Periodic Reporting for period 1 - B-SMART (Biomaterials derived from food waste as a green route for the design of eco-friendly, smart and high performance cementitious composites for the next generation multifunctional built infrastructure)
Reporting period: 2018-09-30 to 2020-09-29
Concrete is ubiquitously applied in the built infrastructure with a worldwide growing consumption of over 30 billion tones each year. The concrete construction industries all over the world face enduring challenges as attempting to curb the carbon emissions by 2050. As an essential component of concrete, the Ordinary Portland Cement (OPC) production requires calcination of the raw limestone and clay materials at a high temperature, which releases significant amount of carbon dioxide (CO2) which is responsible for 8-9% of the global anthropogenic CO2 emissions. Because up to date, no alternative cementitious materials on the horizon that are capable of completely substituting the OPC, the production of OPC is forecast to double in the next 30 years to meet the rising global demand. Significant research efforts were targetd at enhancing the performance of OPC-concrete materials to meet the global CO2 emission goal using different organic/inorganic nanomaterials. However, the broad industrial application of these nano-modified concrete materials is currently facing serious challenges for two major issues: first, these nanomaterials exhibit weak dispersion capacity in water solution and cement paste, as such they tend to agglomerate at high concentrations, leading to the formation of micro defects and nonhomogeneous microstructure development in concrete. Second, the nanomaterials are extremely expensive and energy intensive to produce, and particularly pose significant environmental, health and safety risks. Therefore, there is an urgent need to develop low-cost and low carbon foot-print construction materials to enhance the sustainability of the built infrastructure.
The project proposed a new concept of a green construction material with the objective of helping the construction sector to drastically cut its carbon emissions associated with the consumption of Portland cement (OPC), one of main contributors to anthropogenic carbon dioxide (CO2). The proposed construction material combines intelligent bio-nanomaterials with OPC to produce multifunctional concretes that out perform current concrete at lower OPC dosages, thus lower carbon foot-print. The bio-nanomaterials are in the form nano platelets derived from carrot and sugar beetroot recovered from waste produced the food industry. Unlike current nano materials, the intelligent bio-nanomaterials are low-cost, green and renewable and are highly compatible with existing concrete materials. Their addition to OPC not only enhances the performance of concretes but also induces new functionality in concrete structures that enables to monitor their own health and detect structural damage at early stage, thus improving their resilience and sustainability. It also enbale concrete structures to act as green electricity generation that can be used to power internet of things in smart cities.
The aim of this project is to develop new intelligent cementitious nanocomposites for multifunctional built infrastructure by combining OPC with cheap and reeable bio-based 2D nanomaterials synthesised from root vegetable such as carrot and beetroot waste streams produced by the food processing industry. The microstructure and the molecule model for the biomaterial is shown in Fig 1 in the attached images. These novel cementitious composites are not only superior to current cement products in terms of mechanical and microstructure properties, but also use smaller dosages of cement, thereby, significantly reducing both the energy consumption and CO2 emissions associated with cement manufacturing. The novel cementitious composites also exhibit a piezoelectric effect, enabling concrete structures to perform multiple functions such as: 1) self-monitoring mechanism to sense, feel and diagnose impending catastrophic structural failures and 2) green energy production by converting mechanical energy into inexpensive and readily available electrical energy.
The microstructure evolution and mechanical properties of the proposed bio nano-sheet reinforced cementitious nanocomposites were studied. SEM ,XRD and TEM experiments were conducted to characterize the microstructure of the nanocomposites. Furthermore, molecular dynamics (MD) simulations, as the standard approach to explore atomic level process at small time scales were carried out to provide valuable nanoscale insight into the interaction and reinforcing mechanism as well as evaluate its constitutive responses under uniaxial deformation, the constructed molecular structure is shown in Fig 2 in the attached images. The effect of biomaterial intercalation, Ca/Si ratio and loading direction on the mechanical properties are explored. We found that the bio nanosheet demonstrates remarkable affinity to the calcium silicate hydrate (C-S-H) substrate due to the interfacial Ca-O coordination and H-bond interaction. The functional groups from the biomaterial can act like a root network that are confined by surrounding bulk water molecules at the interfacial transition zone, cross-linking the neighboring silicate calcium layer, thus significantly improve the interfacial properties of the nanocomposites, thus the increasing the mechanical properties of C-S-H as shown in Fig 3.
2. Investigating the hydration mechanism of the bio-nanomaterials
By combining experimental investigation, first-principles calculation and reactive molecular dynamics simulations, we elucidated the effect of the bio-nanomaterials on the hydration of cement particles. We showed that longer-term hydration is primarily controlled by proton exchange and transport through the bulk solid. The presence of the bio-nanomaterials in the water can help improve the dynamic property of water in vicinity of C3S substrate surface and consequently precipitate the H proton hopping from the surface to deeper structure. This increased the depth of the hydration products.
3. Investigating the properties of cementitious materials
The properties of cementitious materials (i.e. cement pastes, mortars and concrete) were investigated. The workability, mechanical properties and fracture resistance were determined using different nanomaterial concentrations and OPC dosages. The nano-materials improved both the mechanical proproperties and fracture resistance of the cementitious materials but reduced their workability. The addition of the bio-nanomaterials reduced the OPC dosage of mortars and concretes without reducing their mechanical properties. The addition of the bio-nanomaterials also increased the piezoelectric constants of the cementitious composites which allowed them to serve as ultrasonic transducers for structural integrity monitoring and energy harvesters to produce electric power from vibration.