Concrete and Ready Mix Production

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Production is a critical factor for the resulting concrete and consists basically of dosing and mixing the raw materials. The following parameters can affect the concrete properties during mixing:

-       Type of mixer                          - Addition of raw materials

-       Size of mixer                            - Plant quality control

-       Mixing intensity                     - Concrete mixer operator

-       Mixing time                             - Cleaning/maintenance of mixer

Super plasticizers should generally be mixed with the mixing water or added to the mix with it (at the earliest). Further information can be found in the relevant Sika Product Data Sheets.

·     Preparation on site

The preparation on site includes the following:

–Installation of the concrete handling/placing systems

–Preparation of the formwork (including release agent application)

–Reinforcement check

–Formwork check (fixing, integrity, form pressure)

–Supply of tools for compacting (vibrators etc.) and finishing (beams and trowels etc.)

·     Delivery

If the concrete is supplied by ready mix trucks, the following additional criteria must be considered:

–Delivery time (traffic conditions, potential hold-ups etc.)

–Define the necessary drum revolutions during the journey

–Do not leave the ready mix truck standing in the sun during waiting periods

–For a fluid consistence (SCC), define the maximum capacity to be carried

–Do not add water or extra doses of admixture (unless specified)

–Mix again thoroughly before unloading (1 minute per m³)

·     Placing the concrete

The concrete is generally placed within a limited and defined time period. The following factors contribute to the success of this operation, which is critical for the concrete quality:

–Delivery note check

–Use of the right equipment (vibrators etc.)

–Avoid over handling the concrete

–Continuous placing and compacting

–Re-compaction on large pours

–Take the appropriate holding measures during interruptions

–Carry out the necessary finishing (final inspection)

·     Curing

To achieve constant and consistent concrete quality, appropriate and correct curing is essential. The following curing measures contribute to this:

–Generally protect from adverse climatic influences (direct sun, wind,rain, frost etc.)

–Prevent vibration (after finishing)

–Use a curing agent

–Cover with sheets or frost blankets

–Keep damp/mist or spray if necessary

–Maintain the curing time relevant to the temperature