--- title: "Workability and its measurement" subject: "Concrete Technology and Masonry Structure" chapter: 3 key: "semester_5/concrete_technology_and_masonry_structure:workability-measure-methods" source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/workability-measure-methods site: BCT Engineering --- # Workability and its measurement Concrete Technology and Masonry Structure · Chapter 3: Mix design of concrete and property of green concrete - Asked in: 2078 Kartik, 6 marks; 2074 Chaitra, 2+3 marks; 2071 Shrawan, 4 marks; 2069 Chaitra, 6 marks (asked 4 times) - Video: [Measurement of Workability (Concrete Technology) By Mr. Amit Daiya](https://www.youtube.com/watch?v=r66xfkMV5t4) — Government Engineering College Bharatpur Raj. - 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/workability-measure-methods - Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-3 ## Question What is workability of concrete? Describe the different methods of measuring workability of concrete (in the laboratory and at the construction site). ## Short answer Workability is ease of mixing, placing, compacting, and finishing fresh concrete. Measurement methods: slump test (cone settlement, 25-125 mm range, field/lab), compaction factor test (weight ratio for low workability, lab), Vee-Bee test (remoulding seconds for dry mixes, lab), flow table test (% spread), and Kelly ball test (penetration, field). Slump and Kelly ball are used on site. ## Answer **Workability** is the property of freshly mixed concrete that determines the ease and homogeneity with which it can be mixed, placed, compacted and finished (IS 6461 Part 7). It combines mobility, stability (resistance to segregation and bleeding) and compactability. IS 456 cl. 7.1 gives the workability required for various placing conditions. #### Methods of measurement (IS 1199) **1. Slump test** (IS 1199; field and laboratory): a cone 300 mm high, with 100 mm top and 200 mm bottom diameter, is filled in four layers of equal height, each tamped with 25 strokes of a 16 mm rod. The cone is lifted vertically, and the **slump** is the settlement of the concrete from the top of the cone. A true slump is recorded; if a shear slump occurs, the test is repeated; a collapse indicates a very wet mix. Range: 25-125 mm. Not suitable for very dry or very wet mixes. IS 456: slump 25-75 mm for lightly reinforced sections, 50-100 mm for heavily reinforced sections. **2. Compaction factor test** (laboratory; useful for low workability, CF 0.7-0.95): concrete falls through two hoppers into a cylinder; weigh the partially compacted concrete ($W_1$), then the fully compacted concrete ($W_2$): $$ \text{CF} = \frac{W_1}{W_2} $$ **3. Vee-Bee test** (very dry mixes): the time in seconds (Vebe seconds) needed to remould the slump-cone concrete into a cylinder under vibration; about 5-30 s. **4. Flow table test** (IS 1199): a 760 mm table is lifted 12.5 mm and dropped 15 times; the average spread diameter gives the flow %; used for flowing concrete. **5. Kelly ball test**: penetration of a 15 cm diameter hemisphere into fresh concrete (field). **6. Others**: remoulding test, K-slump test, and for SCC the slump flow, L-box, V-funnel and J-ring tests. Slump and Kelly ball are used at site, while the compaction factor, Vee-Bee and flow table tests are laboratory tests. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Workability includes which components? A. Mobility, stability and compactability B. Strength, colour, cost C. Slump only D. Density only Answer: A. It is ease of mixing, placing, compacting and finishing without segregation. (Key point: Definition) 2. In the slump test, the cone is filled in... A. Two layers, 10 strokes B. Four equal layers, each 25 strokes of a 16 mm rod C. One layer D. Three layers, 50 strokes Answer: B. Cone 300 mm high, filled in four layers; slump is settlement. (Key point: Slump test) 3. Compaction factor is... A. W2/W1 B. W1/W2 (partly compacted over fully compacted weight) C. Slump / 300 D. Time in seconds Answer: B. CF = W1/W2, suited to low workability. (Key point: Compaction factor) 4. Vee-Bee test suits... A. Very wet mixes B. Very dry mixes, measuring time in seconds C. Self-compacting only D. Hardened concrete Answer: B. Time to remould cone to cylinder under vibration. 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