Aggregates (Part - 01) PDF

AGGREGATES Concrete is TWO Phase material – Paste & Aggregates Paste – Cement + Water 70 TO 80% OF Concrete is aggregates Mostly Naturally available (In Future-Artificial Aggregates) Reduce Shrinkage in concrete Reduce cost Supposed to be INERT (Few Agg are no...

AGGREGATES Concrete is TWO Phase material – Paste & Aggregates Paste – Cement + Water 70 TO 80% OF Concrete is aggregates Mostly Naturally available (In Future-Artificial Aggregates) Reduce Shrinkage in concrete Reduce cost Supposed to be INERT (Few Agg are not INERT – Alkali Agg Reaction) Important to know the properties of aggregates responsible for behavior in concrete GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – AGG1 1  Issues to be Studied Classification Specific Gravity and Bulk Density Size Thermal Properties Source Bulking Factor Shape Soundness Strength Cleanliness Texture Chemical Properties Sieve Analysis – Grading Moisture Content GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – AGG1 2  Classification of Aggregates Natural – River Sand, Gravel, Crushed Rock Artificial – Broken Brick, Air cooled Slag, Sintered Fly Ash, Bloated Clay, Shale, Construction & Demolished waste etc., (C & D Waste) Natural – Igneous rocks, Sedimentary rocks, Metamorphic rocks Igneous rocks – Solidification of molten rock – Granite, Basalt etc., Sedimentary rocks – Deposition of weathered remains of rocks – Limestone, Clay, Sandstone, Shale etc., Metamorphic rocks – Transformation of existing rock – Gneiss, Slate, Marble etc., GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – AGG1 3 GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 4 AGG1  Size of Aggregates Larger the size of aggregates – lower the consumption of cement, water, drying shrinkage – Higher Strength of Concrete Factors influencing – Thickness of section, Spacing of reinforcement, Clear cover, Mixing, handling & Placing techniques. Normally not more than 0.25 times thickness of the member < 4.75 mm – Fine aggregates, > 4.75 mm - Coarse Aggregates Maximum size of aggregate – 80 mm – Normally used in dams Size of aggregate is 5 mm less than the spacing of the reinforcement / Clear Cover For RCC normally – Nominal Size of aggregate shall be 20 mm. GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – AGG1 5  Congested Reinforcement Size of aggregate should be 5 mm less than the spacing of steel & cover to steel GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 6 AGG1 SHAPE OF THE AGGREGATES GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 7 AGG1 Shape of the aggregate Rounded – Water worn, River sands, Desert sands – Lower surface area - Better workability – No interlocking – Lower tensile strength – Satisfactory compressive strength Angular – Naturally irregular – more surface area – Lower workability – Better interlocking – better tensile strength - Desirable Flaky & Elongated – Not desirable Quantification of Flakiness Index & Elongation Index IS 460-1985- Indian Standards For Test Seives ASTM – American Society for Testing Materials GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 8 AGG1 Texture of Aggregate Rough Texture – More Friction – Smooth Texture – Less Friction – Requires more paste for workability Requires less paste for workability Rough Texture – Irregular shaped – desirable GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 9 AGG1  Grading of Aggregate – Sieve Analysis Uniform Graded – Well Graded – All Single Size Aggregate – Sizes of Aggregate – Not Desirable Most Desirable GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 10 AGG1 Grading of Aggregates Minimum Porosity of concrete – Topic active research Maximum strength Minimum permeability – Maximum durability Minimum consumption of cement – Improve durability Good workability – Good compactibility – Good Cohesivity - Hence good strength & durability IS 383 – 2016 IS 2386 (1) - 1963 GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 11 AGG1 GRADING OF AGGREGATES 1. IS 460 Part 1- 1985 (Reaffirmed 1998) Specification for Test Sieves 2. IS 383 – 2016 – Specifications for coarse and fine aggregate from natural sources for concrete 3. IS 2386 – 1963 - METHODS OF TEST FOR AGGREGATES FOR CONCRETE Part I - Particle Size and Shape Part II-Estimation of DeIeterious Materials and Organic Impurities Part III - Specific Gravity, Density, Voids, Absorption and Bulking Part IV - Mechanical Properties Part V - Soundness Part VI - Measuring Mortar Making Properties of Fine Aggreg: _ :’ Part VII - Alkali Aggregate Reactivity Part VIII - Petrographic Examination GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 12 AGG1 Sieve Analysis - Sizes 80 mm 40 mm 20 mm 10 mm 4.75 mm 2.36 mm 1.18 mm 600 Microns 300 Microns 150 Microns Pan GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 13 AGG1 CALCULATION OF FINENESS MODULUS (FM) Wt. Cumulative % Wt. Percentage Sieve Size (mm) Retained(gm) %Wt. Retained Retained Passing 80 0 0.00 0.00 100.00 40 200 6.67 6.67 93.33 20 844 28.13 34.80 65.20 10 823 27.43 62.23 37.77 4.75 582 19.40 81.63 18.37 2.36 551 18.37 100.00 0.00 1.18 0 0.00 100.00 0.00 0.6 0 0.00 100.00 0.00 0.3 0 0.00 100.00 0.00 0.15 0 0.00 100.00 0.00 3000 685.33 FINENESS MODULUS= FM 6.85 GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 14 AGG1 GRADING CURVES 100.00 90.00 80.00 PERCENTAGE PASSING 70.00 POORLY GRADED 60.00 50.00 40.00 WELL GRADED 30.00 20.00 10.00 0.00 0.1 1 10 100 log(SEIVE SIZE) GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 15 AGG1  IS 383 - 2016 GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 16 AGG1 IS 383 - 2016 Zone – I – Coarser Fine Aggregate – Not Suitable for Concreting Zone – II & III – Suitable for Concreting ( FM = 3- 3.2) Zone – IV – Finer Fine Aggregate – Suitable for Plastering Only GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 17 AGG1 Flakiness and Elongation Index Cl. 4.1 of IS 2386 (1) - The flakiness index of an aggregate is the percentage by weight of particles in it whose least dimension ( thickness ) is less than three-fifth (0.6) of their mean dimension. The test is not applicable to sizes smaller than 6.3 mm. Cl. 5.1 of IS 2386 (1) - The elongation index of an aggregate is the percentage by weight of particles whose greatest dimension ( length ) is greater than one and four-fifths (1.8) times their mean dimension. The elongation test is not applicable to sizes smaller than 6.3 mm. GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 18 AGG1 Quantification of Flaky and Elongated Aggregates Cl. 5.3 of IS 383 – 2016 The combined flakiness and elongation index shall not exceed 40 percent for uncrushed or crushed aggregate. GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 19 AGG1 Determination of Flakiness Index GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 20 AGG1 Determination of Elongation Index GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 21 AGG1  If the paste is weaker than aggregate – Strength of Aggregate cracking through the paste – Normal Strength Concrete – Strength Depends on strength of paste If the paste is stronger than aggregate – cracking through the aggregate – High Strength Concrete – Strength Depends on the Strength of Aggregate Quantify the Strength For Roads – Stronger aggregates 1. Aggregate Crushing Value For Buildings – Lesser Strength of 2. 10% fines value 3. Impact Strength of aggregate - Roads aggregates is required GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 22 AGG1 Aggregate Crushing Strength IS 2386(IV) Resistance of an aggregate to crushing under a gradually applied compressive load. Surface dry aggregate passing 12.5 mm and retained on 10 mm sieve Fill the aggregate in 15 cm open ended steel cylinder and plunger Straight metal tamping rod 16 mm dia, 45 to 60 cm length, rounded at one end, 25 blows each time – cylinder is filled in 3 layers Compression testing machine capable of applying 40 tons in 10 minutes Material is sieved through 2.36 mm sieve. Aggregate Crushing Value = (B/A)*100 B – Weight of material passing through 2.36 mm sieve A – Weight of surface dry sample GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 23 AGG1 Cl. 5.4 of IS 383 - 2016 For aggregates to be used for wearing surfaces – ACV shall not exceed 30% If ACV exceeds 30% - Ten percent fines test shall be conducted. GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 24 AGG1 10% fines value test If ACV exceeds 30% - Ten percent fines test shall be conducted Test is conducted on sample passing 12.5 mm and retained 10 mm Some load is applied – sample is sieved through 2.36 mm sieve. – Percentage fines if found out. Test is repeated several times. A Plot of load on Y axis and % fines on X axis is plotted. Load corresponding to 10% fines is found from the plot. The minimum load for 10% fines shall be 50 kN (Cl. 5.4.1 of IS 383 – 2016) GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 25 AGG1 Aggregate Impact Value - IS 2386(IV) Measure of the resistance of an aggregate to sudden shock or impact Dry sample of aggregate passing 12.5 mm and retained on 10 mm shall be used. Sample is placed in a cylindrical container – three layers - standard tamping rod of 16 mm dia 45 to 60 cm long is used – 25 blows each layer. Hammer of weight 13.5 kg to 14 kg is allowed to fall from a height of 380  5mm. 15 blows are given to the sample. Sample is transferred to 2.36 mm seive Aggregate Impact Value = (B/A)*100 B – Weight of material passing through 2.36 mm sieve A – Weight of surface dry sample GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 26 AGG1 Aggregate Impact Value (Cl. 5.4.2 of IS 383 – 2016) GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 27 AGG1  BULKING OF SAND Significant in Volume batching – Volume batching is not correct Sand has minimum volume when it is completely dry or fully saturated When the sand has some moisture – shows higher volume Water in the sand will add to the W/C ratio in concrete Net W/C in concrete will increase – Workability will increase – Strength decreases If you weigh 100 kg of sand, which has 10% bulking – Net sand is 90 kg and excess water is 10 kg Concrete will not be having sufficient quantity of sand (under sanded) – Excess quantity of water Undersanded is not good – Excess quantity of water is not good GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 28 AGG1 BULKING OF SAND GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 29 AGG1 Determination of Bulking of Sand Take a measuring jar (say 1 litre capacity) Fill 500 ml of sand in the measuring jar Slowly add water to make the sand fully saturated Add excess amount of water and shake the jar – Allow the sand to settle Fully saturated sand has minimum volume (Now the sand will occupy 450 ml) Bulking = (500 – 450)*100/500 = 10% Amount of water and sand need to be adjusted GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 30 AGG1 Estimation of Deleterious materials & Organic materials IS 2386 (2) a) Determination of clay lumps, b) Determination of clay, fine silt and fine dust (sedimentation method), c) Determination of light-weight pieces (coal and lignite), d) Determination of soft particles, and e) Estimation of organic impurities GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 31 AGG1 GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 32 AGG1  Concrete Mix Proportions Proportion of Cement : Proportion of FA : Proportion of CA: Water cement Ratio For Example – 1:2:4:0.4 (Nominal mix – approximate) Designed mix – 1: 2.43 : 4.12: 0.42 (Accurate – Important works – Weight batching only) If the Proportion is considered by Weight – Weigh Batching – Accurate – Mostly used in Ready Mixed Concrete (RMC) If the Proportion is considered by Volume – Volume Batching – Approximate – Mostly used on sites – Rural areas – Non important works AVOID VOLUME BATCHING - GARJE RAJESH KUMAR – CE204 CONCRETE TECHNOLOGY – 33 AGG1