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Last edited 21 Feb 2022
 Use of plum concrete
Plum concrete, is where medium and large-sized stones are used as the aggregate. Plum concrete may also referred to as cyclopean or rubble concrete. The stone aggregates (plum) can be 150mm or 200 mm, or 300 mm or larger. The selection of plum size is based on the application, availability and engineering requirements.
This type of concrete maybe recommended for structures like gravity dams, barriers, bridges, or as mass concrete for machine foundations, retaining walls etc. Here the size of the plum would most likely be around 150 mm.
The uses of plum concrete are:
- For mass concreting where a high plain cement concrete (PCC) thickness is required due to strata.
- Under footing applications where the ground slope maybe between 1:10 to 1:50.
- In the construction of gravity dams, retaining walls, steep road slopes, bridge and culvert barriers.
- It is also used for road embankments, surface beds for water channels and machine foundations.
- For back filling deep or uneven sites
 Properties of the plum concrete
The plum should be from trap rock (also know as Trapp or Trap), basalt or any other locally available stone. The stone should have at least 100 Kg/Sq mm minimum crushing strength. The stone should be hard, strong, durable, angular shaped, and with no seams, cracks or other structural defects.
 Mix ratios of plum concrete
The specific application will help in decide the volume or ratio of plum required in the concrete. The plum to concrete ratio will be dictated by the engineering specification, however, when the plum is 150 mm, the plum volume is likely to be between 30% to 50% of finished concrete. When the plums are above 160mm, the volume of plum should be capped at 20% of the volume of finished concrete.
 Preparation for plum concrete
The plum is added directly into the mixer or by spreading the plums over the wet mix followed by a further layer of concrete. When using the former method, the size of the plum should not be more than 1/3rd of the cross-section of the concrete mixer.
- Clean the working surface
- Remove any soft soil, dirt and other loose items, as these may affect the soil bearing capacity.
- Keep the surface moist by sprinkling water prior to pouring, this moisture is to ensure proper bonding.
- If needed Anti-termite treatment, can be spray applied.
In summary, plum concrete can be utilised by civil design and engineering consultants for the strength and economic optimisation of projects, the specifics of this are dependent on suitable advice according to specific site conditions and particular project requirements.
- Admixture, additive or agent.
- Admixtures in concrete.
- Architectural concrete.
- Cast-in-place concrete.
- Cellular concrete.
- Portland cement.
- Recycled concrete aggregate RCA.
- Reinforced concrete.
- Self-compacting concrete.
- Stratification of concrete.
- Testing concrete.
- The properties of concrete.
- The use of concrete structures to protect construction sites.
- Types of concrete.
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