ALTERNATIVE SOLUTIONS SOLUTIONS FOR SLAB In today's world, science and technology is growing rapidly by leaps and bounds. At the same time, the construction of buildings and offices is also taking place at a similar rate. When it comes to constructions, slab is an important element in the building. Slab is a flat piece of concrete carrying by the beams or column or sitting on compacted soil or stone, usually meaning there is no basement. Several materials such as concrete, wood, etc can be used to make slabs. Concrete slabs can be divided in two categories depending on the concrete was cast. They are precast and in situ. In reinforcement concrete concrete steel bars resist the tension in the slab. Lattice girder slabs, biaxial voided slabs and solid concrete units are included in precast concrete slabs. One-way slabs, two-way slabs, ribbed slabs, waffle slabs and flat slabs are included in In-situ reinforced concrete. After the casting in-situ concrete, it also can be pre-stressed and it is known as post-tensioning. In this article, various types of slab systems and their merits and demerits and further, alternative slab systems are discussed.
Flat Slabs This is the one of the most common forms of widely used construction. Construction of flat slab is fast and allowing flexible column grids. Flat slabs are particularly appropriate for areas where tops of partitions need to be sealed to the slab soffit for acoustic or fire reasons. Flat slabs are considered to be faster and more economic than other forms o f construction, as partition heads do not need to be cut around down stand beams or ribs. Flat slabs can be designed d esigned with a good surface finish to the soffit, allowing exposed soffits to be used. This allows exploitation of the building’s thermal mass in the design of heating, ventilation and cooling requirements, increasing increasing energy efficiency. Flat slabs provide the most flexible arrangements for services distribution as services do not have to divert around structural elements. elements. The benefits of using flat slab construction are becoming increasingly recognized. Flat slabs without drops (thickened (thickened areas of slab around the columns to resist punching shear) can be built faster because formwork is simplified and minimized, and rapid turn-around can be achieved using 2 a combination of early striking and flying systems. There are some other advantages of flat slabs are more uniform access to daylight and easier accommodation of the various ducts in the building, faster construction, reduced services and cladding costs, cheaper shuttering, flat underside of slab and flexibility to the occupier who can alter internal layouts to accommodate changes in the use of structure. There are some disadvantages also there in the flat slab when comparing other types of slabs. They are Lack of resistance to lateral loads, such as those due to high winds and earthquakes. Hence, special special features like shear walls must be always provided if they are to be used in high-rise constructions or in earthquake regions, simple analysis limits to certain proportions of slab geometry, low shear capacity, low stiffness, needs more formwork for capital and panels
Ribbed Slabs and waffle Slabs Ribbed and waffle slabs provide a lighter and stiffer s lab, reducing the extend of foundations. The big disadvantage of these slabs is vibration. It is an issue building such as library and hospital. But to prevent the vibration effect, we have to provide 60-65 mm finished with tiling. Ribbed slabs are made up of wide band beams running between columns with equal depth narrow ribs spanning the orthogonal direction. A thick top slab completes the system. Advantages of ribbed slabs are Suitable for medium to long spans, lightweight, holes in topping easily accommodated, large holes can be accommodated, profile may be expressed architecturally, or used for heat transfer in passive cooling, reduction in dead loads due to voids and electrical and mechanical installations can be places between voids. But higher frame work costs than the other slab system and only moderate and uniformly distributed load can be accommodated. If we construct the ribbed slab in both directions, then it is called as waffle slab. Waffle slabs have a thin topping slab and narrow ribs spanning in both directions between column heads or band beams. The column heads or band beams are the same depth as the ribs. It can carry heavy loads, durable finishes and attractive exposed ceilings. Disadvantages of waffle slabs are higher framework cost than for p lain soffits and difficult to prefabricate reinforcement
Dura Slab Panels Dura Slab is ideal for new constructions and it is also well suited for refurbishment applications to replace old, heavy and cumbersome traditional flooring materials and covers. The characteristics of Dura Slab make it more favorable rather than using steel, timber or concrete systems due to its lower weight, lower cost, corrosion resistant, non-conductive, low insulation cost, superior strength, impact resistant, non- magnetic, maintenance free, standard bearing surfaces, anti-slip surface, ease of installation and absence of maintenance. Only disadvantage of Dura panel is difficulties in producing such panels with required dimensions.
Some other alternative slabs
Types of slab Troughed Slab
Hollow pot Slab
Filler Slab
Post-tensioned (PT) slabs
Advantages Longer spans than one-way solid or flat slabs, lightweight, level soffit, profile may be expressed architecturally, or used for heat transfer, holes in ribbed slab areas cause little or no problem Low price, less time is lost, requires placing only, the hollow pots are used as permanent formwork for ribs Consumes less concrete and steel due to reduced weight of slab by the introduction of a less heavy, low cost filler material like two layers of burnt clay tiles, enhances thermal comfort inside the building due to heat resistant qualities of filler materials and the gap between two burnt clay tiles, cost effective, reduces use of concrete and saves cement and steel by about 40%,reduction in materials, energy and cost, reduces unwanted dead load of roofing, thermally comfortable, no health hazards, environment friendly Fire resistance, Cost, Speed, Reduced material use, Sound control, Robustness, Thermal mass and Minimal deliveries
Disadvantages Higher framework costs than for plain soffits
After removal of shuttering, the surface needs to be plastered. Requires more experience and skills for implementation purposes.
More complexity, shrinkage and moments, crack can develop in unexpected place,
