DID YOU KNOW THAT THERE ARE NUMEROUS TYPES OF CONCRETE to meet your project needs?Concrete is one of the most widely used and versatile construction materials in the world. In fact, it is the second most widely used material in the world next to water. A simple mixture of natural ingredients—cement, aggregate, water—creates a plastic, malleable material that can be formed into any shape you want. When it hardens, it becomes as strong as rock with the durability and sustainability to last a lifetime—and longer. That’s pretty fantastic!
The strength, quality, and performance of concrete will depend on its mixing proportions. Adding other carefully selected ingredients to the mix can further increase its strength and enhance its characteristics. Below is a brief rundown of some of the various types of concrete available.
The type of concrete you need depends on your project requirements.
Ready-mix concrete is prepared with high precision in a centrally located concrete plant based on job specifications and the performance you need. The concrete is generally mixed as it is transported to the site via concrete mixer trucks with spinning drums. Once the trucks reach the jobsite, the concrete can be used immediately.
Portland Limestone Cement (PLC)
The PLC mix replaces a portion of portland cement with limestone to reduce the carbon footprint of concrete by about 10%. Almost anywhere you use portland cement concrete, you can use PLC instead. It has the same specifications and the same mix design, but with a better carbon profile. The cement industry has initiated a production switch to ASTM C595 Type 1L cement to encourage widespread use of PLC.
Air can be intentionally entrained in concrete to make it durable in freeze-thaw conditions. When foaming agents (i.e., alcohols, resins, fatty acids) are added to the mix, they develop millions of tiny air bubbles in concrete. These tiny air pockets provide space where water can expand when it freezes, relieving internal pressure on the concrete and preventing cracks and fissures. Concrete used in freezing environments or areas with freeze-thaw cycles is typically air-entrained.
Also called normal or normal-weight concrete, this concrete is made when all the basic ingredients are combined in a common mix design (typically 1:2:4—one part cement, two parts sand, four parts aggregate). The concrete takes about 30 to 90 minutes to set, depending on weather conditions and the mix cement’s properties (i.e., fineness of cement). Its strength varies between 1,450 and 5,800 psi, also depending on mix proportions. It takes about seven days after placement for the concrete to start gaining strength, and about 28 days to reach 75 to 80 percent of its total strength.
Normal-strength concrete is typically used for pavements or buildings that don’t require high tensile strength, like flooring and patios. It is strong in compression and weak in tension, which means that while it can withstand compressive loads (squeezing forces/weight), it is not as durable against the stresses created by vibration or severe weather conditions, such as high winds and freezing temperatures.
Another concrete created with basic ingredients and mix designs, plain concrete has no reinforcement. While it faces the same challenges as normal-strength concrete (weak in tensile strength), it has a very satisfactory durability rating. Plain or ordinary concrete is used in dam construction and in pavement or buildings where there is not a high demand for tensile strength.
We’ve mentioned that plain and normal-strength concrete have low tensile strength. A common way to make concrete stronger is to add steel reinforcement to forms before placing the concrete. Steel reinforcement can include wires, rods, bars (rebar), cables, or mesh. Working together as one structural element, the reinforcements resist tensile forces while the concrete itself resists compressive forces. Most concrete applications use some kind of reinforcement, including buildings, bridges, and roads that require a high level of tensile strength.
Pro Tip: Another way to reinforce concrete is to add steel fibers to the mix. We call this fiber-reinforced concrete.
Prestressed concrete is created using specialized equipment and highly skilled labor. Like reinforced concrete, it involves placing bars or tendons before the concrete is poured. However, these bars or tendons are stressed before the application of the service load. The tensioned bars are placed firmly and held from each end of the structural unit. Once the concrete sets and hardens, the structural unit is put in compression. This process makes the lower section of the unit stronger against tensile forces.
Prestressed concrete is used to build bridges, flyovers (overpasses), heavy-loaded structures and long-span ceilings and roofs.
Concrete elements can be cast in a factory according to exact specifications and then transported to the site and assembled. These elements can include wall panels, bridge girders, concrete blocks, staircase units, pipes, poles, crash barriers and lift stations. The advantages of using precast concrete are its speedy assembly and high quality.
Pro Tip: Tilt-up construction is a form of precast concrete. Also called site precasting, tilt-up involves casting concrete elements in a horizontal position at the jobsite and then lifting and tilting the panels to their final position in a structure.
Ideal for high-rise construction and sidewalks, the compressive strength of high-strength concrete is usually about 6,000 psi. This strength is achieved by decreasing the water to cement (w/c) ratio in the mix. Often, silica fume is added to the mix to prevent any strength reduction during the hardening (hydration) process. Superplasticizers also can be added to increase workability, since a lower w/c ratio makes the concrete mix less fluid and harder to work with.
This concrete has a substantially lower mass per unit volume and is typically created using aggregate that is lighter in weight (aggregate types contribute to the density of concrete). Examples of lightweight aggregate include scoria, pumice, clays, expanded shales, vermiculites, and perlites.
Lightweight concrete is commonly used where less load is applied, such as for wall parapets and road linings. Because this concrete has very low thermal conductivity, it can be used as protection for steel structures and as insulation for water pipes. It also is used for long-span bridge decks and their building blocks.
Also called heavyweight concrete, high-density concrete has a very specific purpose: to shield from radiation. It is created using crushed rock as the coarse aggregate in the mix. The crushed rock most often used is barytes, a colorless or white material that consists of barium sulfate and is the principal ingredient in barium. It is frequently used in the construction of atomic power plants and similar projects.
An alternative to ready-mix concrete, volumetric concrete addresses the problem of transporting a perishable product like concrete from the plant to construction sites located too far away to keep the mix in usable form. Specialized trucks known as volumetric mobile mixers carry the concrete ingredients and water to be mixed at the construction site.
Volumetric concrete also is ideal whenever different kinds of concrete are needed at a single site. It can be mixed and delivered as needed, enabling one truck to produce two different mixes.
Decorative concrete is a great way to customize projects and add a bit of personality to surfaces or structures. These mixtures can contain integral color, specialty aggregate or otherwise be optimized to suit aesthetic needs. For more on decorative concrete work, see “How to Upgrade Your Home with Concrete.”
High Early Strength Concrete
Ideal for fast-track projects, this type of concrete sets fast and gains strength within a few hours after its preparation. Formwork can be removed earlier and road surfaces can be returned to service in just a few hours. It is a low-carbon concrete that also is more resistant to low temperatures than conventional concrete, making it especially useful during winter and in cold climates.
This highly workable concrete is designed to be easily conveyed via pipe or flexible hose to heightened elevations and hard-to-reach areas. Fine aggregates are typically used in the mix to keep the concrete fluid. While pumped concrete is typically conveyed for bridgework or to upper levels of a high-rise construction project, it also can be used to create superflat floors on lower levels.
This concrete mix uses lime instead of cement, along with lightweight aggregates like glass fiber or sharp sand. Limecrete has many environmental and health benefits because it is renewable and easily cleaned. Mainly used for the construction of floors, vaults and domes, it can also be used with radiant floor heating.
Roller-Compacted Concrete (RCC)
RCC is a strong, dense concrete with compressive strengths greater than 4,000 psi. The concrete is placed with asphalt paving equipment and compacted using earthmoving equipment like heavy rollers. It cures into a strong monolithic block—no formwork or reinforcing needed.
RCC is typically used for pavements subject to heavy loads. It can also be used to build concrete dams and for excavation and filling work.
Recycled glass can be used as aggregate in the mix to create this modern, attractive concrete. Shiny or colored glass gives the concrete a splash of color or sparkle. Glass concrete also provides long-term strength and better thermal insulation, due to the thermal properties of the glass aggregate.
What makes shotcrete different from other forms of concrete is the way it is applied. Shotcrete professionals use compressed air to “shoot” the material through a hose and nozzle onto a vertical or overhead frame or structure. Due to the high-velocity force with which it is projected, placement and compaction take place at the same time.
Shotcrete eliminates the need for formwork. It is frequently used against vertical soil or rock surfaces and can be used to repair damaged wood, concrete or steel structures. It is sometimes used for rock support, especially in tunneling. Shotcrete can be used where seepage is an issue to limit the amount of water entering a construction site.
During placement, conventional concrete is consolidated (vibrated) to compact it within the form and eliminate potential flaws, such as honeycombs and air pockets. SCC, on the other hand, compacts by its own weight when placed. No vibration is required. It also is called self-compacting concrete or flowing concrete due to its higher level of workability.
SCC is ideal for locations and applications where vibrating the concrete is difficult to impossible (i.e., underground structures or areas with thick reinforcement). It can save up to 50 percent in labor costs due to a faster pouring cycle and reduced wear and tear on formwork.
High-Performance Concrete (HPC)These types of concrete display a high level of performance, formulated with special ingredients to conform to specific standards that can, but do not always, include high strength. (High-strength concrete is considered high-performance, but not all high-performance concrete mixes are high-strength.) HPC standards can include rapid strength gain, easy placement, high permeability and high durability.
High-Performance Concrete (HPC)
These types of concrete display a high level of performance, formulated with special ingredients to conform to specific standards that can, but do not always, include high strength. (High-strength concrete is considered high-performance, but not all high-performance concrete mixes are high-strength.) HPC standards can include rapid strength gain, easy placement, high permeability and high durability.
These concrete mixtures use polymer, instead of cement, to bind aggregate. Polymer resins commonly used in such mixes include vinyl ester, polyester and epoxy. Based on the type of resin used, the benefits of polymer concrete can include increased strength, fast set times, non-shrink curing and resistance to high temperatures and weathering. Because of its high durability and resistance to several types of corrosion, polymer concrete is ideal for industrial and electrical construction projects.
To select the right concrete for your project, contact a concrete supplier near you.
When developing project-specific concrete requirements, review our overview of codes, standards and specifications.