Precast concrete is highly fireresistant and an excellent material for compartmentalization as it slows the. In practice, a concrete topping layer is often cast in place onto the top surface of hollow core slabs to create a continuous level finished surface. Hollow core plank mid south prestress is the largest producer of precast hollow core plank concrete in the midsouthern united states. Concrete toppings on precast concrete must be tested for moisture as for. In fact, the compressive stress wave travelled across the hollow core slab to the concrete topping, and is reflected back as a tensile wave.
Hollow core covering slabs are characterized with possibility to be used in. Yes, autodesk structural bridge design can be used to analyse and design hollow core slabs. Q i have a 24 by 26foot slab 3 inches thick cast over precast concrete planks on top of 8foot walls. Ch 20 concrete construction site cast precast flashcards. A sitecast topping screed unifies the planks into a monolithic floor, takes out differential levels. Part of the building was left unfinished for later use, and, when it was built out, the owner noticed a crack that was visible on the topping surface but not on the underside of the hollowcore members, which are visible from the floor below. Prepared for the pci hollow core slab producers committee john e. Hollowcore slabs are prestressed floor elements with voids.
Preparation for topping typically, composite topping slabs are placed over the grouted hollow. Jan 07, 2016 over hollow core concrete planks, gypsum underlayments can achieve up to fourhour fire ratings at half the thickness of portlandbased concrete. Concrete toppings on precast concrete must be tested for moisture as for ordinary concrete floor slabs. Ascc concrete contractors will meet the specification requirements for castinplace topping slabs over prestressed members. Cause of cracks in hollowcore panel topping concrete. If moving cracks exist in the base slab, there is a risk they will telegraph through the topping. Figure 1 hollow core slabs are precast, prestressed concrete members with continuous voids provided.
High strength prestressing strands are cast into the planks at the spacing and location required for the given span, loading and fire cover conditions. Standard widths are 48 inches and thickness of 8,10 and 12 inches. Precast concrete hollow core floor slabs hollow core slabs are precast, prestressed concrete elements that are generally used for flooring. Dispelling common myths associated with poured gypsum floors. Jun 21, 20 concrete toppings on precast concrete must be tested for moisture as for ordinary concrete floor slabs. A poured concrete slab is then poured on top of the concrete planks. Give the surface time to dry before placing the topping. Other topping materials such as gypcrete can be added to achieve a fire endurance using different tables. The typical slab is two and half inches to 4 inches. A waterproof barrier of rubber, sometimes vinyl membrane or, more recently, a spray on product is installed over the concrete planks and below the poured slab, sandwiched between the two, to provide a barrier for water that. Repair of crack in topping over precast planks concrete.
The concrete hollow core slabs have between four and six longitudinal cores running through them, the primary purpose of the cores being to decrease the weight, and material within the floor, yet maintain maximal strength. Common depths of prestressed hollowcore slabs range from 6 to 10 in. Common depths of prestressed hollow core slabs range from 6 to 10 in. To obtain a higher slab thickness, normal carbonate concrete field topping can be added to gain a higher total slab thickness. First, it separates the hollow core slab from the topping slab, eliminating the possibility of designing a composite topping to increase bending moment capacity and potentially simplify the diaphragms design. The slab will generally be modeled as a grillage type structure with the longitudinal beam members represented by prestressed or rc beams also defined. Hollowcore slabs vary by depth, length and loading performance with the standard width of a slab being 1200mm. Design examples 84 the following style is used when referring to a section of aci 318 for which a change or insertion is proposed by the provisions. It is common for precast, prestressed hollow core slabs to exhibit camber i.
Sizes and locations of these openings are to be provided to the manufacturer by the respective trades. No cracks were observed on either the top or bottom blocks before failure of any specimen. Similar to icfs and hollow core planks greenbuildingtalk hollow core seems to be the most economical method. Some of the following guidelines will help reduce and control cracking in the concrete topping, but specifiers should understand that the total elimination of cracks is not.
Run the numbers and estimate your next project in oldcastle precast hollowcore plank. Attachments and fixings to the hollow core planks shall be in accordance with the approved details only and shall not impair or reduce the strength of the floor planks. More recently, hollow core slabs with depths as great as 16 in. Using an extruded process, hollow core plank or hollow core slab is a plantmanufactured prestressed concrete slab with. The planks are produced in our plant using an ultra span machine. Also, appropriate placing and curing procedures must be followed to avoid delamination andor curling of the topping slab. Aug 09, 2017 full operation of precast hollow core slab machine shuangli building materials equipment co. For architects engineers contractors builders saycore. Learn vocabulary, terms, and more with flashcards, games, and other study tools. A structural topping can increase that up to a 4hour rating. The topping prevents the finished floor from cracking or loosening from the subfloor. The aci 1996 standard provides guidelines on pages 302. Installation hollowcore slabs are to be located and installed in accordance with expocrete drawing.
We supplied 4x24foot hollowcore slabs for a building floor that received a 2inchthick concrete topping placed by the concrete contractor. Full operation of precast hollow core slab machine shuangli building materials equipment co. The mix design of the topping is the same as the interior slabs on grade 34 aggregate w min. Hollowcore planks can be attached to cmu walls, steel beams or precast wallsbeams. Elematic is a machine extruded, precast, prestressed hollow core plank. These can either be reinforced concrete cast in place voided slabs or hollow section precast units. Pci manual for the design of hollow core slabs and walls.
A hollow core slab, also known as a voided slab, hollow core plank or simply a concrete plank is a precast slab of prestressed concrete typically used in the construction of floors in multistory apartment buildings. Hollow core slab properties prop imperial metric a 290. This tensile wave can be much higher than the allowable interface normal stress between the hollow core slab and the concrete topping, and enhances the debonding problem. Pci manual for the design of hollow core slabs second edition by donald r. Keep the dunnage accurately aligned from slab to slab. Precast topping concrete engineering general discussion. Hollowcore slabs are economical, have good fire resistance and sound insulation properties, and are capable of spanning long distances with relatively shallow depths.
Minimum end bearing is 75mm unless specified otherwise on drawings. Special conditions on a project may require more specific evaluation of practical engineering. Chapter 7 fire resistance of assemblies made with hollow core slabs. As a structural topping over hollow core slabs, generally all that is required is that the surface be clean. Excellent soundreducing qualities, durability and inherent fire resistance make our hollowcore slabs the solution of choice for apartments, care homes, hospitals and commercial projects. Chapter 2 of the pci design handbook3 provides information on dimensions, section properties, and loadcarrying capacities of hollowcore slabs. Trailblazer 4 precast concrete industry 45,865 views. A common misconception is that fire destroys by flames, which can be suppressed by sprinklers. Savings in cost and time will keep your project on time and under budget. Although it protects the membrane, this assembly has two drawbacks. Hollow core slabs are economical, have good fire resistance and sound insulation properties, and are capable of spanning long distances with relatively shallow depths. A layer of 50 mm thickness placed over the hollow core slabs shows an increase of the cracking moment.
The concrete hollow core slabs have between four and six longitudinal cores running through them, the primary. Structural topping thicknesses vary with a minimum of 2. The slabs shall be 6, 8, 10, or 12 depths and 48 standard width. Topping option and is intended to help specifiers, designers, and contractors use the best practices currently available for the design and installation of this material. Therefore, we meet the requirement for a 3 hour slab thickness, but the strand clear cover needs to be met too. In pre cast solid slab construction t he cost of tr ansportation of units. Reference the current edition of the aci manual of concrete.
In order to view pdf documents, you must have adobe acrobat reader installed. Gypsum levelers, when used in combination with sound mats, provide a sound transmissions class stc and impact insulation class iic that will exceed the requirements of section 1207 of the. Hollow core the hollow core slab has a variety of uses, including floors and roofs for buildings and parking garages, decks for piers, and lagging for retaining walls. Hollow core slab properties prop imperial metric a 235. Pdf assessment of cost variation in solid and hollow. Modifications requested after the bid award will result in a change order. Cracks can be filled with a polymer structural filler material such as epoxy. Hollow core planks are used for the economic construction of bridges. Our precast hollowcore floors are available in sections 150, 200, 250 and 260mm deep. Largely because of fast onsite construction, bison hollowcore floors are one of the most economic flooring solutions for the widest variety of situations including masonry, steel and concrete structures for retail, commercial and industrial buildings. Hollowcore floor, discusses the various finishing options available when.
Using an extruded process, hollow core plank or hollow core slab is a plantmanufactured prestressed concrete slab with continuous cores, or voids, which considerably reduces weight up to 50% compared with a pouredinplace flat slab and cost. Hollow core plank, prestressed hollow core slab, precast. How to protect hollowcore slabs in parking structures. Structural topping must be bonded to the planks, continuous from support to support uninterrupted by walls or expansion joints. In practice, this oversimplification can leave both property and human life vulnerable during a fire. Castinplace, composite concrete topping is highly recommended to provide a smooth, level floor surface that serves as a horizontal diaphragm when properly reinforced. However, the slabs can be manufactured to suit the specifications of your construction project. In many floor applications, hollowcore plank may be used without concrete topping. Check here if you wish to receive emails from spancrete. Slabs are manufactured by skilled pci certified plant technicians at our. Penetrations and chases to the hollow core planks shall be in accordance with details agreed by the structural engineer and the product manufacturer. Over hollowcore concrete planks, gypsum underlayments can achieve up to fourhour fire ratings at half the thickness of portlandbased concrete. The planks are cut to length for each project using. Dealing with precast concrete the flooring professionals.
Depends where you are located for solid answers, i have done plenty of hollow core slabs, the footings do need to be calcd by the s. Cracks that are exhibiting substantial movement can also be stabilized by cross. On top of the hollowcore slabs, a 2 in topping slab is placed to finish it off. Details are available in both adobe acrobat reader pdf and cad dxf format.
Saccoman, chairperson james beerbower ernest markle kevin boyle james markle jeffrey butler milo j. They can be delivered nationwide on a supply and install basis by. Please provide your email address to learn more about how one builder maximized the benefits offered by precast. Adobe acrobat reader is free and can be downloaded here. Start studying ch 20 concrete construction site cast precast. Thanks for your interest in building with precast in the residential space. Dxf files can be imported directly into many common cad programs. The safety ropes shall be unhooked only when the slab is in the distance of 10 cm over the place of support as a rule, slabs shall be. Periodically we encounter construction specifications stipulating that the hollow core slabs are to be cambered to overcome dead load deflection due to self. Concrete topping slab is an overlay designed to provide a dense, abrasionresistant, and a finished floor surface for multiple purposes such as providing a wearing course to. Plot of maximum shell stresses on topping slab when stiffness of link element is 100 lbin.
Plans locating and defining all hollow core planks furnished by the manufacturer with all castin openings shown and located. Concrete topping slab is an overlay designed to provide a dense, abrasionresistant, and a finished floor surface for multiple purposes such as providing a wearing course to support traffic loads in parking facilities and bus terminals, providing a level surface for interior floors, providing special base for electrical and mechanical equipment. The depth of each slab usually ranges from 110 mm to 400 mm with spans typically available up to 200 meters. Icfs and hollow core planks greenbuildingtalk insulating concrete forms icfs similar to icfs and hollow core planks greenbuildingtalk hollow core seems to be the most economical method. Concrete topping for hollow core floor slabs structural. The slabs are typically 4 feet wide with standard thicknesses of 8 and 12. The saycore hollow core plank shall be manufactured of high strength concrete, grout key edged, machine extruded slabs. After curing, the slabs shall then be cut andor ripped to the lengths and widths indicated on the approved saycore shop drawings. If not clean and free of laitance, high pressure water cleaning is the best method. The underside of hollowcore plank is steel form smooth, and can be either left as is or painted with a textured paint. Chipped, spalled, or cracked units may be repaired, subject to architects. As a result, hollowcore plank offers a higher spantodepth ratio.
Installation hollow core slabs are to be located and installed in accordance with expocrete drawing. Pdf problem of cracks in prestressed hollow core slabs. After curing, the slabs shall then be cut andor ripped to the lengths. Preparing for a topping concrete construction magazine. The plank is manufactured on 500foot long beds in a standard width. Cracks that are exhibiting substantial movement can also be stabilized by crossstitching where reinforcing bars are epoxied into holes drilled into the slab across the. This underscores the need for diligent underdeck examination to properly characterize the type of deck.
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