--- title: "IS method of mix design steps" subject: "Concrete Technology and Masonry Structure" chapter: 3 key: "semester_5/concrete_technology_and_masonry_structure:is-method-mix-design-steps" source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/is-method-mix-design-steps site: BCT Engineering --- # IS method of mix design steps Concrete Technology and Masonry Structure · Chapter 3: Mix design of concrete and property of green concrete - Asked in: 2080 Baisakh, 7 marks; 2079 Baisakh, 6 marks; 2071 Shrawan, 4 marks (asked 3 times) - Video: [Mix Design M30 Grade | Concrete mix design M30 grade | M30 concrete mix design | Concrte mix design](https://www.youtube.com/watch?v=TZPoRXEM4YQ) — Civil Engineering Mastery - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/is-method-mix-design-steps - Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-3 ## Question Describe the stepwise process of concrete mix design by the IS method (conceptual steps; show sample table and graph wherever possible). ## Short answer Determine target mean strength (f_ck + 1.65s). Select w/c ratio from strength vs w/c relationship and durability limits. Find water content from table for max aggregate size and slump, adjust. Calculate cement content. Determine volume of coarse aggregate per unit total aggregate from zone and w/c. Compute aggregate masses using absolute volume method. ## Answer The **IS method (IS 10262:2009, revised in 2019)** designs a mix for a required grade from the target strength, w/c ratio, water content and aggregate proportions by absolute volume, and is used with IS 456. #### Steps 1. **Design data**: grade, maximum aggregate size, workability, exposure, cement type, specific gravities, absorption. 2. **Target mean strength**: $f'_{ck} = f_{ck} + 1.65 s$ (s from Table 1 of IS 10262: M20 4.0, M25 4.0, M30 5.0, M35 5.0 N/mm$^2$; add 1 N/mm$^2$ if site control is only fair). The 2019 revision also requires $f'_{ck} \geq f_{ck} + X$ (X = 5.0, 5.5, 6.5 for M10-15, M20-25, M30 and above); take the higher value. 3. **w/c ratio** from the strength vs w/c relationship for the materials (in the 2019 revision, the curves of Fig 1 for 33/43/53 grade cement) for the target strength; check against the IS 456 Table 5 limits for the exposure; adopt the lower. 4. **Water content** from Table 2 (186 kg/m$^3$ for 20 mm angular aggregate at 50 mm slump); add 3% for every 25 mm of extra slump; reduce when a superplasticiser is used (by 20% or more). 5. **Cement content** = water / (w/c); check the minimum from IS 456 Table 5 and the maximum of 450 kg/m$^3$. 6. **Volume of coarse aggregate** per unit volume of total aggregate from Table 3 (maximum size and zone of fine aggregate, for w/c 0.5); adjust by $\pm$ 0.01 for each $\mp$ 0.05 change in w/c. 7. **Mix calculations** per m$^3$ using absolute volumes: $$ V_{agg} = 1 - \left[\frac{C}{\rho_c 1000} + \frac{W}{1000} + \frac{\text{admix}}{\rho_a 1000} + \text{air}\right] $$ Mass of CA = $V_{agg} \times V_{CA} \times SG_{CA} \times 1000$; FA = $V_{agg} (1 - V_{CA}) \times SG_{FA} \times 1000$ (entrapped air taken as 2% for 20 mm). 8. **Trial mixes**: three trials with the w/c varied; check the strength and slump; select the best. 9. Apply moisture and absorption corrections. #### Sample table (SG of CA 2.74, FA 2.65) | Item | Value | |---|---| | Grade / target | M30 / 38.25 | | w/c | 0.43 | | Water, cement | 186, 433 kg | | $V_{CA}$ | 0.634 | | FA, CA | 637, 1141 kg | #### Graph ```text f_target (MPa) 50|\ 40| `.\ 38|---`-`. <- read w/c = 0.43 30| `-. +-----------> w/c 0.35 0.5 ``` ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. IS 10262 target mean strength is... A. fck + 1.65 s, or fck + X, whichever is higher B. fck - s C. fck D. 0.5 fck Answer: A. Two formulas are checked and the larger taken. (Key point: Target strength) 2. Water content is raised by... A. 3% for every 25 mm extra slump B. 10% per mm C. Not adjusted D. 50% Answer: A. Base 186 kg/m3 for 20 mm at 50 mm slump; superplasticiser reduces it. (Key point: Water adjustment) 3. w/c from strength curves and exposure limits: adopt... A. The higher B. The lower C. Average D. 0.6 Answer: B. The lower satisfies both strength and durability. (Key point: w/c adopted) 4. How many trial mixes are made? A. One B. Three, varying w/c C. Ten D. None Answer: B. Select the best by strength and slump. (Key point: Trial mixes) ## Related in Concrete Technology and Masonry Structure - [DOE method of mix design steps](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Adoe-mix-design-steps) — Concrete Technology and Masonry Structure, chapter 3, asked 8× - [ACI method of mix design steps](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aaci-mix-design-steps) — Concrete Technology and Masonry Structure, chapter 3, asked 9× - [ACI mix design for M35 concrete (numerical)](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aaci-mix-design-m35-numerical) — Concrete Technology and Masonry Structure, chapter 3, asked 2× - [ACI mix design for M25 concrete (numerical)](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aaci-mix-design-m25-numerical) — Concrete Technology and Masonry Structure, chapter 3, asked 2× - [Fundamental concepts of concrete mix design](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Amix-design-fundamental-concepts) — Concrete Technology and Masonry Structure, chapter 3 - [ACI mix design for 25 MPa concrete (numerical)](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aaci-mix-design-25mpa-numerical) — Concrete Technology and Masonry Structure, chapter 3 ## Related in other subjects - [Steps in the design and synthesis process](https://www.bctengineer.com/question.md?key=semester_6%2Fmachine_design_i%3Adesign-process-steps) — Machine Design I, chapter 1 - [Conceptual design of IS](https://www.bctengineer.com/question.md?key=semester_8%2Finformation_system%3Aconceptual-design-steps) — Information System, chapter 5 - [Chart vs table; bar vs pie graph](https://www.bctengineer.com/question.md?key=semester_5%2Fcommunication_english%3Adifferences-chart-table-bar-pie) — Communication English, chapter 4 - [Site engineer uses weaker mortar and concrete mix](https://www.bctengineer.com/question.md?key=semester_8%2Fengineering_professional_practice%3Amortar-ratio-friend-silence) — Engineering Professional Practice, chapter 7