Cert III Concreting flashcards

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

Water-cement ratio

The mass of water divided by the mass of cement in a mix. Lower ratios increase compressive strength, reduce permeability and shrinkage, but reduce workability, so plasticisers may be needed.

Characteristic strength

The compressive strength in megapascals that 95 percent of test specimens are expected to exceed at 28 days. It forms the basis of concrete grade designations such as N20 or N32.

Slump test

A workability test where a standard cone is filled with concrete and lifted away, and the drop in height is measured. It indicates consistency and helps detect excess water.

Compaction by vibration

Inserting a poker vibrator vertically at regular spacing to remove entrapped air. Withdraw slowly to avoid voids, and avoid over-vibration, which causes segregation of aggregate from mortar.

Curing period

The time concrete is kept moist and at suitable temperature to allow cement hydration. A minimum of seven days is typical for normal concrete, longer for aggressive exposure conditions.

Formwork stripping

Removal of formwork once concrete reaches adequate strength. Sides of beams and columns may be stripped after one to two days; soffits need props until specified strength is reached.

Silica dust control

Cutting, grinding or drilling concrete releases respirable crystalline silica. Controls include water suppression, on-tool extraction, respiratory protection and exclusion of unprotected workers from the area.

Dumpy level use

An optical instrument used with a staff to transfer and check reduced levels. Set up, take a backsight on a known benchmark, then calculate and mark required levels on site.

Fall to drainage

The slope built into external concrete surfaces so water drains away. Common falls are 1:100 to 1:80, checked with a level or straight edge before and after finishing.

Reinforcement cover

The depth of concrete between the steel surface and the outer face. It protects bars from corrosion and provides fire resistance; minimum values depend on exposure classification.

Bar chairs and spacers

Plastic or steel supports that hold reinforcement and mesh at the designed depth during placing. They prevent mesh being trodden down and ensure specified cover is achieved.

Tension lap length

The length over which two bars overlap to transfer tensile force, commonly about 40 bar diameters for deformed bars in tension. Laps should be staggered and confirmed by design.

Contraction joint

A saw-cut or formed joint that controls where shrinkage cracking occurs. Cut depth is typically one-quarter to one-third of slab thickness, spaced about 24 to 36 times thickness.

Saw-cut timing

Contraction joints should be cut when concrete has hardened enough to resist raveling but before shrinkage cracking starts, usually between six and twenty-four hours after finishing.

Hot weather concreting

Placing concrete when ambient conditions accelerate moisture loss and hydration. Limit concrete temperature, shade materials, use chilled water, and cure immediately to prevent plastic shrinkage cracks.

Cold weather concreting

Placing concrete in low temperatures where freezing can damage young concrete. Do not place on frozen ground and keep concrete above 5 degrees Celsius until it reaches adequate strength.

Cold joint

A weak plane formed where fresh concrete is placed against concrete that has already begun to set. Avoided by continuous supply and placing before initial set occurs.

Pump priming

The process of lubricating the pump line with grout or slurry before concrete is pumped. It reduces friction, prevents blockages and must be discharged away from the finished work.

Broom finish

A textured surface produced by dragging a stiff broom across partially set concrete. It provides slip resistance on external paths, driveways and ramps.

Dusting and craze cracking

Surface defects caused by trowelling too early, excess bleed water, or overworking the surface. They produce a weak, powdery top layer and fine shrinkage cracks.

Test cylinder curing

Samples are cast, cured at 20 plus or minus 2 degrees Celsius in water or a moist cabinet, and tested at 7 and 28 days to verify the concrete meets the specified grade.

PCBU duty

A person conducting a business or undertaking must ensure health and safety so far as reasonably practicable. This includes providing safe systems of work, information and training.

High-risk construction work

Work posing serious risk, such as falls above 2 metres, trenches deeper than 1.5 metres, and work near live services. It requires a Safe Work Method Statement before work begins.

SWMS

A Safe Work Method Statement documents how high-risk construction work will be done, the hazards, controls and responsibilities. It must be signed, followed and reviewed when conditions change.

Trench shoring

Support systems such as shields, benching or battering used to prevent excavation collapse. Required for trenches deeper than 1.5 metres, with spoil kept at least 1 metre from the edge.

Hierarchy of control

Risk control order: eliminate the hazard, substitute, use engineering controls, apply administrative controls, then use personal protective equipment as the last line of defence.

Sediment fence

A barrier of geotextile fabric that slows runoff and traps sediment on site. It prevents soil and slurry entering stormwater drains and waterways during earthworks and concrete work.

Concrete washout bay

A lined, contained area where pump lines, tools and trucks are washed. Washout water is highly alkaline and must be contained and disposed of appropriately, never into stormwater.

Construction waste segregation

Separating waste into streams such as timber, metal, concrete and general waste. Concrete rubble may be crushed and reused as fill or base course, reducing landfill.

Inspection and Test Plan

A document listing inspections, tests, acceptance criteria and hold points for a project. Work cannot proceed past a hold point until the required inspection is signed off.

Hold point

A stage in construction where work must stop until a nominated inspector or engineer verifies compliance. Proceeding without release risks non-conforming work and rework.

Batch and delivery docket

Records showing mix design, batch time, quantities, slump and additives for each concrete delivery. They provide traceability and confirm the concrete matches the specification.

Two-way radio signals

Standard communication used between concrete pump or crane operators and placing crews. Clear, agreed signals and a designated spotter prevent injuries and placement errors.