Cracking in Walls Causes And Remedy

There are cracks in all structures, some minor and immaterial, whereas there are some requiring costly repairs and in some extraordinary cases, the one and the only solution is the complete demolition of the structure.

This article is expected to place cracks into setting:  clearly, one of the real worries of house purchasers, “How big of a problem cracks are” is a question I am regularly inquired.

Firstly I think it is essential to comprehend why structures move. The two principle reasons are settlement and subsidence, and these can best be clarified with the pictures shown below.

Settlement happens because of the downward pressure. Subsidence happens because of the elimination of earth underneath the baseline. The settlement is typical without difficulty handled with the help of the cosmetic repair, and where subsidence can show to be difficult and not very economic for repairment.

There is a circumstance in which settlement can lead to subsidence. Drains are attached to a building, and if these sheer or crack because of the settlement the succeeding leakage could lead to subsidence by washing away of the subsoil.

All structures settle when they are built, the thing to do is to keep the resolution to an extremely low level. The other reasons for the movement and cracking are because of the not very satisfactory methodologies of construction, maintenance, and design.

Types of cracks in the wall

In this article we will learn about  with the five most widespread reasons which lead to the cracks:

⧪ Expansion Cracks

Cause

Walls are influenced by a change in temperature and dampness as well.  Materials can experience the ill effects of introductory shrinkage as well as ensuing constriction and development. This kind of development offers ascends to the cracks. The crack appeared in the picture is appeared as vertical, which is frequently the case. Be that as it may, the crack often follows the line of weakest resistance and may end up stepped.

The cracks are frequently observed above window and entryway openings where the opening itself soothes the crack. This sort of crack has a steady width and it is this that recognizes from other more genuine cracks.

Repair

When left to its own devices, the crack does not pose great significance, however, it can let water into the cavity in houses mainly built with bricks, and subsequence leads to the weakening of the wall ties. For that reason, filling that crack with mastic or elastic compound is very essential. On the other hand, for more rigorous cracking, it is sensible to create an expansion joint. The expansion joint would be cut into the wall, filled with a compactable substance with a water-resistant stopper to the exterior. On many modern structures, these are created at the phase of construction stage and then camouflaged behind rainwater downpipes.

⧪ Cracks in openings

Absence of lintels

Cause

In some structures, due to poor decision of the builders there are the absence of lintels and rely on the timber frame of the window to uphold the masonry above, but when the windows are substituted cracks appear.

Repair

The cracks should be repaired and new lintels should be kept.

⧪ Insufficient bearings

Cause

The accurate overhang (bearing) of the lintels ahead of the openings is 150mm (6 inches) on each side. In cases where the bearings are inadequate, the lintels will drop and the cracks will begin to show. On the other hand, on some older structures, massive stone lintels with only 50mm (2 inches) bearings.

Repair

Changing the lintel is suggested. On the other hand, once again repainting will be enough until the window or door is substituted.

⧪ Loads applied directly over the opening

Cause

This usually happens right above first-floor lintels where the roof have been put right above of the window openings. The load forced is very high for the lintel to manage with and the downward pressure leads to cracking

Repair

In this case, as well replacement of the lintel is suggested. The rigorousness and age of these cracks would determine whether mere repainting would be enough until the window is changed.

⧪ Elimination of doors and windows without ample propping

Cause

The most dominant reason for this kind of cracking is the exclusion of on-hand window frames to install the PVCu. In many cases, we have witnessed the absolute collapse of the brickwork above the bay windows.

Repair

The most suitable repair for this method is to reset the whole lintel and build the brickwork above again and refit the window.

⧪ Wall Tie Failure

Causes

Wall ties refer to the metal ties that are constructed into both solid and cavity walls built in stretcher bond to keep hold of the exterior of the brickwork internally. Breakdown usually happens when rusting occurs in ties. When the metal ties experience rusting they increase leading to the cracking usually seen every sixth course parallel to the mortar joints.

Repairs

Replacing the wall ties is very essential. Cracking is the early symptom of a breakdown. When replacement is not done, there are good chances for the wall to collapse. Removing the existing ties are suggested.

⧪ Subsidence

Cause

• Clay subsoil
• Peak subsoil
• Tree root activity
• Mining activity
• Underground drainage leakage

Repair

It usually needs some kind of underpinning. But, advice from the specialist like the structural engineer will be needed.

⧪ Ground Heave

Cause

The pattern of this cause is similar to that of subsidence crack. But, the crack will be the widest at the foundation of the wall. The most dominant cause is the amplification the clay subsoils.

Repair

In rare cases, underpinning the deeper foundation is the only remedy. For most cases, the ideal solution will be to eliminate the clay from baseline as early as possible and substitute it with hardcore.

Do You Know About Brinell Hardness Test?

Objective: To assess the Brinell Hardness number HB of the specified sample

Tool and Equipment

Brinell hardness tester RAB-250, Brinell microscope and indentors (2.5mm and 5mm ball)

Description of Machine

The Brinell Hardness Tester comprises of a loading system, a chief screw and additionally a dial gauge. The loading system which comprises various factors such as weights, leavers and also a hydraulic dashpot and a plunger arrangement is bounded in the cast iron body of the equipment. The chief screw is additionally sheltered from various hindering elements with the help of a rubber bellow. It transmits the test table on its topmost to support the sample and is activated by a pointer at the foundation, the equipment is specifically given with multiple ball indenters (of sizes 2.5mm&5mm) to convey the test load on to the chosen sample.

Theory and Principle

The test experimentation comprises of forcing a steel ball of diameter D beneath a load P into the sample for a given period of time and computing the mean diameter’ of the impression left on the surface after the process of elimination of the load. The Brinell Hardness Number (BHN) is then computed as load (in kg-f) dropped by the surface area of indention (in mm2)

The depth of Indentation (h) is shown by,

Thus,

Where,

D = Diameter of the wall in mm

-P = Applied load in kg-f, and

d = Diameter of indentation in mm.

The test load P, to be exerted is based on the diameter D of the indenter and the substance of the sample. For reference, a table might be utilized which will be helpful. The test surface has to be machined smooth, horizontal and even. The density of the sample should be minimum eight times the depth of indentation.

Procedure

Set up the equipment to the mandatory point of test load. Choose the intention to be utilized and clasp it to the equipment. Position the sample on the test table and, exert a minor load of approximately 10-kg-f on it by rotating the hand wheel and bringing all pointers on the dial gauge to the ‘set’ spots. Exert the major load (the residual portion of the experimentation load) on the sample by turning the loading lever in the reverse position. Sustain the load on the sample precisely for the given dwell time (15 seconds) and then suspended it by turning the loading lever onwards. Detach the sample and compute the diameter of the dent created on it by utilizing the Brinell Microscope.

Observation and calculation

The observations taken at the time of test are logged in table -2. Calculation for trial-1 of steel sample is given below.

Result

Brinell hardness of given steel sample is H B / 2.5 / 187.5/ = ———-

Brinell hardness of given brass sample is HB / 2.5 / 187.5/= ————

Questions

1. Name the type of hardness tests you have the dome in the laboratory.

2. Explain the process of how is load applied to the sample in the Brinell hardness test.

3. State time of application of load in the Brinell hardness test.

4. State the load to be utilized in the Brinell hardness test for (1) brass (2) Cropper (3) aluminum and (40 mild steel.

5. State the minimum thickness necessary for the sample to be utilized for Brinell hardness test.

6. What type of intended is us‘’60 in the Brinell hardness test?

7. State the least count of the scale in the Brinell microscope.

Common Bridge Terminologies Or Bridge Structure Terms Used In General

⧪ Abutment

A retaining wall supporting the ends of a bridge, and, in general, retaining or supporting the approach embankment.

⧪ Approach
The part of the bridge that carries traffic from the land to the main parts of the bridge.

⧪ Approach Span
The span or spans connecting the abutment with the main span or spans.

⧪ Backwater

The increase in the upstream water elevation resulting from an obstruction to flow, such as a bridge and/or embankment placed in the floodplain.

⧪ Barrier Rail
A low, reinforced concrete wall along edges of a bridge to prevent vehicles from going over the sides. The railing may or may not adopt some form of safety shape.

⧪ Beam
A horizontal structural member supporting vertical loads by spanning from one support to another. A box beam is a hollow box; its cross-section is a rectangle or square.

⧪ Bearing
A device at the ends of beams that is placed on top of a pier or abutment. The ends of the beam rest on the bearing, which is an element that provides the interface between the superstructure and the substructure. The bearing transmits the load from the superstructure to the substructure as well as allows for thermal movements and rotations due to traffic.

⧪ Bearing Pile
A member constructed of steel and/or concrete is driven into the ground to carry axial loads. A member of the Substructure.

⧪ Bedrock

The solid rock layer beneath sand or silt.

⧪ Bent
A type of pier comprised of multiple columns. A rigid frame commonly made of reinforced concrete or steel that supports a vertical load and is placed transverse to the length of a structure. Bents are commonly used to support beams and girders. An end bent is the supporting frame forming part of an abutment.

The vertical members of a bent are columns or piles. The horizontal member resting on top of the columns is a bent cap. The columns stand on top of some type of foundation, either a footing or a drilled shaft, that is usually hidden below grade.

⧪ Bent Cap
A horizontal substructure element that receives the load from the superstructure and transfers the load to columns or piles.

⧪ Condition Ratings
According to the National Bridge Inspection Standards (NBIS), condition ratings are used to describe an existing bridge or culvert compared with its condition if it were new.  The ratings are based on the materials, the physical condition of the deck (riding surface), the superstructure (supports immediately beneath the driving surface), and the substructures (foundation and supporting posts and piers). General condition ratings range from 0 (failed condition) to 9 (excellent).

Through periodic safety inspections, data is collected on the condition of the primary components of a structure. Condition ratings, based on a scale of 0-9, are collected for the following components of a bridge. A condition rating of 4 or less on one of the following item classifies a bridge as structurally deficient.

• The bridge deck, including the wearing surface
• The superstructure, including all primary load-carrying members and connections
• The substructure, considering the abutments and all piers

The lower of the three ratings is the overall rating of the bridge:

9 – Excellent 4 – Poor

8 – Very Good 3 – Serious

7 – Good 2 – Critical

6 – Satisfactory 1 – Imminent Failure

5 – Fair 0 – Failed

⧪ Camber
A positive, upward deformation built into a beam due to the application of prestressing forces.

⧪ Cast-in-Place
Concrete poured within formwork on site to create a structural element in its final position. On Safe & Sound bridges, the most likely elements to be cast-in-place include bent, bent cap, abutment, wing wall and in some cases deck.

⧪ Crashworthy
A system that has been crashing tested to establish that its structural and geometric performance is of/at an established level.

⧪ Culvert
A drain, pipe or conduit that allows water to pass under a road or railroad embankment.

⧪ Deck
The component of a bridge which is driven upon, including shoulders. Some Safe & Sound decks are asphalt while others are constructed of reinforced concrete slabs. Average Daily Traffic determines which surface is used.

⧪ Diversion Channel
A bypass created to divert water around a structure so that construction can take place.

⧪ Drilled Shaft
The “legs” of the bridge that support the piers and pile cap or footing located underneath the water or ground line; a deep foundation unit embedded in the ground by placing fresh concrete in a drilled hole with steel reinforcement. Drilled shafts derive their capacity from the surrounding soil and/or rock. Sometimes referred to as caissons, bored piles or drilled piers.

⧪ Embankment

A raised area of fill used in roadway approaches. In some cases, retaining walls are used to support or “hold in” the fill area where other constraints exist adjacent to the approaches.

⧪ End Treatment
The approach end of a parapet or railing that may or may not have a crashworthy configuration depending on approach speeds, geometry and traffic characteristics.

⧪ Fill
Earth, stone or other material used to raise the ground level, form an embankment or fill the inside of an abutment, pier or closed spandrel.

⧪ Flood Frequency

The concept of the probable frequency of a given flood. More precisely it is the inverse of the probability that a flood will be exceeded at least once in a given year.

⧪ Footing
The enlarged lower portion of the substructure or foundation that transfers load from a column directly to the soil, bedrock or piles; usually below grade and not visible.

⧪ Freeboard

The clearance between the bottom of the superstructure and the design high-water elevation.

⧪ Functionally Obsolete
A functionally obsolete bridge is one that was built to standards that are not used today. These bridges are not automatically rated as structurally deficient, nor are they inherently unsafe. Functionally obsolete bridges are those that do not have adequate lane widths, shoulder widths, or vertical clearances to serve current traffic demand, or those that may be occasionally flooded.

A functionally obsolete bridge is similar to an older house. A house built in 1950 might be perfectly acceptable to live in, but it does not meet all of today’s building codes. Yet, when it comes time to consider upgrading that house or making improvements, the owner must look at ways to bring the structure up to current standards.

⧪ Headwall
The device placed at the end of a bridge that comprises a large portion of the abutment.  Headwalls are used to retain the road formation soil around and above the abutments and prevent erosion at the abutment.

⧪ Parapet
A railing system made of reinforced concrete along the outside edge of a bridge deck used to protect vehicles and pedestrians.

⧪ Pier
Also called bent. Typically bents with one column are called piers.

⧪ Pile
A long column is driven deep into the ground to form part of a foundation or substructure. (See Bearing Pile).

⧪ Post-tensioning

Application of tensile forces to the steel tendons after the segments are in place. These forces allow the span to carry the desired loads.

⧪ Pre-Cast Girder
Girder is fabricated off-site of Portland cement using reinforcing steel and post-tensioning cables.  These girders are shipped to the construction site by truck and hoisted into place by cranes.

⧪ Prestressed Concrete
A type of pre-cast concrete girder in which compressive stresses are introduced by the application of prestressing forces in a fabrication facility. The prestressing tendons are stretched, the concrete cast and set around them and then released from the form. These forces allow the member to carry larger loads than conventional reinforcement.

⧪ Reinforced Concrete
Concrete with steel bars or mesh embedded in it for increased strength and durability.

⧪ Revetment

A facing of masonry or stones to protect an embankment from erosion.

⧪ Rip Rap 
Gabions, stones, blocks of concrete or other protective covering material of like nature deposited upon the river and stream beds and banks, to prevent erosion and scour by water flow.

⧪ Scour
Removal of material from the streambed or embankment as a result of the erosive action of stream flow.

⧪ Simple Span
A span in which the effective length is the same as the length of the spanning structure. The spanning superstructure extends from one vertical support, abutment or pier to another without crossing over an intermediate support or creating a cantilever.

⧪ Skew
When the superstructure is not perpendicular to the substructure, a skew angle is created. The skew angle is the angle between the alignment of the superstructure and the alignment of the substructure.

⧪ Span
The horizontal space between two supports of a structure. Also refers to the structure itself. The clear span is the space between the inside surfaces of piers or other vertical supports. The effective span is the distance between the centers of two supports.

⧪ Structurally Deficient
Bridges are considered structurally deficient if significant load-carrying elements are found to be in poor condition due to deterioration or the adequacy of the waterway opening provided by the bridge is determined to be extremely insufficient to the point of causing intolerable traffic interruptions.

Every bridge constructed goes through a natural deterioration or aging process, although each bridge is unique in the way it ages.

The fact that a bridge is classified under the federal definition as “structurally deficient” does not imply that it is unsafe. 

A structurally deficient bridge, when left open to traffic, typically requires significant maintenance and repair to remain in service and eventual rehabilitation or replacement to address deficiencies. To remain in service, structurally deficient bridges are often posted with weight limits to restrict the gross weight of vehicles using the bridges to less than the maximum weight typically allowed by statute.

⧪ Substructure
The substructure consists of all parts that support the superstructure. The main components are:

• Abutments or end-bents
• Piers or interior bents
• Foundation
• Footings
• Piling

⧪ Superstructure
The component of a bridge which supports the deck or riding surface of the bridge. The superstructure consists of the components that actually span the obstacle the bridge is intended to cross. It includes:

• Bridge deck,
• Structural members
• Parapets, handrails, sidewalk, lighting and drainage features

⧪ Tendon
Steel strands used for post-tensioning.

⧪ Wearing Surface
The topmost layer of material applied to a roadway to receive the traffic loads and to resist the resulting disintegrating action; also known as wearing course.

⧪ Wing Walls
The retaining wall extension of an abutment intended to retain the side slope material of an approach roadway embankment.