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8/19/2019 Shotcrete Presentation
1/21
SHOTCRETING
K.V.SUBBA RAO
8/19/2019 Shotcrete Presentation
2/21
Shotcreting
• Shotcreting is a method in concrete or! in hich the
concrete mi" is a##$ied in $a%ers &nder the #ress&re o'com#ressed air
• . Shotcreting is done ith a s#ecia$ &nit( hich consists
o' a mortar g&n or concrete s#ra%er and a com#ressor
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Shotcreting
• A dr% mi" o' cement and aggregate( &s&a$$% sand( is
#re#ared 'or shotcreting.• The com#ressed air 'orces the mi" thro&gh a hose to the
no))$e( moistens it ith ater s#$ied thro&gh another
hose( and then #ro*ects it at high +e$ocit% ,-/0-1/
m2sec3 onto the s&r'ace 4eing shotcreted.
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Shotcreting
• A sing$e shotcrete $a%er is -/0-5 mm thic! and has highmechanica$ strength ,6/01/ meganetons #er s7 m3(densit%( ater tightness( and co$d resistance
• Shotcreting is &sed in 4&i$ding thin8a$$ed rein'orced8concrete str&ct&ra$ com#onents( s&ch as she$$s( +a&$ts(and tan!s( and in #rod&cing the $ining in t&nne$s. It is
a$so &sed 'or h%dra&$ic ins&$ation( 'or 'inishing the *ointso' rein'orced8concrete str&ct&ra$ com#onents( and 'orre#air and strengthening o' concrete and rein'orced8concrete com#onents.
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Shotcreting
• The shotcrete is #$aced $a%er84%8$a%er
• 9or shotcrete #$acing s#ecia$ e7&i#ment are &sed( here4% means o' :dr%: techno$og% the mi"t&re o' cement(
sand and meta$ 4atched in s#eci'ied #ro#ortions is
s7&ee)ed o&t ith #ress&re air 4% means o' '$e"i4$e hose
to the no))$e atomi)er( here the mi"t&re is moist&ri)ed
ith ater. ;hen the :et: techno$og% is &sed( #re#ared
concrete is de$i+ered to the machines
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Shotcreting
• Shotcreting has high strength #ro#erties< resistance o' its
e"tension is -/ #er cent more in com#arison ith
standard concrete. The co+er o' high strength( densit%
and ater#roo'ing ca#acit% is 'ormed 4eca&se o' im#act
$a%ing
• Shotcrete a##$ication a$$os decreasing 'ace thic!ness
and o&t8t&rns< e"c$&ding the necessit% o' 'ormor! and
mechani)ing the concrete or! #rocess tota$$%.
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=ateria$s 'or shotcreting
• Cement
• Sand
• Coarse Aggregates• ;ater
• Chemica$ additi+es
• Com#ressed Air
8/19/2019 Shotcrete Presentation
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=ateria$s 'or shotcreting
• Chemica$ admi"t&res are added 'or acce$eration o'setting and hardening.
• Sodi&m Car4onate > ? Kg #er 5/ Kg 4ag o' cement
• @Sodi&m A$&minate > ? Kg #er 5/ Kg 4ag o' cement
• @Ca$ci&m Car4onate > - Kg #er 5/ Kg 4ag o' cement
• A$ternati+e$%( 'o$$oing additi+es can a$so 4e &sed
• @Ser #$astici)er - 4% eight o' cement
• @ Acce$erator ,sa% sodi&m Si$icate3 5 4% eight o'cement
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Dre#aration o' S&r'ace
• The 'o$$oing #reca&tions are necessar% in #re#aration
o' the s&r'ace 4e'ore the shotcrete is a##$ied
• The s&r'ace sho&$d 4e 'ree 'rom $ose materia$s. It sho&$d4e c$ean to recei+e the shotcrete $a%ers.
• In case the s&r'ace is smooth it sho&$d 4e ro&ghened
ith sand 4$asting. Otherise the s&r'ace co&$d 4e
c$eaned ith air ater *et..
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Dre#aration o' S&r'ace
• The thic!ness o' the shotcrete $a%er 4eing on$% 1 mm
an% &nd&$ations in the s&r'ace more than s&ch thic!nessi$$ ha+e to 4e 4ac!'i$$ed ith either masonr% or $ean
concrete de#ending on the site conditions and
s#eci'ications #rescri4ed.
8/19/2019 Shotcrete Presentation
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=i" o' shotcrete
• Cement 65/ !g 2 m
• Sand --// !g 2 m ,/.1/ m3• Coarse aggregate
• ,5 mm 0 -/ mm si)e3 5// Kg2= ,/./ =3
• Dro#ortion 4% eight -F.66-.--
8/19/2019 Shotcrete Presentation
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A##$ication =ethodo$og%
• S#ra% #ne&matica$$% the 'irst $a%er o' shotcrete o' mmthic!ness
• ;e$ded ire mesh o' -// mm " -// mm " 5 mm isnai$ed ith the he$# o' nai$s. Binding ire is &sed to !ee#the mesh in #$ace.
• The second and 'ina$ $a%er o' mm o' shotcrete is
s#ra%ed #ne&matica$$% o+er the 'irst $a%er.
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Dreca&tions to 4e ta!en
• The 'inished shotcrete $a%er is to 4e !e#t etcontin&o&s$% 'or at $east a ee! a'ter com#$etion.
• There o&$d 4e re4o&nd d&ring the o#erations hichsha$$ not 4e &sed 'or shotcrete.
• The time $ag 4eteen the 'irst $a%er and the second $a%eris to 4e !e#t as minim&m as #ossi4$e.8sa% $ess than
ho&rs.
8/19/2019 Shotcrete Presentation
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Dreca&tions to 4e ta!en
• A'ter com#$eting the shotcrete and a'ter the mi" is set(
the s&r'ace sho&$d 4e thoro&gh$% so&nded 4% a hammer
'or dr&mming areas res&$ting 'rom re4o&nd #oc!ets or
$ac! o' 4ond etc.( hich sho&$d 4e c&t o&t and re#$aced
ith 'resh shotcrete.
• ;here dr% #rocess is ado#ted the *etting o' ater sho&$d
4e s%nchroni)ed ith that o' the concrete mi" 'or a
homogeneo&s shotcrete.
• ;here et mi" is ado#ted the s#eci'ied ater cement
ratio is to 4e strict$% en'orced.
8/19/2019 Shotcrete Presentation
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Shotcreting
8/19/2019 Shotcrete Presentation
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NSRC
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Than! o&