May 28th 2020
What is Concrete Made Of and What is it Used For?
Concrete remains one of the most versatile and durable construction materials in the building market. Concrete is used in everything from industrial construction to domestic renovation. It pavre spour car parks, towns, cities and homes and when mixed by experienced professionals, can last a lifetime.
Are concrete and cement the same?
It is not uncommon for people to assume that concrete and cement are one in the same. Both are used to line industrial areas and provide lifelong flooring and structure solutions. However, the key difference between cement and concrete is that cement is actually a component of concrete.
What are the four main ingredients used in concrete?
Concrete has been used as a building material for thousands of years. The main ingredients have been the same, but new admixture technologies allow designers and engineers to finely tune the final properties of the fully set concrete.
The Four Main Ingredients of Concrete
Although the core ingredients have remained much the same for thousands of years, concrete contractors now implement their own ratios in order to create concrete flooring, cinders and cladding bespoke to the customer’s requirements. This is performed using admixtures, which are added to adjust the mixture accordingly.
Water plays a crucial part in the construction of concrete. Water is responsible for the flow of the concrete and its final strength. Water must be clean and free of impurities when mixed, if anomalies are detected, it will likely affect the structural integrity of the concrete. This is especially important in large scale projects, such as multi-storey car parks.
Getting the water balance right is essential when forming a solid mixture; too much water will allow for an easier flow but will compromise the concrete’s strength during the curing process.
In order for the concrete to harden, it needs to be mixed with water, as it binds all the ingredients together. Most contractors use Portland cement because it’s excellent at binding the other materials together. It enhances both the strength and structural integrity of the mixture to form a sound concrete structure. Additionally, the setting time of Portland cement is much faster than lime and gains its strength earlier.
Portland cement includes the following components:
- And small amounts of other ingredients are also included depending on where it’s sourced
Aggregates are an essential part of what gives concrete its strength. Materials sand, gravel and crushed stone are commonly used as aggregates, but you can use other materials such crushed concrete and glass (glass is usually used in decorative ways), if you so choose. The type of aggregates used depends on the concrete you buy or the company you elect to concrete your property.
While this may not be considered a core ingredient in concrete production, there must be between 1% and 9% entrained air within the mix. This is to ensure that the condition of the concrete does not falter under freezing cold temperatures (this is especially relevant to exterior concretes).
Additional Factors to Consider When Creating and Mixing Concrete
Reinforcement is an essential part of the concrete structure and ensures that the concrete’s naturally low tensile strength is aided by reinforcement that has a higher tensile strength of ductility. This is to compensate for concrete’s low tensile strength. In most cases, the reinforcement consists of steel bars to help line the concrete. At Concrete Flooring Solutions, we used something called composite metal decking, which is now the standard in most constructions in new office builds and retail sites thanks to its strong foundations and durable support properties.
Why does concrete need reinforcement?
Although concrete is one of the strongest materials in terms of compression, it has a weak tensile strength, which can cause cracking if reinforcement is not used. By implementing steel or composite metal decking, it allows the concrete to carry tensile loads.
Materials that are added to concrete to give it bespoke characteristics that cannot be found in standard concrete mixes. Admixtures allow you to customise (to some degree) the appearance of your concrete flooring or concrete structure. The most common admixtures are retarders (calcium sulphate or gypsum) and accelerators which help the concrete be placed in colder conditions without the risk of frost damage. Common accelerators include calcium chloride, calcium nitrate and sodium nitrate.
- Air entraining agents
These agents help concrete maintain its structural integrity in freezing cold conditions, specifically, during freeze-thaw cycles. Air agents work by inserting tiny air bubbles into the concrete, but it’s important that only a certain amount of air agents are inserted, as too much will see the concrete lose compressive strength.
- Bonding agents
As their name suggests, bonding agents bond old and new concrete together with a wide temperature tolerance and corrosion resistance. It’s also used as an admixture for Portland cement compositions.
- Corrosion inhibitors
Essential regarding concrete’s reinforcement networks. If you’re using steel bars as your concrete reinforcement, corrosion inhibitors protect the steel bars from corrosion, ensuring sound structural integrity.
- Crystalline admixtures
Crystalline admixtures provide a water barrier that is applied to the concrete mixture to ensure that any water that comes into contact with the concrete is blocked. If water does enter the concrete through cracks, the crystalline admixtures will react and form new crystals (barriers) to block the water. You can think of crystalline admixtures as having “self-healing” properties, wherein if, at any time water breaches the concrete, the admixture will initiate crystallisation to block any water from entering the site.
Pigments are used to customise and change the colour of the concrete. Pigments are a vanity substance and are simply used to transform the appearance of your concrete flooring or structure and can be used to change the color of concrete, for aesthetics.
Plasticisers or dispersants, essentially help to make concrete more placeable. They are typically composed of lignosulfonate (used as a cement water reducer) and are additives that increase the viscosity of the concrete. They alter the concrete’s physical properties to help for more flexible placement.
A different class of plasticer that helps to increase concrete’s compressive strength. Like it’s predecessor, it helps to make the concrete more fluid for easier placement, the main difference being superplasticisers lead to retarding effects. They also reduce the need for water content by roughly 15–30%. Superplasticizers lead to retarding effects.
Retarders slow down the hydration process of concrete, meaning they delay the concrete’s setting time (for up to an hour). Retarders are typically used when the weather is hot to help stop rapid hardening. By slowing this down, it allows time for mixing and placing.
- Pumping aids
Pumping aids help to thicken the paste as well as reduce separation and bleeding of the concrete.
What are the Different Types of Concrete Made of?
- Normal Strength Concrete
The traditional type of concrete. As mentioned before, it is created by mixing cement, water and aggregate (and air). The setting time for this type of concrete ranges between half an hour to 90 minutes depending on the type of cement used to construct it. It will also depend on the weather conditions.
- Plain Concrete
Plain concrete does not feature reinforcement of any kind. Like normal strength concrete, it consists of water, aggregates and cement. Plain concrete is the most common type of concrete and is typically used to pave roads and create the walls of buildings. It is very durable and has a compressive strength of around 200 – 500kg per cm2.
- Reinforced Concrete
Certain types of concrete require reinforcement when a high tensile strength is required. For example, plain concrete has a poor tensile strength but good compression. The reinforcement makes the plain concrete’s tensile strength stronger so it can be used in more building projects.
Most reinforced concrete structures employ steel rods, bars or in the form of meshes (check our composite metal decking page for more information).
- Prestressed Concrete
Prestressed concrete involves a special construction technique which involves ‘stressing’ the bars before the service load application. the bars are positioned and held at each end of the structure, and are left to harden. Once hardened, the structural unit will be put in compression.
Prestressed concrete is typically used when constructing bridges and large roofs. These are used in the application of bridges, heavy loaded structures, and roofs with longer spans.
- Precast Concrete
As the name suggests, precast concrete is designed (or can be designed) off site, usually at a factory, and is then transported to the construction site when required..precast structures include:
As precast concrete is usually assembled off-site, it allows for faster construction on-site.
The examples of precast concrete units are concrete blocks, the staircase units, precast walls and poles, concrete lintels and many other elements. These units have the advantage of acquiring speedy construction as only assemblage is necessary. As the manufacturing is done at site, quality is assured. The only precaution taken is for their transportation.
- Lightweight Concrete
As the name suggests, lightweight concrete has a lower dentistry than other concrete types. Typically, a concrete that falls less than 1920 kg m/3 would be considered lightweight. What makes lightweight concrete lightweight, is the aggregates used. Common lightweight aggregates include pumice, perlites, and scoria.
- High-Density Concrete
The opposite of lightweight concrete, high density concrete (also known as heavy, or heavyweight concrete) make up the heaviest concrete. Heavy aggregates are used, the most common being Barytes (a dense mineral used in concrete construction). Heavyweight concrete is ideal for structures that require resistance to all types of radiation.
- Air Entrained Concrete
We briefly mentioned air-entrained concrete previously, but to summarise, air entrained concrete is created by adding foams or gasses into the concrete mix. The agents typically consist of alcohols, resins and sometimes acids.
- Ready Mix Concrete
As the name suggests, ready mixed concrete is concrete that is concrete=e that has been previously mixed. It is often transported and unloaded at the construction site via a mixer. In most cases, ready mix concrete is considered a speciality concrete.
The ready-mix concrete is very precise and specialty concrete can be developed based on the specification with utmost quality.
- Polymer Concrete
The main difference with polymer concrete uis that the aggregates are bound with polymer, not cement. The reason this is done is that the conree with help reduce the volume of voids within the aggregate. Meaning, a reduced amount of polymer is required to bind the garage gates.
- High-Strength Concrete
Different to high dentistry concrete; high-strength concrete have a strength higher than 40MPa and they gain this title by having a water-to-cement ratio of lower than 0.35.
- High-Performance Concrete
- A term that may confuse inexperienced concrete contractors; not all high-performance concrete is high strength concrete. What makes a high-performance concrete high performance is the following:
- It attains strength early on in the process
- It’s easy to place
- Very strong and durable
- Mechanical properties
- Self-Consolidated Concrete
Self-consolidated concrete mix, when left alone, will compact by its own weight. Unlike other concretes, no vibration is required and if it is, it will impact the quality of the mixture. On that note, SCC has a high workability and has a slump value of around 600 – 750.
This type of concrete works best where there is thick reinforcement.
- Shotcrete Concrete
The main difference concerning shotcrete concrete is that way it’s applied to the cast area. Shotcrete concrete involves the use of a nozzle when applied into the structure. While the concrete is shot out of the nozzle, the placing and compaction happens at the same time.
- Pervious Concrete
Otherwise known as permeable concrete, this type is constructed to allow water to pass through it. It is particularly helpful when building pathways, drives, pavements and heavy foot traffic areas that frequently suffer with storms and/or heavy floods.
The concrete is designed to allow water to pass through it, reaching the groundwater. This type of concrete alleviates drainage issues.
- Vacuum Concrete
If concrete has more water content that is necessary, then the water is poured into the formwork. A vacuum pump is then used to extract any remaining water without having to wait for the concrete to set. The main benefit is that the structure is ready earlier, compared to the traditional concrete process, obtaining their compressive strength in just 10 days (compared to 28).
- Pumped Concrete
Pumped concrete must attain good workability in order to be filtered through the pipe. This pipe is a rigid but flexible flume then can be positioned and the concrete directed into its desired placement. Fluidity is important in pumped concrete, as it must be viscous enough to fill the voids. Fine materials are essential part of the mix, the finer they are the better they fill the void.
- Stamped Concrete
Stamped concrete involves stamping artistic and architectural designs into the concrete to offer a stunning visual effect. Professional stamping pads are used to obtain this effect and the pads are able to stamp in designs that look akin to stones, panels, tiles and even granites.
You can also apply colour and event textures to form a unique finish on walls and floors. This is a vanity concrete finish and looks great in both domestic settings.
In limecrete concrete, the cement that is used in concrete is replaced by lime. This type of concrete is usually used in doors and domes. Limecrete is far more environmentally friendly than traditional cement and the products are renewable and easy to clean.
- Asphalt Concrete
A composite material that involves a mix of aggregates and asphalt. This type of concrete is primarily used in industrial settings, specifically rp ave roadfs, car parks and even airport runways. It’s incredibly durable and very hardwearing.
- Roller Compacted Concrete
Roller compacted concrete involves the use of a rolling machine to flatten and role the concrete into its desired position. This is a heavy duty machine that is usually used in excavation and filling scenarios. When compacted, this type of concrete has an exceptionally high density and cures into a monolithic block.
22.Rapid Strength Concrete
As the name suggests, rapid strength concrete gains is strength extremely quickly (within a few hours) after manufacturing. Rapid strength concrete has a widespread application and can be used after a few hours. Great for emergency jobs and repairs.
- Glass Concrete
Recycled glass is now a very popular aggregate used in concrete. Glass concrete is predominantly used in domestic settings, such as homes and universities. However, it’s also used to line the floors of multi-storey buildings thanks to its aesthetic appeal. Despite it’s galaxy exterior, glass concrete is exceptionally durable and provides fantastic thermal insulation.
The Concrete Installation Process
Now we know what concrete is made of, we will explain how these above components are used when installing concrete.
The average weight of concrete falls between 140 – 160 pounds (per cubic foot) and you will need to place it as close to its final position as possible. The quicker this is done, th better, as when handled too much, segregation can occur over the fine aggregates. Do not apply water to spread out the concrete if the mixture does not reach its desired position. This will compromise the concrete’s integrity and cause cracking further and improper setting.
How it’s placed
In most cases, concrete is poured via a large chute or truck and then positioned via a buggy or directly from the concrete pump. The concrete is then tested for its slump, this usually requires an experienced concrete contractor to inspect, monitor and pour the concrete to ensure it’s viable for your property.
Concrete is normally specified at a 4-5″ slump. Industrial, commercial, and some residential projects require an inspector on concrete pours who monitors the concrete slump and takes slump measurements at the required intervals.
What is the concrete ‘slump’ and why does it matter?
In layman’s terms, the ‘slump’ of the concrete refers to its consistency before it sets. If the slump is higher, the concrete becomes more fluid, the lower it is, the less fluid it is. The term ‘slump’ can be attributed to how much the concrete slumps down when it’s left to stand. This is tested by filling a cone with concrete, then removing the one and seeing how much it has slumped.
Spreading Concrete and Final Positioning
As stated previously, it’s important that you place the concrete as close to the area where you’d like it to set, as this facilitates creeding the concrete in the coming steps. Do not use a rake when spreading concrete, instead. Use a square shovel or something that has a square shape to spread the concrete. Shovels that are rounded will cause the concrete to spread unevenly. Ensure that any tool used to spread the concrete has a flat edge and is strong enough to push and pull the concrete without bending.
Need Help Laying Your Industrial or Commercial Property? Contact the Experts
If your concrete project is on a larger scale and you would rather employ a team of experienced contractors to undertake the task, we can provide this service. At Concrete Flooring Solutions, we have over 40 years’ experience in the concrete industry and have installed concrete flooring across the UK. From multi-storey car parks and warehouses to huge retail stores and city pavements, we have the experience and technology to provide lifelong concrete flooring for all properties and outdoor areas.
Choose from polished concrete for a stunning, life-long finish for large indoor areas, industrial concrete, for car parks and other heavy traffic areas to composite metal decking to lay the foundations of your concrete.
Now you’re ready to contact us, simply enter your details and enquiry on our contact form, or call us using the number above.