RBSE Sec Voc Construction flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Fineness modulus

An index of aggregate coarseness found by sieve analysis; the sum of cumulative percentages retained on standard sieves divided by 100. Fine sand is 2.0-3.5.

Bulking of sand

Increase in the volume of damp sand due to surface moisture films. It is maximum at about 4-6 percent moisture and disappears when the sand is fully saturated.

Initial setting time

The time from adding water to cement until the paste begins to lose plasticity. For ordinary Portland cement it must not be less than 30 minutes.

Characteristic strength M20

Cube compressive strength of 20 N/mm² at 28 days, below which not more than 5 percent of test results are expected to fall.

English bond

A brick bond with alternating header and stretcher courses. It is strong and used for thick walls, but gives a less attractive face than Flemish bond.

Damp proof course

A 40-50 mm layer of cement concrete with waterproofing compound laid at plinth level across the wall to stop rising damp.

Staircase rule 2R plus T

A comfort rule for stair design where twice the riser plus the tread lies between 600 and 640 mm; typical riser 150-190 mm and tread 250-300 mm.

Raft foundation

A single continuous concrete slab supporting the whole building, used where soil bearing capacity is low or loads are heavy and spread over a large area.

Representative fraction

The ratio of drawing length to actual length, written as 1:100 for a reducing scale. It allows a drawing to be read at any unit of measurement.

Bar bending schedule

A table listing bar mark, diameter, shape, number and cutting length of reinforcement, used for fabrication and for computing the total steel weight.

Plan versus section

A plan is a top view cut about 1.2 m above floor level; a section is a vertical cut showing internal heights and construction layers.

Diagonal scale

A scale that can measure three units of measurement and read to the second decimal of a unit, using diagonal lines to subdivide the smallest division.

Long wall short wall method

An estimating method where long walls are measured centre to centre plus half width at each end, and short walls centre to centre minus half width at each end.

Centre line method

An estimating method using total centre line length times width times depth; junctions are adjusted by half width for each meeting wall.

Plinth area estimate

An approximate estimate obtained by multiplying the plinth area of the building by a plinth area rate for similar construction in that locality.

Earnest money deposit

A sum, usually 2-5 percent of the estimated cost, submitted with a tender to show serious intent; it is returned to unsuccessful bidders.

Ranging in chain survey

Fixing intermediate points on a straight line between two survey stations. Direct ranging is used when stations are intervisible, indirect when they are not.

Height of instrument

The reduced level of the line of sight, equal to the reduced level of a station plus the backsight reading on the staff held there.

Magnetic declination

The angle between magnetic north and true north at a place. True bearing equals magnetic bearing plus or minus the declination according to direction.

Three point problem

A plane table problem of locating the table position from three known points; solved by the Lehmann trial and error method or Bessel method.

Mortise and tenon joint

A carpentry joint where a projecting tenon on one member fits into a mortise hole in another; strong in framing and often pinned or glued.

Needle vibrator

An internal poker vibrator inserted into concrete at 300-500 mm spacing and withdrawn slowly to remove air voids without causing segregation.

Putlog scaffold

A scaffold whose putlogs rest in holes left in the wall; the inner end is supported by the wall and the outer end by standards.

Least count of vernier

The smallest measurement a vernier caliper can read, usually 0.02 mm, found by dividing the value of one main scale division by the number of vernier divisions.

Full body harness

Personal fall protection worn over the body with straps at shoulders, chest and legs; the anchorage point must be above shoulder level.

Silicosis

A lung disease caused by prolonged inhalation of fine silica dust from cutting, grinding or drilling concrete and stone; prevented by dust control and respirators.

Class B fire

A fire involving flammable liquids such as petrol, oil and paint; extinguished with foam, dry powder or carbon dioxide, never with a water jet.

Break even point

The volume of sales or work at which total revenue equals total cost, computed as fixed cost divided by selling price minus variable cost per unit.

Security deposit

A sum, commonly 5-10 percent, retained from running bills of a contractor to secure performance and rectify defects during the liability period.

Defect liability period

A period, commonly 12 months after completion, during which the contractor must rectify defects in the work at their own cost.

Item rate contract

A contract where the contractor quotes rates per unit for each item in the bill of quantities and is paid for measured quantities actually executed.

Curing period

The time concrete is kept moist to gain strength; at least 7 days for ordinary Portland cement and 10-14 days for blended cements.

Slump test

A workability test using a 300 mm cone; the vertical settlement of the concrete after removing the cone gives the slump in millimetres.