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Hollowcore Slabs

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FEATURES & ADVANTAGES

Teemage Hollowcore Slabs are pre-cast in the controlled environment of the factory away from the building site.

The designers have greater flexibility because of the varying thickness (150 - 400 mm) available and larger spans up to 18 meters can be obtained at costs which are lower than conventional flooring systems.

Quality of Hollowcore slabs are much higher than conventional methods just because of the state-of-art machines being used and continuous quality measure taken during the production process.

The casting is sequenced in such a way that every floor of your building are stored and ready to be delivered for installation as quickly as required at the site.

Expensive formwork and propping is eliminated thus improving productivity and access within the site is vastly improved.

A Hollowcore slab, also known as a void Slab or hollowcore plank, is a precast slab of prestressed concrete typically used in the construction of floors in multi-story buildings. They are widely used throughout the world as flooring and roofing solutions.

HollowCore slabs are produced worldwide using a variety of manufacturing processes. Teemage Precast In has chosen to use a Slipformer production system developed by Echo Precast Engineering. This state-of-the-art system is a dry cast, extrusion process where zero slump concrete is forced through the machine. The cores are formed with augers and tubes with the concrete being compacted around the cores using high frequency vibrators.

Teemage Hollowcore slabs are nominally 1200mm wide and are available in thicknesses of 150mm, 200mm, 250mm, 300mm and 400mm. All the slabs are cast with high strength prestressing cables to provide the load carrying capacity. Depending on the requirement of the client, our team of specialised designers will provide the most efficient product.

HOLLOW - CORE APPLICATIONS

Hollowcore slabs are widely known to be used in all forays of construction including but not limited to the following.

Commercial

Shopping malls, Retail showrooms, corporate office buildings

Institutional

Schools, Colleges, Hostel buildings, Auditoriums

Healthcare

Hospitals, Nursing homes, elderly care facilities

Miscellaneous

Boundary walls, tank cover slabs, ramps

Residential

Multi-storey apartments, High-end Villas, Mass housing projects

Industrial

Manufacturing facilities, power generation plants, heavy industries

Parking

Multi-level car parks, underground parking facilities

DESIGN CONSIDERATIONS

The availability of design softwares and load charts derived from the same provides greater flexibility and ease in the application of hollowcore flooring. Teemage Engineers have prepared load charts (provided upon request) that gives the designer the opportunity to quickly size a hollowcore floor slab for a particular load case. The floor span length is the primary consideration during the design process. For a framed structure the most economical grid is to maximise the span of the hollowcore slab and minimise the span of the support beams with a minimum number of load paths. Hollowcore floor slabs are best suited as simply supported one way spanning slabs, where lateral restraint of the building is provided by shear walls. Alternatively, connections between vertical elements and hollowcore flooring can be designed to resist moments generated due to Wind or Earthquake loads. Also, multi-span hollowcore flooring structures can be designed to promote continuity.

Manufacture

The advantage of controlled concrete production in enclosed factories is obvious, Every part of the process can easily be monitored and controlled, because the operations are repetitive and take place at the same location. Hence it is economically justifiable to carry out the necessary investments to meet the demands of our modern, ecologically conscious society.

Floor depth

The load span charts can be used for a preliminary selection of a floor slab. Two options, with and without a nominal concrete topping of 50mm has been used for all slabs and can be chosen based on the load considered.

Slab width

It is preferable that the floor plan dimensions suit a 1200 mm modular width. Non modular dimensions can be accommodated with longitudinally cut slabs or wet-cast slabs.

Slab length

The slabs are cut to the length required for their location in the floor plan. The ends can be cut to an angle to suit skewed layouts.

Loads

The Hollowcore slabs are typically designed to take superimposed uniformly distributed dead and live loads generated based on their occupancy. Concentrated permanent loads and construction loads higher than normal can also be catered to based on their magnitude.

Connections

Teemage Precast uses European and American Standards for connection details between hollowcore floor slabs and the supporting beams or walls. The connection details at a support must not only transfer load but also contribute to the monolithic behaviour of the entire structure. Although, most suitable for a Total Precast system, hollowcore slabs can also be provided for and connected to Cast-in-situ structural framing, steel frames, masonry walls etc. Detailed connections shall be provided during the preliminary meeting with the client based on their exact requirements.

Camber and Screeding

Hollowcore floor slabs are cambered because of the upward bending induced by the prestressing tendons. This camber should be allowed for in detailing the slabs. A cast-in-situ screeding unifies the individual slabs into a monolithic floor, takes out differential levels between slabs and provides a uniform working surface.

Fire resistance level

The FRL is normally varied by changing the cover to the strands and generally adding topping to the floor. This is effective up to a fire resistance period of 180 minutes. Flexural continuity at one end of a span for imposed loads substantially increases the fire resistance period for structural adequacy or enables a reduction in cover. A typical hollowcore slab system is designed for a 2hr fire rating without need for extensive detailing or costs.

SPECIFICATION

    This specification is intended to be used as a guide to preparing the general project specification or as a stand alone specification.

    Design and shop drawings

    The Client Engineer is responsible for the design of the structure and for either the design of the slabs or, where the slab design is carried out by Teemage, the checking of the design. Slabs shall be designed in accordance with IS-875 and IS-456 for loadings supplied by the Engineer. Shop drawings shall be prepared by Teemage from information supplied by the purchaser and shall be submitted prior to manufacture for approval by the purchaser for layout, adequacy and dimensions and by the engineer for the design. All dead, live and other loads shall be shown. The drawings shall show the locations of all slabs and detail all openings as well as fire resistance levels and exposure classifications. Sections and details shall show the connections, edge conditions and end support details.

    Materials

    Cement shall comply with IS-12269 and supplementary cementitious materials with IS Standards. Aggregates shall comply with IS-383, Chemical admixtures shall comply with IS-9103. Prestressing strand shall be stress-relieved low relaxation strand complying with IS-14268 Type II. Strand shall be clean at the time of concreting. Concrete shall have a cube strength (Fck) of 50 MPa and comply with IS-4926. Concrete strength at release (typically 18 hours) shall be a minimum of 30 MPa. screeding concrete shall have a 28 day strength of 25 MPa or as shown on the shop drawings. If screeding concrete is used to grout the keyways the maximum aggregate size shall be 10mm.

    Quality Control

    Continuous quality tests on fresh and hardened concrete shall be performed based on IS-1199, IS-9103 and IS-516. Further based on project requirements, Non-Destructive testing and/or full scale load tests shall be performed under the supervision of experienced engineers.

    Manufacture

    Slabs shall be machine cast on a long line bed and mechanically compacted. The external face shall be finished to an agreed standard, either to take a screeding or otherwise. The underside face shall be off form with surface voids and colour variations limited to an agreed standard.

    Delivery and handling

    slabs shall be lifted and supported during manufacture, storage, transport and erection only at the locations shown on the shop drawings. Slabs shall be stored off the ground supported by full width battens directly above each other or otherwise as directed by Teemage Personnel. Slabs shall be lifted only by methods approved by the relevant authorities.

    Erection

    Slabs shall be installed by Teemage Erection crew or an experienced erection contractor approved by Teemage . The client shall provide suitable site access to enable fully loaded semi-trailers, cranes and other equipment to operate unimpeded. The client shall provide true and level bearing surfaces on all walls and beams supporting the slabs. Bearing strips are to be set where required. Keyways are to be aligned and grouted with a 3:1 sand-cement grout or a screeding concrete. Provide coverblocks in the voids at the slab ends as required.

    Attachments and cutouts

    Attachments to the slabs, cutouts and chases within them shall be carried out only with the approval of the engineer and Teemage.

    Cast-in-situ Screeding

    Where an Cast-in-situ Screeding is shown on the shop drawings it shall be provided by the client. The slabs shall be thoroughly cleaned down and pre-wet so that the surface is moist, but not overly wet, prior to placing the screeding. Reinforcing shall be placed and the screeding finished and cured so that the plastic and shrinkage cracks are controlled to acceptable widths. Construction joints shall be provided as shown on the Engineer’s drawings.

    Inspection and acceptance

    Finished slabs may be inspected within Teemage’s factory by the client or its representatives prior to transportation. In the event of any serious damage or other problems with the slabs rectification shall be carried out by the responsible party as permitted by Teemage and the Engineer.

    Our commitment to produce the best

    We are driven by a single focus to drive product quality, and to ensure that our products meet the standards set by our customers, their clients, and any third party agency. We have undertaken a majority of steps to ensure that this is the case. Firstly, our factory is equipped with the highest standards of machinery. Our batching and mixing plant is equipped with a high performance Wiggert planetary mixer, proven to provide better concrete mixing than the standard pan or twin shaft mixer. The machine has two moisture probes, to ensure that water content in aggregates is accurately monitored. The entire machine is run through an automatic Wiggert system. Our Hollowcore Casting machine is equipped with automatic controls for concrete feeding and vibration control. The machine has been imported from a Belgian company ECHO Precast Engineering with decades of experience in the industry. TEEMAGE have developed a 1,00,000 square foot production shed, equipped with an engineering office and R&D centre, to ensure that production activities are strongly monitored. We are constantly experimenting with admixtures, chemical additives and allied products to improve the efficiency of our plant and the quality of our products. We are continuously working on engineering innovative precast products that are not commonplace in India today. We are confident of launching our products in a much larger scale in the years to come. We follow a rigorous Quality Assurance Plan for our material, process and product testing.

    Available Hollow Core Range

    • Thickness - 150 mm
      • Span - 3- 6 mtr
    • Thickness 200 mm
      • Span 9 mtr
    • Thickness 250 mm
      • Span 12 mtr
    • Thickness 300 mm
      • Span 13.5 mtr
    • Thickness 400 mm
      • Span 16 mtr