What is Concrete?
Concrete – in its basic form, is a blend of aggregate, rocks, and paste. The concrete paste is made out of water and cement, which forms a coat on the smaller or even larger (coarse) aggregates. Through the process of hydration, which is a chemical reaction, this paste becomes harder and stronger to form a mass that’s rock-like, known as concrete.
This entire process is a depiction of the outstanding quality of concrete – it’s malleable and moldable when freshly mixed but durable and robust as hardened. These traits are explanatory of why concrete is an excellent material to build multiple and diverse projects like sidewalks, skyscrapers, bridges, highways, dams, and houses.
Concrete pavement is an essential part of the construction that continually takes place in your city, whether you’re aware or not – without it, there would be no infrastructure for a developed city or a country.
Four different types of concrete pavement:
1. Plain pavement using dowels
Dowels are used to Prevent faulting and to provide transfer of the load
2. Plain pavement without using dowels
Here, faulting is prevented, and loads are transferred across joints through aggregate interlock.
3. Conventionally reinforced pavements
This type of pavement comprises steel reinforcement, and dowels are utilized for joint contraction.
4. Continuously reinforced pavements
Reinforced through continuous longitudinal steel, this kind of pavement has no contraction joints.
Prepping for the pavement process
Subgrade, the native soil on which the paving needs to be installed, or pavement is to be built upon, will need to be compacted and graded before any work can be started. Preparing the subgrade is then followed by the placement of a sub-base, which is a material layer just below the concrete. The integral function of a subbase is the prevention of displacement of the soil below the pavement. Subbases can be built of cement-treated materials, granular materials, lean concrete, or stabilized or unstabilized, highly porous materials. After hardening the subbase – to make it sufficient enough to be able to resist distortion or marring by traffic, tiebars, dowels, or reinforcing steel are put in place and aligned correctly.
There are two methods of paving using concrete
Slipform paving requires a machine riding on treads, similar to train in motion on tracks, over the area that needs to be paved. Fresh concrete – is spread, shaped, consolidated, and floated after being deposited ahead of the paving machine. This utilizes the entire concrete pavement in a single and continuous operation. During this process, a close eye needs to be kept on synchronization between the placement of concrete and the paver’s forward speed.
• Fixed-form paving
Fixed-form paving involves the setting of stationary metal forms and aligning them on a strong base. After the setting of the forms, the final prep and shaping of the subbase or subgrade are finished. Cleaning and oiling of the forms are done to make sure that they are released after the hardening of the concrete. After deposition of concrete close to its subgrades’ final position, spreading on the concrete pavement and preset forms is done using a mechanical spreader. This machine that’s used for spreading is followed by a couple of more tools for shaping, consolidating, and float finishing the concrete. After the concrete is adequately strengthened, the removal of forms and edges starts the curing instantly.
Joints are added and cut by a saw for controlling the pavement cracking. Once the insertion of concrete joints is complete, the aim is to texture the surface.
Texturing is done to acquire the right amount of skid resistance, and it needs to be done right after the water sheen disappears from the concrete and just before concrete firms further. This process involves making use of burlap drag, wire brooming, artificial-turf drag, and adding groove to the soft concrete with a comb or roller equipped plastic roller. These methods can also be combined for a specific texture. The technique chosen varies – depending on the speed, the density of the tentative traffic, and the environment.
After operations are finished, curing begins. Curing compound is often used and is a liquid membrane that is pigmented white and is used during conventional curing methods. Sometimes, curing is done with a waterproof paper or polythene sheets, burlap, or wet cotton mats.
After hardening, concrete pavement can crack due to contraction. Shrinkage cracks occur if contraction joints haven’t been designed or constructed properly. Otherwise, these cracks will occur under the joints. After concrete contraction, the cracks and joints will open and provide space for the concrete to expand in moist or hot weather conditions. After pavement hardening, cleaning and sealing of joints are the next steps. Cleaning and sealing are used to get rid of any particles that could damage concrete on expansion. Concrete pavement is cleaned and finally opened for traffic flow after the curing period and running tests to check concrete’s strength.
Concrete pavement is, therefore, an extensive process. It sounds exciting, and it is, but experts and professionals can only execute it after a lot of planning, preparation, and utilization of skills.