ABSTRACT
Ready-mixed concrete which i s mixed at the plant, using a normal, well-designed concrete mix, should arrive at i t s destination with s u f f i c i e n t workability to enable i t to be properly placed and f u l l y compacted. In such circumstances, where there i s a significant period of time between mixing and placing the concrete, there w i l l be a noticeable reduction in the workability of the fresh concrete. If, for any reason, the placement of the concrete i s unduly delayed, then i t may s t i f f e n to an unacceptable degree and s i t e staff would normally i n s i s t on the rejection of a batch of otherwise good concrete on the grounds of i n s u f f i c i e n t workability. If not rejected, excessive vibration would be needed to attempt to f u l l y compact the concrete, with the risk of incomplete compaction, expensive repair, or, at worst, removal of the hardened concrete.
