To avoid structural damages that may develop during occupancy and as the structure ages, good construction procedures and techniques should be adopted. During the construction process, a structure must go through several stages.Every stage of the construction process is critical to ensuring that the structure being built will not be damaged under any circumstances. The first indicator of damage is the appearance of cracks in the structure. Structural damage not only diminishes the structure’s strength, but it can also render it unfit for usage to the point where it collapses. To avoid structural damage and failure, civil engineers must guarantee that proper building practises are followed at all stages of the construction process.
Vertical extension: Work on an existing building’s vertical extension (adding one or more extra floors) should be done at a uniform level all around to avoid differential strain on the foundation. Despite this precaution, due to increased elastic deformation and creep in RCC columns, cracks emerge in the lower floors (old section) at the junction of RCC columns carrying strong loads and lightly laden brick masonry walls. Such fissures are unavoidable.
Techniques to Prevent Structural Damage
The following are some of the best construction strategies and techniques to use for a high-quality, long-lasting structure:
1. Masonry work: Masonry work in a structure should be done in uniform levels throughout the structure to avoid differential foundation settlement due to differential loading. This will keep masonry walls and other structural parts from crumbling. The difference in masonry height between different components of a building should not exceed 1m at any point during construction.Masonry work should be properly cured for at least 7 to 10 days before use. Masonry work on any RCC elements, such as RCC slabs and beams, should not begin for at least two weeks after the strike off.
2. Concrete work: In reinforced concrete members such as cantilever beams and slabs that are prone to deflection under load, the removal of centering and imposition of load should be postponed for at least one month to allow the concrete to gain sufficient strength before bearing the load.Any concrete member should be allowed to cure for a minimum of 7 to 10 days before being removed gradually to avoid rapid drying.Concrete work in a particularly hot and windy climate should be avoided if at all possible, but if this is not possible, steps should be made to keep the temperature of fresh concrete down and prevent rapid drying. To keep the temperature of freshly prepared concrete down, take the following steps:
RCC frame work
Before beginning work on panel walls for cladding and partitioning, as much frame work as possible should be accomplished. Work on panel walls and partitions should be postponed as much as feasible and should be completed from top to bottom.When partition walls are supported by a floor beam or slab, upward camber in the slab or beam should be supplied to compensate for deflection. When structurally needed, a horizontal movement connection between the top of the panel wall and the soffit of the beam should be supplied, and limited support to the wall should be provided at the top using telescopic anchorage or similar arrangement. A compressible jointing material should be used to fill the horizontal movement joint between the top of the wall and the soffit of the beam/slab.
When providing a door opening in a partition wall, a centre opening is preferred over an off centre entrance. Before the concrete sets, it must be lightly re-vibrated for members and sections that are prone to plastic settlement fractures, such as narrow columns and walls, and at changes in section depth. Plastering: When plastering masonry, the mortar joints should be raked out to a depth of 10 mm while the mortar is still green. Plastering should be completed after the masonry has been thoroughly cured and allowed to dry in order to allow for initial shrinkage. Plastering on a concrete background should be done as soon as possible after the shuttering has been removed, roughing the concrete surface if needed.
Terrazzo and concrete floors:
When RCC and brickwork are used together and are to be plastered, leave enough time (at least 1 month) for the RCC and brickwork to shrink and creep before beginning the plastering process. In this scenario, a groove in the plaster at the junction must be supplied, or a 10cm wide strip of metal mesh or lathing must be installed above the junction to act as reinforcement. Control joints in concrete and terrazzo floors should be provided by installing flooring in alternating panels or introducing strips of glass, aluminium, or some plastic material at close intervals in a grid pattern.When laying flooring on an RCC slab, you can use either a base course of concrete or a base course of wood.
RCC Lintels: When spans are large, bearing for RCC lintels should be on the liberal side to avoid stress accumulation at the jambs. RCC roof slab: To prevent thermal movement of the slab and subsequent cracking in the supporting wall and panel/partition wall, the top of the slab should be provided with adequate insulation or protective cover, as well as some high reflectivity finish cover.A slip joint should be installed between the slab and the supporting/cross walls in a load-bearing construction. Furthermore, the slab should either protrude some distance from the supporting wall or simply rest on a portion of the wall’s breadth, as indicated in the below:
RCC roof slab over a masonry wall
On the inside, a groove of about 10 mm should be used to separate the wall and ceiling plaster. The bearing portion of the supporting wall is smoothed with plaster (ideally with a crisp cement finish), which is then allowed to cure and partly dry before introducing the slip joint. Before casting the slab, it is either given a thick coat of whitewash or 2 to 3 layers of tarred paper are placed over the plaster surface. Installing glazed, terrazzo, or marble tiles vertically: Before installing these tiles on a vertical surface, the backdrop component should be allowed to move due to elastic deformation, shrinkage, and creep, or the tiles will crack and dislodge. RCC work in an open environment:In the case of RCC.
Finishing touches, such as distemper and painting, should be applied after the plaster has cured and shrunk slightly. Construction pace: The construction schedule and pace should be regulated to ensure the following:Before plastering, all masonry objects are properly cured and allowed to dry, allowing the cracks in the masonry to be hidden. Similarly, before adding a finishing coat, plaster work should be cured and allowed to dry. So that the cracks in the plaster can be hidden behind the finish layer. Before beginning masonry work on top of or beside concrete, the majority of the drying shrinkage, creep, and elastic deformation of concrete should be allowed to occur.
reinforcement for thermal stresses:
Adequate temperature reinforcing must be supplied to control cracks in concrete caused by shrinkage and temperature influence. When smaller diameter bars and deformed steel are utilised instead of plain reinforcement, the temperature reinforcement is more effective. Horizontal extension: Because the foundation of an existing building settles as load is applied to it, it is necessary to ensure that new construction is not bonded to the old construction and that the two parts are separated by a slip or expansion joint from the bottom to the top. Otherwise, as the freshly created piece settles, an unattractive fracture at the junction may appear. No excavation should be carried out in the neighbourhood of the historic building.
adopting proper methods of placing & finishing mortars and concrete, sufficient curing.
Solution: Keeping air content below 3% can help avoid such concrete failures to a great extent.
The two most common causes of failure are carbonation and chloride contamination of the concrete.