Common Defects in Concrete – Causes and Effects ✳️Concrete is a strong and durable construction material, but poor workmanship, improper mix design, or inadequate curing can lead to several defects that affect performance and durability. Understanding these defects helps engineers maintain better quality control on site. 1. Honeycombing Voids or cavities in concrete caused by poor compaction or insufficient vibration, resulting in weak concrete and possible exposure of reinforcement. 2. Segregation Separation of aggregates from the cement paste, usually due to excess water or improper handling, leading to a non-uniform and weak mix. 3. Bleeding When water rises to the surface of fresh concrete due to a high water–cement ratio, creating a weak and porous surface layer. 4. Cracks Concrete cracks may occur due to shrinkage, thermal stresses, overloading, or poor curing, which can reduce durability and structural performance. 5. Spalling Chipping or breaking of the concrete surf...
External Static Pressure (ESP) — zero ➜ hero Goal 📌 ESP = fan pressure needed to overcome all losses outside the unit casing. If the AHU has a return fan, compute Supply ESP and Return ESP separately. 1️⃣ Define the system • Airflow (Q) (m³/s). • Paths: supply to most remote diffuser, and return from farthest grille to unit. • What’s outside the unit: ducts, fittings, terminals, silencers, dampers, coils/filters in the duct, louvers. 2️⃣ Sketch the critical path 🧭 One‑line from fan discharge → last diffuser. Do the same back to the unit for return. The longest sum is the critical path. 3️⃣ Collect data • Duct sizes, lengths, number of fittings. • Device drops at design flow (Pa): filters, coils, VAVs, attenuators, grilles/diffusers, louvers. • Air properties: use ρ ≈ 1.2 kg/m³. • Conversions: 1 in.wg = 249 Pa. 4️⃣ Equations (plain text) • Area A = W × H (for round: A = πD²/4). • Velocity v = Q / A. • Velocity pressure q = 0.5 × ρ × v² (Pa). • Rectangular hydrauli...