Before starting on the subject matter, I would like to quote a relevant incident. At the Time of 2nd World War, a long Bridge suddenly started to crack-down when a large number of Soldiers were passing over the Bridge. The reason of this cracking-down is “the Combined Rhythmic Steps of the Soldiers” as they marched along which matched with the Bridge's Natural Frequency, thereby causing resonance. The possibility of this type of situation was not considered at the time of designing the Bridge.
Though we are discussing about ensuring the quality of construction, I quoted this example to throw light on the fact that the proper design of the structure is very much important for quality construction. So, it is the responsibility of construction engineer to ensure that the design of the said construction is proper and perfect. Moreover, before starting the foundation works, the construction engineer needs to ensure proper filing and to check upon the existing utility Lines.
The quality of construction materials like Re-bars, Cement, Stone/ Brick Chips, Sand etc. is very much important for a quality construction. Therefore, it is an important responsibility of the construction engineer to ensure the quality of the construction materials. For each construction material, there are some standard parameters for measuring quality, such as (i) Re-bars: Tensile Strength, Yield Strength, Cross-sectional Area (ii) Cement: Fineness, Soundness, Consistency and initial & final setting time (iii) Stone/ Brick Chips: Abrasion Test,  Sieve Analysis, Water Absorption etc. (iv) Concrete: Compressive Strength etc. So, before starting the Construction, Testing should be done from the standard laboratory at  BUET or BSTI.
To maintain the proper ratio of the casting materials is very much important for a quality construction. The ratio of cement, sands and  stone chips for high-rise construction or heavy duty construction like Bridge should be 1:1.5:3.

For proper bonding, the used water should be clean and mixing of materials should be proper. In the time of casting, removal of air bubbles from the mixed casting materials is important to protect the cavitations. Vibrator may be used for proper compaction of concrete.
After completion of the casting works, it is important to protect the casting area from any shaking up to final setting time of cement. Otherwise, it will decrease the strength of the casting.
To ensure the above things, for a quality construction, close supervision of the professional engineers is important at the time of construction works. If the design is perfect  and the materials are also standard but the supervision is not adequate, it is impossible to achieve Quality Construction.
In a large construction, even if all measures are taken, it is possible to have small deficiency which may cause some faults after completion, like small cracks and plaster removal (due to Dampness / Efflorescence). Therefore, next one year of construction (minimum one Winter & Summer Season), it is mandatory to check the completed construction regularly and also to take necessary measure as required.
Moreover, for the longevity of a quality construction “Regular, Periodic & Preventive Maintenance” is very much essential. So, it is essential to ensure proper maintenance after quality construction.
 

The writer is Director, Operations & Maintenance, Independent University, Bangladesh (IUB) (Project In-charge of New Building Construction)