Flakiness and elongation index of aggregate gilson co. Apr 19, 2006 aggregate shape is considered to be a key parameter for concrete and bituminous mixtures design. Therefore, aggregate properties are very important in hma because it will affect the performances of the hma. Aggregate angularity flakiness elongation index gilson co. What is the use of the elongation and flakiness index. The 3d laser scanning device was used to scan the coarse aggregate particles i. Flakiness index and elongation index of coarse aggregates. Flakiness and elongation index of aggregate youtube. Is the combined flakiness and elongation index of aggregate. The amount of flakiness is denoted by flakiness index. Flakiness and elongation of aggregates and concrete properties published on december 6, 2016 december 6, 2016 27 likes 9 comments. Dec 12, 2017 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.
Fundamental aggregate shape properties anochieboateng et al. According to bs specifications flakiness index of the aggregate used for the road construction should not be greater than 35 % and elongation index should not be greater than 45 %. This method is based on the classification of aggregate particles as flaky when they have a thickness smallest dimension of less than 0. Definition of flakiness index and elongation index civil. Shape tests on coarse aggregates such as flakiness index and elongation index, its importance in concrete construction, methods of. What is the significance of flakiness index and elongation index. Particle aggregate an overview sciencedirect topics. Determination of the flakiness and the elongation index for the given aggregate. The influence of the shape of the coarse aggregate on some. In case of gravel it is determined by its angularity number.
Elongation index is the percentage by weight of particles in it, whose largest dimension i. Aggregate retained on the 75 mm and passing the 4,75 mm sieve is not included in the test. Initially an aggregate samples were collected from the stone crusher two types and prepared with different proportions of flakiness and elongation indices to conduct tests on properties of aggregates and compressive strength and flexural strength tests on concrete. The standardized methods used for this purpose vary among countries, but all of them are. Flakiness index is the percentage by weight of particles in it, whose least dimension i. Quarter the aggregate sample to obtain a minimum of 200 particles passing the 78in. Dec 18, 2017 theory elongation index aggregate particles are classified as elongation when they have a length greatest dimension of more than 1. Aggregate shape is considered to be a key parameter for concrete and bituminous mixtures design. The percentage of flaky and elongated particles that it contains. Aggregate are the important constituent in concrete. Particle shape analysis of coarse aggregate using digital. Dec 06, 2016 flakiness and elongation of aggregates and concrete properties published on december 6, 2016 december 6, 2016 27 likes 9 comments.
Detailed video on laboratory experiments with subtitles. Particle shape and surface texture influence the properties of freshly mixed concrete. This british standard, a section of the bs 812 series, describes methods for determining the flakiness index of coarse aggregate. Similarly, the particle is considered as flaky if its thickness is less than 0.
The particle shape of aggregate is determined by the percentages of flaky and elongated particles contained in it. Interlocking of the aggregate is inversely proportional to the flakiness index or the elongation index. Flakiness and elongation of aggregates and concrete properties. The particle shape of the aggregate is determined by. Pdf determination of the flakiness and the elongation index for. The test is not applicable to materials passing the 6. For pavements either bituminous or nonbituminous, elongation index of coarse aggregate should not be more than 15%. Doc flakiness index and elongation index of coarse. The flakiness index of aggregates is the percentage by weight of particles whose least dimension thickness is less than three fifths 0. Part 8 materials manual april section 933 method for. Surface texture of coarse aggregates surface texture of the aggregates is the property of its surface that classifies it into polished or dull, smooth or rough. May 08, 20 objective for determination of flakiness index of coarse aggregate, where the size of the coarse aggregate are larger than 6. Aggregate are granular material, derived from the most part from the natural rocks, crushed stones, or natural gravels and sands. The test is carried on aggregate sizes between 63 mm and 6.
A study on influence of shape of aggregate on strength and. Aggregate particles are classified as flaky when they have a thickness of less than 0. The procedures for their measurement are specified in bs812, section 105. Roughtextured, angular, and elongated particles require more water to produce workable concrete than smooth, rounded compact aggregate. Flakiness and elongation test construction aggregate road. Aggregate is termed as flaky when its least dimension i.
The elongation index of an aggregate is the percentage by weight. The flakiness index of an aggregate sample is found. Determination of elongation index linkedin slideshare. Bs1241 specifies a flakiness index not exceeding 30% irrespective of the aggregate size. Exp 1 flakiness and elongation index civil engineers pk.
Maximum permitted elongated index is 35, 40 or 45% for aggregate sizes 2. The flakiness index of an aggregate is the mass of particles in that aggregate which will pass the appropriate slot or slots for the individual size fraction expressed as a percentage of the total mass of that aggregate. Effect of aggregate flakiness on the compressive strength of. Plot the grading of the aggregate on a aggregate gradation chart, mat 67. Retained on flakiness percentage of bakiness index. Elongated and flaky stones are normally not very suitable for road works since the shape and the size make them difficult to compact. Objective particle shape and surface texture influence the properties of freshly mixed concrete more than the properties of hardened concrete.
Elongation and flakiness index of coarse aggregate with 0%, 5%, 10%, 15%, 20 % and 25% and impurity of fine aggregate with 0%, 2%, 4%, 6%, 8 % and 10% were adjusted while the amount of stone, sand, cement and water weer kept unchange. Elongation index is the % by weight of particles whose greater dimension is greater than 45 of the mean dimension. Nearly all the samples were found within the specified limits of astm specifications and are appropriate material for concrete, asphalt and suitable as dimension stone. Flakiness and elongation indices of coarse aggregate youtube.
Flakiness and elongation index, properties and testing of. The percentage by weight of flaky particles present in a given test sample. Proportional calipers are efficient devices that quickly determine percentages of elongated and flat particles in coarse aggregate fractions. The standardized methods used for this purpose vary among countries, but all of them are slow and lack precision.
The flakiness index of an aggregate sample is found by separating the flaky particles and expressing their mass as a percentage of the mass of the sample tested. Aggregate is separated into seven sieve fractions from 636. The influence of combined flakiness and elongation indices on marshall properties of coarse aggregate with nmas 12. Aggregates make up between 80% to 90% of total volume or 94% to 95% of the mass of hot mix asphalt hma. May 08, 20 objective for determination of elongation index of coarse aggregate, where the size of the coarse aggregate are larger than 6.
Therefore, aggregate properties are very important. Aggregate is separated into seven sieve fractions from 63. Both flakiness and elongation tests are not applicable to sizes smaller then 6. Effect of aggregate flakiness on the compressive strength. Laserbased approach for determining flakiness index of aggregates used in pavements j anochieboateng, j komba and j oconnell csir built environment, bldg 2c, p o box 395, pretoria, 0001, south africa. Influence of combined flakiness and elongation indices of. Report the elongation index in percentage rounded off to the nearest whole number.
Calculate the total flakiness index in percent as follows. 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. For determination of flakiness index of coarse aggregate, where the size of the coarse aggregate are larger than 6. The percentage by weight of the elongated particles present in a given test sample.
Draw a horizontal line at 50% passing from the vertical scale to intersect with the grading curve. This test is not applicable to sizes smaller than 6. Flakiness index and elongation index test on coarse aggregates. The elongation index is found by separating the elongation particles and expressing their mess as a percentage of the mass of sample tested. 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. What is the significance of flakiness index and elongation. Methods of test for aggregates for concrete, part i.
Flakiness index test is used to determine the particle shape of the aggregate and each particle shape being preferred under specific conditions. Is the combined flakiness and elongation index of aggregate is the numerical sum of separate elongation index and flakiness index. Determination of the flakiness and elongation index for the given aggregate. Generally, this parameter is determined by calculating a ratio between the different dimensions of the particles and by comparing this ratio to a flatness or elongation limit. Roughtextured, angular, and elongated particles require more water. Laserbased approach for determining flakiness index of aggregates used in pavements j anochieboateng, j komba and j oconnell. A flaky particle is the one whose least dimension thickness is less than 0. Apr 07, 20 flakiness and elongation index of aggregate. The computed flakiness indices were in good agreement with the measurements from the standard methods, thus. Thickness the maximum dimension perpendicular to the length and width. Flat particles, elongated particles, or flat and elongated particles in coarse aggregate astm d 4791 glossary flat and elongated particles of aggregate those particles having a ratio of length to thickness greater than a specified value. Regarding shape analysis of the coarse aggregate, only the flakiness and elongation are measured. Elongation index and flakiness index of coarse aggregate.
Flakiness and elongation indices aggregate particle shape characteristics and variations can affect the workability and strength of concrete. Definition 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. Aggregates which are flaky and elongated are detrimental to the higher. Objective for determination of elongation index of coarse aggregate, where the size of the coarse aggregate are larger than 6. Elongation index and flakiness index of coarse aggregate bs. Subsequently slump index and compressive strength of concrete were determined. Elongation index and flakiness index of coarse aggregate bs 812. The particle is considered as elongated if its length is more than 1.