What is Plain Cement Concrete?
Many different types of concrete are used in construction, one of which is PCC or plain cement concrete. As the name implies, this concrete contains no steel or reinforcement, only plain concrete. PCC is a mixture of cement, sand, aggregate and water. It has a high compression strength but a low tension and shear strength. This concrete is also known as mass cement concrete or cement concrete. PCC is laid on the soil surface to avoid direct contact with RCC of soil and water. The following ratios are commonly used for PCC: 1:4:8, 1:3:5, and 1:2:4.
Applications of Plain Cement Concrete PCC
- PCC commonly used in the column foundations, below wall footings and dam
- Rigid pavement construction
- Small scale canal construction
- Some masonry works
- Gardening & Landscaping
- Coping of the parapet wall and compound wall
- Used to make basketball & indoor courts
- For plinth protection
Ingredients of Plain Cement Concrete (PCC)
Follow are the ingredients used in Plain cement concrete (PCC):
Portland pozzolana cement is commonly used to make plain cement concrete. This cement has a high degree of fineness.
Sand (fine aggregate)
Sand for PCC should be angular, hard, and sharp. The size of the fine aggregate should be less than 5 mm. Sand should be dust-free, clean & well graded.
This coarse aggregate is also known as an aggregate. Coarse aggregates should be clean and dust-free. It should be graded properly to keep the void percentage under 42%. When the aggregate size is larger, less cement is used in the concrete.
Water is an important ingredient of PCC. Water must be free of all impurities, including acids, alkalis, salts, and oils. For PCC, water with a pH lower than 6 is not acceptable.
The approx. amount of water needed for each 50 kg cement in a mix to achieve the desired consistency is as follows.
- 1:3:6 mix – Not more than 34 litre
- 1:2:4 mix – Not more than 30 litre
- 1:1 ½:3 mix – Not more than 27 litre
- 1:1:2 mix – Not more than 25 litre
Mixing in Plain Cement Concrete
The process of combining all ingredients, including water, cement, sand, and aggregate, is known as mixing. Depending on the project, various types of concrete admixtures are used for various projects. If you want the best results, use proper mixing methods. Nowadays, a variety of mixing techniques are available, including the following:
- Hand mixing
- Mixer machine
- Batching plant
In this method, concrete is mixed manually without a mixer machine. This method is appropriate for small projects. The base for this method must be steel, a clean floor, or a watertight slab. After thoroughly mixing sand and cement, coarse aggregate is added in these methods. Water is added last to achieve a uniform consistency. After adding water, properly mix to achieve strength.
Mixer machine – Plain Cement Concrete
A mixer machine is the best option when a large quantity of PCC is required continuously. A mixer machine is used in this method. This method first wet the internal surface of the drum. Then add all dry materials to the drum, and mix all ingredients in a dry state. Then water is added while the drum is rotated. The drum can then be rotated to achieve a uniform mixture of the desired consistency.
Ready Mix Concrete
Nowadays, ready-mixed concrete is the most popular choice for quick work. The water to cement ratio with this method can be controlled in comparison to other mixing methods.
Cost of Plain Cement Concrete
A rate analysis is required to determine the cost of PCC. Therefore, we include material costs in our rate analysis!
So, let us begin the calculation.
Step: 1 Calculation of Volume of Dry Concrete
Volume of Wet Concrete = 1 Cumt
Volume of Dry Concrete = 50 to 55% Volume of Wet Concrete
= Volume of Wet Concrete + 54% Volume of Wet Concrete
= 1 + [(54/100 X 1)]
= 1.54 Cumt
Step: 2 Calculate Quantity of Cement
Required Cement = (Part of Cement X Volume of Dry Concrete) / (Sum of the Numerals of Proportion)
= 1 X 1.54 / (1 + 2 + 4)
= 0.22 Cumt
We know Density of Cement = 1440 Kg/Cumt
Required Cement = 0.22 X 1440
= 316.8 Kg
1 cement bag = 50 kg
So, Required Cement Bags = 316.8/50
= 6.34 Bags
Step: 3 Calculate Quantity of Sand
Required Sand = (Part of Sand X Volume of Dry Concrete) / (Sum of the Numerals of Proportion)
= (2 X 1.54) / (1 + 2 + 4) = 0.44 Cumt
Step: 4 Calculate Quantity of Aggregate:
Required Aggregate = (Part of Aggregate X Volume of Dry Concrete) / Sum of the Numerals of Proportion
= (4 X 1.54) / (1 + 2 + 4) = 0.88 Cumt
Step:5 Calculation of Cost of Concrete Per Cubic Meter:
To find out cost of concrete, here we considered some assumptions,
1 bag of cement = RS. 400
1 m3 of sand = Rs. 1300
1 m3 of aggregate = RS. 2500
- Cost of cement = 400*6.34 = 2536
- Cost of Sand = 1300 * 0.44 = 572
- Cost of Aggregate = 2500*0.88 = 2200
Cost of 1 m3 Concrete = Cost of cement + Cost of sand + Cost of coarse aggregate
So, Total cost for 1:2:4 = 2536 + 572 + 2200 = RS. 5308
This calculation is for a 1:2:4 (cement: sand: aggregate) ratio; you can use the same formula to determine other concrete proportions.
Note: We do not include labour costs or other taxes in this calculation; however, if you want, you may include labour and taxes in this calculation.
Alternative additives or Supplementary Cementitious Materials for PCC
Most modern concrete mixtures contain additional cementitious materials that contribute to the cementitious component of concrete in part. Cementitious additives, also known as supplementary cementitious materials, are used in concrete. They can be applied either singly or collectively in concrete. At the ready mixed concrete plant, they can either be added as a blended cement or as a separate batch of ingredients to the concrete mixture.
Supplementary cementitious materials are used to improve the performance of concrete in both its fresh and hardened states. They are primarily used to improve workability, durability, and strength. These materials enable concrete producers to design and modify concrete mixtures to suit specific applications. They reduce the amount of portland cement required per unit volume of concrete.
5 examples of supplementary cementitious materials
- Fly ash
- Ground Granulated Blast Furnace Slag (GGBFS)
- Silica Fume
- Natural Pozzolans
- Metakaolin and calcined shale or clay
Fly ash is a byproduct of powdered coal-burning power plants. Fly ash used in concrete should meet the ASTM C 618. The percentage of fly ash in concrete varies from 5% to 65% by mass of cementitious materials, depending on the source and composition of the fly ash as well as the performance requirements of the concrete.
Ground Granulated Blast Furnace Slag (GGBFS)
GGBFS is a non-metallic manufactured byproduct of an iron blast furnace. The liquid slag is rapidly cooled, forming granules that are then ground to a fineness similar to portland cement. GGBFS has cementitious properties on its own, but when combined with portland cement, these properties are enhanced. Slag accounts for 20% to 70% of the cementitious materials by mass.
Silica fume is a highly reactive pozzolanic byproduct of silicon or ferro silicon metal production. It is derived from flue gases emitted by electric arc furnaces. Silica fume is a fine powder with particles 100 times smaller than the average cement grain. It can be purchased as a densified powder or as a water slurry. ASTM C 1240 is the standard specification for silica fume. It is typically used at a concentration of 5 to 12% by mass of cementitious materials in concrete structures that require high strength or significantly reduced water permeability. Because of its extreme fineness, special precautions must be taken when handling, placing, and curing silica fume concrete.
Various naturally occurring materials have pozzolanic properties or can be processed to have them. Natural pozzolans are typically derived from volcanic sources because siliceous materials are reactive when rapidly cooled. Natural pozzolans include volcanic glass, zeolite trass or tuffis, rice husk ash, and diatomaceous earth.
Metakaolin and calcined shale or clay
Metakaolin is manufactured through the controlled calcination (firing) of naturally occurring minerals. It is made from relatively pure kaolinite clay and is used at a concentration of 5% to 15% by mass in cementitious materials.