Building for a Cooler Summer
Revolutionary research in construction to combat climate change
Reduction of Greenhouse Gases
“The world is on pace to set another high temperature benchmark, with 2016 becoming the third year in a row of record heat,” The New York Times reported this July. In Hong Kong and many other places on earth, we have endured a scorching summer. There is no denying that global warming is happening and happening fast. Ignorance is no longer an excuse for inaction.
The biggest culprit of climate change is greenhouse gas (GHG) emissions from human activities, which trap the sun’s heat on earth. According to the United Nations Environment Programme (UNEP), the building sector, which uses about 40% of global energy, is the largest contributor to global GHG emissions.
Buildings account for around one-third of GHG emissions because of the large amount of energy and natural resources used in manufacturing construction materials and in constructing and powering the buildings.
On the flip side, if more sustainable building materials and technologies can be developed and used, we can significantly reduce the carbon footprint of buildings—this is exactly what IAS Visiting Professor Surendra Shah has been working toward in his research.
Prof Surendra Shah, who has joined HKUST as an IAS Visiting Professor since 2011, is the Walter P Murphy Emeritus Professor of Civil and Environmental Engineering at Northwestern University. He is the only civil engineer who is a member of the national academies of engineering in the US, China and India.
Application of Nanotechnology in Construction Materials
Named one of the most influential people in the industry by Concrete Construction Magazine, Prof Surendra Shah focuses his research on the application of nanotechnology in construction materials, which holds many exciting possibilities for the industry.
“We can increase the use of waste materials in construction, improve the constructability of concrete, solve the inadequacies of existing building materials, and examine materials at a nanoscale to see how we can make them better,” he explained.
With annual global consumption of over 15 billion tons, concrete is the most commonly used material in infrastructure and building construction. The production of its major component, Portland cement, accounts for 5-7% of the world’s manmade carbon dioxide emissions.
Demolished sites produce tons of waste concrete, which can be crushed to become aggregates. However, aggregates are not as durable or strong as standard building materials and make for a poor substitute. Prof Shah is involved in a cross-university project to study the use of nano silica to improve these aggregates and make recycled concrete a more appealing and feasible option.
Another issue with concrete is that it cracks easily. Normally, people reinforce concrete with steel bars. However, this cannot prevent water and harmful chemicals such as salt from eroding the concrete.
Nanotechnology presents a simple and energy-saving solution to this problem. Using as little as 0.05% of carbon nanotubes, we can already make concrete much less brittle and boost its stiffness and effectiveness. At the Gordon Research Conferences hosted by IAS in July 2016, Prof Shah presented information about the role of nano fibers and nano particles in enhancing the durability of concrete based on his work with doctoral students and postdocs. He challenged fellow researchers and industry representatives to “imagine how much greenhouses gases would be reduced if we could recycle instead of making new concrete.”
In addition to improving existing materials, the IAS Visiting Professor is collaborating with Prof Christopher Leung of Civil and Environmental Engineering at HKUST to develop new cement-based composites with ultra-high performance.
The research spans materials science, structural engineering, and engineering mechanics at the nano, micro, and macro levels; they first studied fracture mechanisms and why concrete cracks, then the interfacial interaction between fibers and molecules, and finally the structure as a whole in the macro sense.
“These composites have an unprecedented ductility and a compressive strength which is an order of magnitude higher than concrete used in the past,” said Prof Shah. “The outcome of our research can fundamentally change the construction industry.”
3D Printing and Concrete Construction
3D printing is regarded as a game-changing technology that subverts our traditional concept of production. Nor is it new to the construction industry. Engineers are already using additive manufacturing, a technical synonym for 3D printing, to produce cement board and construct highways onsite. With 3D printing, we can use concrete to build highways in layers as thin as 6 mm and save on the costs and energy of moving and distributing materials.
In May 2016, the world’s first fully 3D-printed office building was completed in Dubai. The 2,700-square-foot office was printed using a 120-foot-long and 40-foot-wide 3D printer. The labor involved included one staff to monitor the printer, seven workers to install the building components, and a team of 10 electricians and specialists to take care of the mechanical and electrical engineering.
It took only 17 days to print the components and two days to install them onsite, which was significantly faster than traditional construction methods. The architectural firm responsible for the project estimated that using 3D printing technology saved 50-80% in labor costs and 30-60% in construction waste.
Despite this achievement, advanced 3D printing technology in construction is still in the research and development phase. One of the key challenges for researchers is to make cement both fluid enough that it can be injected by the printer nozzles and strong enough to retain its shape after injection. At HKUST, Prof Shah has teamed up with Prof Zongjin Li of Civil and Environmental Engineering to revolutionize construction techniques using 3D printing to make the development of complex structures faster, cheaper, and more sustainable.
The first fully 3D-printed building in Dubai proves what the technology can achieve. (Photo source: Government of Dubai Media Office)
Dialogue between Researchers and Industry
Do you know that you can actually repair cracks in a wall with bacteria? With the help of cell biologists, engineers have found that certain types of bacteria can produce biominerals to fill cracks. This organic solution is much more eco-friendly than the synthetic polymers commonly used to repair concrete.
“To achieve substantial research in this field, cross-disciplinary teamwork is essential. In many cases, chemists, physicists, and biologists are involved.” said Prof Shah.
Industry buy-in is important as well. Scientists are motivated by their intellectual curiosity to conduct research. However, unlike the pharmaceutical and some other industries, profits in the construction industry are not driven by research and development.
For the construction industry to adopt more sustainable building materials and technologies, its economic incentives must be increased and the right policies must be put in place.
Prof Shah also encouraged researchers to engage in a continuous dialogue with the industry to understand the critical problems it is facing and how research can solve these challenges. For example, manufacturers have always used fresh water, a valuable and costly resource, to make concrete. What if we could use sea water, of which there is an abundance in coastal regions, as an alternative? In fact, several universities in Hong Kong are currently exploring this cheaper and more sustainable alternative in a joint research project.