AGGREGATES .1 General Requirements

Fine aggregates shall be uncrushed sand or crushed granite fines complying with SS EN 12620. Where crushed granite fines are used, its percentage of the total amount of fine aggregates shall not exceed 30%.

Coarse aggregates shall be crushed or uncrushed gravel, crushed or uncrushed stone complying with SS EN 12620.

Coarse aggregates shall not exceed 40mm in size for lean and mass concrete and 20mm for reinforced concrete, unless otherwise specified.

All-in aggregates as specified in SS EN 12620 and aggregates derived from limestone or other materials inferior to granite shall not be used.

Aggregates shall be stored on clean surfaces in separate stockpiles or bunkers to prevent intermingling of different materials and contamination. Aggregates used for concrete batching plant on site shall be covered with a light roof cover. Fine aggregates shall be tested for moisture content constantly to facilitate moisture compensation during concrete production. The testing shall be carried out based on the Speedy method or other approved equivalent method approved by the SO Rep.

The SO Rep reserves the right to draw samples of aggregates from any stockpile at any time and have them tested for compliance with Approved Standards of SS EN 12620, BS EN 933, BS EN 1097, ASTM C295 and ASTM C289. The samples shall be sent for testing at the HDB’s Engineering Materials Laboratory. Aggregates failing to comply with the Approved Standards shall be rejected.

4.2 AGGREGATES (CONT’D)

4.2.2 Supply From The Contractor’s Source (a) Certificate Of Compliance

The Contractor shall ensure that the quality of his own supply comply fully with the Specifications and Approved Standards. The Contractor shall within one (1) month from the date of the Letter of Acceptance inform and seek the SO Rep’s prior approval in writing of his source of supply together with test reports from SAC-SINGLAS accredited laboratories for each source of his supply on the following properties:

(i) 20mm Aggregate (a) shape;

(b) surface texture;

(c) particle size distribution - sieving method;

(d) flakiness index;

(e) shape index;

(f) aggregate impact value;

(g) aggregate resistance to abrasion;

(h) bulk density;

(i) particle density and water absorption;

(j) clay, silt and dust content;

(k) shell content;

(l) acid soluble sulphate content;

(m) sulphate content;

(n) organic impurities;

(o) chloride ion content;

(p) potential alkali-silica reactivity (chemical method);

(q) petrographic examination and

(r) other properties as specified by the SO Rep.

(ii) Concreting Sand

(a) particle size distribution - sieving method;

(b) clay, silt and dust content by decantation method (not more than 3.00%);

(c) organic impurities (lighter than Organic Plate No 3);

(d) chloride content (not more than 0.01%);

(e) bulk density;

(f) particle density and water absorption;

(g) assessment of fines;

(h) potential alkali-silica reactivity (chemical method);

(i) magnesium sulphate soundness;

(j) elemental analysis (in percentage):

- Silica as SiO₂

(k) any other element(s) which may exist in the concreting sand; and (l) other properties as specified by the SO Rep.

4.2 AGGREGATES (CONT’D)

4.2.2 Supply From The Contractor’s Source (Cont’d) (a) Certificate Of Compliance (Cont’d)

All test reports shall be the original or certified true copies from a SAC-SINGLAS accredited laboratory. The test reports shall not be dated more than three (3) month from the submission date of the test reports to the SO Rep.

Other than due to circumstances beyond the Contractor's control, the Contractor shall not be allowed to change the source of supply at his discretion. The Contractor shall be required seek the SO Rep’s prior approval in writing for any change in his supply sources, together with the documents laid down hereinabove.

(b) Test Requirements

The Contractor shall, in the presence of SO Rep, be required to take and send samples taken from his own supply during the Time for Completion and any time period where liquidated damages are imposed under the Contract for testing at the SAC-SINGLAS accredited laboratory.

The quality of the aggregates to be supplied shall comply in every respect with the Specifications and Approved Standards, and the conditions, analysis and test requirements laid down in the SS EN, BS EN, ASTM (especially SS EN 12620, BS EN 933, BS EN 1097) classification for concreting purposes. The number of tests to be conducted during the Time for Completion and any time period where liquidated damages are imposed under the Contract shall be as follows:

(i) 20mm Aggregate

Properties Frequency of Test

Particle size distribution - sieving method Minimum one test quarterly Flakiness index

Shape index

Aggregate impact value

Aggregate resistance to abrasion Bulk density

Particle density and water absorption Clay, silt and dust content

Shell content

Acid soluble sulphate content Sulphate content

Organic impurities Chloride Ion Content

Potential alkali-silica reactivity (chemical method)

Minimum one test six-monthly

Petrographic examination Minimum one test

The Contractor shall be required to send their 20 mm aggregate supply for the Mortar-Bar test under ASTM Standard C227 if the need arises.

4.2 AGGREGATES (CONT’D)

4.2.2 Supply From The Contractor’s Source (Cont’d) (b) Test Requirements (Cont’d)

(ii) Concreting Sand

Properties Number of Test

Particle size distribution - sieving method Clay, silt and dust content by decantation method (not more than 3%)

Organic Impurities

(lighter than Organic Plate No 3) Chloride content (not more than 0.01%) Bulk Density

Particle density and water absorption Assessment of fines

Elemental analysis (in percentage):

(i) Silica as SiO₂

(ii) Aluminium Oxide as Al2O3

Minimum one test monthly

Full list of properties as specified in the

subclause “Certificate of Compliance”. Minimum one test six-monthly

The Contractor offering from two different supply sources will have both sources subjected to the test requirements.

All costs and expenses in carrying out all the tests and arranging and sending the test samples to the Approved Laboratory as required in the Contract including the cost of samples shall be borne by the Contractor.

4.3 WATER

Potable water supplied by the Public Utilities Board shall be used for mixing concrete, mortar and grout.

For cleaning of formwork, reinforcement and curing of concrete, water other than potable water may be used if approved by the SO Rep. The use of seawater shall be prohibited.

4.4 ADMIXTURES

When admixture is proposed to be used in concrete mix, furnish information concerning the admixture, admixture acceptance tests and additional information as stipulated in SS EN 934 for approval by the SO Rep prior to the use of the admixture.

Admixture used shall comply with SS EN 934 or the relevant British European Standards. Requests for permission to use other types of admixtures not covered by these standards may only be considered when accompanied by full supporting information. Admixture to be used shall be approved by the SO Rep.

The Contractor shall provide the SO Rep every facility for inspection and sampling of the admixture(s).

The sample(s) shall be kept for reference and shall be sent, if requested by the SO Rep, for admixture uniformity tests in accordance with SS EN 934or the relevant British Standards.

4.5 STEEL REINFORCEMENT