| Frequently Asked Soil-Cement Questions
Pavements Home
> Soil-Cement > Soil-Cement FAQs > FDR
Test
Is there a test procedure
to determine how much portland cement to use for a given FDR pavement
project?
METHOD OF TEST FOR LABORATORY DESIGN OF SOIL-CEMENT MATERIAL
A. SCOPE
This method of test covers the procedures for making and testing
hardened soil-cement samples prepared with portland cement. The
laboratory maximum dry density and optimum moisture content are
determined for samples at three different percentages of cement.
Samples are then compacted in a mold before cement hydration to
the established laboratory maximum dry density and optimum moisture
content and tested for unconfined compressive strength.
B. MATERIALS
The materials shall consist of the following:
1. Soil
Soil may consist of any combination of gravel, stone, sand, silt,
clay, caliche, scoria, slag, sand-shell, cinders, ash, waste material
from aggregate production plants, high-quality crushed stone and
gravel base course aggregates, and failed bituminous surfaces.
2. Portland Cement
Portland cement shall comply with the latest ASTM, AASHTO, or
CSA specifications for portland cement or blended hydraulic cements.
3. Water
Water shall be free from substances deleterious to the proper
hardening of the soil-cement material.
4. Pozzolans
If used, pozzolans shall comply with the latest ASTM, AASHTO,
or CSA specifications for fly ash, slag, and silica fume.
C. APPARATUS
The apparatus shall consist of the following:
1. Mold
A cylindrical metal mold approximately 4.0 inches (100 mm) in diameter
and 4.6 inches (115 mm) in height and having a volume of approximately
1/30-cubic foot (940 cc). This mold is fitted with a detachable
base plate and a removable extension approximately 3.1 inches (80
mm) in height.
2. Rammer
A metal rammer having a 2-inch (50 mm) diameter flat circular
face and weighing 5.5 pounds (2.5 kg). The rammer shall be equipped
with a suitable arrangement to control the height of drop to a
free fall of 12.0 inches (300 mm) above the elevation of the soil
sample.
3. Sieve
The ¾-inch (19 mm) sieve shall conform to the “Standard
Specifications for Sieves for Testing Purposes”, AASHTO
Designation: M-92.
4. Sample Extruder
A jack, lever frame, or other device adapted for the purpose of
extruding samples from the mold.
5. Balances
A balance or scale of at least 10,000 gram capacity sensitive
to 1.0 gram.
6. Polyethylene Freezer Bags
Polyethylene freezer bags shall be the ordinary commercial type
freezer bag of 1-quart (950 cc) capacity.
7. Moist Room
Moist room or a suitable covered container capable of maintaining
a temperature of 73.4°F ± 3°F (23.0°C ±
2°C) and having a relative humidity of not less than 90%.
8. Testing Machine
The testing machine may be the hydraulic or screw type with sufficient
opening between the upper bearing surface and the lower bearing
surface of the machine to permit testing of the samples specified
herein. The machine shall be capable of applying at least 20,000
pounds (9,070 kg) to within an accuracy of ± 1% of the
total load.
9. Straightedge
A steel straightedge 12 inches (300 mm) long.
10. Large Pans
Pans of sufficient size to allow the thorough mixing of the material
passing the ¾-inch (19 mm) sieve.
11. Scoops
Scoops or other suitable devices for mixing and sampling the material
passing the ¾-inch (19 mm) sieve.
12. Graduated Cylinder
Glass or plastic graduate of 1,000 ml capacity used for measuring
the mixing water.
13. Small Pans or Dishes
Pie pans or evaporating dishes suitable for weighing the cement
and/or other admixtures.
D. SAMPLE PREPARATION
Sieve a sufficient quantity of the soil material through the ¾-inch
(19 mm) sieve to determine maximum dry density and optimum moisture
content and to provide at least nine, 4.0-inch (100 mm) diameter
by 4.6-inch (115 mm) high compacted specimens having a total volume
of 1/30-cubic foot (940 cc). (Usually about 100 pounds (45 kg) of
dry soil is required.)
E. PROCEDURE
1. Determine Maximum Dry Density and Optimum Moisture Content
a. Weigh out three 4,000 gram batches of dry soil.
b. Weigh out three batches of dry cement to represent 4% (160
grams), 6% (240 grams), and 8% (320 grams) of the batches of
dry soil.
c. Place one 4,000 gram batch of dry soil plus the first percentage
of dry cement (4%) in a large pan and mix the dry ingredients
to uniform color.
d. Determine the laboratory maximum dry density and optimum
moisture content for the soil-cement mixture by following ASTM
D558 – Standard Test Methods for Moisture-Density Relations
of Soil-Cement Mixtures.
e. Determine the laboratory maximum dry density and optimum
moisture content for the 6% and 8% cement batches the same as
in steps E.1.c. and E.1.d.
2. Prepare and Test Specimens for Unconfined Compressive Strength
a. Weigh out three 10,000 gram batches of dry soil.
b. Weigh out three batches of dry cement to represent 4% (400
grams), 6% (600 grams), and 8% (800 grams) of the batches of
dry soil.
c. Place one 10,000 gram batch of dry soil plus the first percentage
of dry cement (4%) in a large pan and mix the dry ingredients
to uniform color.
d. Add sufficient water to bring the soil-cement mixture to
optimum moisture as previously determined in step E.1.d. above.
Mix until uniform moisture content is achieved throughout the
entire batch.
e. Form a specimen by compacting the prepared soil-cement mixture,
in three equal layers, in the mold following standard Proctor
test procedures.
f. Extrude the sample from the mold and seal in a polyethylene
freezer bag.
g. Prepare two more samples as in steps E.2.e. and E.2.f. from
the batch of soil-cement mixture.
h. Prepare the 6% and 8% cement batches the same as in steps
E.2.c. through E.2.g. and place all nine molded samples in the
moist room for curing.
F. TESTING
Three samples for each cement content are tested uncapped for unconfined
compressive strength after 7 days curing in the moist room. These
samples are vertically loaded in a testing machine at a loading
rate of .05 in/min (1.25 mm/min) until failure.
G. CALCULATIONS
Compressive Strength (PSI) = Load (lbs) at failure
area of sample (in²)
Compressive Strength (kg/m²) = Load (kg) at failure
area of sample (m²)
NOTE: No consideration is given to the length-diameter ratio (K-factor).
|