Slump value is too high—what does it indicate? | Q & A

What a High Slump Indicates 1. Excess Water in Concrete (Most Common)

• Water–cement ratio is higher than design

• Leads to:

  • Reduced strength

  • Increased segregation

  • Higher permeability

2. Overdose of Admixture

• Excess superplasticizer can:

  • Increase slump abnormally

  • Cause delayed setting

  • Lead to segregation

3. Improper Mix Proportion

• Low fine aggregate content

• Poor aggregate grading

4. Re-tempering on Site

• Water added at site to increase workability

• Not allowed without approval

Risks of High Slump Concrete

• Segregation of aggregates

• Bleeding

• Honeycombing after hardening

• Lower compressive strength

What Should You Do on Site?

• Stop concreting temporarily

• Recheck:

  • Specified slump

  • Mix design

• Reject the batch if beyond tolerance

• Inform batching plant / senior engineer

• Never add cement to “balance” water

One-Line Interview Answer (Perfect)

A high slump value indicates excessive workability, usually due to excess water or admixture overdose, which can cause segregation, bleeding, and reduction in concrete strength.

Common Interview Follow-Up

Q: Can high slump ever be acceptable?
A: Yes, for pumped concrete—but only within approved limits.

Site Tip for Fresh Engineers

Always:

• Compare slump with approved range, not guess

• Record slump values for every pour