Fresh concrete
- Workability describes how easily concrete can be transported, placed, and compacted without excessive segregation or bleeding.
- Slump, flow-table, and Vebe tests assess consistency over different ranges; none alone captures every rheological property.
- Air content, density, segregation, and bleeding may also be assessed. For self-compacting concrete, filling ability and segregation resistance are important.
Specimen preparation
- Take a representative sample, mix uniformly, and record time, temperature, and transport conditions.
- Fill moulds of specified dimensions and compact using the appropriate method to avoid voids or excessive vibration.
- Identify every specimen and protect it during initial curing to prevent moisture loss or temperature changes.
Hardened concrete
- Standardized curing enables comparison of compressive, flexural, and other properties between batches.
- Loading faces must be flat and parallel; prepare them by grinding or an approved capping method.
- Density and water-penetration tests provide complementary indicators of porosity and durability.
Interpretation
- Relate each result to specimen age, geometry, curing, moisture, and failure mode.
- Use the current standard to select the test and acceptance criteria; fresh-concrete tests do not replace hardened-strength control.
Mix proportions, yield, and control
- Effective water-cement ratio: w/c = effective water/cement by mass. Correct added water for aggregate moisture and absorption as required by the mix procedure.
- Fresh concrete density: ρ = M/V, net concrete mass divided by the calibrated container volume.
- Batch yield: Y = Mb/ρ, where Mb is total batched mass and ρ is measured density. Compare Y with nominal batch volume and record air content.
- Workability, density, and fresh air describe different properties. Do not infer hardened strength from one fresh-concrete test; relate results to specimens, age, and curing.
Educational reference guide. Check the current standard, calculation assumptions, and project specification before applying a procedure or acceptance criterion.