Coarse particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates.
Aggregates are a component of composite materials such as concrete and asphalt concrete
Aggregate serves as reinforcement to add strength to the overall composite material.
Due to the relatively high hydraulic conductivity value as compared to most soils, aggregates are widely used in drainage applications such as foundation and french drains, septic drain fields, retaining wall drains, and road side edge drains.
Aggregates are also used as base material under foundations, roads, and railroads.
Has been widely used since 1920–1930.
The terms asphalt and bitumen are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, asphalt (or asphalt cement) is the carefully refined residue from the distillation process of selected crude oils. Outside the U.S., the product is often called bitumen.
The viscous nature of the bitumen binder allows asphalt concrete to sustain significant plastic deformation, although fatigue from repeated loading over time.
Most asphalt surfaces are laid on a gravel base.
In areas with very soft or expansive subgrades such as clay or peat, thick gravel bases or stabilization of the subgrade with portland cement or lime may be required.
Asphalt is categorized as hot mix asphalt (hma), warm mix asphalt, or cold mix asphalt.
Hot mix asphalt is applied at temperatures over 300 F
Warm mix asphalt is applied at temperatures of 200 to 250 degrees F
cold mix asphalt is often used on lower volume rural roads, where hot mix asphalt would cool too much on the long trip from the asphalt plant to the construction site.
Advantages: low noise, relatively low cost compared with other paving methods, and perceived ease of repair.
Disadvantages:less durability than other paving methods,less tensile strength than concrete, the tendency to become slick and soft in hot weather and a certain amount of hydrocarbon pollutionto soil and groundwater or waterways.
Cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 °C in a kiln.
The resulting hard substance, called 'clinker', is then ground with a small amount of gypsum into a powder to make 'Ordinary Portland Cement', the most commonly used type of cement (often referred to as OPC).
Portland cement is a basic ingredient of concrete, mortar and most non-speciality grout.
The most common use for Portland cement is in the production of concrete.
7 STEEL REINFORCEMENT
Also known as reinforcing steel, reinforcement steel, or a deformed bar, is a common steel bar, and is commonly used as a tensioning device in reinforced concrete and reinforced masonry structures holding the concrete in compression.
usually formed from carbon steel, and is given ridges for better mechanical anchoring into the concrete.
Rebar is available in different grades and specifications that vary in yield strength, ultimate tensile strength, chemical composition, and percentage of elongation.
The grade designation is equal to the minimum yield strength of the bar in ksi (1000 psi) for example grade 60 rebar has a minimum yield strength of 60 ksi. Rebar is typically manufactured in grades 40, 60, and 75.
8 Types And Grades Of Aggregate Three main types of rock are used to produce crushed rock aggregates: Igneous Solidified molten rocks (eg basalt, granite) Sedimentary Created by settlement of particles (eggritstones) or organic remains (eg limestone) in ancient seas Metamorphic Created by heat or pressure (eghornfels, quartzites)
9 TYPES OF TESTS ON MATERIALS a.AggregateImpact Value Test b. Polished Stone Value Test c. Aggregate Crushing Value Test d. Flakiness Index Test e. Elongation Test f. Penetration Test g. Softening Test h. Viscosity Test i. Flash and Fire Point Test j. Ductility Test k.Floatation Test l. Soundness Test.
10 Aggregate Impact Value Test BS 812: Part 112: 1990
Determine aggregate resistance due to impact.
Size aggregate : passing sieve 14mm and retain 10 mm.
Agregate were filling into mould in one layer and will be driven by rod in 25 times.
Defined as the distance (in 1 / 10) standard needle puncture of the time, load and temperature are known.
Using a standard needle under the load of 100 grams for 5 seconds at a temperature of 20 degrees celsius.
High penetration value indicates the material is soft.
16 SOFTENING TEST
To determine the temperature at which phase changes occur in the bitumen.
Soft spot is defined as the temperature at which bitumen is unable to support the steel ball and began to soften.
17 VISCOSITY TEST To determine the viscosity of the bitumen. Defined as the resistance of a fluid to flow. Two types of viscosity : absolute or dynamic viscosity and kinematic.
18 Flash and Fire Point Test When the bitumen is heated at high temperatures, the vapor will be liberated and embrace if any sources of ignition. Flash point indicates the temperature at which bitumen can be heated without danger of fire generated in the presence of the fire. The method used is the Cleveland open cup method.
19 DUCTILITY TEST This test is done to determine the ductility of distillation residue of cutback bitumen, blown type bitumen and other bituminous products as per IS: 1208 – 1978. The principle is : The ductility of a bituminous material is measured by the distance in cm to which it will elongate before breaking when a standard briquette specimen of the material is pulled apart at a specified speed and a specified temperature. The apparatus required for this test: i) Standard mould ii) Water bath iii) Testing machine
21 Objectives of asphalt mix design The design of an asphalt mix is largely a matter of selecting and proportioning materials to optimise the engineering properties in relation to the desired behaviour in service. Procedures for designing asphalt mixes have been generally developed around testing of dense graded mixes and determination of optimum binder content, although most tests can be used for other mix types with suitable interpretation of results. The overall objective for the design of dense graded asphalt paving mixes is to determine (within the limits of project specifications) a cost-effective blend and gradation of aggregates and binder that yields a mix
22 Characteristics of asphaltic concrete mix 1.Sufficient binder to ensure a durable pavement; 2. Sufficient mix stability to satisfy the demands of traffic without distortion or displacement; 3. Sufficient voids in the total compacted mix to allow for a slight amount of in place compaction by traffic and bitumen expansion due to temperature increases, without flushing, bleeding and loss of stability; 4. A maximum void content to limit the permeability of harmful air and moisture into the mix; 5. Sufficient workability to permit efficient placement of the mix without segregation and without sacrificing stability and performance; 6. For surface mixes, proper aggregate texture and hardness to provide sufficient skid resistance.
23 An overview of the design process Asphalt mix design involves the following basic steps that are similar in concept, regardless of the actual tests and procedures used: 1. Selection of mix type. 2. Selection of component materials. 3. Combination of aggregates to meet target grading. 4. Selection of target binder content or range. 5. Mixing and compaction of asphalt mix to a density that is representative of in-service conditions. 6. Measurement of volumetric properties of compacted mix. 7. Mechanical testing of compacted samples, if required. 8. Verification of design properties on samples of manufactured asphalt, if required. 9. Selection of Job Mix.
24 MARSHALL MIX DESIGN METHOD - Developed by Bruce Marshall & the U.S. Corps of Engineers. Objective: To determine the optimum asphalt content for a particular aggregate blend and asphalt to be used.
25 PROCEDURES: 1. Prepare asphalt concrete specimens (4 inches in diameter & 2.5 inches in height) for a range of asphalt content at and near the estimated optimum asphalt content. (A) Mixing temperature: at asphalt viscosity of 170 ± 20 cSt (B) Compaction temperature: at asphalt viscosity of 280 ± 30 cSt (C) Compactive Effort: 35, 50 or 75 blows with a Marshall hammer (10 lbs, 18 inches drop) on each side of the specimen. (D) Number of Samples: 3 replicates at each asphalt content Typically, 5 different asphalt contents are used.
32 % AC at 4% air voids: 6.7 6. Verify mix design criteria at the optimum asphalt content. The five mix criteria to check against are: (A) Marshall stability (B) Marshall flow (C) Air Voids (D) VMA (E) VFA