Modern Quarrying Q4 2021

may contain specific information pertaining to constituent material restrictions, minimum cement con- tent, contents and maximum water cement ratios. It is therefore essential that the readymix concrete supplier has sight of this order to determine if the locally held materials will be suitable or whether alternative materials need to be sourced. “Please note that if you do not supply the full contract specifi- cation, this may lead to incorrect concrete being ordered,” advises Pienaar. Additionally, it is essential that the correct consistency and work- ability requirements are specified for the job. An estimate of the volume of concrete required is also essential. However, any addi- tional information pertaining to “placement rates” would be useful, as forward planning will allow the readymix concrete producer to plan for the use of additional vehicles or late working, among others. Placing orders To avoid confusion, always refer to the quotation and concrete reference number or letter when ordering rather than referring to the concrete description or part of it, as it is highly likely that a number of concretes will have the same compressive strength class but may then differ in terms of the specified maximum water cement ratio and or minimum cement content. Your order and subsequent delivery of readymix concrete will be based upon the requested consistency and workability. Additional cost may be incurred if the original consistency or workability of the concrete is increased, as additional cemen- titious material will be required to maintain the strength and maximum water cement ratio requirements. An important point to remember is to order the correct consistency for the job, rather than adding water on site. This is a bad prac- tice and will adversely affect the quality of the final product. It will also render void any guarantee with regards to the concrete. It is

READYMIX CONCRETE

Some readymix concrete companies can offer specially designed delivery vehicles that incorporate either a concrete pump or conveyor.

Most readymix concrete companies have a selection of delivery vehicles, which vary in design and size to suit the type of work undertaken.

Photo courtesy of Afrimat

affect the production of readymix concrete and how to order it. ASPASA has released a set of guidelines that may be of great significance to the industry. Enquiries and tenders As much information as possible should be provided to the readymix concrete company at the enquiry or tender stage. The contract specification

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MODERN QUARRYING QUARTER 4 - 2021