TM 5-822-7/AFM 88-6, Chap. 8
procedures and properties are mainly due to the
the No. 200 sieve than conventional concrete aggregates
relatively dry consistency of the fresh RCC and the
and, as a result, may produce a "tighter" pavement
selected use of nonconventionally graded aggre-
surface texture. Because these aggregates range in
gates. The primary differences in the properties of
size from 3/4 inch to the No. 200 sieve, control of the
RCC are (1) RCC generally is not air entrained, (2)
grading may be more difficult due to segregation.
RCC has a lower water content, (3) RCC has a lower
Therefore, careful attention must be directed toward
paste content, and (4) RCC generally requires a
stockpile formation and subsequent handling of a
higher fine aggregate content to limit segregation. A
single size group aggregate.
number of methods have been used to proportion
e. Cement. Any available portland cement except
RCC including those found in ACI 211.3, ACI 207.5R,
for Type III portland cement, any blended hydraulic
and ASTM D 558. The first two of these methods
cement, or combination of portland cement with
follow an approach similar to that used in propor-
pozzolan or blended hydraulic cement with pozzolan
tioning conventional concrete. The third method
should be investigated. If sulfate exposure is a
treats the material as cement stabilized soils rather
problem, either Type II, Type V, or a moderate
than concrete and establishes a relationship between
sulfate-resistant blended hydraulic cement should
moisture and the density obtained from a particular
be used. The use of Type III portland cement will
compactive effort.
almost never be justified or practical for use in RCC
b. ACI 207.5R method. WES has used the method
due to shortened working times with this cement.
described in ACI 207.5R, with some modifications,
f. Admixtures. A proper air-void system must be
on all RCCP mixtures proportioned by WE S to date
provided to prevent frost damage in concrete which
(further information on this procedure may be
freezes when critically saturated. Air-entraining
obtained at WESGP/SC, PO Box 631, Vicksburg,
admixtures have not proven to be effective in
MS 39180). The primary consideration when using
creating such air-void systems in RCC even when
this method is proper selection of the ratio (Pv) of the
added at dosage rates 10 times that of conventional
concrete. Therefore, to compensate for an inadequate
air-free volume of paste (Vp) to the air-free volume
air-void system, RCCP should have a low water-
of mortar (Vm). This selection is based primarily
cement ratio, be fully compacted, and have a well
upon the grading and particle shape of the fine
draining base under the pavement. The low water-
aggregate. The Pv affects both the compactability of
cement ratio and good compaction provide a
the mixture and the resulting surface texture of the
material with a minimum amount of freezable water
pavement. Ratios of 0.36 to 0.41 have been found to
in the capillaries and has low permeability. As long
be satisfactory for mixtures having nominal max-
as the RCCP is not critically saturated, it will not be
imum size aggregate of 3/4 or 1 1/2 inch. The fraction of
damaged by freezing and thawing. Durability for
fine aggregate finer than the No. 200 sieve should be
resistance to freezing and thawing of RCCP is
included in Vp when calculations are made using Pv.
currently being investigated. Neither water-reducing
nor retarding admixtures have been shown to
c. Consistency measurements. Since RCC has no
improve the fresh properties of RCC in limited
slump, an alternative means of measuring mixture
laboratory investigations. If the use of these
consistency must be used. Two consistency measure-
admixtures is proposed, such use should be based on
ment methods have been used to date. One uses the
investigations which show them to produce benefits
Vebe apparatus as described in ACI 211.3, with the
greater than their cost.
following modifications: (1) a 29-pound loose-filled
sample is placed in the container and hand leveled,
D-5. Mixture proportioning.
and (2) a total surcharge weight of 27.5 pounds is
a. General. The basic mixture proportioning
added. Consolidation is considered complete when
procedures and properties of conventional concrete
mortar is visible around the bottom edge of the
plastic surcharge disk. The second method follows
and RCC are essentially the same; however, conven-
tional concrete cannot be reproportioned for use as
the procedures generally described in ACI 207.5R.
RCC by any single action such as (1) altering propor-
This method consists of measuring the time required
tions of the mortar and concrete aggregates, (2)
to fully consolidate a sample of no-slump concrete
reducing the water content, (3) changing the water-
by external vibration. Although both methods have
cement ratio, or (4) increasing the fine aggregate
been used successfully, the latter is more subjective
and requires the use of a vibrating table having suffi-
content. Differences in mixture proportioning
D-2
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