In civil engineering knowledge of CEMENT concrete behaviour by using various materials

In this Article I will discuss about behaviour of cement concrete using alternative materials. The requirement of concrete aggregate in India is large corresponding to currentannual production of cement of 300 million tons total requirement of coarse,and fine aggregate for use in cement concrete mortar and plasters of about1,500 metric tons per year is a safe estimate. there is difficulty inobtaining natural aggregates within economic distances. search for alternatesources of aggregates thus assumes importance. one such alternative isrecycled concrete aggregate derived from construction and demolition wastes, whichallow conservation of natural resources and land. aggregate in concrete constructions typically account for 75 percent of the total volume. the majorityof concrete constructions till date essentially resort to aggregatematerials derived from natural resources conforming to is 383. 

However due to the need of conserving natural resources and issues relating to sustainabilitye environment considerations and economy increasing use of recycled and secondary aggregate has been forecasted.

•  To compare the compressive strength of recycled coarse aggregate constructional concrete with the concrete.
• To know it's applications in constructionindustry.  
• To reduce the pressure on naturally available materials byreplacing it with recycled aggregate.
•  To compare the physicalcharacteristics of natural aggregate with recycled aggregate.
•  To study the behavior of fresh and hardened concrete reinforced with recycled coarseaggregate. 

advantages and disadvantages.

•  discuss about the advantages.
• We the following advantages of using recycled aggregates. 

1. it iscost-saving. 
2.  it is better for controlling alkali silica reaction.
3. to save environment recycled aggregates may be used. 
4. its saved time. 
5.  italso have less emission of carbon.
6.  up to 20% replacement of natural aggregatewith RCA or RMA without a need for additional testing for all concrete upto a characteristic strength of 65 mega Pascal as per Indian Standard ispermitted. 

there are also some disadvantages, such as

1.   less quality. 
2.  duration of procurement of materials may affect lifecycle of project. 
3.  landspecial equipment machineries are required.
4.  very high water absorption, 
5. it has higher drying shrinkage. 

properties of recycled concreteaggregate.

 here are some properties which can be seen in recycled concrete.physical properties of fresh concrete containing RCA. you can saw some physicalproperties of fresh concrete which contains RCA such as workability, watercontent, air content. physical properties of hardened concretecontaining RCA. here are some properties of hardened concrete containing RCA, suchas compressive strength, flexural strength, modulus of elasticity,durability, bond strength with reinforcement, creep and drying shrinkage. quantity of material used in the experiment.we use the following quantities of cement, sand, coarse aggregates and water for slump test. for compressive test with normal aggregates, recycled aggregates,and brick Bats, we use the following quantities of cement, sand, coarseaggregates and water and for compressive test with partial replacement of cementwith fly ash, we replace the cement content by 25 percent, 50 percent and 75percent in three different samples. experimental program 

1. first, weconducted specific gravity and water absorption test of aggregates. specificgravity of an aggregate is a measure of strength or quality of the material.stones having low specific gravity are generally weaker than those with higherspecific gravity. behavior of concrete by partial replacement of coarse aggregatewith recycled plastic granules. water absorption indicates strength of rocks.stones having more water absorption are more porous in nature, and are unsuitableunless they are found to be acceptable based on strength impact and hardnesstests. apparatus used in this test. we need beaker of one liter, hot air oven, anweighing balance, and a tray for this test. procedure. first, take about 2kilograms of coarse aggregate sample. wash thoroughly to remove finerparticles and dust and immerse in water for 24 hours at a temperature between 22degrees Celsius and 32 degrees Celsius with a cover of at least 5 centimetersof water above the top of the basket. lift the basket 25 millimetres above thebase of tank and allowing it to drop 25 times at the rate ofmore than one drop per second. the weight is noted while suspending in water as w1.then remove the aggregate from basket and allow it to drain for a few minutes.weight of empty basket in water is measured as W2. take out the immersedaggregate and place in a dry cloth. it shall then be spread out not more thanone stone deep and best exposed to the atmosphere away from direct sunlight orany other source of heat for not less than ten minutes or until it appears tobe completely surface dry. measure weight of the aggregate as W3, then theaggregate shall then be placed in the oven in the shallow tray at atemperature of 100 to 110 degrees Celsius and maintained at thistemperature for 24 hours. after 24 hours it shall then be removedfrom the oven, and cooled in the air tight container, and weighed as W4finally, we determine the specific gravity and water absorption valuesusing these formula. 

In our experiment, we got the following observations. usingthese values, we got the following results. experimental program

 2.  then weconducted a slump test to determine the workability of the concrete. the concreteslump test is used for the measurement of a property of fresh concrete. the testis an empirical test that measures the workability of fresh concrete. morespecifically, it measures consistency between batches. the test is popular dueto the simplicity of apparatus used and simple procedure. principle of slump test.the slump test result is a measure of the behavior of a compacted invertedcone of concrete under the action of gravity. it measures the consistency orthe wetness of concrete. apparatus used a slump cone. a scale for measurement and asteel tamping rod. procedure of concrete slump test. the mould for theslump test is a frustum of a cone of 300 millimetres of height, the base is 200millimeters in diameter and it has a smaller opening attop of 100 millimeters. first of all, the base is placed on a smooth surface, andthe container is filled with concrete in three layers, whose workability is to betested. each layer is temped 25 times with a standard 16 millimetres diameter steelrod, rounded at the end. when the mould is completely filled with concrete, the topsurface is leveled with mold tough opening by means of screening androlling motion of the temping rod. the mould must be firmly held against itsbase during the entire operation, so that it could not move due to the pouring ofconcrete, and this can be done by means of handles or foot, rest spreads to themould. then immediately after filling is completed, and the concrete is levelledthe cone is slowly and carefully lifted vertically, and unsupported concrete willnow slump. the decrease in the height of the center of the slump concrete iscalled slump. now the slump is measured by placing the cone just beside theslump concrete, and the temping rod is placed over the cone, so that it shouldalso come over the area of slumped concrete. the decrease in height ofconcrete to that of mould is noted with scale. it is usually measured to thenearest 5 millimetres. types of concrete slump. the slumped concrete takes variousshapes and according to the profile of slump concrete, the slump is termed ascollapse slump, shear slump and true slump. collapse slump, in a collapse slump,the concrete collapses completely a collapse slump will generally mean thatthe mix is too wet or that it is a high workability mix, for which slump test is not appropriate shear slump in a shear slump the top portion of the concreteshears off and slipped sideways. or if one half of the cone slides down aninclined plane, the slump is said to be a shear slump. if a shear or collapse slumpis achieved, a fresh sample should be taken, and the test is repeated. if theshear slump resists has made. in the case with harsh mixes, this is an indicationof lack of cohesion of the mix. true slump. in a true slump the concretesimply subsides keeping more or less to shape. this is the only slump which is used in various tests. mixes of stiff consistent have azero slump, so that in the rather dry range no variation can be detectedbetween mixes of different workability. depending upon the various slump values,concrete are used in different suitable places. in this table, we can see theiruses for various slump values. experimental program 

3. compressivetest of concrete as per IS 456 : 2000 compressive strength of concrete cubetest provides an idea about all the characteristics of concrete. by thissingle test, one judge that weather concreting has been done properly or not.concrete compressive strength for general construction varies from 15 megaPascal to 30 mega Pascal, and higher in commercial and industrial structures.compressive strength of concrete depends on many factors, such as water-cementratio, cement strength, quality of concrete material, and quality control,during the production of concrete, etc. test for compressive strength is carried outeither on cube or cylinder. various standard codes recommend concretecylinder or concrete cube as the standard specimen for the test. 

AmericanSociety For testing materials ASTM C39 or C39M provides standard testmethod for compressive strength of cylindrical concrete specimens. apparatusfor concrete cube test. it just need a compression testing machine for the test.preparation of concrete cube specimen. the proportion and material for makingthese test specimens are from the same concrete used in the field. specimen. toconduct the test, we need cubes of size 15 centimeters x 15 centimeters x 15centimeters. preparation of concrete cubes for the test. for cube tests twotypes of specimens, either cubes of 15 centimeters or 10 centimeters, dependingupon the size of aggregate are used. for most of the works cubical mould of size15 centimetres are commonly used. theconcrete is poured in the mold and tempered properly so as not to have anyvoids. after 24 hours, these mold are removed and test specimens are put inwater for curing. the top surface of these specimens should be made even andsmooth this is done by putting cement paste and spreading smoothly on wholearea of specimen. these specimens are tested by compression testing machineafter 7 days curing or 28 days curing. load should be applied graduallyat the rate of 140 kg per cm square per minute till the specimens fails. load atthe failure/area of specimen gives the compressive strength of concrete. curingof cubes. the test specimens are stored in moist air for 24 hours. and after thisperiod, the specimens are marked and removed from the molds and kept submerged in clear fresh water until take out prior to test. procedure forcube test. first, remove the specimen from water after specified curing time, andwipe out excess water from the surface. then clean the bearing surface of thetesting machine. now place the specimen in the machine in such a manner that theload shall be applied to the opposite sides of the cube cast. also align thespecimen centrally on the base plate of the machine. 

Next rotate the moveableportion gently by hand, so that it touches the top surface of the specimen.then, apply the load gradually without shock and continuously at the rate of140 kg per cm square per minute till the specimen fails. finally, record themaximum load and note any unusual features in the type of failure. itshould be noted that a minimum three specimens should be tested at eachselected age. if strength of any specimen varies by more than 15%  of averagestrength, results of such specimen should be rejected. average of three specimensgives the crushing strength of concrete. in this table, we can see the compressivestrength of concrete at various ages as per Indian standard recommendation in the second table, we can see the compressive strength of different gradesof concrete at 7 days and 28 days. result of experiments for the specificgravity and water absorption tests of coarse aggregate, we got the followingresults. we also get the slump value of concrete as 15 millimetres. compressivestrength using normal coarse aggregates, we have the following results. when wereplace some normal coarse aggregates with recycled coarse aggregates, we gotthe following compressive strength. and when we replace some normal coarseaggregates with brick Bats, we got the following compressivestrength. now if we compare the compressive strength, we have thesevalues for different coarse aggregates. and here is the graphical representationof the compressive strength using different coarse aggregates. when wereplace the cement content with fly ash, we have the following compressivestrength for different percentages of fly ash. concluding remarks. recycling andreuse of building wastes have been found to be an appropriate solution to theproblems of dumping hundreds of thousands tons of debris accompaniedwith shortage of natural aggregates. the use of recycled aggregates in concreteproved to be a valuable building materials in technical environmental and economical respect. there are several reliable applications using for recycled coarse aggregate in construction. however more research andinitiation of pilot project for application of RCA is needed formodifying our design codes, specifications and procedure for use of  aggregate concrete.