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visit : http://www.sourceinfratech.com contact : 9966871942(rao) ABRAMS WATER CEMENT RATIO LAW: Abrams water-cement ratio law states that for any given conditions of test,the strength of workable concrete mix is dependent only on the water-cement ratio. it follows from this law that provided the concrete is fully compacted,the strength is not affected by aggregate shape,type or surface texture,or the aggregate grading,the workability and the richness of mix.we know that workablilty of mix determine the amount of useful internal work necessary to produce full compaction is dependent the amount of water in the mix, but amount of water in the mix,corresponding to on the amount of water in the mix,but amount of water in a mix,corresponding to a given strength, is governed by the water-cement ratio law,hence the only way to increase the quantity of water to increase the workability of the mix to increase the amount of cement also,how ever as the grading of aggregate does not affect.

visit : http://www.sourceinfratech.com contact : 09966871942(Rao) BOOKS AND BENDS quite often,space available at the end of beam is limited to accommodate the full development length .in that case,hooks and bends are provided.the anchorage value of hooks or bend is accounted as contribution to the development length   shows a semi-circular hook.fully dissension,with respect to a factor,with respect to a factor k. the value K is take as 2 in the case of mild steel conforming to IS:432-1966 FOR 'hot rolled mild steel and medium tensile steel deformed bars for concrete reinforcement . the hook with k =2 with equivalent horizontal lenght of the hook. for the case of medium tensile steel conforming to IS :432 - 1966 in that case of cold worked steel conforming k is taken as 4 the value of bond stress for various grades of concrete is greater by 40% than the plan bars,hence deformed bars may be with out books, provided anchorage requirements are adequately met with,where hook

visit :  http://www.sourceinfratech.com contact : 9966871942 Anchoring shear reinforcement : inclined bars the development lenght shall be as for bars in tension ; the length shall be measured as under : 1) in tension zone from the end of the sloping or inclined portion of the bar, and 2)in the compression zone, from mid depth of the beam  stirrups, not with standing any of the provisions of the standard, in case of secondary reinforcement , such as stirrups and transverse ties,complete development lengths and anchorage shall be deemed to have been provided when the bar is bent through an angle of atleast 90 deg round a bar of at least is own diameter and is continued beyond the end of the curve for a length of atleast eight diameters,or when the bent through an angle of 135 deg and is continued beyond the end of curve for a length of atleast six bar diameters or when the bar is bent through an angle of 180deg and is continued beyond te

visit : http://www.sourceinfratech.com contact : 09966871942(Rao) Curtailment of Tension Reinforcement Tension reinforcement is designed for sections where bending moment is maximum bending moment  varies along the span of a beam depending on the loading and support conditions.for economy its is general practice to curtail the bars where the bending moment is less. the actual point of curtailment shell extend beyond the theoretical point of curtailment towards the support for a distance equal to 12 or the effective depth of the beam which ever is more. in case of cantilever beams, 50% of bars may be curatiled at 0.5 or ld which ever is more from the face of the support. in simply supported beams at least 50 % of bars  shall extend in the support for a length of ld/3 from the face of the support and the remaining 50 % can be curtailed at a distance from the center of the support.s

visit : http://www.sourceinfratech.com contact : 09966871942(rao) BOND,ANCHORAGE AND DEVELOPMENT LENGTH  one of the most important assumptions in the behaviour of reinforced concrete structures is that there is proper bond between concrete and reinforcing bars,when steel bars are embedded in concrete,the concrete,after setting,adheres to the surface of the bars and thus resist any force that tends to  pull or push this rod.the intensity of this adhesive force is called bond stress,thus the term bond is used to describe the means by which slip between steel and concrete is prevented. the bond stresses are the longitudinal shearing stresses acting on the surface between the steel and concrete.

visit : http://www.sourceinfratech.com contact : 09966871942 properties and tests on concrete: durability is the property of concrete by virtue of which it is capable of resisting its disintegration and decay.the concrete should be durable with proper regard to the various weathering conditions such as action of atmospheric gases,moisture changes,temperature variations a) use of unsound cement,which due to some delayed chemical reactions,undergo volume changes after the concrete has hardened. b) use of less durable aggregate,which may either react with cement,or may be reacted upon by atmospheric gases. c)entry of harmful gases and salts through excessive pores and voids present in unsound concrete,causing its disintegration. d)freezing and thawing of water sucked through the cracks or crevices,by capillary action causing its disintegration. e)expansion and contraction resulting from temperature changes or alternate wetting and drying.

visit : http://www.sourceinfratech.com contact : 09966871942(Rao) compostion of portland cement : the principal raw materials used in the manufacture of cement are a)argillaceous or silicates of alumina in the form of clays and shales. b)calcareous or calcium carbonate,in the form of lime stone,chalk and marl which is a mixture of clay state or mixed  and calcium carbonate.  The ingradients are mixed in the proportion of about two parts of calcareous material to one part of arillaceous material and then crused and ground in ball mills in a dry sate or mixed in wet state .the dry powder or the wet slurry is then burnt in a rotary kiln at a temperature between 1400 deg to 1500 deg. The clinker obtained form the kiln is first cooled and then passed on to ball mills where gypsum is added and its is ground to the requisite fineness according to the class of product.

visit :  http://www.sourceinfratech.com contact:  :  Rao(09966871942)   concrete is a product obtained artificially hardening of the mixture of cement,sand,gravel and water in y predetermined proportions,when these ingredents are mixed,they form a plastic mass which can be poured in suitable moulds,called forms,and set on standing into hard solid mass.the chemical reactions of cement and water,in the mix,is relatively slow and requires time and favourable temaperature for its completion.this timeknown as setting time may be divided into three distinct  phase first phase,

visit : http://www.sourceinfratech.com contact : 09966871942 design requirements for columns longitudinal  reinforcement : a) the cross sectional are of longitudinal reinforcement shall not be less than 0.8% and not more than 6% of gross cross sectional area of the column, b) in any column that has larger cross sectional area than that required to support the load,the minimum percentage of steel shall be 0.8% of required area and not the area actually provided, c)minimum number of longitudinal bars to be provided is 4 for rectangular columns and 6 for circular columns. d) minimum diameter of the longitudinal bars is 12mm e)spacing of longitudinal bars measured along the periphery of the column shall not exceed 300 mm

visit : http://www.sourceinfratech.com contact : Rao(09966871942) EQUIVALENT DEVLOPMENT LENGHT OF HOOKS AND BENDS: In situations where straight anchorage length can not be provided due to lack of space to improve the anchorage o f bars many times standarad hooks are provided in plain bars and standard bends are provide in deformed bars . the equivalent develpment lenghts for these standard hooks and bends may be taken a) the anchorage value of a standard U-type hook shall be equal to 16 times the diameter of the bar. b)the anchorage value of a standard bend shell be taken as 4 times the diameter of the bar for each 45 degree bend subjected to a maximum of 16 times the dia CHECK FOR DEVELOPMENT LENGHT FOR FLEXUAL BOND AT SIMPLE SUPPORTS the flexural bond is maximum at the section where the shear force is large.there fore the check for flexural bond is necessary at the sections where shear force is maximum and bending moment is zero.

visit : http://www.sourceinfratech.com contact : Rao(9966871942) Anchorage bond and development lenght  : Anchorage bond arises when a bar carrying certain force is teriminated .in such cases,it is necessary to transfer this force in the bar to the surrounding concrete over a certain lenght. the lenght of the bar Ld required to transfer the force in the bar to the surrounding concrete through bond is called development lenght. the development lenght can be easily etermine by pull out test.   equivalent development lenght of hooks and bends in situtations where straight anchorage lenght can not be provided due to lack of space to improve the anchorage of bars many times standard hooks are provided in plain bars and standard bends are provided in deformed. the equivalent development lenghts for these standard hooks and bends may be taken a) the anchorage value of a standard  U- type hook shall be equal to the 16 times diameter of the bar. b) the anchorage value of a sta

visit : http://www.sourceinfratech.com contact : 09966871942(Rao)   Bond : The important assumption made in the theory of reinforced concrete is that there is a perfect bond between steel and concrete.they have to act together with out any slip. due to bond only the force will be transeferred to the steel from the surrounding concrete and to concrete from steel. Bond stress : Bond stress is the shear stress acting parallel to the bar on the interface between the reinforcing bar and the surrounding concrete.hence,it is the stress developed between the contact surface of steel and concrete to keep them together.its resists any force that tries to pull out the rods from the concrete. Bond is developed due to combined effect of a) adhesion between concrete and steel b) friction (provided by gripping of bars due to shrinkage of concrete) c) interlocking of ribs in bars with concrete Bond stress depends on grade of concrete,diameter of the bar,bar profile condition,nat

visit : http://www.sourceinfratech.com contact : Rao(09966871942) General Design Requirements for Slabs as Per IS 456-2000 1. Effective Span : the effective span of a simply supported slab shall be taken as clear span plus effective depth of the slab or center to center distance between the supports which ever is less the effective span of a cantilever slab shall be taken as its lenght ot he face of the support plus half the effective depth except where it forms the end of a continous slab where the lenght to the centre of support shall be taken. 2. Limiting Stiffiness : the stiffness of slabs is governed by the span to depth ratio. As per Clause 23.2 of IS 456 for spans not exceeding 10 m, the span to depth ratio should not exceed the limits given below   Cantilevers - 7  Simply supported -20 contiuous -26 Depending upon the type of steel and percentage of steel, the above values have be modified for two ways slabs,the shorter span should be used for calculating

visit : http://www.sourceinfratech.com contact : Rao(09966871942) Types of Slabs: Depending up on the ratio of longer span to short span the slabs are classified into a)one way slab b)two way slab a) one way slab : slabs which are supported on all four edges the ratio of longer span to the shorter span is greater than 2 are calles as one way slabs. one way slabs bends in one direction i.e. along the shorter span and hence it needs main reinforcement in one direction only to resist one way bending how ever minimum reinforcement known as distributin steel is provided along the longer span above the main rinforcement to distribute the load uniformly and resist temperature and shrinkage stresses b) two way slab : when the slabs are supported on all the four edges and the ration of longer span to the shorter span is less then or equal to 2,the slabs are likely to bend along the two spans and such slabs are called as two way slabs. the load is transferred in both the directi

visit : http://www.sourceinfratech.com contact : Rao(09966871942) Code of practice of RCC Design all reinforced concrete structural designs in our country should conform to the recently revised indian standard code IS : 456-2000,Code of practice for plain and reinforced concrete the Bureau of Indian standards have released over the years several hand books to facilitate reinforced concrete structural to design routine structural elements quickly by referring to the various tables and graphs presented in the hand books  a) SP 16-1980 - Design aids for Reinforced concrete to IS : 456 b) SP 24-1983 - Explanatory Hand Book on IS : 456 c) SP 34 -1987 -Hand book on concrete reinforcement and Detailing d) SP 23 -1982 - Hand book on concrete Mixez

visit : http://www.sourceinfratech.com contact : 09966871942(Rao) Methods of design of reinforced concrete the aim of design is to decide the size of the member and maount of reinforcement required,so that the structure will perform satisfactorily during its life period with minimum cost. the following three methods have been developed for the design of reinforced concrete structures. a) working stress method b) ultimate load method c) limit state method    in this limit state method , the structural elements are designed for ultimate load and checked for serviceablility( defelctions, cracking etc) at working loads so that the structure is fit for use through out its life period. the details of this method  

visit : http://www.sourceinfratech.com contact : 09966871942 Design mix concrete  for all important works involving large quantites of concrete,it is preferable to use design mix, which results in considerable economy ensuring the required strength. the process of mix design consists of selecting optimum proportions of cement,aggregate and water to produce the grade of concrete with the required workability,strength and durability with minimum cost. over the years,several mix design methods have been developed.the IS code method is explained below IS CODE METHOD OF MIX DESIGN : this method is covered is IS : 10262 - 1982 .

visit : http://www.sourceinfratech.com contact : srinivas (09966871942) workability of concrete : The workability of reshly mixed concrete is that propert which determines the ease and homogeneity with which it can be mixed,placed,compacted and finished.a workable concrete should not show any segregation or bledding . a workable concret possesses required lubrication for handling concrete with out segregation,can be placed in the forms with out loss of homogeneity,compacted with minimum effort and shall be finished easily. the factors which influence the workability are 1)water-cement ratio 2)type and grading of aggregate. 3)ratio of fine and coarse aggregate. 4)use of admixtures. 5)efficiency of mixing.

vist :    http://www.sourceinfratech.com contact : 09966871942 important properties of concrete compressive strength/grade of concrete  The compressive strength of concrete is the charactersitic compressive strength of 150 mm concrete cubes at the age of 28 days in N/mm2. the characteristic strength is defined as the strenght of material below  which not more than 5 % if the test results are expected to fall. IS 456-2000 specifies the characteristic comprssive strength of 150 mm cube at the age of 28 days , as the grades of concrete varying from 15 to 80 disgnated as M 15 to M 80 basesd on the characteristic compressive strenght concrete is grades as given below..  

vist : http://www.sourceinfratech.com contact : Rao(09966871942) admixtures:  Admixtures are added to the concrete before or during mixing,to modify one or more of the specific properties of concrete in the fresh or hardened states.IS:9103 1979 lays down the procedures for evolution of admixtures for concrete.the different types of admixtures used are given below. 1. Accelerating admixtures : these are added to concrete to increase the rate of early strength development,which in turn facilitates earlier removal of form work.common accelerators are calcium chloride,fluosilicates and trietanlamine. 2.Retarding Admixtures : these are added to slow down the rate of setting of cement they are useful in hot weather concreting.common types of retarders are starches and cellulose products,sugar and hydroxyl-carboxylic acids. 3. Water Reducing or plasticizing Admixtures : the addition of plasticizer allows greater workability for given water cement ratio or alternatively retains o

http://www.sourceinfratech.com contact:09966871942 water: water plays an active role in the chemical process of hydration of cement and in curing of concrete.hence,the water used for mixing and curing of concrete should be clean and free from injurious amount of oils,acids,alkalies,salts,organic matter etc.that may be deleterious to concrete and  steel,drinking water is generally considered satisfactory for mixing of concrete. sea water should not be used for mixing and curing because of presence of harmful salts in it. the ph value of water should  not be less than 6. the physical and chemical tests for water should be done as per IS:3025

visit : http://www.sourceinfratech.com contact : 09966871942(Rao) tensile strength the tensile strength of concrete is very low and hence it is not taken in to account in the design of reinforced concrete.but it is an important property which affects the extent and width of cracks in the structure.according to IS456-2000,The tensile strenght of concrete can be calculated from the compressive strength  using the following relation. fcr =o.7 square root of fck n/mm2

visit : http://www.sourceinfratech.com contact : 09966871942     Ingrediants of concrete The main ingredient materials in concrete are a)       Cement       b) Aggregates   c) water Cement Cement is the binding material which is obtained by burning calcareous, siliceous and argillaceous materials   together in definite proportions at high temperature and grinding the resultant clinker in to a fine powder. Various types of cements have been developed for the use in different types of structures under different situations. According to IS:456-200,the types of cements and their suitability for a specific situations are given      

visit : http://www.sourceinfratech.com contact : 9966871942 concrete is a composite material consisting of cement,aggregate and water in suitable proportions.the chemical interaction between cement and water binds the aggregates in to a solid mass.fresh concrete will be plastic,so that it can be moulded to any desired shape in the moulds and compacted to form a dense mass.water has to be applied for few days over the concrete surface soon after its setting because the hydration reactions between cement and water continue for a longer period due to which hardening of concrete takes place.this period when concrete is kept moist during which concrete gains strength called curing period. Hence the strength of concrete increases with age. The process of solidification of concrete from plastic stage is called setting while gaining of strength after is called hardening.usually setting completes with in a maximum duration of 10 hours,while about 90% of hardening is completed by 28

visit : http://www.sourceinfratech.com/lightweightbricksmaterials.html contact: 09966871942 how do we caliculate the self weight of the beam? L=10m,size of the beam 300 * 500 mm sol : volume of the slab = 10*0.3*0.5 = 1.5cubic meter self weight of the RCC  = 2500 KG/M3 Weight of the slab = 2500 * 1.5 = 3750 kg = 3.5 tones