Concrete is a specially created (artificial) stone building material. It consists of water, a binder (most often cement) and fillers of different sizes. Concrete is one of the most widely used building materials in the world. It is the material of choice for most new big roads, buildings, bridges and many other structures because of its durability and relative ease of use. Technologies do not stand still, research teams conduct new research with the presented material, as a result of their work, new developments appear.
Wood concrete: reality or myth?
Previously, wood was one of the most common building materials, but today it has been replaced by concrete mixes. The active development of technologies made it possible to combine 2 types of materials, creating a combined mixture of wood and concrete.
The Swiss National Resource Wood Program (NRP 66) focuses on creating a unique blend. Swiss researchers have succeeded in developing a radical approach to combining wood and concrete: they make resistant concrete, which is 50 percent wood. The high content of wood in the concrete mix has contributed to the good thermal insulation of the material without compromising fire resistance.
The main difference between the described mixture and classic concrete is the replacement of gravel and sand with fine-grained wood.
Creating floating concrete
“They weigh no more than half the weight of ordinary concrete – the lightest of them even float!” says the organizer of the research. In addition, after dismantling, the materials can be reused as fuel for generating heat and electricity. Despite the compliance with fire safety requirements, building materials can be burned together with other waste.
Stress test results have confirmed that the new wood-based concrete is suitable for slabs and wall panels and can be used as load-bearing structures in construction. In the course of the upcoming research, it is required to find out in which areas it is better to apply a certain type of wood-concrete composite and effective methods of its production. According to Daya Tzwicki (organizer), the level of knowledge required for widespread use is still too limited.
Revolutionary graphene concrete
Graphene is a modification of carbon that has been gaining popularity in recent years. Experts from the University of Exeter have developed a groundbreaking technique using nano-engineering to incorporate graphene into classical concrete production. The unique technology has made it possible to create durable, environmentally friendly, and durable concrete. In addition, the water resistance has increased significantly. Testing of the produced material has proven to be in full compliance with British and European building standards.
Importantly, the new graphene-reinforced concentrate has significantly reduced the carbon footprint of traditional concrete production methods, making it more sustainable and environmentally friendly. At the same time, carbon emissions were significantly reduced (by 446 kg / t), and the amount of materials needed to create concrete was reduced by 50 percent. Most scientists are confident that the new technique will allow new nano-materials to be introduced into concrete, thus modernizing the global construction industry.
Finding sustainable construction methods is a step towards reducing global carbon emissions and a way to protect the environment. This is an important investment in creating a progressive construction industry for the future.
Coal ash in concrete
Accurate moisture content within the concrete is difficult to obtain because the powder and aggregates form a dense cementitious matrix, which makes it difficult for moisture to move once it dries. In addition, special atmospheric conditions are required for drying. If the outside of the concrete dries out before the inside hardens, it can result in a weaker product structure.
Pharnam’s lab wanted to develop an aggregate product that had optimal mixing characteristics, strength and porosity, and find a way to make it from a large amount of waste.
Coal ash is a by-product of coal-fired power plants, which is obtained by burning coal. Hundreds of tons of ash are sent to landfill every year. Researchers at Drexel University believe they have found a use for the powdery residue. They are confident that ash can make concrete more durable and free from cracks.
Developed by Farnam
“The solution we came up with was to process the waste coal ash into a porous, lightweight aggregate with superior performance that can be produced at a lower cost than existing natural and synthetic options,” said Farnam (founder of the idea).
It has been scientifically proven that the presented additive will significantly increase the service life of concrete, make it many times stronger. The concept of internal curing has been developed over the last decade, using a porous lightweight aggregate to facilitate the curing process. The additive can maintain a constant moisture level inside the concrete to help it harden evenly from the inside.
Calcium silicate in concrete
Calcium silicate microspheres were developed by scientists at Rice University. It has been proven that the invention will help to obtain more durable and environmentally friendly concrete, with improved mechanical properties (strength, hardness, elasticity and durability) than Portland cement, the most common binder used in concrete. The spheres are 100 to 500 nanometers in diameter. Their use promises to reduce the energy consumption of cement production (one of the most common binders in concrete). Shahsawardi claims the spheres are suitable for bone engineering, insulation, ceramics and composite applications, and cement.
According to Shahsavardi, increasing the strength of the cement will contribute to:
- Reducing the weight of the concrete.
- Less material consumption.
- Reduced energy consumption during concrete production.
- Reducing carbon emissions during the manufacturing process.
The scientist said that the size and shape of the particles in general have a significant impact on the mechanical properties and durability of bulk materials such as concrete.
Recycled tire concrete
UBC engineers have developed a more resilient type of concrete using recycled tires. The substance can be used for concrete structures such as buildings, roads, dams and bridges. At the same time, the volume of waste in landfills will be significantly reduced.
Researchers experimented with varying proportions of recycled tire fibers and other materials used in concrete – cement, sand and water – before finding the perfect mix. It contains 0.35% tire fibers. In the United States, Germany, Spain, Brazil and China, asphalt roads already exist with crumb rubber from shredded tires. It has been proven that the presence of these particles contributed to the improvement of concrete elasticity and prolongation of its service life.
Tire Concrete Research Results
Laboratory tests have confirmed that fiber-reinforced concrete reduces cracking by more than 90 percent compared to a classic mix. This is due to polymer fibers that bridging cracks as they form, helping to protect the structure and extend its life.
“Most of the used tires are for landfill. Adding fiber to concrete can reduce the carbon footprint of the tire industry as well as reduce emissions in the construction industry, as cement production is a significant source of greenhouse gas emissions, ”said Bantia, scientific director of UBC.
New concrete was used to line the steps in front of the Macmillan building on the UBC campus. The Banthia team monitors its condition using sensors embedded in concrete, observing the development of stress, cracks and other factors. At the moment, the observation results confirm the results of laboratory tests and indicate a significant decrease in the formation of cracks.
How to avoid the destruction of concrete from sulfuric acid?
Atmospheric and chemical effects on the concrete pavement adversely affect its condition. The destruction of concrete from sulfuric acid can be avoided by finding ways to prevent its precursor gas from adsorbing into concrete. In the course of his research, Matthew Lasich discovered that pretreatment would be required to protect concrete infrastructure from corrosive effects, targeting the adsorption sites in the cement hydrate where most of the hydrogen sulfide molecules are attached. However, this approach can be difficult due to their widespread use.
The porous structure makes the concrete vulnerable to natural gas adsorption. In their study, the authors conduct nanoscale analysis based on Monte Carlo simulations to simulate the migration of gas molecules into the cement hydrate structure. Their modeling suggests that a certain combination of molecular size and surface area is required for good absorption of cement hydrate.