8. Infrastructural and Environmental Nanostructures Repetition from the Last Lecture • Diamond and graphite – which of these materials is a conductor? • What is the name of the carbon-bonding orbital in the graphene plane and what is the name of the orbital perpendicular to the graphene plane. • What are spherical carbon molecules called? • What is the name of the vector that determines the type of electrical conductivity of nanotubes? • Name at least 3 applications of graphene. The Most Commonly Used Material in Infrastructure – Concrete • Concrete – a composite material consisting of aggregate, binder, water and various additives and admixtures • When cured, it forms a solid artificial conglomerate/composite. • The most common is cement concrete – the binder is cement and the filler is aggregate, all bonded together using water. • Another option is asphalt concrete used for road construction. • The first use of cement concrete is in ancient Rome – the binder is pucolán – volcanic cement. https://cs.wikipedia.org/wiki/Beton Concrete Strength • Concrete is a very strong material in compression • Composite – very brittle and non-deformable filler (stone, sand) and easily deformable binder (cement paste – cement, water, air) • The result is a composite that is also very brittle – linear and very rapidly increasing stress/strain curve L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX Load - Tension L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX Porosity • Porosity makes crack propagation easier; we want to get rid of it • An important characteristic of concrete is the ratio of water to cement, typically 0.35 • At a given water ratio, we can significantly increase the strength of concrete by adding silica fume (microsilica) to reduce porosity, thicken the concrete + SiO2 + CaOH reaction which leads to further cement paste formation L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX https://en.wikipedia.org/wiki/Silica_fume Aggregate and Binder Interfaces • The interface between aggregate and binder is the weakest link in concrete • It is highly porous and permeable • Contains CaOH, which can be a by-product of the hydration reaction • Nanoscale silica fume both fills the pores and prevents the formation of CaOH (Pozzolanic reaction) L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX Additional Nano-Additives to Improve the Interface • Nano TiO2 • Serves as a nucleating core for cement hydration products • Improves volumetric hydration and hardens the bonding matrix, ideal concentration 1% • Carbon nanotubes and graphene oxide • Matrix reinforcement and improved material bending properties • Uniform dispersion is key, which is complicated L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX Effect of Nanomaterials in Concrete Drying • As the cement cures and dries, its volume decreases – cracks form • Chemical shrinkage – reduction of chemical reaction products of cement, water and aggregates • Autogenous shrinkage (selfdecomposition) – evaporation of water during hardening • Drying shrinkage – drying after the concrete has finished hydrating • Shrinkage by reaction with carbon (CO2) from the external atmosphere L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX https://www.ebeton.cz/pojmy/smrstovani-betonu/ Adding Nanomaterials Can Significantly Prevent Shrinkage L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX Long-Term Durability of Concrete – Problems • Corrosion of steel rods in reinforced concrete • Corrosion due to depassivation of the natural passivation oxide layer on the steel due to lower pH of salt, acidic rainwater, etc. (pH of concrete 12-14) • Red rust has approximately 3 times the volume of iron – expansion and significant cracking of reinforced concrete • Cracks are then further enlarged by freeze-thaw cycles • Other problems – flaking, aggregate strength, alkaline reactions of aggregates, sulfate corrosion http://www.sanacninoviny.cz/wp-content/themes/generous/noviny/2014_27.pdf Long-Term Durability of Concrete – Problem Solving • Reinforcement corrosion • Anti-corrosion coatings for steel reinforcement • Cement matrix thickening with nanoparticles L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX Long-Term Durability of Concrete – Problem Solving 2 • Freezing/melting • n-SiO2, n-Al2O3 – nucleation sites, Pozzolanic reaction • Graphene oxide • Nanoclay (cheap and available) • Scaling • n-SiO2, fly ash L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX Self-Healing Concrete • Autonomous repairs • External force leads to the release of encapsulated material that repairs the crack • One-time use and costly L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX Self-Healing Concrete 2 • Autogenous repairs • Concrete repairs itself, no foreign material is added • The repair cycle can be repeated • (1) Additional hydration of unhydrated cement • (2) Formation of calcite CaCO3 • (3) Recrystallization of portlandite from cement paste (dissolution of Ca(OH)2 and recrystallization) • For a good function you need • Unhydrated cement • Water • Relatively small crack (< 150 mm) – cracks are reduced by the presence of (nano)fibres L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX External and Internal Healing • External healing • The source of water is only on the outside of the material, only the surface layer is healed and cracks can spread inside, for example when the concrete dries • Internal healing • The source of water are the particles inside the material that have bound water to themselves. There is high internal moisture in the concrete. L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX Zeolite – Moisture Carrying Particles • Zeolites are used as water carriers • They have many small nanometre-size pores and therefore a large surface area – high water binding capacity L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX Environmental Nanotechnology • Environmental nanotechnologies are those applied to prevent or reduce damage to an already damaged environment • Damage • Air • Water • Soil https://www.eadarsha.com/eng/environment-damage-behind-1-in-4-global-deaths-disease-un/ Water Protection Technology • Wastewater is generated • From agriculture • Residential • Industry • They can have a very negative impact on human health, as well as the health of animals and plants in the environment https://blogs.worldbank.org/water/wastewater-treatment-critical-component-circular-economy Water Purification Options • Physical • Do not use any chemicals • Chemical Chemicals are added to the water, e.g. for coagulation, neutralisation, absorption and disinfection (chlorine, O3) L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX https://www.thewatertreatments.com/disinfection/chlorinators/ Water Purification Options 2 • Biological • Based on bacteria and other microorganisms that break down organic contaminants through standard cellular processes • Options: Aerobic (normal decomposition ), anaerobic (fermentation), anoxic (composting) L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX Standard Wastewater Treatment Plant • Stirring and clarification of water (coagulation) in tanks • Sedimentation – settling of sludge flakes at the bottom of the tank • Filtration through layers of sand or charcoal • (Aeration and biological processes) • Sterilization and disinfection – chlorine, ozone, UV radiation https://www.saferack.com/wastewater-treatment-plant/wastewater-treatment-process-illustrationv2/ Nanotechnology in Water Purification • Adsorbents • High reactivity and chemical specificity • Functionalized carbon nanotubes (MnO2, Fe3O4, Al, Ag,…) for binding organic pollutants and heavy metals (Cd, Ni, Zn, Pb, ...) • Magnetic nanoparticles for the binding of heavy metals https://link.springer.com/article/10.1007/s11356-016-6457-z Nanotechnology in Water Purification 2 • Membranes for filtration • - nanofibre, nanocomposite, ... • Ideal of carbon nanotubes • Water flows through the hydrophobic interior of the CNT without friction (nanofluidic transport) L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX https://www.sciencedirect.com/science/article/abs/pii/S1226086X1200144X Water Photocatalysis • Radicals generated by photocatalyte illumination decompose typically organic impurities • TiO2, ZnOx L. Lu, Nanomaterials for Civil and Environmental Applications, Purdue, EDX Disinfection and Pathogen Control • For inactivation of various types of microbial pathogens – viruses, bacteria, protozoa, other microorganisms • Current disinfectants such as chlorine, ozone, chlorine dioxide and others work, but have a short reactivity time and produce toxic waste products (about 600 of these are known so far and most are carcinogenic) • Therefore, the use of nanoparticles and nanomaterials is being explored https://link.springer.com/article/10.1007/s11356-016-6457-z Pollution Detection • Pollution detection using nanostructures – high surface area – high reactivity; functionalization – chemical selectivity • Quantum dots, CNTs, gold nanoparticles,... https://www.sciencedirect.com/science/article/abs/pii/S0925400517313916 Air Pollution • Air pollution means the spread of pollutants that are harmful to human health and the planet as a whole. • The top ten most important pollutants: • SO2 • CO • CO2 • NOx • Volatile organic compounds • Particulates • O3 • Chlorinated fluorocarbons • Unburned hydrocarbons • Lead and heavy metals https://link.springer.com/article/10.1007/s11356-016-6457-z https://link.springer.com/ar ticle/10.1007/s11356-016- 6457-z Soil Pollution • Contamination by oil, oils, heavy metals or pesticides • Leads to • Climate change • Loss of soil fertility • Damage to human health • Sources of pollution : • Industrial waste – the worst source of pollution. Chemicals in liquid and solid form. • Deforestation – leaves the land open to environmental influences, plus erosion. • Excessive use of fertilizers and pesticides – killing beneficial microorganisms in the soil, contaminating subsurface water • Landfilling of waste Strategies for Soil Protection • Standard soil treatment technologies are extremely expensive. • The best way is to prevent contamination of the soil with pollutants or at least to prevent their spread by immobilisation. https://www.chacompanies.com/projects/contaminated-soil-remediation-and-management/ Strategies for Soil Protection 2 • Soil remediation – adding nanoparticles to the soil • Phytoextraction – mobilization of pollutants for better adsorption in plant roots and their removal from the soil • Phytostabilization – immobilization of pollutants to keep them out of the food chain and groundwater https://link.springer.com/article/10.1007/s11356-016-6457-z Heavy Metal Remediation https://link.springer.com/article/10.1007/s11356-016-6457-z Conclusion • Infrastructure • Structure, mechanical properties and crack propagation in concrete • Cracks in concrete during drying • Nanomaterial admixtures for improved mechanical properties • Long-term stability of concrete – reinforcement corrosion as a major problem in Czechia • Self-repairing concrete • Environmental technologies • Water • Air • Soil