Quality of construction is indeed a critically crucial and vital factor for creating sustainable and durable structures. A lot is being discussed and deliberated these days about sustainable and durable structures at various platforms. Sustainability and durability is not achieved only with super speciality construction chemicals. Quality of construction is indeed a critically crucial and vital factor for creating sustainable and durable structures. Quality covers all factors connected with construction starting from design, selection of materials, construction practices and other administrative aspects connected with construction activity.
There are few practices which are followed (without engineering background) because they have been followed since long time according to persons connected with construction activity. Such notions often lead to silly mistakes resulting in poor quality of construction to shorten life of constructed structure. Close supervision, thorough knowledge about the fundamentals of the construction practice to be followed for the particular construction, avoiding unfair practices etc are few of the many actions leading to good quality of construction.
This paper deals with facts, dos & don’ts, and care to be followed during construction to ensure its highest degree of quality.
Quality related to design, selection of material and execution practice affect durability of constructed structure. These aspects are discussed below.
Optimum design is the fundamental need of a durable structure. Over-designed or under-designed structures don’t last long. Architectural design and structural design of the structure have to complement each other.
Functionality of structure normally decides superiority of design whether architectural design would prevail over structural design or vice versa. Once this is decided; the design playing second part has to fit in total requirement of design playing lead part. Architectural shapes and sizes of structural members in architecturally prevailed design need to be structurally designed with adequate safety. Wherever structural design has to prevail as in the case of any industry or production house; shape and sizes have to be according to the functional needs of the unit / machine to be housed.
At times factors like earthquake or wind pressure are often taken as a big threat to the structure under consideration which ends up in exponentially increasing the factor of safety and expanding sizes of structural members out of proportion. Such special factors causing threat should be rationalized while designing a structure.
In case of architecturally dominated designs, pergola or such decorative items are to be very carefully designed. Design of non structural members placed at strategic location in a structure might add extra resistance to wind pressure or create imbalance in the load transfer phenomena of adjoining members if they are not appropriately designed.
Mix design of concrete to be poured in shutters for members which would not be plastered after opening of shutters as per architectural need of the structure; has to be of appropriate grade such that it has free flow characteristic without segregation.
At times design calculation demand depth of main beam to be more than 500 mm. Sometimes, this can’t be accommodated within the structure or may not clear headway below such beams. Structural design has to be reviewed and modified to bring down depth of beam without sacrificing structural strength and such that comfort and convenience of persons occupying the structure are not harmed.
These are some of those aspects connected with design of a structure which are frequently used. There are also some special applications like protective treatment which are to be designed with special care to ensure its safety and stability. These special applications include anti-corrosive treatments for concrete and steel surfaces, protection lining / coating / treatment for concrete and steel surfaces for their protection from corrosive attack of acid / alkali / chemicals coming in their contact, waterproofing treatment, anti-termite treatment, interior face lifting of offices etc. All these special applications are to be designed with “tailor made” approach. The treatment for one case might be different than another so each case has to be individually evaluated and addressed for designing the same to provide the desired functionality for the same.
Selection of materials:
This is one of the most important aspects to ensure desired quality of execution. Material selection is directly proportional to desired functional life of the structure, budget availability and its availability status.
Materials for concreting, brickwork and general building items have their designated IS codes which can be adopted as general guideline for accepting or rejecting the material at construction site. Flaky or elongated coarse aggregates, clayey and silty sand, untreated water, hardened cement, delaminated wood, rusted steel, cracked glass and roof sheets, damaged sanitary fittings are few of those materials which stand outright rejected at construction site.
Sometimes, examining source of materials is also helpful in this process. Rerolled steel is a classic example for this. When steel bars or rolled sections are rerolled, their ductility is adversely affected. Their material constitution and distribution within the member also gets largely disturbed as a result of which rerolled steel member is not of the same quality as the original member. This often leads to bending, breaking or serious damage and thus life of the construction element constructed with such member gets damaged.
As said earlier, material selection for special application needs to be very precise and meticulous. Material with only desired properties is to be used for each treatment because each one is a special treatment and material not as per the specified one doesn’t give desired result. Such occurrences often lead to stoppage of a production unit. One example narrated below will give a fair idea of what has been said above.
Material for mortar to fix acid resistant bricks in a chemical plant is designed to resist that particular chemical environment. Composition of such mortars is very special and its worth is revealed only when it successfully resists corrosive attack of that chemical to which the surface is exposed. If mortar with other than specified composition is selected for this area, then treatment will not be successful and will allow chemical to react with mortar anf then with concrete or steel surface as a result of which that floor or trench or foundation will start deteriorating, cracking, breaking and ultimately it will fail. If such treatment applied on machine foundation fails, then machine base will be shaken up and finally machine will stop functioning. One wrong selection of material for mortar to resist particular chemical can bring a production unit to halt.
Similarly wrong selection of material for false ceiling or partitions for interior face lifting of an office or selection of wooden items in fire prone areas or unprotected metallic pipes for underground services in a chemical zone or only welded connections of steel members for a structure in earthquake prone zone etc are also few of many examples where wrong selection of materials contribute to reduce life of that structure.
Construction activity is a well defined activity. Sequence of its sub activities, their execution methodology, pre construction and post construction care, safety prior to construction, during construction and after construction, fine tuning of execution methodology with respect to unfavourable site conditions etc are important aspects to be considered for construction practices to give durable structure.
- In case of concreting activity, sequence of mixing of materials is important. Mistake in this sequence can lead to substandard structure.
- Placing of concrete in shutters / forms either manually or mechanically needs to be closely watched to avoid segregation or bulging of shutters during vibration or placing concrete.
- Every layer of bricks laid for brickwork must be checked for its correct plumb and line.
- Plaster needs to be checked preferably with nylon thread by placing it diagonally across the plastered wall to identify depressions or bulging if any.
- Curing is the most important activity. Inadequate curing leads to shrinkage cracks right from next day of plastering and affects life of structure at long run.
- Concreting for slab or heavy machine foundation; must be done without any stoppages and construction joints.
- Subsequent to completion of concreting for slab, its edges must be pressed with some heavy weight so that while initial setting of slab concrete edges don’t develop upward end bending. This is serious because in this case, it is likely that a gap may be created between top of wall and bottom of slab resulting in water seepage through that space which is extremely difficult to repair.
- Sunk slab for wash areas, WC and urinals must be properly water proofed to avoid dropping of dirty liquid below the floor and spoiling the environment.
- Concrete or mortar for brickwork or plaster must be prepared as per Design mix. Adding of additional water for achieving comfort for placing and handling of concrete / mortar must be strictly avoided.
- Slopes must be properly maintained if they are specified in construction drawings at places like slab, drain channels, industrial floors etc.
- Construction activities in industrial areas have to be carried out with more care than construction activities in residential or commercial areas. Exposure of building elements to corrosive chemicals must be carefully examined and appropriate protective measures need to be taken to protect them from corrosive attack of chemicals to which the elements are exposed.
- Common sense has to be applied in every stage of construction. Walkways must be plain and levelled, openable windows must be avoided where they can’t be approached, safe and operatable distance must be maintained between sanitary fixtures and wall / floor etc.
There can be many more points which have to be seriously addressed while ensuring the highest degree of quality in construction activities like design, material selection and execution. Few of them have been discussed above. All these deliberations are made to ultimately proceed towards creating sustainable and durable structures to help the environment and mother earth to stop wastage of construction materials which are mainly sourced for natural resources. Structures with short life – caused by any reason, require more and more resources for their reconstruction which consumes natural resources and spoils ecological balance. Quality assurance is that activity in construction sequence which has the highest significance and importance. Let us maintain its grace and pride for each structure to live its functional designed life.