a[mm]/l - Memorial University of Newfoundland DAI

pracuce a to use s water-ieducmg admixture (ruperplantctzer) m comb~nal#an wtth a
water-reducing retarder.
The type of rulphonsed naphthalene formaldehyde ruperplwl!clur nonrlly
used reducer the amount of water requnred by 154%. However. usmg thns
ruprplmle~zer aften results !n hxgh rate of slump loss. malung ~r difficult lo place the
concrete properly The hlgh nle of $lump Imt will he overcome hy the add~laon of the
water-reduc8ngretardcr whch exlends the lnme of set and -81s the placement af a very
low waterxemenf ratlo concrete.
The compar~b~ltty of the vdmlnture~ wlrh the chorce of ccrnea 8s u very lmponanl
cans~deratton lo order to reduce any underlrahle effeas 8n concrete. all chemtcal
admlxlures rhould meet the requlrcmsntr of $maon C494 of the ASTM 0997).
rpecrficanonr for chemtcal adm~xtures for concrele. The use of retarder rhould be
confomcd la ~ccuon C494 lyp B and D of the ASTM (1997). whllc the use of
ruperpl=stlc!ur should be conformed lo recnon C494 typ F of !he ASTM i 1997).
2.15. Batehing and Mixing Squcnra
The vncarpoalton of rllica fume and hrgh-nnge water ~duesn makes It porstble to artan
htgh-nrengtk concrete at early ages. The followang batchlng and mixmg procedure has
heen developed by carlia rerearchen an the concrete Isbomoq of the Memonal
Untvcnlry of Newfoundland far Ihe product~on of workable high-strength mar.
(I) Charge 1W% of coarse aggregates.
(2) Batch 103% of cement.
(3) Balch lW%of fly ash.