Building Materials
There are more than 76 million residential buildings and nearly 5 million commercial buildings in the U.S. today. These buildings together use one-third of all the energy consumed in the U.S., and two-thirds of all electricity. They consume 25% of all water supplies and 30% of all wood and materials. By the year 2010, another 38 million buildings are expected to be constructed.
Infrared image taken on Mill Ave. near ASU
Buildings are a major source of the pollution that causes urban air quality problems, and of the pollutants that contribute to climate change. They account for 49 percent of sulfur dioxide emissions, 25 percent of nitrous oxide emissions, and 10 percent of particulate emissions, all of which damage urban air quality.
Rapidly urbanizing regions provide unique opportunities to deploy new urban planning, as well as residential, commercial and industrial designs which reduce the reliance on fossil fuels while promoting the use of emerging construction materials and technologies such as fuel cells, wind energy, photovoltaics, hydrogen, geothermal and distributed generation.
Sustainable buildings consume fewer resources, generate less waste, cost less to operate, and provide healthier living and working environments than traditional buildings. In general, green building can be defined as design and construction practices that significantly reduce or eliminate the negative impact of buildings on the environment and occupants.
Energy efficiency is one of five key areas in the development of a sustainable building:
- Sustainable site planning
- Safeguarding water and water efficiency
- Energy efficiency and renewable energy
- Conservation of materials and resources
- Indoor environmental quality
FLIR Thermal image of a residential structure (afternoon), depicting the thermal conductivity of the structure
Testing existing and emerging technologies of building materials(such as cool roofs) for surface temperature and solar properties to develop UHI mitigation strategies through the use of alternate building materials.
Composite Materials
Our society uses in excess of 6 billion tons of concrete products per year worldwide, resulting in a consumption of energy, raw materials, natural resources and the transportation costs associated with such a high demand. This need is so essential that we have effectively downplayed the fact that cement production is a major point source contributor to green house gas generation. Yet according to UN-Habitat estimates 924 million people worldwide, or 31.6 percent of the global urban population, lived in slums in 2001. In the next thirty years, this figure is projected to double to almost 2 billion, unless substantial policy changes are put in place. Even if all the money and resources were available for eradication of poverty through development, we would have to mobilize our resources to address the high demand for decent housing, transportation, infrastructure, and water distribution. How do we approach the right balance between this demand and the supply of materials and technologies? Would it be OK to just increase our production capacity without looking into how we utilize the materials we make today? Are our design approaches which were developed almost 30 years ago too conservative? Are there innovations that can reduce the material and labor costs? How can we achieve long term sustainable cement and concrete production technologies?
In consideration to these questions, our approach is to look at technologies that allow us manufacture cement-based composite materials as thin elements (about 10 mm thickness), such as wall panels; exterior siding; roofing tiles; flooring tiles and pressure pipes. For such elements addition of reinforcement is essential in order to improve the tensile and flexural performance. Without reinforcement cement-based products are brittle, having high compressive strength but low tensile strength and low toughness. The materials our team has produced are as much as 10 times stronger and 1000 times more ductile than ordinary concrete materials. By increasing the mechanical strength, we can reduce the amount of material needed to support a certain load, reducing the demand for raw materials, reducing dead weight of structures, while increasing the resistance to earthquake, impact, wind load, and other natural or man made forces.
Our work addresses the development of industrial cost-effective methods for the production of prefabricated, high performance, thin-sheet fabric-reinforced cement composites. By using fabrics as reinforcement for thin-sheet cement products we have produced a new class of high performance fabric-cement composite materials which far exceeds other available technologies in the marketplace. Such breakthrough may open the way for a multitude of new products and applications.
Fiber cement products provide a great opportunity to reuse discarded conventional materials such as glass, polyethylene and polypropylene as a new and stronger feedstock for building products. With a greater volume of closely spaced fibers, the microcracking can be controlled by crack arrest and bridging mechanisms. This allows the stresses to be transferred back into the matrix thus increasing the toughness considerably. Once the critical volume fraction of fibers is exceeded, the ultimate strength and ultimate strain increase considerably, allowing the design of cement composites as alternatives to wood, steel, and other construction systems.
