Advances and Developments in Self-Responding Construction Materials K EVIN PA INE U N IVERSITY OF BATH 1
2013-2016 2017-2022 2
Current situation Infrastructure materials crack: shrinkage, thermal effects, freeze/thaw & other causes. Cl - CO 2 SO - 3 Therefore our infrastructure invariably requires repair and maintenance.
Current Situation Economic Structural repair & maintenance Social Traffic congestion Environmental Cl - Cement production Cost: 50 bn /year 10% UK traffic congestion 5-7% global CO 2 emissions ½ UK s construction budget spent on infrastructure repair & maintenance Repair ineffective EU: 20% fail in 5yrs, 55% in 10yrs, most in 25yrs Current design material degradation repair cycles
2050 Vision for Self-Responding Biomimetic Materials 2022 A sustainable and resilient infrastructure containing smart materials and structures that: Self-regulate Adapt Repair without external intervention. A transformation in self-healing of construction materials through: A biomimetic approach in which the material self-controls its own diagnosis and healing Evolution of next generation healing systems that cover diverse and complex damage and deterioration scenarios. RESILIENT MATERIALS 4 LIFE
Self-Responding Biomimetic Materials Conventional concrete Self-sensing concrete Sensing Reasoning Self-diagnosing concrete RESILIENT MATERIALS 4 LIFE Self-healing concrete Controlling Adapted from: Han et al (2015) DOI: 10.1177/1045389X15586452
Self-Healing in Cementitious Systems De Rooij et al. (2013) Self-healing phenomena in cement based materials. Springer. Souza (2017). PhD thesis. University of Cambridge.
Materials for Life: Vision & Structure Aim: Development of a temporal and multi-scale self-healing cementitious system Description of damage Healing systems Institutions Structural defects e.g. vacancies due to dissolution or calcium leaching Dislocations between CSH particles Dislocations within the CSH matrix and Ca(OH) 2 crystals Nano / Micro scale healing using microcapsules Micro cracks coalesce to form larger meso cracks. Debonding between aggregate particles and cement matrix Micro / Meso scale healing via bacterial action Continuous macro cracks (visible cracking) Macro / Meso scale healing via vascular flow networks Crack prevention via shape memory polymers
(1) Microencapsulation Mechanical Trigger Damage Control Chemical Trigger Damage Prevention
Microcapsules Cargoes Shells Release mechanisms Cyanoacrylates Urea formaldehyde Cracking Epoxy resins Calcium alginate Cl ion concentration Silicons Gum Arabic-gelatine Reduced ph Alkali-silica solutions Sodium Silicate Polyacrylates Polyurethane Tetraethyl orthosilicate (TEOS) Magnesia
Gum/Arabic shell microcapsules with sodium silicate core Polyurea microcapsules with sodium silicate core microfluidics Monodispersed acrylate microcapsules Surface functionalized monodispersed acrylate microcapsules De Belie et al (2018) DOI: 10.1002/admi.201800074
Microcapsules Concerns: Compatibility within matrix (as with new admixtures) Long-term stability of healing agent Handling safety (with some acrylate) Technical challenges: Optimising the cargo content Repeatability of healing for multiple physical damage Developing effective microcapsules for chemical damage Scale-up of the more tailored manufacturing processes
(2) Use of bacteria Calcite-precipitating bacteria embedded in concrete with calcium-based precursor Precursor e.g. calcium lactate (CaC 6 H 10 O 6 ) Spores from Alkali-resistant Bacteria Nutrients C, N and P CaC 6 H 10 O 6 + 6O 2 CaCO 3 + 5CO 2 + 5H 2 O Calcium Lactate + Oxygen Calcium Carbonate + Carbon Dioxide + Water The CO 2 can react with CaOH 2 to give more CaCO 3
Bacterial healing Normal mortar Mortar + encapsulated calcium Mortar + encapsulated calcium + spores Alazhari et al (2018) DOI: 10.1016/j.conbuildmat.2017.11.086
Complex biology-concrete technology interface Concerns: Leaching/release of bacteria (particular concern in the water industry) Health and Safety implications Technical challenges: Use in non-ideal conditions (influence on selected bacterial species) Demonstrate repeated spore forming cycles of the bacteria Optimise nutrient delivery techniques
(3) Flow networks Toohey, K.S., Sottos, N.R., Lewis, J.A., Moore, J.S. and White, S.R. (2007). Nature Materials, 6, pp. 581-85.
Flow Networks: - Creation of flow networks within beams & slabs -Delivery mechanism for healing agents & bacteria Flow networks
Flow networks Concerns: Might weaken concrete/cause cracks Difficult to install Allows water ingress Technical challenges: Improved flow network formation procedures Healing agents, their longevity and compatibility with the cement matrix Incorporating pressurised reservoirs for repeated healing events
(4) Crack closure via SMP What is a SMP? shape memory polymers polymer with ability to revert to original shape upon activation SMP tendons Steel reinforcement Autogenous healing enhanced by crack closure Cracks prevented or limited to small widths 3D SMP matrix Cracks form after loading Variant I - Crack Closure Tendons activated to close crack Tendons activated before mechanical loading Tendons activated before mechanical loading Variant II - Crack Prevention Variant III Tri-axial Confinement
cracked after polymer activation Jefferson et al, Cement and Concrete Research, V.40, 2010, pp795-801
SMP Concerns: Difficult to fit Longevity of system (inc. electrical activation) Compatibility with cement chemistry Over compression of zones under applied loads Technical challenges: Robust activation system Optimise form of polymer (grid/strand/tendon/fibre) for different applications
Site Trial A465 Heads of the Valleys Section 2: Gilwern to Brynmawr http://a465gilwern2brynmawr.co.uk/ Main contractor: Costain 200M 8.1km in length
Site Trial: Contents
Site Trial: Construction Photos
Site Trial: After Casting Reaction wall Each Panel: 1.85m height 1.00m wide 0.15m thick C40/50 Concrete Panel A MC Base slab Panel B SMP+FN Panel C Bac. +FN Spare Panel Panel D Control Panel E FN
Site Trial: Testing and Monitoring Displacement monitoring Displacement of trial panel & reaction wall using pole-mounted LVDTs Loading through pre-stressing bar Load applied using jack & monitored through load cell Monitoring of external face Crack width & strain monitoring using LVDTs, DIC & optical microscopy Unloading & repeat loading Monitoring over 6 months followed by final loading
Site Trial: Outcomes Outcome SMP & flow networks Panel Microcapsules Bacteria Crack healing (load regain) Crack closure / sealing Logistics & construction challenges Feasibility Future research & development Upscaling production Construction sequence Controls to put in place Cost & time Healing efficiency Resilience Current issues How to improve system EPSRC Programme grant
Resilient Materials for Life (RM4L) EPSRC Programme Grant, 2017-2022
Resilient Materials for Life (RM4L) Self-diagnosis cracks (wounds) chemical attack (infections) ageing (senescence) cyclic damage (RSI) Self-healing RESILIENT MATERIALS 4 LIFE
Self-Responding Biomimetic Materials Conventional concrete Self-sensing concrete Sensing Reasoning Self-diagnosing concrete RESILIENT MATERIALS 4 LIFE Self-healing concrete Controlling Adapted from: Han et al (2015) DOI: 10.1177/1045389X15586452
RM4L Project Plan
NCE Technology Leader - Winner Costain Fiatech Award ICE Wales Award CNBC Interview Thank you Science Festival 2014 Winner research most likely to change the world CNBC Interview www. rm4l.com twitter @materials4life