Experiment - Shape test Table of content Topic Page number Introduction and background 2 Apparatus 23 Procedure 3,4 Result 4 Discussion and Result 45 Reference 5 List of Figures Fig1. Thickness gauge Fig2. length gauge1. Introduction and Background The Flakiness and Elongation Index Test is a crucial quality control procedure in the construction industry, used to assess the suitability of coarse aggregate for use in concrete and other construction materials. Aggregate, the crushed rocks and gravel that form the backbone of concrete, comes in various shapes and sizes. However, excessively flat or elongated particles can negatively impact the performance of the finished product. Conerete's strength and durability rely heavily on the characteristics of its constituent materials. While strength comes from the binding properties of cement, aggregate plays a significant role in filling the matrix, transferring loads, and resisting internal stresses. However, the shape of the aggregate particles influences packing density, internal friction, and crack propagation within the concrete. Flaky particles, with a thickness significantly less than their length and width, tend to slide against each other, reducing internal friction and making the concrete more susceptible to cracking. Similarly, elongated particles can create weak planes within the concrete structure, acting as potential pathways for crack propagation and decreasing the overall load-bearing capacity. 2. Apparatus Sieves: A set of standard sieves conforming to the required sieve sizes for the aggregate being tested. The most common sizes used are 25.0 mm, 20.0 mm, 16.0 mm, 12.5 mm, and 10.0 mm.Thickness gauge: A metal gauge with slots of specified widths for each sieve size. The width of the slot is equal to 0.6 times the mean sieve size. Figt. Thickness gauge Length gauge: A metal gauge with a series of holes of specified lengths for each sieve size. The length of the hole is equal to 1.8 times the mean sieve size. Fig2. Length gauge ¢ Balance: A balance accurate to 0.1 g. Additional equipment: Sieve shaker Weighing pan Spatula Calculator3. Procedure Dry the aggregate sample to constant weight in a drying oven at 110°C. Split the sample into representative fractions using the sample splitter. Sieve each fraction through the specified sieves. Weigh each fraction retained on each sieve. Test each fraction for flakiness using the thickness gauge. Pass each particle through the appropriate slot in the thickness gauge. The particles that pass through the slot are considered flaky. Weigh the flaky particles from each fraction 6. Test each fraction for elongation using the length gauge. Pass each particle through the appropriate hole in the length gauge. The particles that are retained by the hole are considered elongated, Weigh the elongated particles from each fraction 7. Calculate the flakiness index and elongation index for each fraction using the following formulas: © Flakiness Index (%) = (Weight of flaky particles / Weight of fraction retained on sieve) x 100 © Elongation Index (%) = (Weight of elongated particles / Weight of fraction retained on sieve) x 100 8, Calculate the average flakiness index and elongation index for the entire sample by weighting the results for each fraction by the weight of the fraction. PRENS 4. Results Initial weight of the specimen (W): 2894g Flakiness Index Wt of Aggregate Passing Through Thickness’ gauge(Y): 460g Elongation index wt. of aggregate retained on length gauge(X): 10569 Flakiness Index: Y/W * 100% = 15.89% Combined Elongation Index: X/(W-Y) * 100% = 32.54% Combined Index: 15.89% + 32.54% = 48.43% 5. Discussion and Conclusion Discussion: © Flakiness index: The flakiness index of 15.89% is well within the typical common allowable limit of 25%. This indicates that the aggregate particles arenot excessively thin or flaky, which can lead to weak concrete due to poor packing and internal voids. © Elongation index: The combined elongation index of 32.54% is not within the common limit of 20%. This suggests that the aggregate particles are overly elongated, increasing the potential for increased cracking and reduced workability in the concrete mix. Combined index: While not a standard metric, the combined index of 48.43% provides a general assessment of the aggregate's shape characteristics. This value, being well above the allowable limits for sub base / base course (30%) , further reinforces the unsuitability of the aggregate for pavement construction. Conclusion: Based on the flakiness and elongation index test results, the aggregate sample does not meet the typical requirements for use in concrete. The particle shape characteristics do not fall within acceptable ranges. 6. References ASTM C1235 / AASHTO T 85: Standard Test Method for Determining Length and Flakiness of Coarse Aggregate © IS 2386-1 (1963): Methods of Test for Aggregates for Concrete, Part I: Particle Size and Shape