EXPLORE PRECAST

Inventaa offers a wide variety of precast panels, divided into two categories: cladding panels and solid panels. They are used in high-rise buildings, villas, commercial, office and industrial buildings where emphasis is on prestige and aesthetic appeal, or economy and durability. Early involvement in the design phase ensures the most optimal, cost-saving solution for each project.

Cladding Panels

Cladding panels are non-load-bearing architectural panels that only fulfil an enclosing and decorative function in the facade. The combination of finish and shape contributes to the architectural expression and finished appearance of the structure. They are normally single-skin units, but can be made as a sandwich panel if required. Each panel supports only itself and does not contribute to the overall building structure; the only loads are self-weight and wind load, for which a 45 m/s wind speed is allowed as per quality codes.

Three design parts are covered when designing a structure with precast cladding:

• Design of the precast cladding part.
• The support of the precast panels, providing vertical and horizontal support.
• The connection that joins the precast units to their support.

Cladding can be fixed to steel-frame or concrete-frame structures. In general, the panel is supported vertically on a corbel in only one location, with mechanical fixing taking the horizontal load and allowing the panel to expand and contract with thermal movement. For steel building frames, the static system can be the same as for concrete structures, though fixing arrangements are normally pre-welded to the steel. In another static system, cladding panels are self-supported directly on the foundation and only horizontally fixed to the main structure.

Advantages

• Where future expansion is planned, panels allow space to be added easily using the same design, without disrupting the rest of the facility.
• Eliminates the risk of hand-setting stone or brickwork in potentially hazardous locations.
• Custom-made steel moulds create panels in exact sizes and shapes, and introduce reveals, joints, patterns and other architectural detailing.
• Specific colour effects through varied aggregates, cements, pigments and surface treatments.

Solid Panels

Solid panels can be used as interior and exterior panels. For exterior panels the cladding-panel advantages can be achieved; as load-bearing panels, basic structural requirements must be fulfilled to transfer horizontal and vertical forces. Where solid panels form the building system, the height and length match room height and length, so grouted connections appear only at room junctions. In plan, panels connect by a shear-key arrangement. Vertically, a dowel-bar projecting from the lower panel fixes into a slot in the upper panel; horizontal connections are normally grouted shear keys. A proper tying system is needed to transfer lateral forces by diaphragm action of hollowcore slabs.

Advantages

• Can be designed to act as shear walls, eliminating the need to resize columns and beams for lateral forces.
• 150 mm thick panels provide more floor space than load-bearing block walls and column-and-beam frames.
• Erection is very fast and time-saving.
• Electrical conduits and boxes are cast into the panels.
• Manufactured with smooth internal surfaces, ready for painting.
• High durability on external surfaces, with no cracks or defects and a long-lasting appearance.

Solid Panels

Solid panels can be used as interior and exterior panels. For exterior panels the advantages mentioned under cladding panels can be achieved; for load-bearing panels, basic structural requirements must be fulfilled to transfer horizontal and vertical forces. Where solid panels form the building system, the height and length match room height and length, so grouted connections appear only at room junctions. In plan, panels connect by a shear-key arrangement. Vertically, a dowel-bar projecting from the lower panel fixes into a slot in the upper panel, and horizontal connections are normally grouted shear keys. A proper tying system is needed to transfer lateral forces by diaphragm action of hollowcore slabs.

Advantages

• Can be designed to act as shear walls, eliminating the need to resize columns and beams for lateral forces.
• Erection is very fast and time-saving.
• Electrical conduits and boxes are cast into the panels.
• Manufactured with smooth internal surfaces, ready for painting.
• High durability, important on external surfaces, with no cracks or defects and a long-lasting appearance.

Inventaa panels can be made in a variety of colours and surfaces. In general, surfaces are either fair-faced or with exposed aggregate, however the group can also offer polished or acid-washed surfaces. It is also possible to have different surfaces on the same panel, separated by grooves.

Fair-faced

Grey fair-faced surfaces are normally chosen when the panel is to be painted afterwards. Using coloured concrete eliminates the need for paint, reducing finishing time and minimising maintenance cost to almost nil.

Polished

Polished surfaces are smooth and expose all aggregates. A grinder/polishing machine polishes the surface until the middle of the surface-stone is reached. Generally recommended for smaller areas or as part of a panel.

Exposed aggregate

Achieved by sandblasting the front of the panel after casting, or by using a retarder on the mould surface before casting (the panel is then cleaned with high-pressure water immediately after demoulding). The retarder method removes cement paste to about half a stone depth, leaving the stones intact; sandblasting rounds all aggregate edges and removes sharp corners.

Acid-washed

Prepared by washing the surface in a solution of water and acid, leaving it slightly rough (like sandpaper) depending on the solution and number of washes. Recommended to be limited to part of a panel, as the roughness can vary slightly from panel to panel.

Product Characteristics

Noise resistance

Choosing the right materials and connection details, along with the quality of work on site, are essential factors in achieving satisfying noise reduction and good living conditions inside a building. Due to high-quality materials and high density, Inventaa's precast concrete panels have excellent noise-reduction qualities and can be designed to achieve all the building's requirements.

Fire resistance

Panels meet the highest requirements for non-flammability and fire resistance, and can be designed for up to 4 hours fire resistance.

Thermal resistance

Sandwich panels can achieve U-values as low as 0.25 W/m2K. To reduce power consumption in residential, commercial and industrial buildings, local municipalities issue a maximum allowable thermal transmission U-value, and Inventaa can design panels to meet these requirements.

General Specifications

Inventaa has developed standard types of boundary walls, where the static system is similar but the connection details and appearance vary. The walls are designed to a height of 1.2 metres, and can be custom-designed to meet individual project requirements in terms of height, width, design features and colours.

Boundary walls are designed as self-standing and resisting wind force only. Special designs can also be incorporated where there is a significant level difference between the inside and outside ground levels, so the wall has to retain earth pressure in the horizontal direction in addition to wind force. All designs are according to standards for wind loads, soil pressures and concrete strength.

Boundary Wall (standard system)

This standard system consists of separate eccentric or concentric foundations with columns erected directly on compacted road-base soil. The columns are provided with a recess in which the hollowcore slabs or panels are placed; the slabs are supported on the foundations for vertical load and on the columns for horizontal load. Surfaces can be delivered fair-faced, ready to paint on one side and broomed or fair-faced on the other. The system is economical and used for residential and industrial areas.

Casting

Boundary wall panels and columns are cast into purpose-built moulds. Prior to casting, all cast-in parts are fixed in position and the mould is treated with a release agent. Reinforcement, normally prepared and prefabricated in our own workshop, is kept in position with adequate spacers for correct position and cover, and the mould sides are fixed. Specially manufactured casting equipment pours the concrete, which is manufactured under controlled conditions in our own batching and mixer plants for captive use only and transported directly to the casting equipment. Hand-held and fixed table vibrators achieve the best possible compaction, with the type, duration and amplitude of vibration set from pre-tests and the element being cast. After casting, elements are covered with sheets to avoid vaporisation and left to develop initial strength; concrete strength is ensured before the panels are demoulded and transported to curing and finishing. Finishing is done after curing, and all precast items below ground level are normally painted with bitumen paint.

Quality Control

• Performed to Inventaa standard procedures in well-equipped laboratories, with calibrated, maintained testing equipment.
• Materials used in concrete production are inspected and tested to company procedures and standards, and reinforcement steel is to standards.
• Compressive strength of concrete is determined from standard test cubes of the green concrete.
• All moulds are individually checked before casting; the final product is checked for finish and freedom from snags.
• Panels are cured to standard and kept watered and covered with polythene to retain moisture.
• A full QC schedule is available on request, and a per-project QC report can be agreed with the sales department.

Installation

• Excavation and compaction of the road base and access road are normally carried out by the client.
• After excavation, 200 mm road base is placed and compacted to a load-bearing capacity of at least 120-150 kN/m2, with level tolerance within +10 mm.
• Shims are placed on the footing to level the panels, with final alignment by adjustable props.
• When level, the joints between footing and panel are grouted, and below-ground items are painted with bitumen paint (which may also be applied in the factory).
• Where the wall consists of footing, column and panel, the column is placed in the footing, levelled and grouted before the panel is slid into the column pockets.
• If bitumen paint is applied on site, elements are left for it to dry; once dry, excavation in front and behind the wall is filled and compacted on both sides simultaneously to avoid overloading the wall.

Inventaa's boundary walls can be made in a variety of colours and surfaces. The various designs can be customised to the taste of the client and architects, and recesses and grooves of different finishes can be added within single panels.

Surfaces

Boundary walls can be made in a variety of colours and surfaces. Surfaces are generally either fair-faced or exposed aggregate, however we can also offer polished or acid-washed surfaces. It is also possible to have different surfaces on the same panel, separated by grooves.

General Specifications

RB-beams

RB-beams have a rectangular cross-section and are designated RB w/h, where w is the width and h the height. They are produced in standard widths of 20, 24, 30 and 36 cm, with heights from 40 to 90 cm in steps of 10 cm.

IB-beams

IB-beams have a predominantly I-shaped cross-section with rectangular sections at the ends, designated IB w/h. They are produced in standard widths of 30, 36 and 42 cm, with heights from 70 to 160 cm in steps of 30 cm. RB and IB-beams with alternative width and height can be produced within the limitations of size and weight; beam weight is based on a concrete density of 25 kN/m3.

Application: RB and IB-beams are usually used as roof and floor beams supporting hollowcore slabs or TT-slabs, and as bridge beams. Roof beams can also support steel purlins and sheeting to create a lightweight roof.

ITB-beams

ITB-beams have an inverted-T shape, designated ITB h/t, where h is the height and t is the thickness of the hollowcore slab supported on the beam. They are produced in a standard width of 48 cm, with depth below the slabs from 15 to 50 cm; special beams can also be designed.

LB-beams

LB-beams have an L-shaped cross-section, designated LB h/t, where h is the height and t is the thickness of the hollowcore slab supported on the beam. They are produced in a standard width of 36 cm, with depth below the slabs from 15 to 50 cm in steps of 10 cm. ITB and L-beams with alternative width and height can be produced within the limitations of size and weight; weight is based on a concrete density of 25 kN/m3.

Application: ITB and LB-beams are usually used as roof and floor beams supporting hollowcore slabs or TT-slabs.

FB-beams

FB-beams are flat beams with nibs, designated FB W, where W is the thickness of the slab supported on the beam. They are produced in a standard width of 120 cm with a depth below the slabs of 15 cm. FB-beams with alternative sizes can be produced within the limitations of size and weight; weight is based on 25 kN/m3.

Application: FB-beams are usually used as roof and floor beams supporting hollowcore slabs. The 15 cm depth below the slabs suits structures where minimum obstacles for services are required.

Columns

Production

Columns are produced in steel or plywood moulds. Rectangular columns are cast horizontally, leaving the bottom and both sides fair-faced and the top surface smooth. Circular columns are cast vertically with a fair-faced surface; vertical casting limits the maximum height of circular columns to 8000 mm, while rectangular columns are only limited by size and weight.

Cast-in parts

As standard, all columns are delivered with dowel holes or projecting bars at the top, lifting holes or anchors, and bracing inserts. Other project-specific cast-in parts in rectangular columns can include openings, welding plates, inserts and bolts; cast-in parts are not allowed to project through the bottom and sides of the column. Cast-in parts in circular columns should be discussed with our design office.

Corbels

Rectangular columns can be provided with corbels to support structures such as beams, at the top and on both sides; corbels at the bottom of the mould side should be avoided. Circular columns can have corbels only at the top.

Casting

Prestressed beams are produced in steel or plywood moulds, so the bottom and two sides are fair-faced while the top is smooth or rough. The two ends have a rough character, with the prestressing strands cut flush with the concrete and sealed with epoxy paint. Moulds are generally manufactured by our fabricators in our workshop as steel moulds with sufficient rigidity to produce units within the needed tolerances.

Prestressed and normal reinforced beams and rectangular columns are produced in horizontal steel moulds, with only the base made in full length and the side shuttering moved down the line for casting each individual beam. Circular columns are normally produced in vertical steel moulds. Prior to casting, all cast-in parts are fixed in position and the mould is treated with a release agent; reinforcement, prefabricated in our own workshop, is placed with adequate spacers for correct position and cover. Where beams are prestressed, all beams with similar strand patterns are prepared for casting in the same line.

Specially manufactured casting equipment pours the concrete, all of which is mixed in our own plants and transported directly to the mould. Each beam or column is cast in one continuous operation. When beams are prestressed, side moulds are removed and fixed to the adjacent beam position and cast in the same way until all beams on the line are cast. The mix is compacted using a combination of mould and hand-held vibrators for both beams and columns. After casting, all exposed surfaces are covered with a tarpaulin to avoid vaporisation.

Prestressed strands are cut only after the concrete on the last-cast beam has attained the prescribed strength of 40 N/mm2, enabling it to take the prestressing force. Normal reinforced beams and columns are demoulded 16-24 hours after casting and lifted to the stockyard for further curing, where they are covered with tarpaulin or Hessian and kept in a humid environment for another 5 days.

Finishes

Beam sides and soffit have a smooth, fair-faced off-mould finish. The corbels of inverted-T and L-beams have some minor blow-holes due to the casting method. The beam top is usually fair-faced; where exposed reinforcement is needed, such as for composite structures, the surface is made rough for a better bond to the top concrete.

Quality Control

• Performed to Inventaa standard procedures in well-equipped laboratories, with calibrated, maintained testing equipment.
• Materials used in concrete production undergo inspection and testing to company procedures; compressive strength is determined from standard test cubes of the green concrete.
• All moulds are individually checked before casting; the final product is checked for finish and freedom from snags.
• Elements are cured to standard and kept watered and covered with polythene to retain moisture.
• A full QC schedule and a per-project QC report are available on request.

Transportation and installation

• Columns and beams are normally transported on flat-bed trailers and lifted directly from the trailer into position.
• Columns are placed in the foundation and aligned using jacks; with pocket foundations, temporary support is removed after final alignment and grouting.
• Once the grout has cured, the columns are ready to receive precast beams.
• Beams are placed directly on the column or on shims depending on tolerances and surface quality; in some cases a dowel bar projects from the column into a slotted hole in the beam.

Beams - Design Example

A single-span roof structure, with hollowcore slabs spanning 17 m supported on prestressed beams spanning 10 m. Characteristic loads:

Total characteristic load Pk = ½ x 17 (1.00+0.25+1.50+4.95+0.75) = 71.83 kN/m. Total ultimate design load Pd = ½ x 17 (1.4(1.00+0.25+1.50+4.95) + 1.6 x 0.75) = 101.83 kN/m.

Required beam size. From the load and deformation tables, these beams have sufficient capacity: RB 36/90 (quls = 150.7 kN/m > Pd; qsls = 81.7 kN/m > Pk) and RB 36/100 (quls = 158.0 kN/m > Pd; qsls = 93.5 kN/m > Pk). Assuming little or no eccentricity, an IB 36/100 beam is the most economical, as its self-weight is only 75% of an RB 36/90. For eccentric load causing significant torsion, an RB 36/90 is a better choice. Shear reinforcement is designed for the specific loads.

Deformation (IB 36/100 beam). Short-term camber Csh = 8.8 mm; short-term deflection for live load ash = ½ x 17 x 0.75 x 1.4/10 = 0.9 mm; short-term deflection for dead load ash = ½ x 17 (1.00+0.25+1.50+4.95) x 1.4/10 = 9.2 mm; resulting short-term dead-load deflection a1 = -8.8 + 9.2 = 0.4 mm. Elastic settlement for full live load is 0.9 mm < span/130, and combined short-term dead-load deflection and camber is 0.4 mm < span/250.

Concentrated loads. Where beams support concentrated loads, the overall moment and shear capacity is checked. Service and ultimate moment capacities (Msls and Muls) can be derived from the load tables, while shear capacity is calculated in each individual case.

Columns - Design Specifications

Columns are designed to quality standards. Capacity depends on the cross-section, reinforcement, material properties, column length and the combination of applied axial force and moment. As an alternative, rectangular columns can be prestressed, which is advantageous for slender columns subjected to relatively high moments compared to axial load; we can advise on the use of prestressing.

Connections

Connections between column and column, or column and beam, are usually a pinned dowel connection transferring only axial and horizontal forces; transferring moments requires special design. The column-to-foundation connection can be pinned or fixed. Fixation is most easily done by forming a pocket in the foundation where the column is inserted and grouted. For moderate loads, a precast foundation is a preferred solution.

Cross-section

RC-columns have a rectangular cross-section, designated RC w/h; CC-columns have a circular cross-section, designated CC d, where d is the diameter. Both are produced in standard cross-sections from 200 to 700 mm.

General Mix Specifications

Beam Dimensions & Tolerances

Column Dimensions & Tolerances

*whichever is the larger.

Capacities

The capacity of the beams is based on standards and shown for simply supported beams in both curve and table format. Capacities are shown for maximum reinforcement and specified as Muls, Msls, quls and qsls; where maximum reinforcement is not necessary, a lower degree is specified.

• Muls / quls - ultimate moment capacity and ultimate load (kN/m) that can be applied above self-weight. These may never be exceeded.
• Msls / qsls - service moment capacity and service load (kN/m) above self-weight, based on stress limitations for class 2 members per standards. Our design office can verify capacities at serviceability limit state for class 1 and class 3 members.
• Class 1 and class 2 members are usually controlled by concrete tension and compression limitations for service load conditions, while class 3 members are usually controlled by ultimate limit state conditions.
• The shear capacity is checked in each individual case.

Fire resistance

The beams meet the requirements of 1.5 hours fire resistance as standard, which can be increased if required on individual projects.

Inventaa has three standard type systems depending on your requirement and taste.

Stair type S1

Normally made with 2 flights, 1 intermediate landing and one main landing per floor; it is also possible to combine the landing and flights in one unit. The height of the steps can be modified to suit all level heights.

Stair type S2

Constructed with 2 flight beams for each flight, on which the steps are mounted, with landings supported directly on the flight-beam extensions. This makes the whole system considerably lighter than the S1. The height of the steps can be modified to suit all level heights.

Stair type S3 (Newel)

Our Newel stair is constructed step by step with a supporting column integrated in each step unit. The finished result is a highly aesthetic staircase, light and elegant in appearance and needing only little space. The height of the steps can be modified to suit all level heights.

Staircases are normally fair-faced ready for paint, and the step and landing plate surfaces can be polished, fair-faced or roughened.

Casting

Stair flights and landings are cast into purpose-built moulds. Prior to casting, all cast-in parts are fixed in position and the mould is treated with a release agent; reinforcement, prefabricated in our own workshop, is placed with adequate spacers for correct position and cover, and the mould sides are fixed. Specially manufactured casting equipment pours the concrete, which is manufactured under controlled conditions in our own batching and mixer plants for captive use only and transported directly to the casting equipment. Hand-held and fixed table vibrators achieve the best possible compaction, with the type, duration and amplitude of vibration set from pre-tests and the element being cast. After casting, flights and landings are covered with polythene sheets to avoid vaporisation and left to develop initial strength; concrete strength is ensured before demoulding and transport to curing and finishing.

Quality Control

• Performed to Inventaa standard procedures in well-equipped laboratories, with calibrated, maintained testing equipment.
• Materials used in concrete production are inspected and tested to company procedures and standards; reinforcement steel is to standards.
• Compressive strength is determined from standard test cubes of the fresh concrete.
• All moulds are individually checked before casting; the final product is checked for finish and freedom from snags.
• Flights and landings are cured to standard and kept watered and covered with polythene to retain moisture.
• A full QC schedule and a per-project QC report are available on request, agreed with the sales department.

Transportation and installation

• Flights and landings are normally transported on flat-bed trailers and lifted directly from the trailer into position.
• Each unit is placed on PVC or steel shims to achieve the exact level required, with the gap to the supporting structure filled with a relatively dry sand-cement mortar.
• Dowel holes with projecting steel are grouted using a low-shrink, easy-flow cement mix.

Comfortable Proportions

Staircases are designed considering the length of flights, step rises and application. To achieve a comfortable walk, the proportion 2 x rise + 1 going = 600 is maintained. Recommended sizes:

General Specifications