Concrete is the most used building material in the universe. Concrete is used to construct roadway, tunnel, dam, parking lot, parking deck and skyscraper. Any development in the engineering of concrete advantage to all of us. The upgrade can consist of cost, strength, durability, or ease of application. And as the material progresses, our buildings and roads become shielded.
As stated by the American Concrete Institute (ACI), high-performance concrete (HPC) is concrete joining special mixture of performance and uniformity necessity that cannot always be attained routinely using typical constituents and normal mixing, placing and curing practices. High-performance concrete is not the lone type of concrete, but preferably, any number of concretes engineered to hold some properties good for a particular construction.
HPC is more durable than standard concrete, and stronger also. HPC is basically expensive than traditional concrete, not only because of the ingredients securitized in it but also due to the special mixing and curing methods for the HPC to carry out to its design specifications.
HPC contains many of the same materials as standard concrete, but the ratio is different, based on the essentials of the project. Some of the ingredients used are fly ash, ground blast furnace slag, micro silica fume, calcined clay, calcined shale, superplasticizers, corrosion inhibitors, shrinkage reducers, and polymer modifiers.
If a project requires high-strength concrete, it will have a strength of 8,000 psi (pounds per square inch) or 55MPa. The value of 8,000 psi was chosen to define high-strength concrete because it requires special care when producing it. Extensive testing is conducted to demonstrate a specific HPC performs as expected before a construction project can begin.
Properties of HPC:
High-performance concrete applications include roadway and bridge construction, tunnels, and tall buildings. The design of HPC for these projects is more about high density, low permeability, and resistance to the elements, than for compressive strength. High-performance concrete may by high strength, but not all high strength concrete is high performance.
Some of the properties of HPC can be:
- High compressive strength – concrete can bear a high load.
- High early strength – The concrete, often known as “fast-track concrete,” sets up faster, allowing for less shoring time.
- High modulus of elasticity – A measure of the stress which the concrete will endure during use.
- High abrasion resistance – The amount of wear that the HPC concrete will bear from vehicular traffic, wind, or flowing water.
- High durability and good longevity in under severe conditions such as weather, the freeze-thaw cycle, or high traffic.
- Low permeability – Water and chemicals do not penetrate below the surface.
- Resistance to chemicals.
- High resistance to de-icing agents (aka penetration) – The depth to which de-icing agents (which are usually made from some type of salt) will penetrate the HPC.
- High impact resistance.
- Ease of placement.
- Compaction without segregation.
- Resistance to bacterial and mold growth.
Ultra-high performance concrete (UHPC):
In addition to HPC, ultra-high performance concrete (UHPC) is under development. This material is being developed with the objective of shoring up and protecting our infrastructure. It is the cement that is reinforced by a steel fiber with a compressive strength rating that is between 150 and 250 MPa. The formula for UHPC includes high-grade Portland cement, fine-grained sand, silica fume, and small steel fibers. The creation of this category of cement is deemed sufficiently important that several government agencies, as well as universities in several different countries, are working on its development.
HPC is not just for roads and skyscrapers. A farmer who was raising pigs in a huge-scale operation was losing about 3 pounds per pig through a diarrhea problem because their pens were not sanitary sufficient to save them from contracting gastrointestinal infections. He resolved the problem by rebuilding his pig pens with HPC. The properties of the concrete that made this application successful were:
- Surface smoothness.
- The Surface was non-slip.
- The concrete had good thermal conductivity so heat distribution was uniform.
- The surface was impermeable to the growth of bacteria, mold, and viruses.
- The HPC was easy to use in the construction of the new pig pens.
- The concrete was resistant to acid (from pig’s urine and other waste).
- The project was cost-effective.
Uses of HPC:
Although the cost is higher because of the ingredients used and the care needed in the construction process, HPC can save money due to the reduced need for other building materials such as spans and supports. In addition to the cost savings, when HPC is used in construction projects, safer structures that require less maintenance are built.