6.5 Admixtures—Powdered admixtures that are entirely or
largely insoluble, that do not contain hygroscopic salts and are
to be added in small quantities, should be mixed with a portion
of the cement before introduction into the batch in the mixer so
as to ensure thorough distribution throughout the concrete.
Essentially insoluble materials which are used in amounts
exceeding 10 % by mass of cement, such as pozzolans, should
be handled and added to the batch in the same manner as
cement. Powdered admixtures which are largely insoluble but
contain hygroscopic salts may cause balling of cement and
should be mixed with the sand. Water-soluble and liquid
admixtures should be added to the mixer in solution in the
mixing water. The quantity of such solution used shall be
included in the calculation of the water content of the concrete.
Admixtures, incompatible in concentrated form, such as solutions
of calcium chloride and certain air-entraining and setretarding
admixtures, should not be intermixed prior to their
addition to concrete. The time, sequence, and method of adding
some admixtures to a batch of concrete can have important
effects on concrete properties such as time of set and air
content. The method selected must remain unchanged from
batch to batch
6.5 Admixtures—Powdered admixtures that are entirely orlargely insoluble, that do not contain hygroscopic salts and areto be added in small quantities, should be mixed with a portionof the cement before introduction into the batch in the mixer soas to ensure thorough distribution throughout the concrete.Essentially insoluble materials which are used in amountsexceeding 10 % by mass of cement, such as pozzolans, shouldbe handled and added to the batch in the same manner ascement. Powdered admixtures which are largely insoluble butcontain hygroscopic salts may cause balling of cement andshould be mixed with the sand. Water-soluble and liquidadmixtures should be added to the mixer in solution in themixing water. The quantity of such solution used shall beincluded in the calculation of the water content of the concrete.Admixtures, incompatible in concentrated form, such as solutionsof calcium chloride and certain air-entraining and setretardingadmixtures, should not be intermixed prior to theiraddition to concrete. The time, sequence, and method of addingsome admixtures to a batch of concrete can have importanteffects on concrete properties such as time of set and aircontent. The method selected must remain unchanged frombatch to batch
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