Experimentally verified atomistic modelling of lime in construction materials

Lead Research Organisation: University of Bath
Department Name: Architecture and Civil Engineering

Abstract

Since antiquity the construction industry has been using lime based binders to manufacture mortars, plasters and renders...Despite this history there is still a lack of fundamental understanding of the hardening processes and how these influence time dependent mechanical properties. In addition dolomitic limes, containing magnesium, exhibit enhanced properties when compared to their pure lime counterparts, however there is limited knowledge of the underlying reasons.

Lime based mortars are ideal candidates to replace cement mortars in many applications where lower strength is an advantage such as new build housing, forms of construction utilising organic fillers such as lime-hemp, and conservation and restoration applications. Indeed lime mortars offer many advantages over cement in terms of moisture permittivity, ability to accommodate movement, self-healing properties and ability to sequester carbon dioxide. Cementious binders are produced at much higher temperatures compared to lime and have large carbon dioxide emissions associated with their manufacture.

Atomistic modelling provides a unique opportunity to probe these mechanisms at a fundamental level thereby elucidating the processes responsible for developing the properties of industrial importance. Many existing and past studies of building lime binders have focused on bulk properties for instance through large scale bulk property testing, whilst not taking into account atom level processes. In recent years the cement industry has employed atomistic modelling of hydrated silicates as a means of understanding material behaviour.

Recent studies have demonstrated that the morphology and composition of a lime crystal can influence the carbonation process, and by association mechanical behaviour. In addition magnesium containing dolomitic limes show improved performance in many respects including strength development. Rate of carbonation is an extremely important issue as this can dictate the speed at which a building can be erected and therefore the associated costs. The ability to improve the carbonation rate and therefore hardening rate through control of composition and morphology will lead to enhanced products with better environmental credentials.

In the first instance this proposal seeks to develop atomistic models to describe the important aspects of lime binder behaviour and validate these against laboratory samples. Atomistic models will generate Raman spectra and X-ray diffraction patterns for direct comparison with experimental measurements. These initial models will then be developed further to investigate firstly carbonation and then time dependent and plastic mechanical properties.

Additionally the research will investigate the underlying reasons for the improved performance observed in magnesium containing dolomitic limes. The project is expected to bring long term benefits to the construction industry over the coming decades. In the shorter term industry will benefit through planned workshops and site visits which will showcase the application of atomistic modelling to lime manufacturers. The project will support the development of enhanced projects through the new knowledge gained.

Planned Impact

The main thrust of this project is to use a combination of experiment and atomistic simulation to give an improved understanding of lime at a fundamental level and to link that understanding to the properties that make limes attractive to the construction industry. Academia, industry and society will benefit from this project primarily through a greater understanding of the way lime behaves in construction materials. In particular the knowledge gained will be essential for the greater exploitation of lime in the future through engineering the crystalline morphology and composition. Understanding of the important processes responsible for movement (creep and shrinkage) and hardening (carbonation) will impact the construction industry through better and more efficient use of lime.

Data from the project will impact the policy makers responsible for building regulations by allowing standards to be based on our scientific results for lime mortars. A greater understanding of the hardening and movement characteristic will impact thin wall construction by providing quantitative information to architects and engineers relevant to the prediction of long term behaviour from fundamental materials properties. The proposal will impact the conservation and restoration industries who exploit lime for its vapour permeable properties.

A significant impact of the project will be guidance for material specifications issued by the manufacturers. The greater depth of knowledge of lime carbonation behaviour will impact long term durability by promoting the optimisation of these materials. This will thereby support government targets to reduce the use of materials with high embodied energy such as Portland cement. The atomistic models developed during the project will provide a foundation upon which more complex models to address important issues such as the influence of ions leached from low embodied energy and waste materials can be based. Such materials include pulverised fuel ash, ground granulated blast furnace slag, silica fume and organic fillers such as hemp. Lime displays a propensity to react with airborne pollutants such as sulphur dioxide. The atomistic models developed will provide the foundation needed not only to model such interactions on the surface of buildings, for instance in a lime render, but also to inform upon surface reactions of industrial flue cleaning materials. Under polluted conditions dolomitic lime can display increased reactivity and this project will contribute towards elucidating the role of magnesium.

The post-doctoral researchers working on the project will gain valuable experience of the experimental and modelling techniques in addition to experience attending and presenting at conferences. The large amount of publishable data expected to be generated from the project will provide opportunity for the post-doctoral researchers to gain experience in writing technical reports and for journal publication. The project investigators who, between them, are professional members of the Institute of Materials, Minerals and Mining (IOM3) and the Royal Society of Chemistry (RSC) will provide relevant training and support on continuing professional development (CPD). Such activities will be appropriate for progression through these institutions, or similar. Provision to allow each PDRA, to attend post-doctoral training courses (as appropriate), will provide an enhanced research and development environment.
 
Description This research has focused on the application of atomistic modelling and experimental studies to understand the carbonation process in lime based construction materials. In addition to construction lime is used in a variety of other applications including ground stabilisation, air pollution control, water treatment, sugar production and the manufacture of products for cosmetics and paints. Carbonation is of great interest to scientists studying climate change as it involves locking-up carbon dioxide which is a well-known greenhouse gas. Our research has provided an in-depth understanding of the carbonation mechanism using a new methodology we developed during the project which is based on isotopically labelled calcium hydroxide. Many building conservators have highlighted dolomitic lime (containing magnesium) as being superior when compared to pure calcium lime. Using our experimental and computational methods we were able to confirm that under thermal decomposition dolomite phase separates into lime and periclase. These findings indicate that only pure phases need be considered and that for the construction industry, superior artificial mortars should be obtained from mixing fine powders of pure magnesium and calcium hydroxide.
Exploitation Route This proposal aimed to achieve a step change in the application of atomistic modelling to lime based materials in the construction industry. The project objectives were met through the following work packages. (WP1) To prepare and evaluate the structural and physical properties of single and mixed cation hydroxide and carbonate lime phases. Our initial investigations of mixed cation hydroxides highlighted a phase separation mechanism. This led to a computational study to resolve the composition of dolomitic lime, a naturally occurring hydroxide containing calcium and magnesium cations. We have highlighted a novel approach to the verification of atomistic models with experimental studies. These findings might be taken forward by manufacturers developing artificial lime mortars with superior properties. (WP2) Develop atomistic models and verify against structural and physical data. Following the development of a novel methodology employing isotopically labelled oxygen we were able to apply density functional theory (DFT) to elucidate the carbonation mechanism. Importantly, we were able to prove that hydroxide ions originating from calcium hydroxide react directly with aqueous carbon dioxide. This is contrary to popular thought which assumes that the hydroxide ions originate from the water, in fact this is better described as a second stage in the carbonation process. Our unique approach could be adopted in industrial applications including construction, geological disposal repositories for nuclear waste, and green technologies for carbon capture. (WP3) Investigate kinetics of carbonation at an atomistic level. Prior to developing the kinetics we realised that the thermodynamics were also poorly described and hence focused on ensuring that we had accurate thermodynamic data of the carbonation process. We were able to develop a phase diagram generation strategy using ab initio thermodynamics for the MgO-CO2-H2O system. A significant outcome was the ability to identify metastable phases allowing a deeper integration of experimental measurements and modelling. Atomistic models were complimented through study of kinetics using atomic force microscopy. Our novel methodology allowed accurate measurement of carbonate build-up on the surface of Portlandite and interestingly evidence of accelerated dissolution in material believed to be poorly crystalline. This work may be taken forward by nanolime consoloidant manufacturers who are interested in controlling the carbonation process through modifying crystal morphology. (WP5) Field testing of limes for comparison with atomistic modelling. We have developed a number of tests to evaluate the efficiency of nanolime for the consolidation of weathered stone. Environmental factors on site such as humidity, temperature and carbon dioxide in addition to stone morphology and severity of weathering influence the carbonation process and thus benefits of the treatment. Our findings have shown how laboratory based experimental studies and atomistic modelling can reveal the underlying mechanism of carbonation and be translated to a real-world example helping to protect and preserve our heritage buildings.
Sectors Agriculture, Food and Drink,Chemicals,Construction,Education,Environment,Manufacturing, including Industrial Biotechology,Culture, Heritage, Museums and Collections

URL https://researchportal.bath.ac.uk/en/persons/richard-ball/publications/?type=%2Fdk%2Fatira%2Fpure%2Fresearchoutput%2Fresearchoutputtypes%2Fcontributiontoconference%2Fpaper
 
Description Many of the heritage buildings in the UK and around the world are built from natural limestone. Application of a treatment designed to consolidate and strengthen the surface is a common remedy. Material compatibility is of key importance, and in the case of limestone, nanolime is of great interest to the conservation sector. Nanolime consists a suspension of calcium hydroxide crystals around 100nm in size which are suspended in alcohol. The stone treatment process involves the deposition of these crystals within the surface of the stone followed by carbonation. The atomistic modelling and experimental work carried out during this project has focused our understanding of the thermodynamics, kinetics and mechanism of the carbonation process. This knowledge has been particularly useful in the interpretation of results from laboratory and field study trials on real stone specimens. A major impact of the work was an International Workshop held in 2015 on the Application of Nano-lime for Consolidation of Weathered Stones held in collaboration with Historic England. The workshop was attended by over 50 practitioners who received and discussed practical advice on the use of nanolime which was informed by the scientific data produced through the EPSRC project. Results of the workshop and grant have subsequently informed an Historic England publication 'Nanolime: A practical guide to its use for consolidating Weathered Limestone'. A further international workshop based on the projects findings was held in 2016, 'Optimising lime in construction materials: from atoms to buildings'. Attended by over 20 academics, industrialists, post-doctoral researchers and PhD students the event showcased the project highlights and facilitated in depth discussion between the attendees with emphasis on the development of project outputs to solve industrial engineering requirements. For example the role of carbonation in purification of sugar.
First Year Of Impact 2015
Sector Construction,Culture, Heritage, Museums and Collections
Impact Types Cultural,Societal,Economic

 
Title An experimental and computational study to resolve the composition of dolomitic lime. 
Description Experimental and computational data. 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
 
Title Data set for Carbonation of Hydrous Materials at the Molecular Level: a ToF-SIMS, Raman and DFT Study 
Description Experimental and computational data to support article: 'Carbonation of Hydrous Materials at the Molecular Level: a ToF-SIMS, Raman and DFT Study'. Includes ToFSims Data, Raman Data from the study of hydration of portlandite containing O18 and computational DFT data using VASP to support the analysis. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
 
Title Dataset related to the paper "Environmental performance of nano-structured Ca(OH)2/TiO2 photocatalytic coatings for buildings" 
Description Dataset related to the paper: "Environmental performance of nano-structured Ca(OH)2/TiO2 photocatalytic coatings for buildings" published in "Building and Environment" in June 2015 
Type Of Material Database/Collection of data 
Year Produced 2015 
Provided To Others? Yes  
 
Description Collaboration with Intertek Wilton Laboratory 
Organisation Intertek
Country United Kingdom 
Sector Private 
PI Contribution We collaborated with Prof Ian Fletcher based at Intertek Wilton Laboratory, The Wilton Centre, Redcar, UK, to investigate the application of time of flight-secondary ion mass spectrometry for the study of the carbonation mechanism of calcium hydroxide. The research team provided isotopically labelled spesimens for analysis and also undertook experimental work at the partners laboratory.
Collaborator Contribution Our partners provided access to a time of flight-secondary ion mass spectrometer and helped design and carry out experiments to elucidate the carbonation mechanism of calcium hydroxide. A large part of this work required the development of a methodology to process and analyse the data produced. Challenges involved the manufacture and commissioning of a glove box to prevent surface contamination.
Impact The collaboration has resulted in a publication, DOI:10.1021/acs.cgd.6b01303.
Start Year 2014
 
Description Euro AFM Forum - June 2016 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The Euro AFM Forum is an excellent opportunity for researchers to share their research results, increase their understanding of AFM technology, and learn from other scientists that have successfully used AFM for innovative solutions in their research in both material and life science disciplines.

•Three days of lecture by international guest speakers
•Poster session and image contest
•Live equipment demonstration / "Ask an Expert"
•Evening program and workshops

We presented our work as a poster and discussed EPSRC research with delegates.
Year(s) Of Engagement Activity 2016
URL http://cms.unige.ch/sciences/physique/euro-afm-forum-june-2016/
 
Description Goldschmidt International Conference 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Spoke in session on Structure, Dynamics, and Reactivity of Mineral-Water and Mineral-Gas Interfaces
Year(s) Of Engagement Activity 2015
URL http://goldschmidt.info/2015/
 
Description Innovation in Low Carbon Cement and Concrete 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Sponsored under the Newton Fund Researcher Links scheme, University College London (UCL) and China
Building Materials Academy (CBMA) are jointly hosting this workshop on the theme related to low-carbon
cement and concrete in University College London between 21st - 24th September, 2016. This workshop is
aimed to create a platform where the early career researchers can be mentored by established researchers
to speed up their career development and also to bring together the communities from cement chemist,
concrete technologist, engineers and physicists from both academic and industrial background from the UK
and China to share their latest research outcome and innovations in order to promote industrial application
of low-carbon cement and concrete in real world.

In the next three days, 40 oral presentations and 14 posters will be presented by senior researchers and,
mostly, early career researchers from both the UK and China. Two additional sessions have been purposely
designed to facilitate the career development of our young researchers.

Presentation Given by Dr Giovanni Pesce

Atomistic Modelling for Low-carbon Cement and Concrete Technologies
Year(s) Of Engagement Activity 2016
 
Description International Workshop on the Application of Nano-lime for Consolidation of Weathered Stones 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Many of the heritage buildings in the UK and around the world are built from natural limestone. These stones are susceptible to a range of mechanisms which result in damage and deterioration of the surface. Both weathering and environmental factors, including atmospheric pollutants, can lead to significant increases in porosity and mechanical weakening. Application of a treatment designed to consolidate and strengthen the surface is a common remedy, however there are numerous examples of inappropriate use of incompatible treatments leading to greater damage. Material compatibility is of key importance, and in the case of limestone, nanolime is of great interest to the conservation sector. However a lack of knowledge into its long term performance means there is no reliable guidance for its appropriate use.
The workshop was attended by over 70 representatives from organisations working in conservation in the UK. This was an effective opportunity to disseminate the research directly to practitioners and ensure immediate impact of the most important findings. The direct impact is a reduced risk of buildings being subjected to harmful practices leading to subsequent damage.
Year(s) Of Engagement Activity 2015
 
Description International workshop on a Molecular Understanding of Crystal Growth 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The aim of this meeting is to bring together experts in crystal growth from both experiment, theory and computation for a discussion regarding the molecular mechanisms of crystal growth.

Talk given on Atomistic simulation of hydroxylated mineral surfaces in aqueous conditions
Year(s) Of Engagement Activity 2016
URL https://nanochemistry.curtin.edu.au/local/docs/gulp/
 
Description LIME BASED MATERIALS IN CONSTRUCTION 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Talk generated a number of questions directly related to the EPSRC project. A greater awareness of lime was brought to the audience.

Following the talk a great interest was shown in developing a collaborative project to strengthen interational links between Indonesia and the UK.
Year(s) Of Engagement Activity 2014
 
Description Nanolime: update on current research 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Talk presented at the
THE BUILDING LIMES FORUM
2014 CONFERENCE & GATHERING
Friday 5 - Sunday 7 September
Bath and Wells, Somerset

Great interest was stimulated in the large international audience.
Year(s) Of Engagement Activity 2014
 
Description Optimizing lime in construction materials: from atoms to buildings 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact An international workshop was held. Presentations were given by academics and industry representatives. The focus of the meeting was application of atomistic modelling to industrial processes involving carbonation.

Presentations included:-

Dr Richard Ball - Dept. of Architecture and Civil Engineering, University of Bath, UK
Introduction/overview of workshop

Prof Steve Parker - Dept. of Chemistry, University of Bath, UK
Overview of atomistic modelling

Dr James Grant - Dept. of Chemistry, University of Bath, UK
Atomistic modelling applied to lime-based materials

Dr Charles Fentiman - Shire Green Roof Substrate Ltd, UK
Green roof substrates with lime-rich secondary aggregates

Mr Simon Wones - British Sugar, UK
Carbonatation as purification in the sugar industry

Prof Özlem Cizer - Building Materials and Technology Division, KU Leuven, BE
Fundamental insights into lime mortar carbonation and its biocatalyzation

Dr Gianluca Pesce - University of Northumbria, UK A mechanistic study of carbonation using 18O labelled calcium hydroxide
Year(s) Of Engagement Activity 2016
 
Description Visit to Bath Royal Literary and Scientific Institution 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach Local
Primary Audience Schools
Results and Impact School children were encouraged to develop their own small research project.

School children will invistigate environmental pollution issues and the impact on buildings.
Year(s) Of Engagement Activity 2014
 
Description Workshop on molecular modelling of hydroxylated mineral surfaces 
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 A workshop on molecular modelling of hydroxylated mineral surfaces, where the underlying theory was described and the students were given training in using key pieces of software by following prepared exercises.
Year(s) Of Engagement Activity 2016
 
Description Young Researchers Project 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact This is a 8 month project aims to enable young people (13+yrs of age) to learn from and with University of Bath doctoral students and post doctoral research associates: 1) what it is like to be a researcher by completing a meaningful research project of their choosing and design; 2) develop their ability to enquire in a disciplined and creative scientific manner; 3) improve their observation, presentation and communication skills. Participants attend monthly meetings, every 2nd Saturday in the month, work on their research in between times, produce a research poster, present it at a conference and contribute to a publication about the BRLSI Researchers project.
Year(s) Of Engagement Activity 2015
URL http://www.brlsiyouthgallery.org/brlsi-researchers/brlsi-young-researchers-2015-2016/