Ensuring quality of structures
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How engineers and workers can scrupulously adhere to norms and procedures for upholding quality at the worksite.
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Watchword: Quality should be focussed upon at every stage.
“Everyone lives by selling something,” said Robert Louis Stevenson. When there are too many sellers, competition becomes stiff, becoming a struggle for existence marked by the survival of the fittest.
An organisation must survive and grow. Essential for this customer confidence in the quality of its product or service. This applies to the construction industry also.
Quality in construction has a dimension different from that of the manufacturing industry. If a manufactured product, such as washing machine or refrigerator, turns out to be defective, the supplier or manufacturer can still win customer confidence by repairing or replacing it.
But the construction industry’s products, such as buildings, dams and bridges, are irreplaceable. Even if repairs can be done, the defect will mar the reputation of the contractor and the work will prove costly. Hence, quality should be ensured at every stage, from design to completion.
The role of design engineers in ensuring quality has not been understood in all its aspects. The structural engineer’s responsibility in ensuring strength of the structure is easily understood and acknowledged.
The design engineers need to pay adequate attention to detailing to make quality of construction possible. For example, presence of many reinforcement steel rods in column-beam junctions makes pouring of concrete and vibration difficult, resulting in hollow spaces in concrete and honeycombing. Architects, at times, come out with designs which make ensuring quality of construction difficult.
Elevation with complicated shapes and design does not always add beauty to the structure and can cause defects.
Selection of materials
The next step in ensuring quality is selection of materials. This is done after conducting the prescribed tests in the laboratory and on the field.
Materials such as cement and steel, manufactured under controlled conditions, do not show significant variations in quality. The quality control laboratories of reputable manufacturers issue dependable test certificates. But there is the possibility of adulteration of materials such as cement during transit from manufacturing plant to the worksite. Transportation, handling and storage during transit with inadequate precautions can also affect quality.
Re-rolling mills, and not reputable manufacturers, supply a significant portion of the steel used.
The quality of steel from such sources has to be checked. So, even if manufacturers’ certificates are furnished, random samples of steel and cement should be tested in the laboratory and on the site.
Materials such as sand, metal, bricks and concrete blocks are not manufactured under strict control as in the case of steel or cement. In most cases, they are not tested at the manufacturers’ worksite. Hence, these materials have to be tested at site before use. Materials not meeting quality standards should be immediately discarded to prevent their use.
Ready-mixed concrete has appeared on the construction scene recently. It is manufactured under better-controlled conditions than concrete mixed on the site. But the selection of materials may not be controlled that strictly. Also, when the plants are located a long way from the site, the concrete may reach the latter late.
When the concrete remains in the rotating transit drums for long, its temperature rises, affecting the quality. Besides this, the concrete loses its workability by the time it is discharged into the pump, choking the pipes. To avoid this, the operators add extra water to easily pump the concrete. This reduces its strength. Hence, ready-mixed concrete should be tested at site, the sample taken from the end of the discharge pipe.
Laboratories
All materials must be tested as prescribed by the relevant Indian Standards. So, a fully equipped field laboratory, manned by qualified technicians, should be set up on the sites of major projects. The records of tests must be kept for reference.
Another aspect affecting quality of materials is storage. In most sites, cement is stored properly but not steel rods. Steel is mostly dumped on the ground. If the soil is wet, steel corrodes. Steel should be kept above the ground with sleepers. The storage and fabrication yards should be preferably of lean concrete. Steel should preferably be given anti-corrosive treatment, especially if it is to be used after a long period or the atmosphere is contaminated with corrosive gases.
Sand and metal should be stored on prepared surfaces to avoid getting mixed with soil and other foreign materials. Materials such as construction chemicals should be kept in covered and enclosed stores. Wooden door and window frames should be kept on sleepers and covered from the sun and rain.
Procedure
Now comes the quality of construction procedure. Even use of materials of the highest quality will not result in a quality product, if an incorrect construction procedure is followed.
Every work, whether it be concreting, masonry, plastering or painting, has a prescribed procedure. For example, producing good concrete follows this: erection of form work, proportioning of aggregates and cement, controlling amount of water, addition of admixtures, mixing, transporting, placing, consolidating, curing and removal of shuttering.
Failure to adhere to it will adversely affect the quality of concrete. Usually, the construction procedure is left to the decision of the workers, such as masons, carpenters, and concrete mixer operators. This should be avoided and qualified and experienced technical personnel should supervise the work.
It is better to use printed formats to record adherence to proper practice. Standard check lists are available to record the result of checking of every activity. The supervisor must be made to fill up and sign the check lists. Dilution of procedures for faster completion of work is common. Both the owner and the contractor must resist this temptation. Speed thrills, but it may kill quality.
Accuracy of the tests on materials and quality of construction procedure depend on the accuracy and quality of machines. So, proper maintenance of the machines is of great importance in ensuring quality. Machines such as weigh batcher, balances and compression testing machines should be calibrated at the prescribed frequency. Machines such as concrete mixer and builders’ hoist should be periodically tested.
Constant vigil and religious adherence to prescribed practices are essential for ensuring quality. Over a period of time, engineers and workers become complacent and lax in following prescribed procedures. This should be avoided. For this, a positive attitude on the part of every person associated with the work is essential.
An awareness about the importance of maintaining quality at all levels must be created through proper training. This is necessary not only for the supervisory staff but for the workers also. Achieving quality is everybody’s responsibility, and not that of those directly connected with the work alone. For example, one may wonder how human resources personnel are responsible in ensuring quality of concrete. Well, they must select people with the right attitude and ensure a congenial working environment to enable everyone to do his best. The purchase department should buy materials conforming to specifications. The entire organisation must make well- coordinated and determined efforts. The top management should be closely involved in the process.
The quality control and audit department should report directly to the top management. In such a situation, there is likely to be friction between the functional departments and the audit department. It is the responsibility of the top management to educate everyone about the need for systematic inspection and audit.
The audit reports should be used as a useful document for monitoring and taking corrective steps to avoid recurrence of mistakes, and not for victimising employees who make inadvertent mistakes. Employees should be convinced that inspection and audit are meant to help them improve their performance. When committed people work with good materials and efficient machines following prescribed procedures, the result will be a product of the highest quality — a thing of beauty which will be joy for ever and for everyone.
