Precast concrete specification

1. PRECAST LIGHTWEIGHT CONCRETE PARTITIONS
1. GENERAL
Precast lightweight concrete partitions shall be used on all typical storeys at locations as shown in the
Architectural Drawings
The precast lightweight concrete partitions shall be obtained from suppliers approved by the SO Rep. The
list of approved Suppliers can be obtained from the HDB’s Contracts & Administration Department of
Structural Engineering Department.
2. TECHNICAL SPECIFICATIONS AND TESTS
- PRECAST LIGHTWEIGHT FOAM CONCRETE PARTITIONS
The precast lightweight concrete partitions shall satisfy the following technical specifications:
2.1 Manufacturing Requirements
a) A characteristic compressive strength of 4.5N per mm2 at 28 days.
b) A density (air dry) of between 1400 kg per m3 and 1800 kg per m3.
c) A drying shrinkage not exceeding 0.09% when tested to SS 271.
d) A total water absorption not exceeding 23.5% when tested to SS 271.
e) A minimum fire rating of 1 hour.
f) Materials used in the manufacturing of precast lightweight foam concrete partitions shall
comply with Section 3 “Structural Concrete”. The foaming agent used in the manufacturing of
lightweight foam concrete partitions shall comply with the performance requirement of
BS5075: Part 2. No foaming agent shall be used unless prior approval has been given by the SO
Rep.
g) Reference shall be made to the Employer’s standard detailed drawings regarding steel
reinforcement and guidelines on panelling and layout of partitions.
h) Partitions shall be cast using steel moulds in horizontal position to conform to the shape, lines
and dimensions of the partitions to be produced. The mould should be sufficiently rigid to
produce the casting tolerances, shapes, orientation and surface finishes specified:
i. Casting tolerance for partition height and width shall be ±5mm and ±3mm respectively.
ii. Casting tolerance of thickness is ±3mm for either 75mm or 90mm thick partition as shown
in the Architectural Drawings.
iii. The shapes and location of tongues and grooves of partitions after casting shall be correct
and accurate such that the off-set between two adjacent panels after installation is within
2mm on both faces of the partitions.
iv. The geometry and arrangement of the steel moulds far casting partitions shall be such that
the off-form surfaces to two adjacent panels after installation are in the same plane with
compatible interlocking tongues and grooves.
v. Bowing and warpage after casting shall not exceed 3mm in 2 metres along the height of
each panel and 1mm in 600mm along the width of each panel.
i) The partitions shall be provided with openings where required for services.
j) Standard fixing and connection details (including those for frames). As shown in the
Employer’s Standard Structural and Architectural Drawings shall be used. Details different
from the Employer’s standard details may only be used if submitted by a Professional Engineer
with complete detailed drawings and calculations and approved by the SO Rep.
2.2 Requirements Prior to Delivery
Prior to delivery of partitions to site, ensure that the partitions are manufactured to satisfy the
following requirements:
a) Casting Tolerance
i. Height : ±5mm
ii. Width : ±3mm

2. iii. Thickness : ±3mm
iv. Bowing/Warpage : 3mm in 2 metres along the height
1mm in 600mm along the width
b) Surface Finish
The surface finish of partitions shall be smooth and free from excessive voids, the Contractor
shall allow in his tender sum for the cost of touching up or other remedial work to smoothen the
surface to the satisfaction of the SO Rep.
For the purpose of this Clause, a smooth surface shall be defined as one with:
i. No voids of bug holes greater than 7mm in diameter within a 50mm border around the
edges of the panels; and
ii. For the remaining centre portion, the number of air voids greater than 1.5mm and smaller
than 3mm in diameter shall not exceed 20 in any 100 x 100m square. No void greater than
3mm in diameter shall be allowed.
c) Tongues And Grooves
The accuracy of shapes and locations of tongues and grooves of partitions after casting are
verified by two special steel templates. This is to ensure that the offset between any two panels
after installation is within 2mm on both faces of partitions.
d) No partition is delivered prematurely to site before sufficient strength has been gained to
withstand stresses due to transportation, handling or erection.
e) Provision of adequate supports for partitions to prevent chipping off of panel edges during
transportation and handling.
3. TECHNICAL SPECIFICATIONS AND TESTS
- PRECAST LIGHTWEIGHT WOODFIBRE CONCRETE PARTITIONS
The precast lightweight woodfibre concrete partitions, an alternative to the lightweight foam concrete
partitions, shall be obtained from suppliers approved by the SO Rep for the supply of this product.
3.1 Over-riding Clause
The Contractor and his Specialist executing the works as required in this Clause including sub-
clauses have to ensure that the works, goods or materials used shall be suitable and reasonably fit for
the purposes for which they are required (hereinafter referred as “Performance Requirement”). In the
event the works, goods and materials to be used as specified in this Clause including sub-clauses are
upgraded in order to meet as Performance Requirement, the Contractor and his Specialist shall do all
necessary upgrading at no extra cost to the Employer, subject always to the approval of the SO Rep.
but such approval shall not in any way affect the Contractor’s and his Specialist’s duties or
obligations arising under the Contract.
3.2 Manufacturing Requirements
The partitions shall satisfy the following technical specifications:
a) A characteristic compressive strength of 4.5N per mm2 at 28 days.
b) A density (air dry) of between 1400 kg per m3 and 1800 kg per m3.
c) A drying shrinkage not exceeding 0.09% when tested to modified RILEM CPC9-1975(E) or
approved equivalent.
d) A total water absorption not exceeding 20% when tested to VTT Test 359-87 or approved
equivalent.
e) A minimum fire rating of 1 hour.
f) Materials used in the manufacturing of precast lightweight concrete partitions shall comply
with Section 3 “Structural Concrete”. The woodfibres used in the manufacturing shall be of the
quality, when tested, complying with VTT Test Standards stipulated in Dno 4/6/8/BET. The
test report for the woodfibres used shall be submitted to the SO Rep as and when requested.
g) Reference shall be made to the Employer’s standard detail Drawings regarding guidelines on
panelling and layout of partitions.

3. h) Partitions shall be cast using steel moulds in horizontal position or by method of extrusion by
automated machine to conform to the shape, lines and dimensions of the partitions to be
produced. The steel mould, if use, shall be sufficiently rigid to produce the casting tolerances,
shapes, orientation and surface finishes specified:
i. Casting tolerance for partition height and width shall be ±5mm and ±3mm respectively.
ii. Casting tolerance of thickness is ±3mm for either 75mm or 90mm thick partition as shown
in the Architectural Drawings.
iii. The shapes and location of tongues and grooves of partitions after casting shall be correct
and accurate such that the off-set between two adjacent panels after installation is within
2mm on both faces of the partitions.
iv. The geometry and arrangement of the steel moulds, if use, for casting partitions shall be
such that the off-form surfaces to two adjacent panels after installation are in the same
plane with compatible interlocking tongues and grooves.
v. Bowing and warpage after casting shall not exceed 3mm in 2 metres along the height of
each panel and 1mm in 300mm along the width of each panel.
i) The partitions shall be provided with openings where required for services.
j) Standard fixing and connection details (including those for frames), as shown in the Employer’s
Standard Structural and Architectural Drawings shall be used. Details different from the
Employer’s standard details may only be used if submitted by a Professional Engineer with
complete detailed drawings and calculations and approved by the SO Rep.
3.3 Requirements Prior to Delivery
Prior to delivery of partitions to site, that the partitions are manufactured to satisfy the following
requirements:
a) Casting Tolerance
i. Height : ±5mm
ii. Width : ±3mm
iii. Thickness : ±3mm
iv. Bowing/Warpage : 3mm in 2 metres along the height
1mm in 600mm along the width
b) Surface Finish
The surface finish of partitions shall be skimmed to smooth such that painting can be applied
onto it. The Contractor shall allow in the Contract Sum for the cost of surface finish for
skimming.
c) Tongues And Grooves
The accuracy of shapes and locations of tongues and grooves of partitions after casting are
verified by two special steel templates. This is to ensure that the offset between any two panels
after installation is within 2mm on both faces of partitions.
d) Sufficient Strength Before Delivery
No partition is delivered prematurely to site before sufficient strength has been gained to
withstand stresses due to transportation, handling or erection.
e) Care During Delivery
Provision of adequate supports for partitions to prevent chipping off of panel edges during
transportation and handling.
3.4 Warranty
The Contractor and his Specialist shall warrant the works on the terms and conditions as stipulated in the
Deed of Warranty for Precast Lightweight Woodfibre Concrete Partition as produced in Appendix A2. In
this respect, the Contractor and his Specialist shall submit such Deed of Warranty to the Employer or to
such other party or such Town Council(s) as the SO Rep may at its discretion decide. In the event the
Deed of Warranty for part of the works or for the whole works is to be submitted to such Town
Council(s), the Contractor and his Specialist shall submit such Deed of Warranty as produced in
Appendix A2(TC) to such Town Council(s). The duly executed Warranty shall be submitted

4. immediately upon request by the SO Rep, and if no such request is made, then as such time when the SO
Rep considers the work have been substantially completed in accordance with the Contract. In the event
the Contractor and his Specialist shall fail to execute and submit the Deed of Warranty within the time
specified, the SO Rep shall be allowed to withhold 15% of the payment of any sums due to the
Contractor in relation to the execution of such works, subject to the minimum sum of s$5,000.00 per
Deed of Warranty. However, such sums withheld shall be released to the Contractor upon submission by
him of the duly executed Deed of Warranty.
4. QUALITY OF PRECAST LIGHTWEIGHT CONCRETE PARTITIONS
The identification and date of casting shall be neatly and suitably marked on all partitions, as soon as is
practicable after casting.
The compressive strength of the lightweight concrete shall be measured by crushing tests on 150mm cubes.
The quality and consistency of the concrete shall be tested by the SO Rep in accordance with SS 78.
For every 50 m3 or part thereof of concrete used for production, at least 1 sample of 3 cubes shall be made
from each batch chosen by the SO Rep, subject to a minimum of 1 sample of 3 cubes for each day of
production. The cubes shall be taken at the point of discharge from the mixer. In addition to the minimum
numbers specified above, the SO Rep may, at his absolute discretion, instruct the Contractor to make
additional test cubes from whichever batch as he may choose.
For the storage of test cubes, the Contractor shall provide lockable watertight curing tank/s at the factory
made of approved material and design. The keys shall be held in custody by the SO Rep.
The appropriate strength requirement shall be considered to be satisfied if, for each sample of 3 cubes tested
at 28 days, both the following conditions are satisfied:
a) The average strength of 3 cubes is greater than or equal to the specified characteristics strength of 4.5 N
per mm2 at 28 days.
b) None of the strength of the 3 cubes is below the specified characteristic strength of 4.5 N per mm2 at 28
days.
If the cubes test result do not comply with any of the above conditions, the Contractor shall be subjected to
charges imposed based on Clause 1.6 “Nuisance and Irregularities”.
If the average compressive strength of 3 cubes falls below 3.5 N per mm2 at 28 days, the entire affected
lightweight concrete partitions shall be rejected. If the partitions are already installed, the Contractor shall
remove them and install new partitions of adequate specified compressive strength at no extra cost to the
Employer.
The cubes shall be tested at HDB Engineering Materials Laboratory or any other laboratory approved by the
SO Rep.
5. PRICING AND CONTRACTUAL ASPECTS
All concreting materials, including cement, sand and steel reinforcement, required for the lightweight
partitions shall be obtained from the Employer’s sources as specified in Clause 1.2.3 “ Supply of Materials
from Employer’s Sources”.
Submit together with the tender, the name/s of the Supplier/s and quantities to be supplied by each Supplier.
The Contractor shall not change the Supplier/s without the written consent of the SO Rep.
Within 2 weeks from the date of the Employer’s Letter of Acceptance of the Contractor’s Tender, submit to
the SO Rep the written contractual agreement/s with his Supplier/s.
6. SUBMISSION OF INFORMATION AND TEST REPORTS
Submit the following details to the SO Rep for approval before the manufacturing of precast lightweight
concrete partition:
a) Name/s of Supplier/s.

5. b) Details of factories including addresses, size of workshops, equipment used and number of trained
personnel.
c) Production process, curing and storage.
d) Mix design including foaming agent and dosage used.
e) Test report by SISIR or approved laboratories on compliance with the technical property requirements
specified in sub-clauses 9.2.1 “Manufacturing Requirements” (a) to (d) (inclusive).
f) Test reports on compliance with the drying shrinkage and total water absorption requirements in
accordance with SS 271. The test reports shall be dated within the validity period of six months prior to
the date of submission of such reports to the SO Rep.
g) Mix proportions of cement mortar used. Admixture used to prevent shrinkage, efflorescence and
cracking of cement mortar.
h) Partition layout and marking for each type of dwelling unit floor plan applicable in the contract. The
partition layout shall be in accordance with the guidelines stipulated in the structural Drawings.
i) Quantity of lightweight partitions for each thickness in square metre.
j) Delivery and erection schedules.
7. DELIVERY AND INSTALLATION
7.1 Provision of Access
Provide and maintain reasonable access into and within the site to allow the transportation and
delivery of partitions by the Contractor’s suppliers. The suitability of such access shall be decided by
the SO Rep.
7.2 Erection
a) Before starting erection, check with the SO Rep whether skimming or plastering to the adjoining
reinforced concrete structure is required. If this is required, erection and alignment of partitions
shall allow for this., so that, in general, unless otherwise shown or noted in the Architectural
Drawings, the finished surfaces of partitions shall flush with that of reinforced concrete
structures.
b) The accurate location of tongue and groove of each partition panel shall be such that the offset
between adjacent panels is within 2mm on both faces and the width of the resultant joint
between the two adjacent panels is 10mm ±2mm.
c) In general, permanent connections shall be made as soon as the partitions are erected and
aligned. Ensure that the workers have been properly trained in the handling and erection of the
lightweight concrete partitions. Only qualified welders shall be employed for all welding
required.
d) Unless otherwise indicated in the Drawings, a groove shall be formed in the cement mortar joint
between the lightweight concrete partition and the reinforced concrete structure. No lime shall
be added to the cement mortar. En appropriate admixture, to be approved by the SO Rep, shall
be used to prevent shrinkage, efflorescence and cracking.
e) Where in the case, the partition wall layout does not permit the use of 300mm wide precast
lightweight concrete partitions ant the SO Rep approves the Contractor’s proposal to replace
them with solid blocks, notwithstanding the details or notes as shown in the Drawings, there
shall be no cost adjustment to the Contract Sum.
7.3 Acceptable Final Surface Finish
Check and ensure that visible air voids, bug holes and uneven or rough surfaces of the partitions and
joints are properly skimmed at his own costs and expenses to achieve an even smooth surfaces such
that painting can be applied directly. All such finishing work at the Site shall be to the satisfaction of
the SO Rep.
7.4 Ensure that his workers have been properly trained in the handling and erection of the lightweight
partitions. Only qualified welders shall be employed for all welding required.

6. 8. STORAGE AND PROTECTION
At all times the precast lightweight concrete partitions shall be properly stored and protected to prevent
warping, bowing, cracking chipping, staining and other defects.
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