Ready Mixed Concrete

Given two types of batching plant i.e.. complete batch and mix or dry mix (where materials are weighed off and finally mixed within the transit trucks) which plant would be the preferred machine to produce consistent concrete to provide constant slump concrete at the concrete pump.

Hong Kong,  Hong Kong
Assuming everything works as designed, I would expect the dry mix trucks to produce a more consistent slump at the pump.  Mainly because there is no element of travel time and mixing time that will cause the most variation.

Additional advantage is the ability to batch exactly what you need when you need it - reducing waste and scheduling problems.

Other considerations include better control of aggregate moisture in the dry mix truck - if the equipment works properly...  moisture meters in the batch plant are notoriously inaccurate for many reasons.  It is much easier to maintain uniform moisture conditions in the relatively small bin on the dry mix truck.

I do not know what type of equipment is used in either batch plant in Hong Kong, but in our area the variation between loads of wet-mixed concrete at the pump can be significant (+- 1 or 2 inches).