The materials that make up buildings play a key role in their overall performance. The way these materials interact with one another, in fact, largely depends on their chemistry.
For example, concrete is a good material for holding up a building’s weight because it performs well under what engineers call compression. But quake-generated inertial forces can stretch and pull concrete walls and columns, and this can weaken them.
Wood
Wood is one of the oldest and most versatile building materials in the world. People have been using it for thousands of years, and it was the main construction material until iron beams became available in the early 1800s. Now, the use of wood is making a comeback, thanks to advanced processing technologies and an awareness of environmental sustainability.
Modern architects are rethinking old assumptions about the limits of wood. A growing number of them are choosing to build with cross-laminated timber (CLT) and other forms of engineered wood. This wood is extremely strong, and it can be prefabricated in production plants to make building more efficient. This allows for shorter construction periods, and it reduces the need to lay foundations of concrete or steel.
Engineered wood is a composite, and it has unique properties. At the molecular level, it contains long glucose chains of cellulose and lignin. The cellulose is found in cell walls, while the lignin is what gives wood its incredible rigidity. Wood also acts as a natural insulator, and it can absorb more energy than concrete or steel.
For the most part, wood is a sustainable material because it regenerates quickly and does not release large quantities of carbon dioxide during its processing into lumber. It is also a good choice for urban environments because it can be easily shaped into different architectural styles and has high fire resistance.
Steel
A key characteristic of the most durable building materials is their strength. Engineers and architects must balance the benefits of different building materials against their shortcomings to create safe, strong structures.
Steel is a versatile material with a high-strength-to-weight ratio. It can be easily formed into a range of shapes, and it is also highly durable and resistant to corrosion. It has a high resistance to both compression (resistance to pressing) and tension (resistance to stretching). Concrete, which is very strong in compression but weak in tension, is often reinforced with steel rebar to increase its tensile strength.
The most common type of steel used in construction is cold-formed steel (CFS), which has been rolled and bent into its current shape and size. It has very high tensile and compressive strengths, making it perfect for forming into long, thin sections that can be joined together with bolts or welding.
Another important property of steel is that it is ductile, meaning it can be deformed significantly without losing its structural integrity. This is a good thing during an earthquake, as it will help to dissipate the energy of seismic waves. Think of the way a wire coat hanger bends when you pull on it – that’s what happens to a steel-framed building during an earthquake. It is still strong enough to hold up the building, but the bending of the steel will help to dissipate some of the energy from the seismic waves.
Concrete
Concrete is a popular building material that’s known for its high resistance to fire and natural phenomena like earthquakes. This helps keep buildings safe and minimize damage, which is good for people. It’s also a good thermal insulator, so it can help reduce energy consumption by moderating diurnal temperature variations and cutting the demand for heating and air-conditioning.
There are a number of ways to make stronger concrete, including adding admixtures to the mix. Admixtures are used to improve the physical properties of a wet concrete mixture, such as water absorption, workability and strength. These admixtures are often called “superplasticizers” and “pozzolans.”
The proportions of ingredients in concrete are adjusted depending on its purpose. The mix is composed of water, Portland cement and aggregates (sand and rock). The amount of water can be adjusted to suit the conditions under which the concrete will be placed. During mixing, the ingredients must be perfectly proportioned for them to react properly and reach their maximum strength. The concrete is then cured for 28 days to prevent shrinkage and damage from environmental factors such as moisture and low temperatures.
Many materials science specialists are working to give concrete a modern upgrade. They are developing concrete that heals its own cracks using limestone-attracting bacteria; and concrete that uses magnesium oxide to absorb carbon dioxide from the atmosphere.
Polyurethane
Polyurethane, or PU, is an organic polymer that contains multiple organic units linked via urethane bonds. It is made by reacting polyols (alcohols with more than two reactive hydroxyl groups in each molecule) and diisocyanates with suitable catalysts and additives. The resulting polymer has properties that make it useful in many building applications. These properties include high wear and abrasion resistance, elasticity, resilience, and thermal and sound insulation. It can also be formulated to resist a wide range of chemicals, including oils and solvents.
Polyols and isocyanates can be substituted for each other, allowing the production of a wide variety of polyurethane densities and hardnesses. This allows for the manufacture of a broad range of products, including flexible and rigid foams, specialty adhesives and coatings, and sealants.
The material flow analysis in figure 1 shows the amount of polyurethane produced or traded in previous years and that remained in use in 2016. This includes imports of precursors, intermediates, and end-use product waste. The building and construction, transportation, and EEE, machinery, and foundry categories consume the most imported polyurethane, a result of their large annual production and long lifetimes.
Rigid polyurethane products are often shredded and mixed with unsaturated polyester resin (UPR) to fabricate a composite materials that is then used in the construction industry. During this process, the material releases significant amounts of elastomeric polyurethane dust, or PUD, which can be collected for reuse.