Construction Materials & Testing CE 122 Lesson 2: Aggregates PDF

CONSTRUCTION MATERIALS & TESTING CE 122 ENGR. MANUEL A. RANGEL JR. Faculty  LESSON 2: AGGREGATES WOODGROVE Engr. Manuel A. Rangel BANK 2 INTRODUCTION TO AGGREGATES AGGREGATE - refers to coa...

CONSTRUCTION MATERIALS & TESTING CE 122 ENGR. MANUEL A. RANGEL JR. Faculty  LESSON 2: AGGREGATES WOODGROVE Engr. Manuel A. Rangel BANK 2 INTRODUCTION TO AGGREGATES AGGREGATE - refers to coarse particulate rock-like material consisting of a collection of disparate elements of size ranging from a small fraction of a millimeter to tens of millimeters. It includes natural gravel, crushed rock, sand, recycled concrete, slag, and synthetic or artificial aggregate. It is the inert filler materials, such as sand or stone, used in making concrete WOODGROVE BANK INTRODUCTION TO AGGREGATES WOODGROVE BANK CLASSIFICATION OF AGGREGATES BASED ON ORIGIN A. Natural Mineral Aggregate – decomposed rock that has been naturally sorted by the action of water, wind or ice. It is also obtained by crushing from quarries of igneous, sedimentary or metamorphic rocks. Example: Gravel River sand Beach sand WOODGROVE BANK CLASSIFICATION OF AGGREGATES BASED ON ORIGIN B. Manufactured Mineral Aggregate – produced as an end product or byproduct of an industrial process Example: Crushed stone Manufactured sand (M-sand) Ground blast furnace slag (GBFS) Expanded shale, clay, or slate (ESCS) WOODGROVE BANK CLASSIFICATION OF AGGREGATES BASED ON SHAPE A. Rounded aggregates – Fully water-worn or completely shaped by attrition. Come from river or sea shore and it is unsuitable for high-strength concrete & pavements. Examples: River or seashore gravels Desert, seashore, wind blown sands WOODGROVE BANK CLASSIFICATION OF AGGREGATES BASED ON SHAPE B. Irregular aggregates – Naturally irregular or partly attrition, having rounded edges. It develops a good bond and is suitable for making ordinary concrete. Examples: Pit sand and gravels Land or dug flints Cuboid rock WOODGROVE BANK CLASSIFICATION OF AGGREGATES BASED ON SHAPE C. Angular aggregate – Possesses well-defined edges formed at the intersection of roughly planar faces. It has sharp, angular & rough particles which provide a very good bond and are suitable for high-strength concrete and pavements. Example: Crushed rocks of all types WOODGROVE BANK CLASSIFICATION OF AGGREGATES BASED ON SHAPE D. Flaky aggregates – Material, usually angular of which the thickness is small relative to the width and/or length. Also known as elongated aggregate, the least lateral dimension should be less than 0.6 times the mean dimension Example: Laminated rock WOODGROVE BANK PHYSICAL PROPERTIES OF AGGREGATES Unit weight and Voids Specific gravity Particle shape and surface texture Shrinkage of aggregates Absorption and surface moisture Resistance to freezing and thawing WOODGROVE BANK PROPERTIES RELATED TO SUITABILITY Shape Surface texture Strength and Toughness Resistance to wear Resistance to freeze/thaw Resistance to wetting/drying Resistance to deicing salts Alkali resistivity WOODGROVE BANK PROPERTIES NEEDED FOR MIX DESIGN Absorption Moisture content Bulk Density Unit Weight Particle Density Specific Gravity Gradation WOODGROVE BANK PHYSICAL PROPERTIES OF AGGREGATES a. Unit Weight (unit mass or bulk density) - the weight of the aggregate required to fill a container of a specified unit volume. Volume is occupied by both the aggregates and the voids between the aggregate particles Depends on the size distribution and shape of particles and how densely the aggregate is packed Loose bulk density Rodded or compact bulk density WOODGROVE BANK PHYSICAL PROPERTIES OF AGGREGATES b. Specific Gravity Absolute – the ratio of the weight of the solid to the weight of an equal volume of water. It refers to the volume of the material excluding all pores Apparent – the ratio of the weight of the aggregate (dried in an oven at 212-230°F for 24 hours) to the weight of water occupying a volume equal to that of the solid including the impermeable pores. It is the volume of solid including impermeable pores (but not capillary pores) Used for calculating the yield of concrete or the quantity of aggregate required for a given volume of concrete. WOODGROVE BANK PHYSICAL PROPERTIES OF AGGREGATES c. Particle Shape and Surface Texture Rough textured, angular, elongated particles require more water to produce workable concrete that smooth, rounded, compact aggregates Aggregates should be relatively free of flat and elongated particles (limit to 15% by weight of total aggregate) Important for coarse and crushed fine aggregate – these require an increase in mixing water and may affect the strength of the concrete if cement water ratio is not maintained WOODGROVE BANK PHYSICAL PROPERTIES OF AGGREGATES d. Shrinkage of Aggregates Large shrinkage – fine-grained sandstones, slate, basalt, trap rock, clay-containing Low shrinkage – quartz, limestone, granite, feldspar WOODGROVE BANK PHYSICAL PROPERTIES OF AGGREGATES What happens if abnormal aggregate shrinkage occurs? WOODGROVE BANK PHYSICAL PROPERTIES OF AGGREGATES Excessive cracking Large deflection of reinforced beams and slabs Some spalling (chipping or crumbling) Note: if more than 0.08% shrinkage occurs, the aggregate is considered undesirable WOODGROVE BANK PHYSICAL PROPERTIES OF AGGREGATES e. Absorption and Surface Moisture – the moisture content in the SSD condition. It affects the following concrete behaviors: mix design, strength/ abrasion resistance. WOODGROVE BANK PHYSICAL PROPERTIES OF AGGREGATES f. Resistance to Freezing and Thawing Important for exterior concrete Affected by an aggregate’s high porosity, absorption, permeability, and pore structure If aggregates or concrete absorbs so much water that when the water freezes and expands, the concrete cannot accommodate the build-up of internal pressure, pop- outs may occur WOODGROVE BANK THANK YOU