Table of Contents for Types of Concrete-
- Types of Concrete for Modern World Construction Requirements
- Self-Compacting Concrete
- Self-Healing Concrete
- High Performance Concrete
- Light Weight Concrete
- 3-D Printed Concrete
The current construction industry is changing too fast. The designs have become robust than ever, the materials are produced with a higher degree of quality control and the process of making concrete has been locally standardised. The new ideas, big data, sophisticated software, high precision technology are aiding the supply of higher quality concrete.
Concrete is the flag-bearer product in the construction material research field. No wonder, it is the most used product. Concrete is their core element of sky-kissing buildings to giant bridges to your favourite hotels & malls.
In this article, I present to you the five types of concrete that have been developed considering the modern-day requirements. Their properties are unique in their own way and have their application from place to place. A type of concrete needs no compaction, the other can repair its’ cracks and some other concrete type is lighter than the normal concrete.
Let us dive in.
2. Types of Concrete for Modern World Construction Requirements
21st Century is the era of smartness. Smartness reflects in our surroundings. To match the pace with the constantly developing new requirements, the concrete has become smarter too. With access to better techniques, focus on sustainability, better utilisation of resources and time and cost-effective requirements, the developments in concrete are bound to happen.
The modern world construction designs are higher, thinner, complex and more unique than before. This leads to the development of materials that can cater to challenging needs. The materials need to have the following characteristics-
- Higher Strength to carry higher loads. Thus, resulting in slimmer design.
- Sustainability- The carbon footprints of the material should be least from its’ production to the use and disposal after useful life.
- Easy to produce- Such materials would be generally more economical.
- Easy to handle, transport and use- The material should be able to be transported to higher levels and used in different conditions.
- Maintenance free- The maintenance cost of the structure should be lower to justify the capital expenditure on the structure. Thus, the material used in construction should have no or least maintenance.
- Light weight- This will enable the designs to me slimmer as the self-weight will be lesser.
- Easily Available- The local availability of the material will have lesser transportation cost and higher acceptance.
3. Types of Concrete: Self-Compacting Concrete
If you are a civil engineer, you already know the importance of the compaction of concrete. The uncompacted concrete contains tiny air pockets that weaken the concrete. For 1% volume of air bubbles in a concrete sample, the compressive strength of concrete is reduced by 5%. However, the flexural strength is not affected much.
Now, consider concrete that doesn’t need compaction. It flows into every corner of the formworks, fills all the empty spaces between the reinforcement bars and leaves no room for air. This way, your structure will be free of honeycombs due to improper filling of concrete between formwork and heavy reinforcement. Such type of concrete exists and is known as Self-Compacting concrete.
The self-compacting concrete has higher workability and doesn’t need external vibrations for compaction. Moreover, a well-prepared self-compacting concrete mixture is free of segregation and bleeding.
3.1 Composition of Self-Compacting Concrete-
It is prepared as normal concrete but with additives. The chemical additives used are superplasticisers that maintain the concrete’s fluidity. The air-entraining agents added to the concrete prevent the concrete from freezing and thawing.
The mineral additives used are ground granulated blast furnace slag, fly ash, silica etc.
3.2 Uses of Self Compacting Concrete-
- Pile foundation
- Heavily Reinforced Sections
- Columns with higher lift height where external vibration is difficult
- Jacketing of existing structure
4. Types of Concrete: Self-Healing Concrete
The weak nature of concrete in tension is one of the biggest drawbacks of concrete. The cracks develop in the tension zone leading to lesser durability. The reduced life of the structure is mainly because of the entry of harmful liquids and gases into the cracks. If the crack is up to the reinforcement, the foreign material may corrode it causing deterioration of the structure.
The concrete has the property of healing the cracks itself by hydration of cement. This property only works for tiny cracks when sufficient water is available. However, the property of crack repairing can be induced in the concrete by adding additives. The concrete that can heal its’ cracks is called Self-healing concrete or Self-repairing concrete.
The researches have been going on since 1994 to develop Self-Healing Concrete and implement the technology on real structures. The lab-results are promising but it is yet to be tested on the real structures on a vast scale.
4.1 Methods of Self-Healing
- Capsule Based Self-Healing Method- Urea-Formaldehyde capsules of 20-70 micron filled with epoxy resins and gelatine microcapsules achieved self-healing of concrete under compression and splitting.
- Vascular Self-Healing Method- Air curing healing agent provided by glass tubes. The tubes depleted upon cracking of concrete. The external healing agent could be added to the cracks for enabling self-healing mechanism.
- Electrodeposition Self-Healing Method- Theconcrete cracks are treated with solution and electric current is passed through it. This enables the electrolysis and deposits the electrode material to deposit on the crack. Read the full article on electrodeposition method here.
- Microbial Self-Healing Method- The bacterial action can heal the cracks and also makes the concrete water-tight.
- Self-Healing by Embedding Shape Memory Alloys- Shape Memory Alloys used as reinforcing material can repair the damage in emergency. The super-elastic behaviour closes the cracks.
4.2 Uses of Self-Healing Concrete
The bacteria-based self-healing concrete has been used in a canal project in Ecuador. After one year of canal usage, the concrete was found to be crack-free and water-tight.
- Liquid Storing or Conveying Structures.
- Structures subjected to tension.
5. Types of Concrete: High-Performance Concrete
“A concrete meeting special combinations of performance and uniformity requirements that cannot always be achieved routinely using conventional constituents and normal mixing, placing, and curing practices.”American Concrete Institute
In Europe, concrete having a compressive strength of more than 60 MPa and a water-cement ratio lower than 0.4 is termed high-performance concrete. The
High-performance concrete is generally prepared with the same material as normal concrete. It is the proportion, procedure of preparing, placing and curing the concrete that makes it high-performance.
5.1 Materials Used for High-Performance Concrete
- Cement- The cement used is OPC of grade 43 and 53.
- Superplasticisers- The superplasticisers used should be compatible with the cement. The optimum % of superplasticiser against the cement content should be determined in lab. It is generally 0.8-1.5%.
- Silica- The addition of silica fumes makes the concrete more impervious and economical.
- Aggregate- The aggregate size used is smaller than in the normal concrete.
The attached image shows the prediction and actual effects of water content, cement content and coarse to fine aggregate ratio on the slump of High-Performance concrete prepared using super-plasticisers.
5.2 Uses of High-Performance Concrete-
The high-performance concrete can be used where the strength requirement is more and the member cross-section is to be kept minimum.
- High Rise Structures
- Highway Pavements
6. Types of Concrete: Light Weight Concrete-
The weight of the normal concrete ranges between 2250 to 2400 kg/m^3 (140-150 lb/ft^3). The self-weight of the concrete is considered in the design. Thus, resulting in bigger cross-sections. However, if the concrete weight is reduced by some method, the design will be more optimum for cost. The concrete that is lighter in weight than normal concrete is called lightweight concrete.
The light-weight concrete has a density of 1440-1840 kg/m^3 (90-115 lb/ft^3). The 20-35% reduction in self-weight causes a significant reduction in structural member sizes. Also, lightweight concrete has better thermal insulation. High-strength lightweight concrete up to 50-60 MPa can be produced by adding suitable binding material and admixture but it will also increase the density of the concrete.
6.1 Types of Light Weight Concrete-
- Light Weight Aggregate Concrete- One of the methods of reducing the weight of the concrete is to use light weight aggregates. Pumice, expanded shale, kiln fired clay or slate, air-cooled blast furnace slag etc. are light weight due to porous nature. These materials are good to be used as light weight aggregate. The porous nature of aggregate requires more water. Hence, pre-soaking of aggregate is recommended to control the water-cement ratio.
- Aerated Concrete- The concrete is light weight due to increase in volume. The air voids are created in the concrete by means of chemical reaction or using air-entraining agent. It is also self-compacting concrete. Thus, the water requirement is low and it can be used for hard-to-reach spaces. The aerated concrete is easy to handle, place and finish.
- No Fines Concrete- Another method of making concrete light weight is by using only coarse aggregate. Due to absence of fine aggregate, the air voids are present in the concrete, that reduces the weight of the concrete. The shrinkage is also lesser for No fine concrete.
6.2 Uses of Light Weight Concrete
The main purpose of lightweight concrete is to reduce cost and to increase thermal insulation. However, strength is a limiting factor. As a result, it is best suited for the following uses-
- Partition Walls
- Thermal Insulation
- Sewer systems
- Addition of new floors over existing structures
- Precast Members
6.3 Limitations of Light Weight Concrete
- The primary setback of light weight concrete is the limiting strength. High- performance light weight concrete has an upper cap to the strength of 50-60 MPa.
- No fines concrete is not suitable for RCC.
- As the water requirement of light weight aggregate concrete is low, it takes more time for drying.
- No fines concrete easily leads to segregation due to improper mixing.
7. Types of Concrete- 3D Printed Concrete
The construction industry has started to witness the breakthrough to a completely new technology i.e., 3D concrete printing. It is the process of placing concrete into flat thin layers through a computer-controlled nozzle called a 3D printer. A 3D concrete printer can place the concrete into any shape and size with a high degree of precision.
The 3D printed concrete is the gateway to futuristic designs. The designs that were not possible due to the limitation of formwork application can be easily constructed. The 3D printed concrete doesn’t need formwork or labour.
A 3D printer deposits the layers of concrete over another by moving back and forth. It can be a gantry type or a robotic arm type. The concrete is aerated to allow easy flow through the nozzle. The materials used for the concrete are essentially the same as the normal concrete.
7.1 Benefits of 3D Printed Concrete-
- Reduced time of construction.
- No formwork requirement.
- No labour requirement.
- Higher quality control.
- Lesser curing time. Minimum of 3 days.
- Increased safety due to no workmen requirement.
- Cost effective.
- Sustainable. As the formwork wastage is not generated.
- Can construct mass-accommodation in tight schedule in case of disaster or rehabilitation.
7.2 Limitations of 3D Printed Concrete-
- Equipment- For some complex shapes and size, project specific printers are to me made.
- Unsuitability for hot regions- Higher temperature adversely affects the hydration of concrete resulting in poor quality control.
- High Capex Cost- The 3D printed construction is cheaper but the printers are not. The printer costs from $180K to $1M.
All the above mentioned six types of concrete have their own pros and cons. However, their utility in modern construction is undeniable. The uses of each type of concrete are in multiple domains that offer more choice to the consumer.
The extensive ongoing researches on concrete throughout the world will provide more efficient solutions to the construction industry. It is evident with the current developments that the future holds many promising concrete types that will be cost-effective, high-strength, more durable and sustainable.
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