I am currently working on a precast of bridge segment. We had carried out the slump test for concrete before pouring and our requirement for slump is 200 +/- 25. However, the slump did not achieve the slump required. Our material engineer requested for the additon of admixtures (Superplasticiser) to the concrete to achieve the required slump. For information, our concrete design has the addition of admixtures (superplasticiser). I want to know if the instruction given is tecnhically correct or not ?and
should i reject the concrete when the slump is unachievable or additonal of the admixtures is the solution ?

Please advise.

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