Types of Turnout

Left Hand Turnout.

Y Turnout.

Diamond Crossing.

3-Way Turnout.

Single Slip.

Double Slip.

Admixtures for Concrete

ACI 116R-00 defines the term admixture as “a material other than water, aggregates, hydraulic cement, and fiber reinforcement, used as an ingredient of a cementitious mixture to modify its freshly mixed, setting, or hardened properties and that is added to the batch before or during its mixing.”

Functions of Admixtures:
  • Increase workability without increasing water content or decrease the water content at the same workability;
  • Retard or accelerate time of initial setting;
  • Reduce or prevent shrinkage or create slight expansion;
  • Modify the rate or capacity for bleeding;
  • Reduce segregation;
  • Improve pumpability;
  • Reduce rate of slump loss;
  • Retard or reduce heat evolution during early hardening;
  • Accelerate the rate of strength development at early ages;
  • Increase strength (compressive, tensile, or flexural);
  • Increase durability or resistance to severe conditions of exposure, including application of deicing salts and other chemicals;
  • Decrease permeability of concrete;
  • Control expansion caused by the reaction of alkalies with potentially reactive aggregate constituents;
  • Increase bond of concrete to steel reinforcement;
  • Increase bond between existing and new concrete;
  • Improve impact and abrasion resistance;
  • Inhibit corrosion of embedded metal; and
  • Produce colored concrete or mortar.

Standards Used for Admixtures:
  • Air-Entraining Admixtures ASTM C 260
  • Standard Specification for Air-Entraining
  • Admixtures for Concrete AASHTO M 154
  • Standard Specification for Air-Entraining
  • Admixtures for Concrete CRD-C 13
  • Chemical Admixtures ASTM C 494
  • Standard Specification for Chemical
  • Admixtures for Concrete AASHTO M 194
  • Standard Specification for Chemical
  • Admixtures for Concrete CRD-C 87
  • Calcium Chloride ASTM D 98
  • Standard Specification for Calcium Chloride AASHTO M 144
  • Foaming Agents ASTM C 869
  • Admixtures for Shotcrete ASTM C 1141
  • Admixtures for Use in Producing
  • Flowing Concrete ASTM C 1017
  • Grout Fluidifier For Preplaced Aggregate
  • Concrete ASTM C 937
  • Pigments For Integrally Colored Concrete ASTM C 979

Types of Admixtures:
  • Chemical Admixtures:
    • Accelerators
    • Retarders
    • Air entrainments
    • Plasticizers
    • Pigments
    • Corrosion inhibitors
    • Bonding agents
    • Pumping aids
  • Mineral Admixtures:
    • Fly ash
    • Mineral
    • Ground granulated blast furnace slag (GGBFS or GGBS)
    • Silica fume
    • High reactivity Metakaolin (HRM)
  • According to ASTM:
    • Type A—Water-reducing admixtures,
    • Type B—Retarding admixtures,
    • Type C—Accelerating admixtures,
    • Type D—Water-reducing and retarding admixtures,
    • Type E—Water-reducing and accelerating admixtures,
    • Type F—Water-reducing, high range admixtures,
    • Type G—Water-reducing, high range, and retarding admixtures, and
    • Type S—Specific performance admixtures.

Civil Engineering Standards

The mostly known Codes & Standards are as follows:
  • American Association of State Highway and Transportation Officials (AASHTO)
  • American Concrete Institute (ACI)
  • American Society of Civil Engineers (ASCE)
  • American Society for Testing and Materials (ASTM)
  • British Standards (BS)
  • British Standards Insititution (BSI)
  • International Organization for Standardization (ISO)

Components of a Turnout (Point & Crossing)

A Turnout Contains the Following Components:
    A set of Point or Switch:
  • a pair of stock rails,
  • a pair of tongue rails,
  • a pair of heel blocks,
  • a number of chairs,
  • two or more stretcher bars,
  • a gauge tie plate,
    • A Crossing:
  • a nose consisting of point  rail and splice rails,
  • two wing rails,
  • two check rails,
    • Lead Rails:
  • four sets of lead rails.

Materials & Required Properties of Ballast

Materials Used for Ballast
  1. Broken stone
  2. Gravel
  3. Coarse sand
  4. Brick bats
  5. Selected earth
Required Properties
  • Aggregate Abrasion Values: Maximum 30%
  • Aggregate Impact Test: Maximum 20%
  • Soundness: Maximum 10%
  • Elongation Index: Maximum 50%
  • Flakiness Index: Maximum 50%
  • Specific Gravity: Minimum 2.65
  • Water Absorption: Maximum 1%

Ballast: Functions & Properties


Functions
  • Provide a hard and level bed for sleepers
  • Hold sleepers in place during passage of trains
  • Transfers and distributes load from sleepers to larger area
  • Provides effective drainage and keep sleeper dry
  • Prevent vegetation growth
  • Prevents water from percolating (capillary rise)
  • Provide track stability


Desirable Properties of Ballast
  • Good bearing capacity and crushing value
  • Tough and wear resistant
  • Good drainage property
  • Non porous
  • Should resist attrition and abrasion
  • --Attrition: getting carried/ rubbed away by means of friction
  • -- Abrasion: wearing down by means of friction
  • Weather resistant
  • Low lifecycle cost

Gauge of Railway

Track gauge or rail gauge is the distance between the inner sides of the heads of the two load bearing rails that make up a single railway line. Clear distance measured at a certain vertical distance below the rail table (upper surface) e.g. Europe: 14mm below, Japan 16mm below.


Types of Gauges

Broad gauge:
1.524m- 1.676m (5’ 0’’ -5’ 6”)
Standard gauge:
1.435m-1.451m (4’ 8.5’’ -4’ 9.125”)
Meter gauge:
1m- 1.067m (3’ 3.375’’ -3’ 6”)
Narrow gauge:
0.610m-0.762m (2’ 0’’ -2’ 6”)
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