrained and drying conditions in the field. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
Impact Experiment could lead to high cost that contractors are not willing to adopt the new technology. Through our comprehensive parametric studies based on our validated numerical model, practicing engineers can select the appropriate ring geometry to map the restrained and drying condition of concrete in the field. Therefore it reduces the cost linked to try-and-error and enhance the acceptance of construction industry to adapt the new technology. 
 
Title Finite element based damage model for analyzing cracking initiation of concrete in restrained ring specimens 
Description We have developed a finite element based damage model for analysing cracking initiation of concrete in restrained ring specimens. This model has been disseminated in various publications. It has been used to support a successful grant application to National Natural Science Foundation of China. The grant is held by Dr Wei Dong at Dalian University of Technology, China. 
Type Of Material Computer model/algorithm 
Year Produced 2015 
Provided To Others? Yes  
Impact This model has been used to guide practising engineers to select appropriate ring geometry for mapping the restrained condition of concrete in the field. Therefore it helps to promote the developed elliptical ring test for assessing cracking potential of concrete which is the key objective of this EPSRC award. 
 
Title Finite element based fracture model for concrete in elliptical ring tests 
Description We have developed a finite element based fracture model for analysing cracking evolution in elliptical concrete rings subjected to restraint. This model has been disseminated in various publications and has been used for other follow-on research. 
Type Of Material Computer model/algorithm 
Year Produced 2015 
Provided To Others? Yes  
Impact This finite element based fracture model for analysing cracking evolution in restrained concrete rings has been used for supporting the successful application of a grant from National Natural Science Foundation of China. The grant holder is Dr Wei Dong from Dalian University of Technology, China. 
 
Description Collaboration with Dalian University of Technology, China 
Organisation Dalian University of Technology
Country China 
Sector Academic/University 
PI Contribution We have transfer our knowledge and ideas on elliptical ring test method and numerical models to Dalian University of Technology. We have several joint papers with them published.
Collaborator Contribution Dalian University has successfully applied grant from National Natural Science Foundation of China (NSFC) to continue the research of elliptical ring test (while EPSRC project has finished). We have several joint papers on the research topic.
Impact Journal paper published in Computers & Structures; Journal paper published in Engineering Fracture Mechanics; Journal paper published in Journal of Materials in Civil Engineering; Three journal papers published in Construction and Building Materials; Several conference papers published in relevant conference
Start Year 2012
 
Description Collaboration with Hong Kong University of Science & Technology 
Organisation University of California, Davis
Department Department of Civil & Environmental Engineering
Country United States 
Sector Academic/University 
PI Contribution This research was initiated at Prof Zongjin LI's group at Hong Kong University of Science & Technology when I was a PhD student there. After I left Hong Kong University of Science & Technology, I have been maintain my collaboration with Prof Zongjin Li continuously.
Collaborator Contribution Prof Zongjin LI initiated the original and basic ideas of elliptical ring test which was proposed and implemented to accelerate cracking test for investigation of alkali on early age shrinkage cracking of concrete. The concrete rings were used as a tool while I was the first researcher who studied the mechanism of elliptical ring test for assessing cracking potential of concrete and other cement-based materials.
Impact A Royal Academy of Engineering Distinguished Visiting Fellowship was awarded to Prof Zongjin Li in 2014 which enabled him to visit my team for one month. During his visit, we further discussed the elliptical ring test and planned the new research directions. These led to several publications published by me and other team members.
Start Year 2007
 
Description Collaboration with India Institute of Technology, Madras 
Organisation Indian Institute of Technology Madras
Country India 
Sector Academic/University 
PI Contribution The collaboration just started though I, the PI at Brunel, had already known the PI at IIT Madras. In this project, the Brunel team will bring their knowledge of characterization of concrete cracking via elliptical ring test method and their research on valorization of construction and demolition waste. I will also contribute to project management. The Brunel team will also contribute the study to use the recycled porous particles from waste concrete to capture CO2.
Collaborator Contribution Our Indian partner will contribute to the study of the most economic and environmental friendly separation method for separating waste concrete into (1) authentic course aggregates; (2) sand; and (3) fine cementitious powders based on their previous research. They will also contribute to life-cycle assessment of this new high value added recycling technology of concrete.
Impact So far there is no output or outcome from this collaboration. It is expected a number of high quality journal papers will be published to disseminate the research into academic community. Two knowledge transfer workshops will be organised, one in the UK and the other in India, to disseminate the research outputs into construction industry. In addition, early stage researchers, i.e. PhD students, will be trained under the project framework.
Start Year 2019
 
Description A seminar 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Around 50 postgraduate and senior undergraduate students attended my lecture on the research outputs of this EPSRC award at University of Ji'nan, Shangdong, China on 11th August 2016.
Year(s) Of Engagement Activity 2016
 
Description A talk on elliptical ring test method at University of Jinan 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact I was invited to give a talk on the research of elliptical ring test to a group of academics and postgraduate research students at the Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of Jinan. I was appointed as a visiting professor at the University and jointly published a few papers with colleagues from University of Jinan.
Year(s) Of Engagement Activity 2016
 
Description Seminar at Hunan University 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Around 100 postgraduate students, academic staff and technician attended my lecture on elliptical ring test for assessing cracking tendency of concrete on 10 Jul 2013 at College of Civil Engineering, Hunan University. Discussion was held during the seminar and audience, particularly, postgraduate research students reported the seminar broadened their horizon.
Year(s) Of Engagement Activity 2013
 
Description Seminar at School of Civil Engineering and Architecture, Zhejiang University, China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I gave a seminar on elliptical ring test and simulation which was sponsored by EPSRC to a group of postgraduate research students, researchers and academic staff. Most audience regarded the seminar was interesting and inspired them.
Year(s) Of Engagement Activity 2014
 
Description Seminar at School of Civil Engineering, Dalian Univeristy of Technology, China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I gave a talk on my research sponsored by EPSRC grant as well as other research to a group of postgraduate research students, research staff and academic staff. Most of the audience responded that they were inspired by my talk. There were two postgraduate students decided to do similar research as their degree dissertation project.
Year(s) Of Engagement Activity 2014
URL http://sche.dlut.edu.cn/info/1264/12136.htm