What is Plum Concrete?
In some mass concrete foundations, boulders of say 150 mm size up to 30% of the total quantity of concrete, are mixed in the wet concrete. This adds to economics and saves heat generation.
Such concretes are called plum concretes.
After at least two layers of wet concrete is completed, well-shaped and thoroughly washed, angular rock pieces using a maximum size of not more than 60% of a layer of pour thickness are placed in the concrete, keeping a distance of more than one-and-a-half times of the biggest size of aggregates in the concrete.
The bottom of the boulders should be embedded in the wet concrete to avoid voids at the bottom. Concreting is continued without stopping.
These rock pieces become an integral part of a concrete structure.
Difference Between PCC Concrete and Plum Concrete
- Plum Concrete normally use on the uneven surface of the ground and another area. This uneven surface level by plum concrete. This method to reduce the cost of construction.
- Because of plum concrete, you are using large material part near about 60% of Stone and 40 % of concrete so this method to use cost-efficient in construction.
- Plum concrete original concept by the aggregate in concrete. This plum concrete use a maximum of 300 mm size aggregate
P.C.C (Plain Cement Concrete)
- P.C.C (Plain Cement Concert) is a base of concrete. Commonly use of PCC all construction work. P.C.C is a mixture of cement, water, fine aggregate, coarse aggregate, and water this simply mixture called P.C.C
- M 7.5, M 10 both grades of Plain Cement Concrete
- Use of P.C.C it is as a protective layer for the RCC above so that water from the RCC is not absorbed bt the earth below
- Moisture available in soil should not be absorbed by RCC footing which causes correction of reinforcement
- Provided a base for the concrete and also helped workers to set out the structure above in easied way.
Application of plum Concrete
- Normal use plum concreter below footing as a base of footing, so that water from the footing is not absorbed bt the earth below.
- Plum Concrete can be utilized in areas that need massive concrete placements such as concrete dams or bridge piers. In these instances, pieces of stone roughly 150millimeters in size function as coarse aggregates to mix a plum concrete.
- Plum concrete using 150 mm size plums and with an effective cement content of 177 Kg/m3 was used for the construction of an original dam.
- It was thought that using the state-of-the-art high-speed mixers of sufficient capacity, a more cohesive concrete mix of 150 MSA could be obtained very easily.
- Similarly, in a different case, suppose the foundation pit for the bed of a machine is suggested to have a particular thickness; however, the hard stratum can be found in 3 m below the bottom level.
- Whereas in layout It had been suggested that the depth of foundation for bed could be 1.5 m.
- Considering that the foundation needs to be rested on the hard strata of soil, therefore plum concrete of thin ratio using 80mm -100millimeter size stones will be poured that is rammed up to 1.5 m and subsequently ordinarily designed raft, footings might be laid.
Purpose of Plum Concrete
Plum concrete is used to attain the required surface-level below the foundation and footing. It is used to lessen the cost of PCC if the required thickness of PCC is large. Primarily it is used in mass concreting work such as side slops, barrier, and gravity dams.
For instance, in the construction of a residential building, the small area under a footing is too steep, then to use plum concrete.
Mix Design of Plum Concrete
- PPC Cement 53 Grade: 220 Kg
- Water Cement ratio (w/c) : 0.6
- Free Water: 132 liters
- 300 mm Metal: 666 kg
- 20 mm Aggregates: 666 Kg
- 10 mm Aggregates: 539 Kg
- Fine Aggregate (Sand):1038 Kg
- Admixture Dosage :0.6%
- Admixture: 1.4 liter
- The density of Concrete: 2596 Kg/cum
You’re able to alter the mix design by altering the specific gravities of materials that can help it become applicable in accordance with the substance available at your location.
Changing that specific gravity will change the weight of material in mix design that is automatically calculated.
Do not use these mixes directly without doing prior trials of it; the data provided is for educational and better understanding of mixes.
After doing a trial, if any issue observed, you can make a modification by adjusting the % of each size of aggregate to attain the required properties of fresh concrete.
To ensure a total of all aggregate percentage in a mix should some to 100%
In general, for direct placement concrete
A ration of fine aggregates to coarse aggregates kept between 35:75 to 40:60
Also, add stone of total wattage of all concrete 40% near about 666 kg of plum(Stone) in Plum concrete
In the case of pump concrete, the fine content is kept over 45%
You’ll be able to adjust the percentages of fines and coarse by taking a look at the concrete produced during trial.
Admixtures play an important role in the properties of fresh concrete, especially in retention and workability.
Do select admixture properly to ensure no failure during the real usage of concrete.
All can answer to the thread with there mix design of the same grade; this can help others to understand design in a better way and certainly will do a cost optimization.
Methodology of Plum Concrete
Transportation of Plum concrete.
- The boulders are the size of a boulder (Size) near about 300 mm, which may be lifted by laborers easily, not too big or small. maximum
Before placing of plum concrete in leaving and cleaning
- The very first step that’s done initially is cleaning and leveling of the surface by the elimination of soft soil, which could lead to low bearing capacity.
- After clearing and grubbing, water is sprayed on the surface to allow it to be moist before placement of plum concrete.
- The cause of sprinkling water would be to ensure a proper bond of plum concrete together with the ground surface.
- Following a sprinkling of plain water anti-termite compound is sprayed, which is essential today for the perfect foundation of a structure.
Pacing and Spreading
- Boulders are spread across the ground with very little gapping layer by layer, and concrete has been spread with pump all over the boulders in each layer, which slowly permeates within the gapping between boulders.
- This will help to bind it properly, after pouring concrete, boulders are thrown to the concrete, and the process repeats till the required level surface is reached.
Plum Concrete curing
- Curing ought to be done for the next 7 days minimum. Jute bags are spread over the entire area of plum concrete to retain moisture for quite a while after curing.
Also, read: Procedure for Rcc Concrete
Details & Specification of Plum concrete
- Each layer plum concert maximum height 900mm did not exceed more hight in one layer
- Maximum crevices in one layer 150 mm only
- The volume of the plum from the concrete will not exceed 40% (percent) of overall volume.
- Plum concrete in use maximum M10 Grade concrete in this concrete aggregate of maximum size 25mm.
- Plum will comprise of black trap basalt of crushing strength of minimum 100 Kg /Sq.cm.
- Plum concrete density 1650 kg/Cubic.meter
This nominal maximum size of coarse aggregate should be as big as possible within that the limits given but in no case greater than one-fourth of their minimum thickness of this member, provided the concrete may be placed without difficulty so as to surround all reinforcement thoroughly and fill the comers of the form.
In terms of the need of the aggregate size, which may be utilized from the plum concrete, there are different recommendations from the IS code; the code says that for most of the common works that the size of 20 aggregates is best and suitable.
If there are not any restrictions for the flow of concrete to part 40 mm or larger is also utilized. However, where you will find reinforcement or the cover is small with all the formwork, 10 mm nominal maximum size plums should be used in plum concrete.
Plums above 150 mm and around any reasonable size could possibly be utilized in plain concrete work up to a maximum limit of 20 percent by volume of concrete if specifically permitted by the engineer-in-charge.
But for all the cases, the plums will likely be dispersed evenly and will not be closer than 150 mm from the surface.