Sanskruti Bhagat joined the Portland studio as a summer design intern, participating in the firm’s robust internship program that includes conducting an in-depth research project. Currently pursuing a Master of Science in Architecture at Georgia Institute of Technology, Sanskruti also received a Bachelor of Architecture at Yashwantrao Chavan Maharashtra Open University in India. Read more from our 2024 internship cohort and all our past intern research projects here.
Evolution of Concrete & Need for Low-Carbon Alternatives
Timeline of Concrete Material
Concrete has been essential in construction for millennia. Ancient Romans and Greeks used early concrete made from volcanic ash, lime, and seawater. The modern era of concrete began in the 18th century with Joseph Aspdin’s invention of Portland cement, a major advancement that led to widespread use. Over time, concrete technology has progressed with new additives and reinforcement techniques to improve performance.
Concrete Carbon Emissions
Concrete production is a major source of carbon emissions, contributing about 8% of global CO2 emissions. The main source of these emissions is cement production, which involves heating limestone and releasing significant CO2. Given concrete’s widespread use, reducing its carbon footprint is crucial for sustainable development.
Cement Production
Cement production involves quarrying raw materials, grinding, blending, and heating them in a kiln at about 1450°C. This process emits CO2 both from the chemical reaction of limestone and from burning fossil fuels. Reducing the carbon intensity of cement production is vital for minimizing environmental impact.
Concrete Components
The mix of these components affects concrete’s strength, durability, and workability. Technological innovations aim to enhance these characteristics and improve sustainability. However, the main source of carbon emissions in concrete production is the cement manufacturing process, particularly due to the energy-intensive preheating of materials and high-temperature kiln firing required to produce clinker, the essential binding agent.
Need for Low-Carbon Concrete
With growing environmental concerns, there is an urgent need for low-carbon concrete solutions. Researchers and industry professionals are exploring various approaches to reduce the carbon footprint of concrete, including the use of alternative binders, recycled materials, and advanced additives. Nano-modified concrete represents a promising avenue for achieving these goals.
Nano-Modified Concrete: Technology & Benefits
What is Nano-Modified Concrete?
Nano-modified concrete incorporates nanoparticles into the concrete mix to enhance its properties. These nanoparticles interact with the cement matrix at a microscopic level, improving strength, durability, and overall performance. Examples of nanoparticles used in concrete include silica fume, titanium dioxide, and carbon nanotubes.
How is Nano-Modified Concrete Made?
The bottom-up strategy involves creating nanoparticles from the atomic level using methods like chemical vapor deposition and sol-gel processes; the nanoparticles are then mixed into cement paste to enhance concrete performance. In contrast, the top-down strategy entails reducing larger particles to nanoscale dimensions through techniques like ball milling or high-energy milling; the nanoparticles are then added to the concrete mix.
Changes in Chemical Composition and Microstructure
When nanoparticles are added to the concrete mix, they influence the chemical composition and microstructure. Nanoparticles fill voids in the cement paste, leading to a denser microstructure. This results in enhanced mechanical properties, reduced permeability, and improved resistance to environmental stresses. Additionally, the incorporation of nanoparticles can reduce the amount of cement required by up to 30%, contributing to lower carbon emissions.
During the cast-in-place process
Why Nano-Modified Concrete is Not Yet Popular
Despite its advantages, nano-modified concrete faces several challenges, including the following.
- Implementing new technologies requires buy-in from local plant operators, who may be resistant to change due to cost or complexity.
- Proper training is essential for handling and mixing nano-modified concrete. The lack of training resources can hinder adoption.
- Handling nanoparticles requires specific safety protocols to prevent health hazards, which can add complexity to its use.
Overview of Exposed Concrete Surfaces
Exposed Concrete Surfaces
Exposed concrete provides a raw, industrial look that can enhance a building’s visual appeal, but achieving high quality can be challenging. The quality of exposed concrete surfaces depends on factors, such as:
- the concrete mix, which can suffer from issues like segregation and weak spots if not properly proportioned
- the formation of Calcium-Silicate-Hydrate (C-S-H) gel, which can lead to cracks if insufficient
- chemical reactions like carbonation and freeze-thaw cycles that affect durability.
Additionally, environmental and sociological conditions, including extreme temperatures, poor coordination, and inadequate skills or budget constraints, can impact curing and overall quality. To achieve a smooth, durable finish, careful application practices such as adequate vibration, thorough formwork cleaning, and proper curing are essential.
Defects and Factors
Conclusion
In conclusion, nano-modified concrete offers a promising solution for addressing the challenges associated with exposed concrete surfaces. The incorporation of nanomaterials, particularly those that enhance the formation of Calcium-Silicate-Hydrate (C-S-H) gel, significantly increases the concrete’s strength. This improvement allows for a reduction in cement content, contributing to a more sustainable mix and minimizing the risk of common defects. The enhanced microstructure of nano-modified concrete reduces porosity, fills voids, and leads to fewer surface imperfections and reduced cracking.
Additionally, the improved hydration process results in shorter curing times and faster construction schedules. Enhanced flowability allows for a smoother finish and a higher surface quality compared to conventional concrete. Although nano-modified concrete may increase permeability, which requires careful consideration and potential mitigation, its overall benefits in terms of strength, finish quality, and efficiency make it a valuable advancement for improving the durability and appearance of exposed concrete surfaces.
By staying informed about advancements in concrete technology, such as nano-modified concrete, we can drive progress in building practices and contribute to a more sustainable future.
Research References
- ACI Guide to Concrete Surfaces. American Concrete Institute, 2014
- Smart Nano Concrete and Cement Based Materials, Properties, Modeling and Applications, edited by Mohd Shahir Liew, Phuong Nguyen-Tri, Tuan Anh Nguyen, Saeid Kakooei, 2020
- Advancements in nano-enabled cement and concrete: Innovative properties and environmental implications, Helena Monteiro, Bruna Moura, Nelson Soares, 2020
- Back to basics: The four steps to creating effective concrete – Construction Specifier
- Discussion with Chris Forney founder of Sustainability Brightworks
- Discussion with Chris Bennett founder of Bennett Build