What Is Plum Concrete?
Plum concrete is created mostly by the participation of large and medium rocks of usual size to 300mm or perhaps even greater as filling.
It’s being used to improve the evident yielding of concrete for a provided weight of the cement that is to prevent utilizing an excessive quantity of concrete without compromise on the strength.
Plums are indeed the massive stones which are used. Such plums are being used to make mass concrete. The volumes of plums, moreover, must not surpass 30% – 40% of the overall amount of the hardened cement paste.
Rubble concrete and Cyclopean concrete are other names for plum concrete. The Plum should be no more than one-third the size of the concrete mixer’s cross-section.
Plum applies to tough, tidy natural materials used during mass concrete foundations, gravity dams, embankments, as well as other mass concrete structures.
Purpose of Plum Concrete:
- Plum concrete is a combination of concrete that is used when the ground is rough and also to greatly reduce the cost-effectiveness of the concrete.
- Just below footings of housing units, where even the slope of the ground under a single footing is 1:10 through 1:50, plum is commonly favored to save money on concrete.
- Plum concrete reduces the overall building value of the property.
- Plum concrete is used in mountain terrain to provide even a firm platform for retaining walls, terrain read, including building foundations.
- Plum concrete is a cost-cutting measure.
- Plum concrete is done beneath the foundations, where even the amount of elevation course may be extreme due to the high slope of the strata.
How to Prepare Plum Concrete?
Plum concrete, also known as Rubble concrete or Cyclopean concrete, can be done in two ways. This can be made either by inserting the plum to the concrete mix mostly during the mixing process or by scattering the plums over the regular concrete layer but instead distributing an additional layer of concrete.
To avoid air traps, special care must be taken when putting the plums in the concrete. The following is the general production process:
- Check the Quality of Plum Material used: The stones used for the plum material should be sturdy and durable and ideally made from the very same rock as aggregate particles. It shouldn’t be flaky and shouldn’t have any dirt or clay in it. If there is any dirt on the top of the plum substance, it should be washed before using it.
- Batching of Plum Material checked: First, the stones needed for the plum concrete manufacturing process are hand-picked. As a result, the plum stuff has been batch-processed. The plum material can be up to 300mm in bulk. The plum material’s size should be limited to approximately one-third of the total volume of concrete. The plum material will be hand-picked or randomly selected by the workers and taken to the site.
- Placing of Plum Concrete: The plum material is applied to the surface with a spacing set by the NHA (National Highway Authority ). If the plum materials are positioned close together, the amount of concrete needed will be reduced by up to 50%, while the quantity of plum will increase by up to 50% of the total volume of plum concrete. Following the application of the plum material, a concrete slab is sprayed over it. Only after concrete gradually fills in the gaps between both the plum elements, an additional layer of plum substance is applied to the concrete. This procedure is repeated several times the level is attained. When putting plum concrete, special care must be taken to avoid air traps, which can reduce the strength of the plum concrete. It is therefore essential to ensure that they will be put at once.
- The Finishing and Curing of plum concrete: After all of the layers of plum concrete have been carefully placed, they are neatly finished and left to cure for at least 14 days. Curing can be accomplished in a variety of ways. Water can be dumped on the plum concrete at regular intervals, or it can be covered with moist jute containers.
Plum Concrete Specifications
- The plum concrete must’ve been Class B concrete because it contains massive boulders embedded in it.
- The overall amount of the plums did not affect one-third of the total volume of the work in which it has been positioned. (that is, 33% )
- The grades of plum concrete that is used in the production must be determined by its ultimate use as well as strength requirements. However, M20 is the bare minimum.
- In some cases, the smallest dimension of stone/plum is 150mm, while the maximum size is determined by the size of the structure.
- The formwork used to pour the plum concrete should be made of steel plates or plywood.
- The plum ought to be a trap, basalt, and any other available locally stone with a crushing strength of at least 100 kg/cm2.
- The concrete used during plum concrete ought to be a nominal blend of M10, with aggregate no larger than 25 mm in size.
- The volumes of the plum in concrete must not exceed 50% of the overall amount.
- The thickness of each tier must not exceed 900mm, and the separation must not be just under 150mm. IS 456:2000 clause 5.3.3 could also be used to describe plum.
- The water-cement ratio can be adjusted so that the concrete flows properly to fill all of the crevices at the site.
- The plums are laid out in layers with cement concrete as the mortar.
- Plum concrete should be kept moist for at least seven days.
- Plum concrete has a density of 2580 kg/m3.
Advantages of Plum Concrete:
- Plum concrete is made by first laying down a layer of regular concrete, then adding plums, followed by some other surface of a material, and so forth.
- Procedures should be followed to eliminate air traps beneath stone surfaces.
- Plums do not have a going to adhere coat and therefore resist the extent of hardened concrete and discontinuity among plums. Furthermore, plums offer consistent permeability.
- Sand/cement/aggregates are blended in the same way as plain concrete, but the aggregate (stone) size is much larger, up to 300 mm, to the growth and yield concrete for a given quantity of cement.
- This type of concrete is commonly used in massive concrete masses (gravity dams, embankments, and under the structure).
- The relevant plum size should be limited to one-third of the minimum dimension to be concreted.
- The volume of plum should not exceed 20 to 30% of the total volume of the finished concrete, which should be uniformly distributed across the concrete mass.
- Plum concrete is used on the beds of the water channels.
- It is widely used in mass concrete works such as concrete gravity dams or bridge piers. Here, coarse aggregates of about 150 mm in size are used to mix plum concrete.
- It is used on embankment side slopes to create a protective layer to earthen foundations and bases.
Disadvantages of Plum Concrete
- Plum Concrete does have a very low tensile strength and should be reinforced with reinforcement steel in the concrete tensile area.
- For casting and moulding, as well as holding the plum concrete in place until everything hardens properly, costly formwork is needed.
- Plum Concrete’s low strength per unit weight results in heavy members, which is an important factor for tall buildings and long-span structures, resulting in Concrete drawbacks.
- Plum Concrete placement and curing are not as tightly regulated as that of the manufacture of many other materials, including such structural steel as well as laminated wood.
- Plum Concrete is not malleable.
- Plum Concrete is semi-brittle and has a strain-softening property.
- Plum Concrete has a far lower hardness than steel. Concrete’s toughness is just 1-2 percent that of steel.
- Shrinkage in concrete results in the formation of cracks and a loss of strength.
- Plum Concrete necessitates the use of formwork to shape it and support its own weight.
- Full strength construction in concrete necessitates adequate curing for up to 28 days, implying that concrete necessitates additional care and a large quantity of water, which is a disadvantage.
- Concrete manufacturing is not environmentally friendly because it consumes far more energy and emits far more carbon dioxide than other building materials such as steel and glass.
Difference Between Plain Cement Concrete and Plum Concrete
Plain Cement Concrete
- Plain cement concrete is a blend of cement, fine aggregate (sand), and coarse aggregate (PCC).
- Plain cement concrete (PCC) is used in foundations where the earth is soft and yielding to provide a stiff impervious bed for RCC. PCC can be installed with or without brick flat soling.
- Materials used for producing PCC are Cement, Fine Aggregate, Coarse Aggregate.
- Plum concrete is viewed as a combination of coarse aggregate as well as the cement that’s also positioned beneath a structure’s foundation or footing to reach a flat surface for equitable load distribution.
- The name plum refers to big stones that are officially known as boulders or coarse aggregates.
- Plum concrete is truly a low-cost variant of mass concrete.
- If the necessary thickness of PCC is excessive or big, plum concrete is preferred.