Failure to follow established rules and good practise, as well as open recklessness, can result in construction mishaps on the job site. Although most of these mistakes do not result in concrete failure or deterioration, they might have a long-term negative impact on the structure. Construction Errors on the Jobsite The types of construction errors that are likely to occur on the jobsite, as well as preventative methods, are covered in length below. These errors can arise not just during initial construction, but also during repair and restoration.Watering down concrete In one or both of the following situations, water is frequently added to concrete:
Improper alignment of formwork
To improve slump and reduce pouring or placement effort, water is first added to the concrete in a delivery truck. As a result, the strength and durability of concrete will be compromised. The strength and durability of concrete will decrease as the water/cement ratio rises. Water is typically introduced during the finishing of structural members in the second situation. Scaling, crazing, and dusting of the concrete result as a result of this.construcion-concreting Formwork is not aligned properly. Discontinuities on the concrete surface will result from improper formwork alignment. While these discontinuities are ugly in any situation, they may be especially problematic in places susceptible to high-velocity water flow, where cavitation-erosion can occur, or in lock chambers where the “rubbing” can occur.
Concrete that has not been properly consolidated or compacted Bug holes, honeycomb ingredients, and cold joints are some of the most prevalent flaws caused by improper concrete compaction. When little pockets of air or water are trapped against the forms, bugholes occur. To help eliminate bugholes, a tweak in the mixture to make it less “sticky” or the use of small vibrators integrated into the form have been used. Honeycombing can be reduced by entering the vibrator more frequently, inserting it as close to the form face as feasible without touching it, and withdrawing the vibrator more slowly. Any or all of these flaws, obviously, make it considerably easier for any damage-causing mechanism to cause concrete deterioration.
Inadequate curing
Fear of overconsolidation is frequently invoked to justify a lack of concrete consolidation effort. Over consolidation is a condition in which the consolidation effort leads all of the coarse aggregate to settle to the bottom while the paste rises to the top. If this happens, it’s reasonable to assume that the problem is due to a poorly proportioned concrete rather than excessive consolidation Curing is possibly the most misunderstood aspect of concrete building. Concrete will not develop the required and necessary qualities for durability unless it is given enough time to cure at the right humidity and temperature. Cracking of various forms can be a symptom of inadequately cured concrete.
Structural cracking may occur in extreme circumstances where poor curing results in inability to attain predicted concrete strengths. Reinforcing steel is installed incorrectly. This section relates to reinforcing steel that has been installed incorrectly or is not securely fastened. Either of these flaws can result in one of two types of issues. For starters, the steel may not perform structurally as anticipated, leading to structural cracking or failure. The use of welded wire mesh in floor slabs is a particularly common example. Because the steel is not in the appropriate area, the mesh frequently ends up on the bottom of the slab, causing it to split. The second type of issue that can arise as a result of incorrectly placed or linked reinforcing steel is one of.
Movement of formwork
The second issue that can arise as a result of incorrectly placed or knotted reinforcing steel is one of durability. The steel appears to have a tendency to end up towards the concrete’s surface. Corrosion is considerably easy to start when the concrete layer over the steel is lowered. Formwork in motion During the transition from a fluid to a stiff material, movement of the formwork may cause cracking and separation inside the concrete. Water will be able to enter the inside of the concrete through a crack on the surface. If an interior void becomes saturated, it might cause freezing or corrosion difficulties. Removal of shores or reshores too soon If beaches or reshores are removed too soon.
The heavier components of the concrete will sink under the pull of gravity during the time between placement and early setting. The usage of extremely fluid concretes may aggravate the condition.Cracking or separations may occur if any restriction seeks to impede this settling. If these fissures or separations become saturated, they may cause corrosion or freezing difficulties. The subgrade is settling. Cracking may develop if the subgrade settles during the period after the concrete begins to become rigid but before it gains enough strength to sustain its own weight. Concrete that has just been laid vibrates. Vibration is generated on most construction sites by a variety of sources, including blasting, pile driving, and the operation of heavy machinery.
Finishing a flat concrete surface incorrectly
When freshly laid concrete is subjected to forces that disrupt the concrete matrix during the setting process, its qualities are susceptible to deterioration. Finishing a flat concrete surface incorrectly The following are the most typical inappropriate finishing processes that are harmful to the durability of a flat concrete surface: Adding water to the surface: The presence of a large paint brush, as well as other finishing tools, indicates that water is being added to the surface. Water is “slung” onto the area being finished after the brush has been dipped in it. Finishing procedures should be completed once the concrete has reached its initial set and bleeding has stopped. The amount of water, cement, and admixtures in the mixture determines the waiting period.
Tampering: On many jobs, a tamper, often known as a “jitterbug,” is utilised unnecessarily. This tool pushes the coarse aggregate away from the surface, making it easier to finish. However, this approach results in a cement-rich mortar surface layer that can scale or craze. With a well-designed mixture, a jitterbug should not be permitted. If you need to finish a tough mixture, judicious usage of a jitterbug could be beneficial.Jointing: The most common cause of cracking in flatwork is inadequate joint spacing and placement.
Improper consolidation or compaction of concrete
Bugholes, honeycombing, and cold joints are the most common faults caused by improper concrete compaction. Where the constructions become caught in tiny pocks of air or water, bugholes form. A change in the mix to make it less “sticky” or the inclusion of tiny vibrators in the shape can help remove bugholes even more effectively. Concrete that has not been properly consolidated or compacted Honey combing can be reduced by vibrating more frequently, putting the vibrator as close to the form’s face as possible without striking the object, and pushing the vibrator out. Clearly, the presence of more of these defects makes it significantly easier for any harmful activity to begin degrading concrete. Over consolidation is a term that is occasionally used to explain a problem.
Water is generally applied to concrete in one or more of the following situations: To begin, water is injected to concrete in a transport vehicle to raise the slump and reduce the dumping or placing attempt. As a result, the concrete would be weaker and have a shorter lifespan. The strength and lifespan of concrete are affected by the water/cement ratio. In the second case, water is frequently used to complete structural components. This causes the concrete to crack, fracture, and scale. Formwork misalignment: Improper formwork alignment can result in concrete surface discontinuities. Although such discontinuities are ugly in all cases, they can be more noticeable in situations prone to high-velocity water movement, where cavitation-erosion might occur, or in lock chambers.
Problems with concrete include construction errors, disintegration, scaling, cracking, efflorescence, erosion, spalling, and popouts.
Concrete Shrinkage. Excessive thermal stresses in concrete. Reinforcement corrosion. Presence of excessive water in concrete.
Solution: Keeping air content below 3% can help avoid such concrete failures to a great extent.
Also Check
Roles and Work of Surveyor in Construction