Material properties - SR97

Table 2. Mixture proportions (units are kg unless noted).

Part I

Denver

Part II

Concrete

Mortar

Airport

Concrete

Ingredients

(6 Feb 96) (6 Feb 96)

Mix 10

(18 April 96) (18 April 96)

Cement

14.75

25.65

10.47

14.75

Flyash

--

3.49

--

Coarse agg.

47.51

--

44.69

47.51

Fine agg.

34.51

62.60

33.80

34.51

Plasticizer (mL/kg)*

--

1.74

9.8

Air entrainer (g)

12

10

12

Water

6.07

10.26

5.82

6.07

w/cm (water/

0.41

0.40

0.41

cemetitious ratio)

Slump (mm)

12.7

--

38.1

25.4

38.1

Air content

3.5%

1.05%

5.4%

3.0%

3.75%

C. agg.-- s.g.

2.89

--

2.72

2.89

F. agg.-- s.g.

2.67

2.64

2.67

Flyash-- s.g.

--

2.63

--

Cement-- s.g.

3.15

* Rheobuild 1000 used for the Part II mixes. The plasticizer for the Denver mix is

unknown. Dosage is per kg of cement.

Dates denote time of mixing. All mixtures are based on a 0.045-m3 batch size.

TDR probe would be exposed to the same dielec-

coarse aggregate ahead of the probe. The coarse

tric mix in the lab as in Denver. The mortar was

aggregate arrangement should not be affected

designed to duplicate the mortar fraction of the

with the second method.

Denver concrete.

Two concrete mixtures were used for part II. The

Material properties

first mixture duplicated the mixture used in part I,

The cement used for the concrete and mortar

except that it contained a plasticizer to achieve

was an ASTM Type I portland cement. The aggre-

more workability. The part I concrete mixture was

gate were obtained from a source local to CRREL (it

very stiff; its slump was 12.7 mm. With the plasti-

was impractical to ship aggregate from Denver). The

cizer, the slump was improved to 25.4 mm without

coarse aggregate, a crushed ledge (amphibolite),

the aggregate-to-paste ratio being changed. The

had a bulk specific gravity, saturated-surface-dry

second mixture also duplicated the part I concrete,

(ssd), of 2.89 and an absorption of 0.52%. The fine

except it was made with a smaller-sized coarse

aggregate, a natural sand, had a bulk specific grav-

aggregate. The purpose of using a smaller aggre-

ity (ssd) of 2.67 and an absorption of 1.1%. Tables 3

gate was to determine if aggregate size could affect

and 4 list the particle size distributions, specific

dielectric readings.

gravities, and absorptions for the aggregates used

in each mixture, including the Denver mixture.

Sample preparation

The mineralogical type for the coarse aggregate

The concrete and mortar were mixed at room

used in Denver was unknown, but Table 3 shows

temperature in separate batches in a 0.1-m3 rotary-

that the specific gravity and absorption are similar

drum mixer following standard laboratory mixing

to those of the ledge. This suggests that the ledge

procedures. The mixing procedure for the concrete

should be dielectrically similar to the coarse aggre-

followed ASTM C192. Mixing procedures for the

gate at Denver. The sand used in this study was

mortar followed ASTM C305. Once the concrete or

essentially identical to the Denver sand.

mortar was mixed, it was placed into 76- 152-mm

cylindrical plastic molds. For part I, the molds

Sample curing

were filled and then the TDR probes were jiggled

Once the probes were embedded in the concrete

into the fresh concrete or mortar. For part II, the

or the mortar, the plastic molds were sealed to pre-

vent moisture loss and stored at 20C for 24 hours.

concrete was carefully placed around each probe

as it was held in place. The purpose of using two

After this, the molds were removed and the speci-

mens were placed in 20C lime-saturated water for a

methods of embedding the probes into the speci-

mens was to determine if the tips of the probes,

minimum of 28 days before any TDR readings were

during the jiggling process, might rearrange the

taken.

3