Relative Density and Absorption Important Properties Gradation Relative density and absorption Hardness (resistance to wear) Durability (resistance to weathering) Shape and surface texture Deleterious substances Crushing strength Soft and lightweight particles Chemical stability CIVL 3137 2 Absorption Dry SSD Wet CIVL 3137 3 Absorption MD M % AbsAW 100% MD MAW CIVL 3137 4 Question A 1-ft3 bucket holds 100 lb. of aggregate. How much volume is occupied by the air and how much by the aggregate particles? CIVL 3137 5 Particle Density Particle density is the ratio of the mass of an aggregate particle to its own volume (also called mass density of solids). Mkg g or 33 V mcm CIVL 3137 6 Particle Density Particle density can also be expressed as the ratio of the weight of an aggregate particle to its own volume. Wlb 3 V ft CIVL 3137 7 Relative Density Relative density is the mass density of an object relative to the mass density of water (also called specific gravity). MV M RD w w V w CIVL 3137 8 Relative Density Relative density (specific gravity)can also be expressed in weight-based units. WV W RD w w V w CIVL 3137 9 Relative Density Relative density depends on the volume you assume for the aggregate particles. Net Bulk Volume Volume CIVL 3137 10 Relative Density It also depends on the mass you assume for the aggregate particles. Dry SSD Mass Mass CIVL 3137 11 Apparent Relative Density MD RDA VN w Net volume CIVL 3137 12 Bulk (OD) Relative Density MD RDB VB w Bulk volume CIVL 3137 13 SSD Relative Density MSSD RDSSD VB w SSD aggregate CIVL 3137 14 Example An aggregate sample has an oven-dry mass of 3954.2 g, an SSD mass of 4006.8 g, and a net volume of 1532.6 cm3. Find RDA, RDB, RDSSD, and %Abs CIVL 3137 15 Question A 1-ft3 bucket holds 100 lb of aggregate from the last example. How much volume is occupied by the air and how much by the aggregate particles? CIVL 3137 18 Question A 1-m3 bucket holds 1500 kg of aggregate from the last example. How much volume is occupied by the air and how much by the aggregate particles? CIVL 3137 21 Measuring Relative Density Lab 4.8-2 CIVL 3137 24 Measuring Relative Density M RD V w mass of water displaced CIVL 3137 25 Measuring Relative Density M RD aggregate Mwater displaced CIVL 3137 26 Buoyancy Mwater displaced × g = Min water × g Min air × g CIVL 3137 27 Measuring Relative Density MMMwater displaced in air in water CIVL 3137 28 Apparent Relative Density OD Min air RDA OD MMin air in water Net volume CIVL 3137 29 Bulk (OD) Relative Density OD Min air RDB SSD MMin air in water Bulk volume CIVL 3137 30 SSD Relative Density SSD Min air RDSSD SSD MMinair inwater Bulk volume CIVL 3137 31 Measuring Relative Density Lab 4.8-3 CIVL 3137 32 Measuring Relative Density ~ 500 g ~ 500 g ~ 500 g Mwater Msand Mblend CIVL 3137 33 Measuring Relative Density MMMMwater displaced water sand blend CIVL 3137 34 Apparent Relative Density MOD RD sand A OD MMMwater sand blend Net volume CIVL 3137 35 Bulk (OD) Relative Density MOD RD sand B SSD MMMwater sand blend Bulk volume CIVL 3137 36 SSD Relative Density MSSD RD sand SSD SSD MMMwater sand blend Bulk volume CIVL 3137 37 Achieving an SSD State Coarse aggregate should be soaked in room temperature water for 24±4 h then rolled in a large absorbent cloth to remove all visible surface moisture. CIVL 3137 38 Achieving an SSD State Fine aggregate should be brought to a moisture content of at least 6% and allowed to stand for 24±4 h. Aggregate is then spread out on a nonabsorbent surface and air is blown across it until it attains a free flowing condition. CIVL 3137 39 Achieving an SSD State CIVL 3137 40 CIVL 3137 41.