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". Due to moisture changes.

The formation of crack" in ma"onr# epen " upon the t#pe" of material u"e in ma"onr# an "trength of mortar%Similarl# In ca"e of concrete! "hrinkage re"ult" ecrea"ing thevolume an if the component i" re"traine again"t freemovement "tre""e" are evelope which ma# cau"e crack"%

#. Due to e!!ect o! chemical reaction.

The carbon io,i e an "ulphate" pre"ent in air or "oil whichma# re"ult in increa"e the volume lea ing to the formation of crack"%

$. Due to elastic de!ormation.

The ifferent component" of buil ing like wall! column! beam etc% un ergo ela"tic eformation when loa e % The magnitu e of "uch eformation epen " upon materialu"e in con"truction! "pan" of the "tructural member an theloa ing con ition%

%. Due to tem&erature ariation

In ca"e of roof "lab "upporte on loa bearing wall"! crack" areoccure" ue to temperature variation% The "lab being e,po"eto the "un! i" "ub.ecte to alternate e,pan"ion an contraction

ue to thi" movement of "lab ma# re"ult in pu"hing thema"onr# an "o eveloping crack" in "upporting wall%

' . Due to egetation

The effect of vegetation near the buil ing become" moreamaging when "oil at "ite i" "hrinkable t#pe%

The root" of growing tree" cau"e" r#ing an "hrinkage of the"ub&"oil an thi" can re"ult in une+ual "ettlement of foun ationlea ing to crack"%

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()*ES OF CRACKS

There are variou" t#pe" of crack" are a" follow"'1. 6ori7ontal crack 1% 8ertical crack

3. Diagonal crack 3% Ran om crack

RE*A+R OF CRACKS

Crack" are mo"t angerou" to the "tructure "o it i" alwa#"repaire to maintain the "trength of "tructure% There are both"mall an large crack" are pre"ent in "tructure% Small crack"are repaire with filling pa"te of cement mi,% 9arge crack" canal"o be repaire b# variou" metho "! which are a" follow"'

1. E&o,- in ection:

Crack" a" narrow a" :%::1 in% ):%:4 mm* can be bon e b# thein.ection of epo,#% The techni+ue generall# con"i"t" ofe"tabli"hing entr# an venting port" at clo"e interval" along thecrack"! "ealing the crack on e,po"e "urface"! an in.ectingthe epo,# un er pre""ure% Epo,# in.ection ha" been"ucce""full# u"e in the repair of crack" in buil ing"! bri ge"!

am"! an other t#pe" of concrete "tructure"Clean the cracks ' The fir"t "tep i" to clean the crack" thathave been contaminate ; to the e,tent thi" i" po""ible an

practical% Contaminant" "uch a" oil! grea"e! irt! or fine

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particle" of concrete prevent epo,# penetration an bon ing!an re uce the effectivene"" of repair"%Seal the sur!aces: Surface crack" "houl be "eale to keep theepo,# from leaking out before it ha" gelle %

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pre""ure tight connection with the in.ection apparatu"*; "ealingthe crack between the "eat" with a cement paint! "ealant! orgrout; flu"hing the crack to clean it an te"t the "eal; an thengrouting the whole area% >rout mi,ture" ma# contain cementan water or cement plu" "an an water! epen ing on thewi th of the crack%

%. Dr- &acking

Dr# packing i" the han placement of a low water contentmortar followe b# tamping or ramming of the mortar into

place! pro ucing intimate contact between the mortar an thee,i"ting concrete% ?ecau"e of the low water&cement ratio ofthe material! there i" little "hrinkage! an the patch remain"tight an can have goo +ualit# with re"pect to urabilit#!"trength! an water tightne""%

Conclu"ion'Crack" are the efect" which are mo"t harmful to the

"tructure an it i" ver# angerou" to the "tructure "o! it "houl be repaire % Thi" repair can al"o pla#" an important role for the"afet# of the "tructure%