Standard depths available: | 120mm, 150mm, 170mm, 200mm and 250mm |
Standard widths: | 1 200mm |
Non-standard widths: | In 100mm increments |
Min. concrete strength at detensioning: | 35mPa for 120mm, 150mm, 170mm and 200mm deep slabs, 40mPa for 250mm deep slabs |
Min. concrete strength at 28 days: | 50mPa |
Suggested max. span/depth ratio: | L/50 |
Prestressing wire type: | 5mm dia. triple indented low relaxation wire |
Prestressing strand type: | 9,53mm dia. stabilized strand 12,5mm dia. stabilized strand |
Suggested bearings: | On brickwork – 100mm On steel – 75mm On concrete – 75mm |
Fire rating: | 1 hour standard. Higher ratings are possible. |
SELF WEIGHT AND FINISHES – Weight – Kg/m2
Depth of Slab |
120mm |
150mm |
170mm |
200mm |
250mm |
Slab only |
222 |
253 |
275 |
306 |
358 |
Slab and Joint |
237 |
270 |
292 |
328 |
383 |
Slab, Joint & 40mm levelling screed |
337 |
370 |
392 |
428 |
483 |
The above self weights of the various slab depths are 30% lighter than an in-situ slab of a similar depth.
Prestressed slabs achieve longer spans than in-situ concrete of a similar depth. This achievement is attributed to high strength concrete and prestressed wire and strand.
Echo Prestress may be specified with cantilevers by incorporating reinforcing into the hollow cores which are grouted in the factory during the casting process.
Where Echo Prestress is used as roof slabs or balconies, a minimum Ref. 100 mesh is required in the insulating screed over the panels, as well as a slip joint on the walls. On indoor areas where tiles are specified a minimum Ref. 100 mesh is required in the screed. Expansion joints are required in tiled areas. All unfinished areas also require the same mesh. Refer to the detailed screeding specifications.
SECTIONAL INFORMATION
Cross section area |
102,365 10e3mm2 | Conc. 28 day strength | 50N/mm2 |
Moment of inertia |
154.393 10e6mm4 | Conc. strength at transfer | 35N/mm2 |
Section modulus top |
2,549 10e6mm3 | Mod. of elasticity of conc. | 34kNm/m2 |
Section modulus bottom |
2,598 10e6mm3 | Stressing of strand/wire |
70% |
Total breadth of webs |
468mm | Check: stresses at transfer | O.K. |
Centroidal axis from bottom |
32,5mm | Cover to steel | 30,0mm |
Core cover | 25,0mm |
STRUCTURAL INFORMATION
Moment & Shear Capacities |
Wiring Pattern |
|||
B |
C |
D |
E |
|
Service moment |
20,66kNm/m |
24,83kNm/m |
27,44kNm/m |
31.10kNm/m |
Ultimate moment |
28,14kNm/m |
37,73kNm/m |
43,25kNm/m |
50.38kNm/m |
Ultimate shear resistance |
99,56kN |
104,75kN |
107,06kN |
109.39kN |
STANDARD WIRING PATTERNS
B = 12 x 5mm wires | C = 9 x 5mm wires + 3 x 9.53mm strand |
D = 7 x 5mm wires + 5 x 9.53mm strand | E = 4 x 5mm wires + 8 x 9.53mm strand |
LOAD CAPACITY TABLE
Note: Span=Clear span +100mm
Live Load |
Wiring Pattern / Span | |||
B |
C |
D |
E |
|
Span |
Span |
Span |
Span |
|
0,75 |
5,5 |
6,2 |
6,5 |
6,8 |
1,5 |
5,1 |
5,7 |
6,0 |
6,4 |
2,5 |
4,6 |
5,2 |
5,5 |
5,9 |
4,0 |
4,1 |
4,7 |
4,9 |
5,2 |
5,0 |
3,8 |
4,4 |
4,6 |
4,9 |
7,5 |
3,3 |
3,9 |
4,1 |
4,3 |
10,0 |
3,0 |
3,5 |
3,7 |
3,9 |
Note: Design loads include self weight, grouting between joints and finishes up to 1,5kNm/m2.
CROSS SECTIONAL DIMENSIONS
SECTIONAL INFORMATION
Cross section area |
117.248 10e3mm 2 | Conc. 28 day strength | 50N/mm2 |
Moment of inertia |
286.517 10e6mm4 | Conc. strength at transfer | 35N/mm2 |
Section modulus top |
3.790 10e6mm3 | Mod. of elasticity or conc. | 34kNm/m2 |
Section modulus bottom |
3.851 10e6mm3 | Stressing of strand/wire | 70% |
Total breadth of webs |
468mm | Check: stresses at transfer | O.K. |
Centroidal axis from bottom |
32,5mm | Cover to steelCore Cover | 30,0mm25,0mm |
STRUCTURAL INFORMATION
Moment & Shear Capacities |
Wiring Pattern |
||||
B |
C |
D |
E |
F+2 |
|
Service moment |
29,94kNm/m |
36,03kNm/m |
39.83kNm/m |
45.15kNm/m |
51.51kNm/m |
Ultimate moment |
38.50kNm/m |
52.60kNm/m |
61,64kNm/m |
73,53kNm/m |
86.03kNm/m |
Ultimate shear resistance |
121.83kN |
128.35kN |
131.28kN |
134.27kN |
141.47kN |
STANDARD WIRING PATTERNS
B = 12 x 5mm wires | C = 9 x 5mm wires + 3 x 9.53mm strand |
D = 7 x 5mm wires + 5 x 9.53mm strand | E = 4 x 5mm wires + 8 x 9.53mm strand |
F +2 = 12 x 9.53mm + 2x5mm wire (top) |
LOAD CAPACITY TABLE
Wiring Pattern
|
|||||
Live Load |
B |
C |
D |
E |
F+2 |
0,75 |
6,2 |
7,2 |
7,6 |
7,8 |
8,6 |
1,5 |
5,7 |
6,7 |
7.0 |
7,5 |
8.0 |
2,5 |
5,2 |
6.1 |
6,5 |
6,9 |
7.4 |
4,0 |
4,7 |
5,5 |
5,8 |
6.2 |
6,6 |
5,0 |
4,4 |
5,1 |
5,5 |
5,8 |
6.2 |
7,5 |
3,8 |
4,5 |
4,8 |
5.2 |
5,5 |
10,0 |
3,5 |
4,0 |
4,4 |
4,7 |
4,9 |
Note: Design loads include self weight, grouting between joints and finishes up to 1,5kNm/m 2 .
Span=clear spam +100mm
CROSS SECTIONAL DIMENSIONS
SECTIONAL INFORMATION
Cross section area |
126.715 10e3mm2 | Conc. 28 day strength | 50N/mm² |
Moment of inertia |
403.072 10e6mm4 | Conc. strength at transfer | 35N/mm² |
Section modulus top |
4.715 10e6mm3 | Mod. of elasticity of conc. | 34kNm/m² |
Section modulus bottom |
4.770 10e6mm3 | Stressing of strand/wire | 70% |
Total breadth of webs |
468 | Check: stresses at transfer | O.K. |
Centroidal axis from bottom |
32,5mm | Cover to steel Core Cover |
30,0mm 25,0mm |
STRUCTURAL INFORMATION
Moment & Shear Capacities |
Wiring Pattern |
||||
B |
C |
D |
E |
F+2 |
|
Service moment |
36.40kNm/m |
44.06kNm/m |
48.68kNm/m |
55.16kNm/m |
62.91kNm/m |
Ultimate moment |
45.53kNm/m |
62.35kNm/m |
73.27kNm/m |
88.72kNm/m |
105.60kNm/m |
Ultimate shear resistance |
136.4kN |
143.34kN |
146.73kN |
150.21kN |
158.407kN |
STANDARD WIRING PATTERNS
B = 12 x 5mm wires | C = 9 x 5mm wires + 3 x 9.53mm strand |
D = 7 x 5mm wires + 5 x 9.53mm strand | E = 4 x 5mm wires + 8 x 9.53mm strand |
F+2 = 12 x 9.53mm strand + 2 x 5mm wires (top) |
LOAD CAPACITY TABLE
Note: Span=Clear span + 100mm
Wiring Pattern
|
|||||
Live Load |
B |
C |
D |
E |
F+2 |
0,75 |
6,7 |
7,8 |
8,2 |
8,7 |
9,3 |
1,5 |
6.1 |
7,2 |
7.6 |
8,1 |
8,7 |
2,5 |
5,6 |
6.5 |
7,0 |
7,5 |
8,0 |
4,0 |
5.0 |
5,9 |
6.3 |
6,8 |
7,2 |
5,0 |
4,7 |
5,5 |
6,0 |
6,4 |
6,8 |
7,5 |
4,2 |
4,8 |
5,3 |
5,6 |
6,0 |
10,0 |
3,7 |
4,4 |
4,7 |
5,1 |
5,5 |
Note: Design loads include self weight, grouting between joints and finishes up to 1,5kNm/m ² .
CROSS SECTIONAL DIMENSIONS
SECTIONAL INFORMATION
Cross section area |
141.325 10e3mm2 | Conc. 28 day strength | 50N/mm² |
Moment of inertia |
626.385 10e6mm4 | Conc. strength at transfer | 35N/mm² |
Section modulus top |
6.240 10e6mm3 | Mod. of elasticity of conc. | 34kNm/m² |
Section modulus bottom |
6.287 10e6mm3 | Stressing of strand/wire | 70% |
Total breadth of webs |
468mm | Check: stresses at transfer | O.K. |
Centroidal axis from bottom |
32,5mm | Cover to steel Core Cover |
30,0mm 25,0mm |
STRUCTURAL INFORMATION
Moment & Shear Capacities |
Wiring Pattern |
||||||
B |
C |
D |
E |
F+2 |
|||
Service moment |
46.48kNm/m |
55.79kNm/m |
61.61kNm/m |
69.76kNm/m |
80.64kNm/m |
||
Ultimate moment |
55.47kNm/m |
76.98kNm/m |
90.73kNm/m |
110.80kNm/m |
137.75kNm/m |
||
Ultimate shear resistance |
157.61kN |
166.63kN |
170.77kN |
175.07kN |
184.22kN |
LOAD CAPACITY TABLE
Note: Span=Clear span + 100mm
Live Load |
||||||||||||||||||||||||||||||||||||||||||||||||
|
Note: Design loads include self weight, grouting between joints and finishes up to 1,5kNm/m².
CROSS SECTIONAL DIMENSIONS
SECTIONAL INFORMATION
Cross section area |
165.675 10e3mm2 | Conc. 28 day strength | 50N/mm2 |
Moment of inertia |
1143.163 10e6mm4 | Conc. strength at transfer | 35N/mm2 |
Section modulus top |
9.137 10e6mm3 | Mod. of elasticity of conc. | 34kNm/m2 |
Section modulus bottom |
9.154 10e6mm3 | Stressing of strand/wire | 70% |
Total breadth of webs |
468mm | Check: stresses at transfer | O.K. |
Centroidal axis from bottom |
34,5mm | Cover to steelCore Cover | 30,0mm25,0mm |
STRUCTURAL INFORMATION
Moment & Shear Capacities |
Wiring Pattern |
||||||
C |
D |
E |
G+2 |
H+2 |
J+4 |
||
Service moment |
77.07 kNm/m |
85.03 kNm/m |
96.27 kNm/m |
118.87 kNm/m |
127.18 kNm/m |
141.96 kNm/m
|
|
Ultimate moment |
101.17 kNm/m |
119.86 kNm/m |
147.01 kNm/m |
205.42 kNm/m |
227.22 kNm/m |
263.67 kNm/m
|
|
Ultimate shear resistance |
204.44 kN |
211.64kN |
217.16 kN |
235.08 kN |
238.96 kN |
252.03 kN
|
STANDARD WIRING PATTERNS
C = 9 x 5mm wire + 3 x 9.53mm strand | D = 7x 5mm wire + 5 x 9.53mm strand |
E = 4 x 5mm wires + 8 x 9.53mm strand | G+2 = 10 x 9.53mm strand + 2 x 12mm strand + 2 x 5mm wires (top) |
H+2 = 8 x 9.53mm strand + 4 x 12.5mm strand + 2 x 5mm wires (top) | J+4 = 4 x 9.53mm strand + 8 x 12.5mm strand + 4 x 5mm wires (top) |
LOAD CAPACITY TABLE
Span = clear span + 100mm
Wiring Pattern
|
|||||||
Live Load |
C |
D |
E |
G+2 |
H+2 |
J+4 |
|
0,75 |
9,2 |
10,0 |
10,8 |
12,0 |
12,4 |
13,0 |
|
1,5 |
8,6 |
9,4 |
10,1 |
11,2 |
11,6 |
12,2 |
|
2,5 |
7,9 |
8,6 |
9,4 |
10,4 |
10,8 |
11,4 |
|
4,0 |
7,2 |
7,8 |
8,5 |
9,5 |
9,8 |
10,4 |
|
5,0 |
6,8 |
7,4 |
8,1 |
9,0 |
9,3 |
9,8 |
|
7,5 |
6,0 |
6,5 |
7,2 |
8,0 |
8,3 |
8,8 |
|
10,0 |
5,5 |
5,9 |
6,6 |
7,3 |
7,6 |
8,0 |
Note: Design loads include self weight, grouting between joints and finishes up to 1,5kNm/m 2 .
CROSS SECTIONAL DIMENSIONS
- Larger cut-outs can be formed in the factory. These holes require more specific strengthening, but can be catered for at the design stage.
- Skylight and stair openings are formed by specifically fabricated steel hangers which are supplied and erected by Echo Prestress. Alternatively a steel, brick or concrete beam can be used as support around the opening.
- The tops of the hollow cores can be opened to take steel when the units are used in composite action with steel or concrete beams.
- Skew ends can be cut in the factory with a diamond tipped saw blade specifically manufactured to accurately cut any angle.
For suspended or other light fittings, simply drill a hole through the slab and into the slab’s hollow core to fit the electrical wiring through.
Any excessive edge chipping is easily repaired with ‘Rhinolite’ or similar material.
Costs of such electrical light points also become more economical as electrical wires and single light transformers can be placed into the horizontal hollow cores of the slabs the day after installation, instead of the traditional light boxes and conduits.
As the panels are designed and manufactured specifically for your project, site dimensions need to be accurate to avoid delays. Site dimensions are checked by Echo prior to manufacture. Sand and cement for grouting between the Echo panels are to be supplied by the customer. The actual grouting is done by Echo.
Window and door openings in load bearing walls up to 2,0 meters wide can be covered by lintols side by side with five courses of brickwork with brick force in every course for slab spans up to 7 meters. Openings wider than 2 meters must be referred to the engineer for detailing of additional structural steel supports.

Electrical conduits should be run over the top of the Echo slab with a 40mm river sand and cement leveling screed placed over the top.
- The underside or soffit of the slab is smooth and does not require plastering.
- To finish, rake the underside of the joint clean soon after grouting.
- Trowel a small quantity of Rhinolite or similar into the underside of the joints.
- Finish to a smooth rounded shape by running a piece of plastic conduit along the joint.
- N.B. It is not recommended that the joints are plastered closed. (Should you wish to do so, ask Echo for a recommended specification).
- Apply a bonding liquid to the soffit before applying a textured paint.
APPLICATION OF SCREED
All loose material is to be removed from the tops of the slabs. The slabs should be thoroughly wetted and screed applied immediately. The levelling screed should comprise a 1:4 mix by volume of cement and clean river sand. Water should be added to the mixture to an extent that the mixture is relatively dry but remains easy to float finish. The screed should be laid to an approximate thickness of 40mm. Note that in some areas additional screed may be necessary to level out the camber in the units. After laying the screed it should be steel floated and then wetted for 48 hours to prevent shrinkage cracks.
In certain areas, namely balconies, roofs, walkways, tiled areas, car parks and areas where the screed is to be left unfinished, the screed specifications change slightly. On balconies, roofs, walkways etc., i.e. all areas where Echo Prestress slabs are exposed to the elements – a Ref. 100 mesh* must be placed in the leveling screed to counteract the transverse forces created by large temperature differences.
Where tiles are to be used on the slab, a Ref. 100 mesh* must be placed in the levelling screed as for balconies, roofs and walkways. Expansion joints should be allowed in the tiles every 3 metres and particularly where the section alters shape such as doorways. It is recommended that a flexible tile adhesive be used. TAL (Pty) Ltd. have produced a technical specification for tiling on Echo slabs which is available on request from Echo Prestress.
On car parks a Ref. 193 mesh** must be placed in a structural topping of not less than 50mm thickness to help spread the load from one panel to the next. The screed can be left rough to suit the clients requirements.
In areas with exposed screed a Ref. 100* mesh is required to control shrinkage/drying stresses. These areas would also require adequate movement joints.
Where the screed thickness is 50mm or less the mesh should be laid flat on top of the slab and the screed placed on top. Where the screed depth exceeds 50mm the mesh should be placed 20mm from the top surface of the screed.
Providing the above procedures are followed, the screed will adhere extremely well to the prepared surface of the slab. Experience has shown that it is impossible to remove the leveling screed from the top surface of the slab after a few days.
* A ref. 100 mesh is a 4,0mm wire in a square pattern at 200mm centres.
** A ref. 193 mesh is a 5,6mm wire in a square pattern at 200mm centres.
Specifications for the following are available from Echo prestress on request:
- The tiling of Echo Prestressed slabs
- Grouting between joints (generally undertaken by Echo Prestress)
- Structural toppings to enhance the slab capacity
- Methods of finishing Echo Prestress slabs
The Cement and Concrete Institute (Tel. 011 315 0300) have produced a standard specification for sand/cement screeds and concrete toppings for all types of floors. Request a copy from Echo Prestress.

The term ‘composite’ refers to structures where Echo Prestress slabs and in-situ concrete work together to form an integral structural component.
The Echo Prestress slab can be made composite with the supporting beams to increase the overall structural depth of the supporting beams. Echo Prestress has pioneered the use of Prestressed concrete panels utilizing composite action between the support beams and the slab construction. Echo Prestress have a versatile approach in that various schemes may be proposed using Prestressed Hollow Core slabs in conjunction with the following:
- Reinforced precast beams supplied by Echo
- Cast in-situ reinforced, prestressed or post tensioned beams.
- Structural steel framework with shear connectors welded to the beam to provide composite action.
- Mixed Use – Load bearing masonry perimeter walls with internal in-situ columns and precast beams in composite action with Echo Prestress slabs.
DESIGN SYNOPSIS
As in any composite structure, the design principal is to bond separate elements together to form one element which by virtue of shear interaction, is considerably stiffer than the two elements acting independently.
In the case of Prestressed Hollow Core concrete panels and concrete support beams this shear interaction is provided by steel stirrups projecting above the surface of the beam and transverse shear steel, which facilitates the transfer of the forces between the slab and the beam.
Structural steel beams are provided with shear connectors on the top flange in the form of channels or welded studs to provide the shear interaction.
The support framework is generally designed to support the loads imposed by the Prestressed Hollow Core floor panels and a nominal construction loading with or without the use of props, depending on the budget. Provision is made for continuity steel in the slab across the support beams to accommodate the increased mass imposed by finishes, partitions and super- imposed loading.