Study on control of cracks in a Structure through Visual Identification & Inspection

Study on control of cracks in a Structure through Visual Identification & Inspection

Abstract:

Structural Cracks are a common occurrence in all types of buildings. To ensure the longevity of the structure, engineers are often required to look into their causes and carry out suitable repairs and remedial measures. For repairs and remedies to be effective, it is essential that the engineer should have a proper understanding of various causes of occurrence of cracks. For investigating the causes it is necessary to observe carefully the location, shape, size, depth, behavior and other characteristics of the cracks, and to collect information about specifications of the job and time of construction. It is also necessary for the engineer to keep track of when the cracks first came to notice. This paper talks about how visual inspection of cracks can be helpful in order to identify and categorize them with respect to various parameters by taking case study of an institutional building.

Keywords:

1. Cracks, 
2. Shrinkage,
3. Structural Failure,
4. Stresses and 
5. Grouting.                                                                                                             INTRODUCTION AND BACKGROUND STUDY                                                            Cracks in buildings are of common occurrence. A building component develops cracks whenever stress in the component exceeds its strength. Stress in a building component could be caused by externally applied forces, such as dead, live, wind or seismic loads, or foundation settlement or it could be induced internally due to thermal variations, moisture changes, chemical action, etc. Cracks could be broadly classified as Structural and Non-Structural. Structural cracks which are due to incorrect design, faulty construction or overloading and Non-structural cracks are mostly due to internally induced stresses in building materials and these generally do not directly result in structural weakening. These are due to penetration of moisture or thermal variation. Cracks may appreciably vary in width from very thin hair cracks barely visible to naked eye (about 0.01 mm in width) to gaping cracks 5 mm or more in width. A commonly known classification of cracks, based on their width is:
   (a) Thin — less than 1 mm in width,
   (b) Medium — 1 to 2 mm in width, and
   (c) Wide — more than 2 mm in width.

   Cracks may be of uniform width throughout or may be narrow at one end, gradually widening at the other. Cracks may be straight, toothed, stepped, map pattern or random and may be vertical, horizontal or diagonal.Cracks may be only at the surface or may extend to more than one layer of materials.                                                                                                                                                                   Author Information:                                                                                               Kishor Kunal, Namesh Killemsetty                                                                      Department of Civil Engineering, O.P. Jindal Institute of Technology ,India     IOSR Journal of Mechanical and Civil Engineering                                      (IOSR-JMCE) e-ISSN: 2278-1684,p-ISSN: 2320-334X,                                Volume 11, Issue 5 Ver. VI (Sep-Oct. 2014), PP 64-72                                                 www.iosrjournals.org                                                                   

Masonry Cracks: A Review of the Literature

                 Masonry Cracks: A Review of the Literature 

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Source: STP27272S

Abstract

Masonry surface cracks are objectionable because they are the primary source of water permeance and may be aesthetically displeasing or indicative of structural distress. Cracks are the most frequent cause for masonry's failure to perform as intended. The types, locations, patterns, sizes, and causes of cracks are discussed. Methods are described for their prevention and repair.

Keywords:

1. block (concrete), 
2. bricks, corrosion,
3.  cracks, 
4. expansion, 
5.  failure, 
6. inspection,
7.  masonry, 
8. motar, movement (structural)
9.  repair,
10.  sealants, 
11. shrinkage and 
12.  strain

Author Information:

Grimm, CT
Consulting architectural engineer and senior lecturer in architectural engineering, University of Texas at Austin, Austin, TX

Committee/Subcommittee: C15.04
DOI: 10.1520/STP27272S

Self-consolidating concrete or self-compacting concrete

Self-consolidating concrete or self-compacting concrete (commonly abbreviated to SCC)[1] may be a concrete combine that contains a low yield stress, high deformability, smart segregation resistance (prevents separation of particles within the mix), and moderate viscousness (necessary to make sure uniform suspension of solid particles throughout transportation, placement (without external compaction), and thenceforth till the concrete sets).

In everyday terms, once poured, SCC is a particularly|an especially} fluid combine with the subsequent distinctive sensible options - it flows very simply at intervals and round the formwork, will flow through obstructions and around corners ("passing ability"), is near self-levelling (although not truly self-levelling), doesn't need vibration or tamping when gushing, and follows the form and surface texture of a mould (or form) terribly closely once set. As a result, gushing SCC is additionally a lot of less effortful compared to plain concrete mixes. Once poured, SCC is typically just like customary concrete in terms of its setting and action time (gaining strength), and strength. SCC doesn't use a high proportion of water to become fluid - actually SCC might contain less water than customary concretes. Instead, SCC gains its fluid properties from a strangely high proportion of fine combination, like sand (typically 50%), combined with superplasticizers (additives that guarantee particles disperse and don't settle within the fluid mix) and viscosity-enhancing admixtures (VEA).

Ordinarily, concrete may be a dense, vicous material once mixed, and once utilized in construction, needs the employment of vibration or alternative techniques (known as compaction[disambiguation needed]) to get rid of air bubbles (cavitation), and honeycomb-like holes, particularly at the surfaces, wherever air has been unfree throughout gushing. this type of air content (unlike that in aerated concrete) isn't desired and weakens the concrete if left. but it's punishing and takes time to get rid of by vibration, and improper or inadequate vibration will result in undetected  issues later. to boot some complicated forms cannot simply be vibrated. Self-consolidating concrete is meant to avoid this downside, and not need compaction, so reducing labor, time, and a doable supply of technical and internal control problems.

SCC was conceptualized in 1986 by academic. Okamura at Ouchi University, Japan, at a time once skilled  labor was in restricted offer, inflicting difficulties in concrete-related industries. the primary generation of SCC utilized in North America was characterised by the employment of comparatively high content of binder additionally as high dosages of chemicals admixtures, typically superplasticizer to reinforce flowability and stability. Such superior concrete had been used principally in repair applications and for casting concrete in restricted areas. the primary generation of SCC was so characterised and nominative for specialised applications.

SCC may be used for casting heavily bolstered sections, places wherever there may be no access to vibrators for compaction and in complicated shapes of formwork which can preferably be not possible to solid, giving a way superior surface than typical concrete. The comparatively high value of fabric utilized in such concrete continues to hinder its widespread use in numerous segments of the development trade, as well as industrial construction, but the productivity political economy take over in achieving favorable performance edges and works intent on be economical in pre-cast trade. The incorporation of powder, as well as supplementary building material materials and filler, will increase the degree of the paste, therefore enhancing deformability, and may conjointly increase the cohesiveness of the paste and stability of the concrete. The reduction in cement content and increase in packing density of materials finer than eighty µm, like ash etc. will cut back the water-cement magnitude relation, and also the high-range water reducer (HRWR) demand. The reduction in free water will cut back the concentration of viscosity-enhancing admixture (VEA) necessary to make sure correct stability throughout casting and thenceforth till the onset of hardening. it's been incontestable  that a complete fine combination content ("fines", typically sand) of regarding five hundredth of total combination is suitable in AN SCC combine.

Contents

  

• 1Overview
• 2References
• 3See also
• 
  
  Overview
  • SCC is measured using the slump-flow test (or "flow table") rather than the usual slump test, as it is too fluid to keep its shape when the cone is removed. A typical SCC mix will have slump-flow of around 500 - 700mm.
  • SCC is weakened, not strengthened, by vibration. As vibration is not needed for compacting the mix, all that it achieves is to separate and segregate it,

  References

  1. Jump up^ selfconsolidatingconcrete.org National Ready Mixed Concrete Association

  See also

  • Concrete slump test
  • Flow table test

  
  

  
  
  
  
  
  
  
  

Hoe to find out number of bricks

Calculating bricks and blocks

One facet of masonry which frequently causes confusion is estimating what percentage bricks or blocks are needed for a planned wall - you do not need to run out before you end however you furthermore may don't need a pallet load of fabric left unused once you have finished. creating these estimates is fairly easy mistreatment simply some figures.

First the amount of bricks/blocks for the full wall is calculated, then the extra variety of bricks for any piers. These ar other along so a tenth allowance ought to be other for wastage and breakages - the figures below don't embrace this allowance.

Calculating the amount of bricks

Standard, UK, metric bricks square measure roughly 215 x 102.5 x 65mm, the mortar joints used square measure commonly concerning 10mm each horizontally and vertically.

Half brick wall

A half brick wide wall requires 60 bricks per square metre.

So the first stage is just to measure the height and length (including any piers) of the wall in metres, multiply them together to give the area in square metres, and then multiply this by 60.

So the total number of bricks for the wall is:

wall height (metres) x wall length (metres) x 60 = number of bricks

                                                                       
                                                                 
                                                                                                         

One brick wall

A one brick wide wall requires 120 bricks per square metre.

So the first stage is just to measure the height and length of the wall in metres, multiply them together to give the area in square metres, and then multiply this by 120.

So the total number of bricks for the wall is:

wall height (metres) x wall length (metres) x 120 = number of bricks

Single brick piers in half brick walls

Where single brick piers are built into a half brick wall, each pier requires an additional 14 bricks per vertical metre.

So the total number of bricks for the piers is:

number of piers x wall height (metres) x 14 = number of bricks

One and a half brick piers in a half brick wall

Where one and a half brick piers are built into a half brick wall, each pier requires an additional 34 bricks per vertical metre.

So the total number of bricks for the piers is:

number of piers x wall height (metres) x 34 = number of bricks

Calculating the number of blocks

Standard, UK, metric blocks are roughly 450 x 215 x 100mm (some are thicker but this will not effect the number of blocks required per square metre of wall), the mortar joints used are normally about 10mm both horizontally and vertically.

A single block wall requires 10 blocks per square metre.

So the total number of blocks for the wall is:

wall height (metres) x wall length (metres) x 10 = number of blocks