SHOTS - CONCRETE TECHNOLOGY

💥 Bleeding-separation of water or water cement mixture from the concrete. 

💥 Segregation-separation of aggregates from the concrete. 

💥 Workability of the concrete directly proportional to the grading of the aggregate. 

💥 Workability of the concrete inversely proportional to the time of transit. 

💥 Approximate value of shrinkage strain is 0.0003. 

💥 Air entrainment in the concrete increases workability. 

💥 Strength of the concrete increases with increase in fineness of cement. 

💥 Characteristic strength of concrete is given by 0.7 (fck)^(1/2). 

💥 The compressive strength of 100mm cube is more compare to the 150mm cube. 

💥 Modulus elasticity of concrete is 5700(fck)^(1/2). 

💥 Increase in moisture content in concrete reduces the strength in concrete. 

💥 The purpose of accelerator is to cause early setting and hardening. 

💥 Gypsum is most commonly used admixture. 

💥 The percentage of voids in cement approximately 40%. 

💥 The strength of concrete after one year as compare to the 28 days is 20 to 25% more. 

💥 Modulus of rupture of concrete is the measure of flexural tensile strength. 

💥 In order to obtain the best workability rounded shape aggregates used. 

💥 Bulking of sand is maximum if moisture content is about 4%. 

💥 Finer grinding affects only the early development of strength. 

💥 Poisons ratio increases with richer mix. 

💥 1% of voids in concrete reduces the strength by 5%. 

💥 The fineness modulus of fine aggregate is in the range of 2-3.5. 

💥 The factor of safety of steel is lower than concrete. 

💥 For a reinforced concrete section the shape of the shear stress diagram is parabolic above neutral axis and rectangular below neutral axis. 

💥 Modulus of elasticity of steel as per IRC 456- 1978 is 200kn/mm^2. 

💥 M15 grade of concrete is used in reinforced concrete. 

💥 Heavily reinforced sections the workability of the concrete is above 0.92. 

💥 In case of hand mixing of concrete extra cement is added is 10%. 

💥 For walls, columns and vertical faces of members the form work removed after 1-2 days. 

💥 According to IS 456-1978, the column or strut is the member whose effective length is greater than 3 times lateral dimension. 

💥 Slenderness ratio for short column is <12. 

💥 The ratio of the diameter of reinforcing bar and the slab thickness is 1/8. 

💥 According to IS456-1978, the maximum reinforcement for columns is 6%, 4% for beams and 0.12% for slabs. 

💥 Maximum distance between the expansion joints is 45m. 

💥 Minimum thickness of load bearing RCC wall should be 100mm. 

💥 One way slab ratio of long span to short span>2. 

💥 Two way slab the ratio of long span to short span is <2. 

💥 Modular ratio is 280/3cbc. 

💥 The purpose of providing the reinforcing bar is to resist bond stress. 

💥 12mm is the minimum diameter of longitudinal bar. 

💥 The load carrying capacity of a helically reinforced column as compare to the tied column is 5% more. 

💥 Counter fort type retaining wall is suitable for height beyond 6m. 

💥 T shaped retaining wall mainly consists of three cantilevers. 

💥 While designing the pile has column one end is fixed and other end is hinged. 

💥 The design yield stress of steel according to the IS 456-1978 is 0.87fy. 

💥 According to IS 456-1978, the maximum compressive stress in concrete is taken as 0.446fck. 

💥 Partial safety factor for steel is 1.15 and 1.5 for concrete. 

💥 0.0035 is the maximum strain. 

💥 The creep strains are caused due to dead load only. 

💥 The effect of creep on modular ratio is to increase it. 

💥 A beam curved in plan is designed for bending moment, shear and torsion. 

💥 Normally pre stressing wires are arranged in the lower part of beam. 

💥 3*10^-14 is the coefficient of shrinkage. 

💥 Cold drawn wires has high tensile strength. 

💥 In concrete use of angular aggregates in place of natural aggregates affects flexural tensile strength. 

💥 Ratio of compressive strength to tensile strength is increases with age. 

💥 The grading of fine aggregates is divided into 4 zones. 

💥 Endurance limit of mild steel is approximately 0.5. 

💥 Soundness test gives unsoundness due to free lime only. 

💥 Vee bee test used for very low workability. 

💥 0.9 is called medium workability. 

💥 0.36 water cement ratio required for full hydration of cement. 

💥 Addition of sugar in concrete results in increasing the setting time about 4 hour. 

💥 7 days required for minimum curing. 

💥 M20 grade of concrete is used for the structures exposed to the sulphate attack. 

💥 Shape of idealized stress strain curve for concrete as per IS456-1978 is rectangular parabolic. 

💥 The purpose of lateral ties in short RCC column is to avoid buckling of longitudinal bars. 

💥 The side face reinforcement of T beam will be 0.1%. 

💥 Relaxation-loss of stress with time at constant strain. 

💥 Deep beams are designed for bending moment only. 

💥 In the limit state design the concrete structures are assumed to be linear. 

💥 Deflection can be controlled by using the appropriate span/depth ratio. 

💥 Spacing of main reinforcement controls cracking. 

💥 Unequal top and bottom reinforcement in a reinforced concrete section leads to shrinkage deflection. 

💥 Drops are provided in flat slabs to resist shear. 

💥 Flexural failure in over reinforced beams is due to primary compression failure. 

💥 In an RCC beam ,side reinforcement is provided if its depth exceeds 750mm.