Govt. Exams
Entrance Exams
Concrete gains approximately 40-50% strength in 7 days due to rapid hydration, then strength gain slows down gradually.
Pozzolanic materials like fly ash and silica fume react with calcium hydroxide to improve strength and durability.
IS 456:2000 specifies 50 mm minimum concrete cover for reinforcement in submerged/buried foundations.
CSH (Calcium Silicate Hydrate) and CH (Calcium Hydroxide) are the main hydration products that give strength to concrete.
For RCC columns, the recommended slump is 25-50 mm to ensure adequate compaction and workability.
For M20 concrete, the maximum water-cement ratio is 0.55 to achieve the specified 28-day compressive strength.
Virtual work principle applies universally to all structures, both determinate and indeterminate, and rigid/deformable bodies.
Fixed-end moment for fixed beam with UDL = wL²/12 at each end (opposite signs).
For symmetrical continuous beam with equal spans and loads, negative moments at all interior supports are equal.
Three-hinged arch has 4 reactions with 3 global + 1 local equilibrium equation at crown, making it statically determinate (DSI=0).
