Steps Involved in Mix Proportioning as per IS 10262:2009 (with solved example)

General Steps Involved in Mix Proportioning

Step 1. Choice of Slump

• Stiffest possible consistency that can be easily placed and compacted without segregation
• Pumping are typically designed for 100 mm to 150 mm slump

Step 2. Choice of Max. Size of Aggregate

• For given volume of coarse aggregate,

Step 3. Estimation of the mixing water content and air content

Depends on ,

• The maximum particle size of the aggregate
• Entrained air

Step 4. Selection of water-cement ratio

• Develop the relationship between strength and water-cement ratio for the materials to be used actually
• Checked for durability criteria

Step 5: Calculation of the cement content

• Computed by dividing the mixing water content by the water-cement ratio
• Adjustments to Min. cement content for aggregates other than 20 mm nominal max. size, as per IS 456: 2000

Step 6: Estimation of the coarse aggregate content

• Estimated from Maximum aggregate size & fineness modulus of fine aggregate
• Dry weight obtained by multiplying with Dry Rodded unit weight
• Range in proportions of materials used in concrete, by absolute volume

Step 7: Estimation of the fine aggregate content

• Weight Method
• Absolute volume Method

Step 8: Adjustments for the aggregate moisture

• Mixing water reduced depending on Free Moisture
• Amounts of aggregates increased accordingly

Step 9: Trial batch adjustments

• Mixture satisfying the desired criteria of workability and strength is obtained
• Mixture proportions of the laboratory-size trial batch are scaled up for producing full-size field batches

Data required for Proportioning

Road Aggregates

• Grade Designation
• Type of Cement
• Maximum Nominal size of Aggregate
• Minimum Cement Content
• Maximum w/c ratio
• Workability in terms of Slump
• Exposure conditions
• Method of placing
• Type of aggregate
• Maximum cement content
• Test data of Materials
• Admixture type and condition of use if any

Mix Proportioning as per IS 10262:2009

• Target strength for mix proportioning
• Selection of w/ c ratio
• Selection of water content
• Corrections in water content
• Calculation of cement content
• Proportion of volume of coarse aggregate and fine aggregate content
• Corrections
• Mix calculations

Design stipulations for proportioning

• Grade designation   : M20
• Type of cement   : OPC 43 grade, IS 8112
• Max. nominal size of agg.   : 20 mm
• Minimum cement content  : 320 kg/m3
• Maximum water cement ratio   : 0.55
• Workability   : 75 mm (slump)
• Exposure condition   : Mild
• Degree of supervision  : Good
• Type of agg.   : Crushed angular agg.
•  Maximum cement content   : 450 kg/m3
• Chemical admixture   : Not used
• EXAMPLE: