PCC is plain concrete used as a non‑structural bedding/blinding layer (strong in compression only); RCC is concrete with steel reinforcement used for all load‑bearing members (resists tension, bending, shear) — in projects, use PCC for leveling/blinding and RCC for beams, slabs, columns, and footings.
Definitions and core engineering differences
Plain Cement Concrete (PCC): cement + sand + coarse aggregate + water; no steel reinforcement. Used where only compressive strength is required.
Reinforced Cement Concrete (RCC): same concrete matrix plus steel reinforcement (rebars/mesh) so the composite resists tension, bending, and shear; used for structural elements.
Design considerations (engineering view)
Load paths: Concrete carries compressive forces; steel carries tensile forces and controls crack widths. Design must follow relevant codes (e.g., BS/EN, ACI, or local BNBC/BD codes, depending on project).
Material properties: Typical PCC mixes on site: 1:2:4 or 1:3:6 (cement : sand: aggregate) for non‑structural work; RCC uses a designed mix (e.g., M20, M25) with specified slump, cover, and rebar grade.
Construction practices
PCC placement: Used as blinding under footings, leveling bed, sub‑base for slabs and pavements; compact, finish, and cure for a minimum of 7 days to reduce shrinkage cracks.
RCC placement: Requires formwork, accurate rebar placement with specified cover, staged concreting, vibration, and curing; quality control (cube tests, slump tests) is essential. Poor cover or inadequate compaction leads to corrosion and loss of capacity.
Uses and typical examples
PCC: blinding under footings, base for floor finishes, temporary access roads, pipe bedding.
RCC: beams, slabs, columns, footings, retaining walls, water tanks, bridges, seismic‑resistant frames.
Quick comparison table
| Criterion | PCC | RCC | |
|---|---|---|---|
| Composition | Cement; sand; aggregate; water | Same + steel reinforcement | |
| Primary strength | Compression only | Compression + tension (via steel) | |
| Typical uses | Blinding; sub‑base; non‑structural | Structural members: beams, slabs, columns | |
| Cost & labor | Lower | Higher (steel, formwork, skilled labor) | |
| Durability under bending/quake | Poor | Good if designed per code |
Decision guide and practical tips for projects
If the element carries bending/tension or supports live loads → RCC.
If only leveling/blinding/sub‑base → PCC.
Specify concrete grade, rebar grade, minimum cover, and curing regime in drawings.
Risks, maintenance, and lifecycle
Risk: Inadequate cover or poor compaction in RCC → corrosion of steel and structural failure.
Maintenance: Inspect for cracks, ensure drainage to avoid saturation; repair spalls and maintain protective covers.
Recommended Mix Designs (M‑grades)
Short answer — engineering, design, and local cost: Use PCC (plain concrete) for non‑structural blinding and bedding; use RCC (reinforced concrete) for all load‑bearing members because steel carries tension while concrete carries compression. Recommended design mixes: M20 (typical RCC), M25 (common design mix), and M30 (higher strength) with the material quantities below; typical rebar choices for slabs/beams/columns are listed, and Ready‑Mix Concrete (RMC) in Dhaka currently costs about ৳11,300–৳14,100 per m³ (based on RMC rates per CFT).
1) Recommended mix designs (per 1 m³, engineering values)
| Grade | Cement (kg/m³) | Water (kg/m³) | Fine agg (kg/m³) | Coarse agg (kg/m³) |
|---|---|---|---|---|
| M20 (nominal) | 383 | ~192 | ~575 | ~1150. |
| M25 (design mix) | 426 | 191.6 | 662.8 | 1101.8. |
| M30 (design mix) | 450 | 180 | ~600 | ~1150. |
Notes: M20 is often used for general residential RCC; M25/M30 should be design‑mixed per IS/ACI using local aggregate tests and target mean strength. Always run trial mixes and control w/c ratio for durability.
2) Typical rebar schedules (practical engineering guidance)
| Member | Typical main bars | Stirrups/ties | Approx. steel (kg/m³ concrete) |
|---|---|---|---|
| One‑way slab | 8–10 mm @ spacing | 6–8 mm distribution | 80–100 kg/m³ (typical). |
| Two‑way slab / flat slab | 10–12 mm | 8 mm | 100–150 kg/m³. |
| Beams (residential) | 12–16 mm main; 16 mm for larger spans | 8–10 mm stirrups | 150–250 kg/m³ (varies with span). |
| Columns | 16–25 mm (4–8 bars) | 8–10 mm ties @ 100–200 mm | 200–300+ kg/m³ (depends on load). |
| Footings | 10–20 mm depending on size | 8–10 mm | 75–200 kg/m³ (varies). |
Important: These are typical site practice ranges for preliminary estimating; final bar sizes/spacing must come from structural design drawings and code checks.
3) Localized cost guidance for Dhaka (practical estimate)
RMC price in Dhaka: ৳320–৳400 per CFT → ≈৳11,300–৳14,100 per m³ (1 m³ = 35.3147 CFT).
Material retail prices (examples): Cement 50 kg bag ≈ ৳520–৳600; sand ≈ ৳45–৳65 per CFT; stone chips ≈ ৳90–৳130 per CFT. Use these to estimate site‑mixed concrete cost if not using RMC.
Rule of thumb: For small jobs, RMC is often cost‑competitive once labour, formwork, and curing are included; for remote or tiny pours, site‑mixing with local materials may be cheaper but requires strict quality control.
4) Design & construction tips (risks and mitigation)
Control w/c ratio and curing to meet target strength and durability; specify minimum cover for rebar to avoid corrosion in Dhaka’s humid climate.
Use design mix for M25+ (lab‑tested) rather than nominal mixes for critical members.
Quality checks: slump tests, 7/28‑day cube tests, and inspection of rebar placement and cover.
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