C.R.R.I. charts are used to obtain a relationship between strength of concrete and a
Correct Answer: A. water cement ratio
📚 Detailed Explanation: CRRI Charts
CRRI (Central Road Research Institute), located in New Delhi, has been a key institution in developing design guidelines for roads, bridges, and concrete structures suited to Indian materials and climatic conditions.
Why A (water cement ratio) is correct: CRRI charts are graphical design tools (nomograms) that relate compressive strength of concrete to water-cement ratio for specific Indian cement types, aggregate types, and curing ages. They serve a similar purpose to Abrams' Law curves but are calibrated to Indian construction materials. Before IS 10262 (mix design code), CRRI charts were the primary reference for selecting w/c ratio in Indian concrete practice. Other options: workability (B) is measured by slump/VB tests; grading (C) is checked by sieve analysis; fineness modulus (D) is a single-number aggregate property — none are specifically linked to CRRI charts.
Key Features of CRRI Charts
| Feature | Description |
|---|---|
| Developed by | Central Road Research Institute, New Delhi |
| X-axis | Water-cement ratio |
| Y-axis | Compressive strength (28-day) |
| Purpose | Select w/c for target strength |
| Indian Standard reference | Used before IS 10262 was widely adopted |
Key Concepts for Students
- CRRI charts = strength vs. w/c nomograms developed for Indian materials.
- They incorporate the effect of cement grade (33/43/53) and curing age on the strength-w/c relationship.
- IS 10262:2019 is now the primary mix design standard; CRRI charts remain useful as a quick cross-check.