Civil Engineers notes

Yaseen ali shah

Monolithic:A monolithic structure is something carved or cast from a single piece of a material. Usually (and literally, from the translation of monolith being "one stone") the material is stone, but it could equally be applied to a structure cut from a single block of metal, or cast in metal in a single pieceDEFFERENCE BETWEEN SHELL, MEMEBRANE & PLATE (ETABS)Hi.. Someone asked here for the differences between shell, membrane, and plate on slab category using in Etabs and when to apply what. OK.. here I am clearing the fact in details that you can see from the attached image. In general for Etabs modeling, shell is used but when in practical designing in high rise structures, we can use membrane as then the moment generated by Etabs for the slab will be greater, as a result the reinforcement will be increased,hence factor of safety will be increased but always keep in mind about the economic condition. So, frequently use the shell option. Again, use the options to take the values for specific parameters.(FACEBOOK)

REPAIR OF SMALL AND LARGE CRACKS IN CONCRETE

Repair of small, medium and large cracks inconcreteand repair of crushedconcreteis required to enhance the strength and durability of damaged concrete members.Repair of small and medium cracks in concrete:Small and medium cracks in reinforced concrete and masonry structures reduce their strength considerably to bear the designloads. Thus repair of such cracks is necessary to restore the designed strength of members.The repair of small and medium cracks is done by first marking out the critical damaged zones in concrete members. Then these cracks can be repaired by injectingcementgrout or chemical grouts or by providing jacketing. The smaller cracks less than 0.75 mm width can be effectively repair by using pressure injection of epoxy.The surface of the member near cracks is thoroughly cleaned. Loose materials are removed and plastic injection ports are placed along the length of crack at an interval equal to the thickness of the structural member. These ports are placed on both sides of the member and secured in placed with the help of epoxy seal.When the epoxy seal has hardened, the low viscosity resin is injected into one port at a time starting from the port at lowest level and moving upwards. The injection through port is continued till the resin flows out from the adjacent port or from the other side of the member. Then the current injection port is closed and epoxy injection is continued from the adjacent port.

This process is carried out in sequence till all the ports and cracks are filled with the grout. This method can be used for all types of structural members such are beams, columns,wallsand slabs. This method can also to repair of small cracks in individual masonry blocks or for filling large continuous cracks.Repair of Large Cracks and Crushed Concrete:Repair of large cracks (cracks wider than 5mm) and crushed concrete and masonry structure cannot be done using pressure injection or grouting. For repair of large cracks and crushed concrete, following procedure can be adopted:1. The surface of cracks or crushed concrete is cleaned and all the loose materials are removed. These are then filled with quick setting cement mortar grouts.2. If the cracks are large, then these cracks are dressed to have a V groove at both sides of the member for easy placement of grouts.

Fig: Filling of cement mortar and stone chips in large cracks in masonry walls.3. For cracks which are very large, filler materials such as stone chips can be used.4. Additional reinforcement and shear reinforcements can be used for heavily damaged concrete members or wherever necessary based on requirements.These additional reinforcement should be protected from corrosion by using polymer mortar or epoxy coatings.5. For damaged walls and roofs, additional reinforcement in the form of mesh is used on one side or both sides of the members. These mesh should sufficiently tied with existing members.

Fig: Reinforcement meshes in repair of roof slabs and walls. 1. Wire mesh on front face, 2. Clamps, 3. Wire mesh on back face, 4. Cement plaster, 5. Crack in member.6. Stitching of cracks are done to prevent the widening of the existing cracks. In this case, holes of 6 to 10mm are drilled on both sides of the crack. Then these drilled holes are cleaned, legs of stitching dogs are anchored with short legs. The stitching of cracks is not a method of crack repair or to gain the lost strength, this method is used to prevent the cracks from propagating and widening.

Percentage of Bricks and Mortar in a Masonry WallCase 1:When thickness of the wall is 4.5 and that of mortar is 12mm, having the following plan.

In this caseHeight of the wall along with the mortar = (10 x 3) + [(9 x 12)/25.4] = 34.252In the above equation10 = No of Brick Layers9 = No of layers of Mortar of 12mm each3 = Brick Height in inchesWidth= 4.5Length of the wall along with the mortar= (5.5 x 9) + [(512)/25.4]Volume of the wall along with the mortar=LWHVolume of the wall along with the mortar= 7993.72 cubic inchVolume of the wall along with the mortar= 4.626 cftNow Number of Bricks= 55Volume of One Brick= (9/128) cftTotal volume of bricks used= 55 x (9/128) = 3.867 cft%age of bricks used = (3.867 / 4.626)*100 = 83.6 = 84%%age of mortar used= 16.4%Case 2:When thickness of the wall is 9 and that of mortar is 12mm, having the following plan.

In this caseHeight of the wall along with the mortar = (10 x 3 ) + [( 9 x 12 )/25.4] =34.252Width of the wall along with the mortar =(9+12/25.4) = 9.472Length of the wall along with the mortar= (5.5 x 9) + (5 x 12/25.4) = 51.862Volume of the wall along with the mortar=LWHVolume of the wall along with the mortar=16826.678 cubic inchVolume of the wall along with the mortar= 9.7376 cftNow Number of Bricks= 110Volume of One Brick= 9/128 cftTotal volume of bricks used= 110 x (9/128) = 7.7344 cftSo%age of bricks used = (7.7344 / 9.7376) x 100 = 79.43% = 80%%age of mortar used= 20.57%= 21%Case 3:When thickness of the wall is 4.5 and that of mortar is 10mm, having the following plan.

In this caseHeight of the wall along with the mortar = (10 x 3) + (9x10/25.4) = 33.543width = 4.5Length of the wall along with the mortar= (5.5 x 9) + (5 x 10/25.4) = 51.468Volume of the wall along with the mortar=LWHVolume of the wall along with the mortar= 4.4959 cftNow Number of Bricks= 55Volume of One Brick= 9/128 cftTotal volume of bricks used= 55 x 9/128 = 3.8672 cft%age of bricks used = (3.8672 / 4.4959) x 100 = 86%%age of mortar used = 14%Case 4:When thickness of the wall is 9 and that of mortar is 10mm, having the following plan.

In this caseHeight of the wall along with the mortar = (10 x 3) + (9x10/25.4) = 33.543width = (9 + 10/25.4) 9.3937Length of the wall along with the mortar= (5.5 x 9) + (5 x 10/25.4) = 51.468Volume of the wall along with the mortar=LWHVolume of the wall along with the mortar= 9.38513cftNow Number of Bricks=110Volume of One Brick= 9/128 cftTotal volume of bricks used= 110x 9/128 = 7.7344cft%age of bricks used = (7.7344 / 9.38513) x 100 = 82.4% = 82%%age of mortar used = 17.6% = 18%Conclusion

Where in itW= wall thickness in inchesm= thickness of the mortar in mmThe answer will be the %age of mortar, and for better results round it off.ItsVerificationis given below after the example from observation.EXAMPLE:If thickness of the wall is 4.5 and that of mortar is 12mm, then what will the percentage of mortar used in the wall?Solution:

Specification of 'Bricks Walls'

Brick walls are probably the most common building elements in construction of a house in India. These walls form basic units for creating rooms that make up a house. The walls besides being space dividers are also structural elements that transfer the load of the roof to the ground. Brick walls are constructed on strip spread or raft foundations that support the walls. The walls are constructed using bricks and mortar. These can also be constructed with various structural qualities and thicknesses.BrickworkBrick walls are constructed by joining bricks with cement mortar in arrangements called English Bond, Flemish Bond or Rat Trap Bond. These bonds give different external appearances to the wall. All construction systems of brick walls are such devised that vertical cross joints in any layers are staggered. The bricks thus bonded form a solid mass that does not split when the wall is loaded with live loads and dead loads.Classification of Brick WorkThe classification of brick work according to the quality of brick is following. First class brick work Second class brick work Third class brick workFirst Class Brick WorkFirst class brick work is made by using first class bricks and cement mortar. This brick work is used for load bearing walls. It is made in rich mortar in which the cement and sand ratio is from 1:3 to 1: 6.First class bricks are identified by their uniform color and a ringing sound when struck. The bricks are equal in size and have even edges and surfaces. These bricks do not chip and dont have any cracks. First class bricks do not absorb water more than 1/6 of their weight. There is no salty residue when the bricks are dry. First class bricks have a minimum crushing strength of 105.kg. Per sq. cm

Bricks of first class qualitySecond Class Brick WorkSecond class bricks work is made by using second class bricks and cement mortar. These bricks also have the property of first class bricks but are not very regular or even in shape. These bricks should not be used for load bearing walls for more than two storey buildings. Second class bricks have minimum crushing strength 70.kg per sq. meter.

Second classquality of bricksThird Class Brick WorkThis type of brick work is made by using third class bricks and cement mortar or mud mortar. Third class brick work is not made in any Govt. work. Generally this type of brick work is made for temporary work in private sector.MortarMortar is a mix used to bind brick, stone etc to each other.It can thus be seen as a binding material that bonds bricks, stones to make a wall or for cladding purpose. Normally cement mortar is used in brickwork in present day construction though lime mortar can also be used but it requires superior craftsmanship and is hence infrequently used.Cement MortarCement mortar is a mix of cement and sand with water. The cement is binding material which requires sand as a filler material. This cement mortar mix in wet state is plastic and binds two materials when it dries. Mortar is generally defined as 1:2 or 1:3 or 1:7 etc. This means that one part of cement is mixed with 2, 3 or 7 parts of sand.Precaution for mixing cement mortarThe following steps should be taken carefully while mixing materials for cement mortar. The mix should be made on a dry, clean, flat surface. The mix should be as per specifications. The mix should be by volume. The quantity of water should be such that the mix can be easily spread over bricks or applied on a vertical surface. Water more then required quantity may spoil the mix and it can reduce the strength of masonry. The mix should be used within half an hour of its preparation.

Brick Wall FoundationsBrick wall foundations are normally made as strip foundations.These are continuous along the length of wall and hence called as strip foundations. These form structural components of construction system by which the load of whole building is transferred to the ground.Foundations are made in dug out trenches so that a hard stable surface on which the building is supported can be obtained because the top surface of the ground normally does not have load bearing capacity to take the load of the building. The other reason is that foundations can by this method be hidden from view. The architect needs to provide a foundation plan that indicates exactly where the foundation trenches are to be dug.The foundation trenches are dug after being marked on center line principle on the site according to architects drawings. The size of trench varies with the thickness of walls and the load bearing capacity of the soil. The base of dug trench is rammed to solidify the surface. On rammed surface a layer of cement concrete is laid. This is normally 6 to 8 inches thick. This base concrete layer needs to be cured for it attains its expected strength. Base concrete layers or courses of bricks are laid to create a stepped base that would help in distributing the load over a larger surface of the foundation.Precautions during construction of brick wall foundations The marking of foundations must be absolutely accurate as the location of walls depends on these markings. The trenches should not be dug in rainy season. The bricks, mortar mix and cement concrete mix should be as per specifications. The width and depth of the trenches depends on loading and soil conditions. As the foundation is an expanded base to distribute the load coming on it over a large area on ground. The width of the wall foundation depends on whether the wall is a load bearing wall, a non load bearing wall, a partition wall or a toe wall.Load Bearing WallsThe walls that support beams and roof slabs. These walls take the load of super structure and transmit it to the ground through foundation. These can also serve the purpose of dividing the space into required rooms etc. These are also accommodating door and windows where required. These are of 9 or more thickness. Such walls are made in first class bricks and rich mortar.

Non Load Bearing Walls These walls serve the purpose of dividing the space into required rooms etc. These are also accommodating door and windows where required. These can be made into thin sections to save the space. Non load bearing walls are only partition having no load of super structure so these can be easily changed whenever required to change the space of the room. These walls are made 3 inches, 4.5 inches and 9 inches thick as per the requirement of the site.

Super Structure:The word super structure used in construction work means/denotes following. Brick work from DPC level to the roof level/slab level. If columns provided in drawings then RCC columns to be laid. Rain water pipe is to be embedded in walls. Fixing doors, windows and ventilators frames in walls. RCC (Reinforced Beam & slab for roof) including M S Steel bars according to the designs. Tile terracing lay with brick tiles on the top of the roof slab. Fixing doors and windows shutters. Fixing cupboard in the rooms and Kitchen etc. Fixing iron grills for safety of the house. Providing cement plaster on ceiling and walls. Laying floors including base coat.

CATCHMENT AREA METHOD

By Catchment Area Method you calculate Column load

HOW TO DO IT ?

1) Suppose you want to calculate load on column c1 AS shown in figure , now as shown in figure , Purple Hatched one are columns and Blue Hatched one are Beams and i Have Marked Area with Inclined Pink Lines

Now Catchement means Hatchmed pink line area is Catchment on Column C1 , means Half of Slab Area and Half of Horizontal Beam and Half of vertical Beam is the total catchment area on Column C1

How To Calculate Load on column C1 ?

1) Consider Slab area first

in it You have Live load , finishes load or any other uniform pressure load in psf

now to convert that uniform pressure load (including self weight )in psf into point load which will be Load on COLUMN C1 , for that you have to multiply Pressure load (in psf ) by area of slab(in ft^2) ,

Area will be Pink Hatched area as shown in Figure

2) Consider Beam now

Above Beams you have Wall Load which is in Kip/ft

Now to Convert that Wall load into point load which will be Load on Column C1 , for that you have to multiply wall load (in Kip/ft) by half length of beam

As shown in Figure , it is clearly shown that half length of horizontal beam and half length of vertical beam will be catchment length on column C1

now first find out Horizontal half length and vertical half length and then for horizontal half length multiply it by Wall load which is in kip/ft and for vertical half length multiply it by wall load which is in kip/ft , now that will be the Point Load in Kips on Column C1

Also include Self Weight of Beam

3) Column Self Weight also , means if column height is from floor to floor is 12 feet and beam depth is 24 inch then column height will be 12 feet - 2feet(24 inch beam depth)

FOR example

LOAD ON SLABS :

1) LIVE LOAD = 60 psf2) Finishes Load = 36 psf3) sunk Load = 90 psf4) Slab self weight ( thickness x 0.15(density) = answer in psf

Wall Load on Beam :

1) Height of Wall is 10 feet , thickness of wall is 6 inch then Wall load will be 10 x (6/12) x 0.144 = 0.72 kip/ft

BEAM SELF WEIGHT ALSO

Size of Column is 6" x 24" , Height of Column is 12 feet from floor to floor and width of beam is 6 inch and depth of beam is 24 inch , and length of Horizontal Beam is 10 feet and Length of Vertical Beam is 12 feet ,

Now you have to calculate Load on Column C1 from Slab and Beam , as i described above ,

CALCULATE QUANTITIES OF MATERIALS FOR CONCRETEQuantities of materials for the production of required quantity ofconcreteof given mix proportions can be calculated by absolute volume method. This method is based on the principle that the volume of fully compactedconcreteis equal to the absolute volume of all the materials of concrete, i.e.cement, sand, coarseaggregatesand water.

The formula for calculation of materials for required volume of concreteis given by:

Where, Vc= Absolute volume of fully compactedfresh concreteW =Mass of waterC = Mass of cementFa = Mass of fine aggregatesCa = Mass of coarse aggregatesSc, Sfaand Scaare the specific gravities of cement, fine aggregates and coarse aggregates respectively.The air content has been ignored in this calculation.This method of calculation for quantities of materials for concrete takes into account the mix proportions from design mix or nominal mixes for structural strength and durability requirement.Now we will learn the material calculation by an example.Consider concrete with mix proportion of 1:1.5:3 where, 1 is part of cement, 1.5 is part of fine aggregates and 3 is part of coarse aggregates of maximum size of 20mm. The water cement ratio required for mixing of concrete is taken as 0.45.Assuming bulk densities of materials as follows:Cement = 1500 kg/m3Sand = 1700 kg/m3Coarse aggregates = 1650 kg/m3Specific gravities of concrete materials are as follows:Cement = 3.15Sand = 2.6Coarse aggregates = 2.6.The percentage of entrained air assumed is 2%.The mix proportion of 1:1.5:3 by dry volume of materials can be expressed in terms of masses as:Cement = 1 x 1500 = 1500Sand = 1.5 x 1700 = 2550Coarse aggregate = 3 x 1650 = 4950.Therefore, the ratio of masses of these materials w.r.t. cement will as follows =

= 1 : 1.7 : 3.3The water cement ratio = 0.45Now we willcalculate the volume of concretethat can be produced with one bag of cement (i.e. 50 kg cement) for the mass proportions of concrete materials.Thus, theabsolute volume of concretefor 50 kg of cement =

Thus, for the proportion of mix considered, with on3 bag of cement of 50 kg, 0.1345 m3of concrete can be produced.We have considered an entrained air of 2%. Thus the actual volume of concrete for 1 cubic meter of compacted concrete construction will be = 1 -0.02 = 0.98 m3.Thus, the quantity of cement required for 1 cubic meter of concrete = 0.98/0.1345 = 7.29 bags of cement.The quantities of materials for 1 m3 of concreteproduction can be calculated as follows:The weight of cement required = 7.29 x 50 = 364.5 kg.Weight of fine aggregate (sand) = 1.5 x 364.5 = 546.75 kg.Weight of coarse aggregate = 3 x 364.5 = 1093.5 kg.

POOR CONSTRUCTION METHODS AND WORKMANSHIP TO AVOIDPoorconstructionmethods and workmanship is responsible for the failure ofbuildings and structure. The poor construction methods and workmanship is caused due to negligence and inadequate quality control at construction site. The effects of some of the poor construction methods are discussed below:(a) Incorrect placement of steelIncorrect placement of steel can result in insufficient cover, leading to corrosion of the reinforcement. If the bars are placed grossly out of position or in the wrong position, collapse can occur when the element is fully loaded.(b) Inadequate cover to reinforcementInadequate cover to reinforcement permits ingress of moisture, gases and other substances and leads to corrosion of the reinforcement and cracking and spalling of theconcrete.(c) Incorrectly made construction jointsThe main faults in construction joints are lack of preparation and poor compaction. The oldconcreteshould be washed and a layer of rich concrete laid before pouring is continued. Poor joints allow ingress of moisture and staining of the concrete face.(d) Grout leakageGrout leakage occurs where formwork joints do not fit together properly. The result is a porous area of concrete that has little or nocementand fine aggregate. All formwork joints should be properly sealed.(e) Poor compactionIf concrete is not properly compacted by ramming or vibration the result is a portion of porous honeycomb concrete. This part must be hacked out and recast. Complete compaction is essential to give a dense, impermeable concrete.(f) SegregationSegregation occurs when the mix ingredients become separated. It is the result of1. dropping the mix through too great a height in placing (chutes or pipes should be used in such cases)2. using a harsh mix with high coarse aggregate content3. large aggregate sinking due to over-vibration or use of too much plasticizer

Fig: Seggregation of concreteSegregation results in uneven concrete texture, or porous concrete in some cases.(g) Poor curingA poor curing procedure can result in loss of water through evaporation. This can cause a reduction in strength if there is not sufficient water for complete hydration of the cement. Loss of water can cause shrinkage cracking. During curing the concrete should be kept damp and covered.(h) Too high a water contentExcess water increases workability but decreases the strength and increases the porosity and permeability of the hardened concrete,which can lead to corrosion of the reinforcement. The correct water-to-cement ratio for the mix should be strictly enforced.

Concrete Mix Proportion MaterialsDry Volume and Wet Volume:Dry Volume : Bulk Volume with air spaces etc.Wet Volume : Real Volume to be used.In dry mix volume empty spaces between particles in bulk material are filled with air. When we add water to concrete the empty spaces are filled with water, So the reduction in volume from dry to wet is not by shrinkage of material.For example100kg of each material, their dry volume and wet volumes typically are:Cement: Dry V - 66L, Wet V - 32 LSand: Dry V - 62L, Wet V - 38 LCoarse aggregate: Dry V - 59L, Wet V - 38LThe factor of 1.54 to convert dry volume is just approximate. For each batch of materials we have to measure dry volume and actual density to accurately convert.Cement Concrete Rule of 6

A good concrete depends onproper quantities of its gradients like cement, crush, sand and water.Here is a simple rule for proper quantities ratio is the rule of 6's!

1- Minimum cement bags are required for cubic yard concrete = 6 bags2- Maximum water required per cement bag = 6 gallon3- Minimum curing days required to keep moisture = 6 days4- Air contents required (if concrete will be subject to freezing and thawing) = 6 %

How to calculate materials for different-ratio concrete

Mix design is commonly referred by mix proportion in a selective zone where same materials are used in concrete. Suppose, in Bangladesh, most of the structural designers refer concrete mix design as ratio in drawing. Because materials of same properties are used in all over the Bangladesh.The question is,

How do we estimate materials for different ratio concrete?

The most common ratio referred here in Bangladesh for column concrete 1:1.5:3 and for slab 1:2:4. When we mix cement, sand and stone chips at 1:1.5:3 ratio, the concrete strength of 28 days cube test's result comes around 3500 psi. If we mix cement, sand and brick chips at 1:2:4 ratio the 28 days cube test result will come around 3000 psi, which is referred for slab concrete.

I will estimate materials for 1:1.5:3 ratio concrete. After learning this process you will be able to estimate materials for any concrete ratio.

Now lets estimate the required materials for the volume of 100 cft concrete of 1:1.5:3 ratio:

Wet volume of concrete = 100 cft.Dry volume of concrete= 100 x 1.54 = 154 cft.Sum of ratio 1:1.5:3, 1 + 1.5+ 3 = 5.5.So, Cement content in concrete = (154/5.5) x 1=28 cft.Sand content= (154 / 5.5) x 1.5 = 42 cft.Stone chips = (154/5.5) x 3 = 84 cft.

As we know, Cement is available as 50 kg bag in the market. The volume of 50 kg cement bag is 1.25 cft. So the required cement is 28 divided by 1.25 equal to 22.4 bag.

Summary:Cement : 22.4 bag,Sand : 42 cft,Stone chips: 84 cft.

In this estimation, we use cubic feet as our concrete unit. If you want to use cubic meter, same method can be applied. But that will be time-consuming. The easiest way to estimate concrete materials for different unit is, apply the above result as percentage. That means,Cementcontent for 100 unit of 1:1.5:3 ratio concrete is 28% (unit will be as concrete unit),Sandis 42% andStone chipsis 84%.

Now lets calculate the water content of concrete. Suppose, water-cement ratio for concrete is specified 0.45. That means, water/cement = 0.45, or W/C = 0.45.for 1 bag cement, water is, = 0.45 x 1.25 (as we know, 1 bag cement equal to 1.25 cft),Water = 0.5625 cft.We know 1 cubic feet water is equal to 28.31685 litre,So we can write, water = 0.5625 x 28.31685 = 15.92 litre, say, 16 litre.So One bag cement needs 16 liter of water for 0.45 W/C ratio.That's it.

Here, one thing should be cleared that someone assume the dry volume of concrete is equal to one and half times of wet volume. But it is better to use 1.54 for calculating dry volume.

Defects in Brick Work and their Remedies

"sulphate attack on mortars, unsound materials, frost action, corrosion of iron and steel, crystallization of salts, linear changes resulting from variation in moisture content"While doing brickwork and after the brick is completed there are certain defects which has to be faced, these defects they must be avoided and remedial measure must be taken. These defects not only ruins the physical quality andaestheticsof the project but also ruins its structuralstrength. So to avoid any mishap and loss we must know what are certain defects in brick work and how to avoid them.

Common defects occurring in Brick work are; sulphate attack on mortars, unsound materials, frost action, corrosion of iron and steel, crystallization of salts, linear changes resulting from variation in moisture content.

Sulphate attack on mortarsSulphate attack leads to expansion of mortar, thereby causing cracking of brickwork, spalling of brick edges, deterioration of mortar, wide horizontal and vertical cracks in the plaster and falling of the plastered surface.

The cause of this attack is the chemical action between the sulphate salts in bricks and constituents of Portland cement.

Sulphate Attack on Bricks

This action is rapid in the presence of water and hence wherever moisture penetrates, excessive dampness occurs. This type of defect may be prevented by preventing moisture penetration. It will avoid the defect to a large extent. Bricks of low sulphate content and the sulphate resisting cement should be used.

Unsound MaterialsUnsound materials cause the formation of small pits at the mortar joints. General expansion and cracking of brick work is visible. Unsoundness in lime is caused by the presence of un-slaked particles of lime. Similarly un-slaked lime particles may be present in the bricks also.

Unsound Material

Frost actionDefects due to frost action would cause cracking in brickwork. Prevention of water accumulation would prevent this defect.Corrosion of MetalsBrickwork may get opened or cracked or stained due to corrosion of metals lying adjacent to it. Unprotected iron and steel are liable to get corroded when acted upon by moisture and they increase in bulk, thereby causing cracks in masonry.

Corrosion of Bricks due to Metals

Protecting the metal surface with cement mortar up to a layer of 1 to 2 cm thick is essential to prevent corrosion. Partially embedded steel or iron members should be surrounded with bituminous compound for portions not embedded in mortar.

Metal Corrosion

Crystallization of Salt and EfflorescenceThis is a prominent defect in brick masonry. In moist climate, in damp places, like basements or under leaky gutter, masonry often gets disfigured by the formation of a white deposit called efflorescence. Deposit originates from the mortar and frequently spreads over a part or entire face of the wall.

Efflorescence

Absorbed water dissolves the salts of sodium, potassium and evaporating, forms a crystalline deposit on the surface. In addition to unsightly appearance, the crystallization of salts in the pores of the bricks or mortar may cause disruptive expansion resulting in disintegration due to cracking.To avoid Efflorescence do not use porous bricks in contact with limestone. Protect brickwork against contamination of salt-bearing materials during building operations. Bricks should be thoroughly soaked during construction. Correct design of DPC should be used.Shrinkage EffectsBrick work may crack due to the shrinkage movements arising from changes in moisture content. This defect is more common with concrete and lime mortars.

Shrinkage Effects

10+ FIELD TIPS FOR INSPECTION OF REBARS OR REINFORCEMENT

Good quality bricks should be used in dry condition. All of work should be protected from rain.

In construction of a mega project there is always insightful sort of technicalities involved which has to be checked / identified technically. The process demands a sound technical engineering judgment and careful observation. Reinforced Cement Concrete, despite of other important checks, needs to be checked for rebar against the provided construction drawings / shop drawings or technical specifications.It must be kept in mind that the difficulty and cost involved in this activity makes it vulnerable for shortcomings from the contractors end and it needs to be rectified / adjusted by a sound consulting firm deputing on the inspection of execution.

Inspection of Steel Rebar

No doubt it needs experience and also needs know-how of the steel rebar binding process. But here are some of the tips from top peers who are doing this in the field for years :-a.Start from the drawings, one must be well aware of how to read a rebar drawing. As drawings is a language for engineers one must know how to communicate with it in the field. Make a habit of reading drawings that will be your first step towards a successful rebar checker.b.Always keep a measuring tape with yourself that will help you in checking the spacing as well as the splice length or development length.c.Always wear plastic gloves while inspection because holding steel with naked hands will damage the skin of yours badly.d.You must be well aware of the physical features of the construction component i.e. if some sort of drainage pipe or electrical conduit is to be installed or water stopper to be placed or any other pipes / embedded item to be placed.e.Some important things one must check are the rebar diameter You can use vernier caliper for this purpose, rebar spacing, rebar development length, lap / splice length, alignment or rebar there must be no sag or buckling in the bars, couplers if any must be properly fixed tightened, bars must be properly fixed, bars must not be rusted, clear cover is one very important factor to be checked, no of bars must be counted and must be equal to given in drawings and must not be less or more than 2 bars be placed there.f.If you are a new comer try to establish a conversation between contractors foreman or site engineer because they will know how these bars are placed but never every show to them that you dont know much and are here to learn things.g.You must be well aware of the steel quality tests like tensile strength check or torsion failure strength or coupler tension strength check etc. You must ensure that the steel being used is from the checked lot and must not be of a failed quality.h.No doubt in field a true implementation of the design is very difficult due to harsh field conditions and difficultly in installation / fixing of rebars but never ever compromise with the design as it is a driving factor that can even results in collapse of a building if completely ignored / violated.i.One very important factor is the orientation of bars like main rebars are always below the distribution or temperature rebars you can check this from the drawings provided to you.

So we can say that in a nutshell one must be very keen observer and should be well conversant with the design methodology and sound technical knowledge.

Checking of rebars is not difficult neither never testing process so dont get confused or get upset with your duty enjoy the work and let the structure have its strength as it is designed.

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