Concrete Finishing Techniques Quiz

Introduction to Detailing in Reinforced Concrete Members

• Course: CIVIL 3811/8811/9811
• School of Civil Engineering, Faculty of Engineering, The University of Sydney

What's in Concrete

• Concrete composition: sand, cement, aggregate, water
• Ratio balance: strength, shrinkage, workability
• Additives/admixtures: increase workability (e.g., plasticizers), decrease shrinkage, adjust curing time, inhibit corrosion
• Mix design: by specialist concrete technologist
• Structural design engineers provide performance specifications

Performance Specification vs. Mixed Design

• Performance specifications: minimum structural requirements—strength, shrinkage, elastic modulus, slump, curing time, time to reach design strength, workability
• Mix design: specifies concrete mix ingredients

Procuring Concrete

• Engineers provide performance specifications
• Concrete suppliers create mixed design
• Builders order correct concrete quantity
• Concreters use pumps for placement
• Concreters vibrate concrete to remove air bubbles
• Concrete samples tested for strength (generally at 7 and 28 days)

Pumping Concrete - Mobile Pumps

• Truck-mounted pump
• Heavy, requires a good working platform
• Limited access to tall buildings

Pumping Concrete - Tower Boom Pumps

• For high-rise buildings
• Fed from ground floor off the street

Concrete Trucks

• Concrete trucks (agitators) filled in batching plant
• Maximum elapsed time for deliveries is important
• Each truck holds approximately 6-8 cubic meters of concrete

Maximum Pouring Height for Monolithic Columns

• 1.5 meters free fall is typically allowed
• Two options for taller columns: use a concrete pump with flexible hose inside the column, or a different method for casting the column

Concrete Segregation

• Concrete segregation is the separation of ingredients, due to inappropriate mixing.
• Issues during transport, handling, and placement
• Problems impacting concrete properties; strength reduces, cracking likely
• Proper mixing of concrete is essential

Compacting Concrete

• Freshly poured concrete often has air bubbles, more noticeable in tall columns and walls.
• Honeycombing can result from trapped air.
• Compaction process (vibrating) removes air bubbles.

Pouring, Compacting, and Finishing Concrete

• Steps are outlined in the given slides

Finishing Concrete

• Concrete slabs are leveled using surveying procedures and a "float."
• Finishing options include trowel, burnished, and broom finishes.
• Finishes are chosen based on intended use (e.g., tiles, carpeting for trowel finish).
• Broom finish is used for footpaths and ramps due to slip resistance.

Curing and Testing Concrete

• Curing is a chemical reaction transitioning concrete from plastic (wet) to solid.
• Concrete needs proper curing time
• Testing on samples ensures correct strength and other properties.

Terminology

• Bar: Individual reinforcing bars in bundles (e.g., N12 to N36).
• Mesh: Small bars (wires) welded together, "square" or "rectangular."
  • Specified by diameter and spacing (e.g., SL72, SL101, RL818)
• Reinforcing material: bars frequently used rather than mesh

Deformed bar and mesh

• Images presented showing the product/material.

Basic Purpose

• Reinforcing: ties together cracks in concrete preventing further damage and breaking
• Deformities are key to bond strength
• Common types: normal ductility (N) used mostly in mesh
• Low ductility (L) used mostly in mesh

Placing Reinforcement

• Steel fixers place reinforcement within formwork for slabs beams, columns, and walls.
• Cover is the distance from the reinforcement face to the formwork face, varying by exposure (e.g., indoors vs. coastal environments, 20mm to 75mm).
• Reinforcement is fastened with tie wire.
• Chairs support reinforcement at a fixed distance from formwork.

Placing Reinforcement – Exposure Classifications

• Exposure classifications (AS3600) define the environment's effect on concrete cover.
• Concrete cover protects reinforcing bars from corrosion.

Placing Reinforcement – Order

• Reinforcement placement order: Ties, Bottom reinforcement, Top reinforcement
• Incorrect placement can be difficult or impossible to fix later.

Procuring Reinforcement

• Engineers define size and spacing for reinforcement (examples: N12-200).
• Reinforcement Types (various)
• Reinforcement labels and spacing are shown in a table.

Procuring Reinforcement – Additional Abbreviations

• Common abbreviations for convenience (e.g., EW, EF, T+B, NF, FF, V/Vert., H/Horiz.)
• Specifies reinforcement direction and location within slab/wall/other forms

Procuring Reinforcement – Reinforcement Schedules

• Schedules outline lengths and bends needed for reinforcement.
• Needed for creation of reinforcement.

Each Bar or "Bundle" of Reinforcement

• Each bar/bundle of bars is tagged & delivered for placement.
• Tables presented including BOQ numbers.

Identification and Notations

• Codes and notations presented for understanding and proper identification of reinforcement.
• Diagrams and table provide additional information.

One-way or Two-way Slabs Deemed-to-comply Arrangement

• Diagrams to understand reinforcement placement in primary and secondary directions.

One-way or Two-way Slabs Anchorage at Supports

• Minimum distance needed between reinforcement from support, using different cases for appropriate situations
• Diagrams/tables presented for a clearer picture

Anchorage Requirements – Development Length

• Sufficient anchorage necessary between concrete and reinforcement
• Extension required based on the type of situation or location

anchorage Requirements – Basic Development Length

• Formulas for calculating development length (Lst) from different types of conditions
• Consideration of cover/distance from bars when measuring

Anchorage Requirements – Refined Development Length

• Incorporation of transverse reinforcement's positive effect on anchorage.
• Additional calculations for different scenarios

Anchorage Requirements – Standard Hooks and Cogs

• Minimum lengths for different types of hooks (e.g., 180°, 90°, 135°).
• Standard Hook/Cog table

Standard Details – Lap Splices for Bars in Tension

• Lap lengths required for reinforcement.

Standard Details – Lap Splices for Bars in Tension

• Additional detail for calculation of lap splices in tension

Openings in Slabs – Small Openings

• Reinforcing bars close to holes need to be adjusted.

Openings in Slabs – Larger Openings

• Reinforcement near holes need to be adjusted for larger openings.

Openings in Slabs – Adjacent to a Beam

• Reinforcement near holes adjacent to beams needs additional adjustment.

Footings – Reinforcement Details

• Requirements for reinforcing footings
• Additional information concerning sizes/levels for footings.

Columns – Standard Details

• Reinforcement details unique to columns
• Details on how to place & position column reinforcement materials

Columns – Column Schedule

• Multiple columns & their reinforcement
• Table featuring different marks/types, footing sizes, levels, and grades

Lateral Shear Forces at Column Joints

• Reinforcement details specific to columns/beam junctions (often including continuity bars to provide reinforcement within the joint.)

The Offset

• Location and issues of the offset for specific details.

Test your knowledge on various concrete finishing techniques, including broom finish and burnishing. This quiz covers essential aspects such as curing times and characteristics of materials used in concrete work. Challenge yourself and see how well you understand concrete applications!