Why Do We Cast Cubes?
- Cube Strength = Strength of Concrete
- Strength of Concrete = Strength of Structure
Cube Moulds
- Standard Cube Mould size – 150mm * 150mm * 150mm
- Cube moulds should be non absorbent, non reactive and metal moulds to be used ( Cast iron).
- Two piece cube moulds are recommended.
- Cube moulds with extended base plates ate mandatory requirement.
- Tamping rod shall be 16±0.5 mm dia and 600±2 mm long with a rounded working end and shall be made of mild steel.
Preparation of Cube Moulds
- Before assembling the moulds, make sure that there is no hardened mortar or dirt on the faces of the flange that prevent the sections from fitting together closely.
- All the bolts should be fully tight. It is important that cube side faces must be parallel
- These faces must be thinly coated with mould oil to prevent leakage during filling, and a similar oil film should be provided between the contact surfaces of the bottom of the mould and the base. The inside of the mould must also be oiled to prevent the concrete from sticking to it.
- The two sections must be bolted firmly together, and the moulds held down firmly on the base plates
Sampling Process
- Sampling should be done from middle batch of the concrete.
- Sample the concrete by collecting two or more portions of concrete at regular intervals during the discharge.
- Concrete should not be stopped while sampling process. Min of 0.02cum (6 cubes)of concrete should be sampled
Cube Casting Process
- Fill the mould with concrete in 50mm layers using the tamping bar
- Fill the mould with concrete in 50 mm layers using the tamping bar, compact the concrete with no fewer than 35 tamps for each of the three layers in a 150 mm mould
- The slump of the sample should be 80 – 100mm.
- After tamping of each layer, tap the sides of the mould with the hide hammer until large bubbles of air cease to appear on the surface and the holes left by the tamping bar are closed
- Remove surplus concrete and smooth over with a float
- Wipe clean the mould edges.
- Number the moulds for identification and record details
- Cover each mould with a damp cloth and plastic sheet.
- Store the cube moulds at room temperature and free from vibration.
- Demould the cubes after 24 hours
Cube Identification
- Casted cubes to be marked for the Following details
- Grade
- Date Of Casting
- Location
- Element
- Batch No/TM No
- Concrete Source
- Different grades of concrete to be stored separately.
- Concrete cubes to be engraved with nail or binding wire. No marker pen is to be used on the cubes
Curing Of Cubes
- Clean the Curing tank and fill with water tested for construction purpose.
- Check that the water temperature is for 27± 3⁰ C
- The cubes should be removed from the moulds after 24 hours after casting
- Place the 1 day, 3days, 7 days, 28 days Cubes separately in designated Tanks .
- Cubes should be immersed in water always.
- Check that the water temperature is controlled at 27± 3⁰ C and the cubes are covered by water
- Monitor the temperature of the water and make record of it.