The aggregate to be classified is separated into seven sieve fractions from 6. Shape tests on coarse aggregates such as flakiness index and elongation index, its importance in concrete construction, methods of determination is discussed. Exp 1 flakiness and elongation index civil engineers pk. The test is carried on aggregate sizes between 63 mm and 6. Flakiness index test is conducted by using a metal thickness gauge. The flakiness index is taken as the total weight of the. The percentage by weight of the elongated particles present in a given test sample. Flakiness and elongation index of aggregate youtube. This method is based on the classification of aggregate particles as flaky when they have a thickness smallest dimension of less than 0. Maximum permitted elongated index is 35, 40 or 45% for aggregate sizes 2.
Pdf determination of the flakiness and the elongation. Both flakiness and elongation tests are not applicable to sizes smaller then 6. Flat and elongated particles of coarse aggregates have a tendency to fracture more easily than other aggregate particles. Flakiness index is weight of flaky stone metal divided by weight of stone sample. It is expressed as the percentage by weight of particles in a sample of more than 200 whose smallest dimension is less than 0. In this paper effects of aggregate flakiness on the compressive strength of concrete cubes have been studied using experiments. Aashto t 11200 clay lumps and friable particles in aggregate. The flakiness index test fi is not applicable passing 6. Pdf determination of the flakiness and the elongation index. Two procedures, method a and method b, are presented in this standard.
Elongation index wt of aggregate retained on specified gauge total wt of aggregate taken flakiness index is the % by weight of particles whose least dimension is lesser than 35 of the mean dimension. The strength of coarse aggregate may be assessed by aggregate crushing test. What is the use of the elongation and flakiness index. For crushed aggregate, the particle shape and surface texture depend on the nature of the parent material and on the type of crusher and its reduction ratio. Elongation index wt of aggregate retained on specified gauge total wt of aggregate taken flakiness index is the % by weight of particles whose least. Elongation index is the percentage by weight of particles in it, whose largest dimension i. The percentage of flaky and elongated particles that it contains. Roughtextured, angular, and elongated particles require more water to produce workable concrete than smooth, rounded compact aggregate. This british standard, a section of the bs 812 series, describes methods for determining the flakiness index of coarse aggregate.
Flakiness index and elongation index test on coarse aggregates. The particle shape of the aggregate is determined by. Chapter 2 bituminous tex224f, determining flakiness index manual of testing procedures 1 899 1004 tex224f, determining flakiness index overview effective date. The flakiness index of a coarse aggregate is the mass of particles in that aggregate, expressed as a percentage of the total mass of that aggregate, which will pass the slot or slots of specified width for the appropriate size fraction, as given in table i below. This procedure discusses how to determine the number of flat or elongated particles in a coarse aggregate material. Flakiness and elongation index of aggregate duration. For more information read our blog characteristics of aggregates.
Flakiness index is the percentage by weight of particles in it, whose least dimension i. Effect of aggregate flakiness on the compressive strength. Retained on flakiness percentage of bakiness index. The flakiness index parameters obtained from the 3d laser scanning were compared with the results obtained from tmh 1 method b3. Objective for determination of flakiness index of coarse aggregate, where the size of the coarse aggregate are larger than 6. Bulk density and voias of coarse aggregate duration. For all type of coarse aggregate, 75 cubes 150 x 150 mm were cast to permit the compressive strength to be observed. What is the significance of flakiness index and elongation. Aggregate angularity flakiness elongation index gilson co. May 08, 20 objective for determination of flakiness index of coarse aggregate, where the size of the coarse aggregate are larger than 6. The computed flakiness indices were in good agreement with the measurements from the standard methods, thus validating the correctness of the laser approach and the effectiveness of the volume method.
The particle shape of aggregate is determined by the percentages of flaky and elongated particles contained in it. The scope of this test is to provide test methods for determining the elongation index of coarse aggregate. Recommended limits for aggegates linkedin slideshare. Flakiness and elongation flakiness index sieve set uta0410. Aug 11, 2014 the flakiness index test fi is not applicable passing 6. Each fraction is gauged in turn for thickness on the metal gauge. Elongation index test on coarse aggreagtes elongation index of an aggregate is the percentage by weight of particles whose greatest dimension length is greater than one and fourfifth times 1. What various tests are done for the water, fine aggregates.
Definition of flakiness index and elongation index civil. Astm d4791 19 standard test method for flat particles. The flakiness index is the weight of flaky particles as a % of the sample weight. Only the elongated particles be separated out from the remaining nonflaky stone metal. In case of gravel it is determined by its angularity number. Flakiness index test is not applicable for aggregates sizes smaller than 6. Relative density weighing in air and in water bs not less than 2. Aggregates which are flaky and elongated are detrimental to the higher. Flakiness index sieve set uta0410 when an aggregate particle has a thickness less than 0.
Flakiness index and elongation index of coarse aggregates. Bs1241 specifies a flakiness index not exceeding 30% irrespective of the aggregate size. Effect of aggregate flakiness on the compressive strength of. Elongation index and flakiness index of coarse aggregate.
Flakiness and elongation index of aggregate gilson co. The weight of retained aggregate on each sieve is measured and determined the percentage of retained. Determination of the flakiness and the elongation index. Following tests are conducted on coarse aggregates under shape tests. This standard specifies a method for determining the flakiness index of coarse aggregate that passes a sieve of aperture size 75 mm and that is retained on a sieve of aperture size 4 750 om.
This standard sets out a method for determining the flakiness index of an aggregate. When an aggregate particle has a thickness less than 0. The method makes reference to a particle size distribution procedure which is required for determination of flakiness index. Flakiness sieves, aggregates testing equipment, controls.
Additionally, flat and elongated particles of aggregate, for some construction uses, may interfere with. Aggregate quality for road construction will also influence the road performance. The flakiness index of an aggregate sample is found. Aggregate is separated into seven sieve fractions from 636. May 08, 20 objective for determination of elongation index of coarse aggregate, where the size of the coarse aggregate are larger than 6. The dried aggregates sample is allowed to passing and retained on a set of sieve. Mar 03, 2012 the value that we get from this test is 15. The test is not applicable to sizes smaller than 6. Elongation index and flakiness index of coarse aggregate bs. Flakiness index the flakiness index of aggregate is the percentage by weight of particles in it whose least dimension thickness is less than threefifths of their mean dimension. Determination of the flakiness and the elongation index for the given aggregate sample. Elongation value is 0% because the aggregate is rounded so no any retain value. When the coarse aggregate does fracture, the gradation will likely change which may be detrimental to the mix.
Total 30 cubes have been cast using normal, 5% of 8 mm, 10 mm and 12 mm size of flaky. Aashto t 8514 specific gravity and absorption of coarse aggregate. Method a is a reflection of the original procedure as developed prior to superpave and is intended for all nonsuperpave applications. An aggregate is classified as being elongated if it has a. An adequate quantity of course aggregate is taken such that the minimum number of 200 pieces of any fraction can be tested. Coarse aggregates of basalt and granite were used in the study. Aggregate generally occupy about 70% to 80% of the volume of concrete and can therefore be expected to have an important influence on it properties. The method applies to aggregates having a nominal size not greater than 63. Flakiness and elongation index of coarse aggregate particle shape and surface texture influence the properties of freshly mixed concrete more than the properties of hardened concrete. The apparatus for the shape tests consists of the following. Objective for determination of elongation index of coarse aggregate, where the size of the coarse aggregate are larger than 6. The flakiness index of course aggregate is defined in percentage by weight of aggregate particles and least dimension thickness of those particles should not be less than 0. The percentage by weight of flaky particles present in a given test sample.
What is the significance of flakiness index and elongation index. The aggregate crushing value provides a relative measure of resistance to crushing under gradually applied compressive load. Determinations for the flakiness index and flakiness and elongation of aggregate use a british standard classification system consisting of a thickness gauge for determining flakiness index and a metal length gauge for determining elongation index. The flakiness index can be obtained from the shapevolume.