Fine and coarse aggregates shall be stored in such a way so as to avoid the two materials from becom- ing intermixed. 

## Tests on Aggregates 

The Contractor shall submit to the Engineer samples of the fine and coarse aggregates proposed for use in the Works. Samples shall be of a size sufficient to carry out all preliminary tests specified which the Engineer may order in addition to the concrete tests. The Contractor shall provide 50 kg samples for comparison purposes as described below. The samples shall then be tested in the presence of the Engineer by the Contractor in accordance with the herewith Employer’s Requirements or as the Engi- neer may direct. 

If the source of aggregates is changed at the Contractor’s request and with the approval of the Engi- neer at any time during the course of the Works, all sampling and testing described in the relevant sec- tions shall be repeated at the Contractor’s expense. 

After approval has been given for any particular aggregate, a sample weighing at least 50 kg of the approved aggregate shall be retained by the Engineer as a standard against which all future samples shall be compared. 

During the course of the Contract, fine and coarse aggregates shall be tested at site as often as required by the Engineer and at the Contractors expense. 

## Delivery of Samples 

Samples of cement, water and fine and coarse aggregates called for in the foregoing sections shall be delivered to the Engineer for testing by the Contractor before concreting. Cube tests shall be complet- ed before work is due to start. 

## 6.1.8 Mixing and testing 

All common site tests, especially slump tests, shall be carried out on samples taken from every trans- mixer. 

If the cubes fail to attain the required compressive strength as specified, the concrete which they repre- sent shall be cut out, removed and replaced with concrete complying with the herewith Employer’s Requirements to the satisfaction of the Engineer. 

The cost of sampling, making and curing Works test cubes together with the provision of moulds, all other necessary equipment and apparatus and the packing and transport to the laboratory shall be in- cluded in the prices. 

All cubes shall be marked at the time of casting, with the date, class of concrete and other necessary markings to identify the part of the Works from which they are taken. 

## 6.1.9 Formwork 

Formwork for concrete shall be rigidly constructed of approved materials and shall be true to the shape and dimensions. Formwork shall be constructed of material or lined with materials as may be neces- sary to achieve the finishes specified in this section. The formwork design shall be submitted to the Engineer for approval before construction commences. 

All material brought onto the site as forms, struts or braces shall be new materials. 

