Concrete mixing equipment must enable effective mixing of concrete constituents to provide uniform and required consistence, based on an approved testing frequency. Performance of the mixer must comply with uniformity tests (ASTM C94) performed regularly. Micro-silica shall be incorporated in slurry from and must be thoroughly dispersed in the concrete. No additional water shall be added during mixing except with approval of the Engineer. The entire batch shall be discharged before the mixer is recharged. 2.5.2 Admixtures Admixtures shall be dosed into the mixing water within the time allocated for adding water to the mix, using approved dispensing equipment. 2.6 Transporting 2.6.1 Equipment Concrete shall be transported by means, which prevent contamination (by dust, rain, and so on) segregation or loss of ingredients, and shall be transported and placed within the planned period and without significant loss of workability. Ready-mixed concrete mixer trucks shall be subject to approval. Truck-type concrete mixers shall be painted white and shall comply with the requirements of BS EN 12001. 2.6.2 Delivery Control Ready-mix concrete delivery notes shall record the following information: • • • • • • • • • Type of cement and cement content Type of cement replacement materials and content Maximum specified water/cement ratio Estimated free water/cement ratio of delivery Acceptance strength (AS) of concrete Date, time and place of commencement of concrete mixing Registration number of truck and name of depot Date and time of truck arrival Date and time of discharge of concrete from truck The Contractor shall also record for each delivery: • • • • Position in the structure where the concrete delivery is placed Whether test cubes were taken from the delivery Actual slump measurements The amount of any water added on site 2.7 Placing and Finishing 2.7.1 General Concrete shall be placed in the position and sequence indicated on the Drawings, or as directed by the Engineer. Placing shall not commence until the following requirements have been completed: • the fixing and condition of reinforcement and items to be embedded has been approved Page 37