Post on 16-Oct-2021
GULF COAST TESTING LA BORA TORY INC. PINELLAS PARK, FL 33781
CONSTRUCTION MATERIALS ENGINEERING COUNCIL CERTIFIED
October II, 2019
Deuel & Associates, Inc. 565 South Hercules A venue Clearwater, Florida 33764
Attn: Mr. AI Carrier, PE
Subject: Report of Geotechnical Exploration Addendum No.1 Roadway Improvements Madeira Beach, Florida GCTL Project No. 25279
Dear Mr. Carrier:
Gulf Coast Testing Laboratory, Inc. (GCTL) has completed the requested evaluation for the use of
a revised pavement structure for the above-referenced project. Specifically, the use of a flexible
pavement structure with soil-cement base has been evaluated. In this regard, the recommendations for
a soil-cement based flexible pavement are presented in this Report of Geotechnical Exploration
Addendum No. I.
This report is intended to be utilized in direct conjunction with the initial Report of Geotechnical
Exploration (project No. 25279, dated June 3, 20 19) and presents a review of the project information
provided to us, a description of the site and subsurface conditions encountered as well as our pavement
recommendations.
5671 70th A VENUE NORTH PINELLAS PARK, FL 33781
CONSTRUCTION MATERIALS ENGINEERING COUNCIL CERTIFIED CERTIFICATE of AUTHORIZATION # 00002370
PHONE: (727) 544-4080 FAX: (727) 544-7532 Email: info(@gctlfl.com
Roadway Improvements, Madeira Beach, Florida GCTL Project No. 25279
October/!, 2019 Report ofGeoteclmical Exploration Addendum No. I
We appreciate this opportunity to provide our services to you and we look forward to serving as your
geotechnical consultant throughout this project. Should you have any questions in regard to the
information presented in this report, please do not hesitate to contact us at your earliest convenience.
Sincerely,
GULF COAST TESTING LABORATORY, INC.
Don R. Stites, P.E.
Digitally signed by Don R Stites Date: 2019.10.13 22:1 1:02 -04'00'
Principal Geotechnical Engineer Florida Registration No. 42290
II
Rick Davis President
TABLE OF CONTENTS
1.0 INTRODUCTION ..................................................................................................................... 1-1 1.1 PROJECT CHARACTERISTICS ............................................................................ 1-1
2.0 GENERALIZED SUBSURFACE CONDITIONS .............................................................. 2-1 2.1 SUB SURF ACE CONDITIONS ............................................................................... 2-1 2.1. I Existing Pavement Structure ..................................................................................... 2-1 2. I .2 Subgrade Soils ............................................................................................................ 2-2 2. I .3 Groundwater Conditions ............................................................................................ 2-2
3.0 EVALUATIONS AND DESIGN RECOMMENDATIONS .............................................. 3-1 3. I GENERAL ................................................................................................................. 3-1 3.2 SUBGRADE .............................................................................................................. 3-2 3.3 BASE .......................................................................................................................... 3-3 3.4 ASPHALTIC CONCRETE ....................................................................................... 3-4 3.5 PAVEMENT THICKNESS DESIGN ...................................................................... 3-4
4.0 CONSTRUCTION CONSIDERATIONS ............................................................................. 4-1 4.I FILL PLACEMENT AND SUBGRADE PREPARATION ................................. .4-I 4.2 GROUNDWATER CONTROL ............................................................................... 4-2
5.0 BASIS FOR RECOMMENDATIONS .................................................................................. 5-1
APPENDIX
SUGGESTED SPECIFICATIONS FOR SOIL-CEMENT BASE COURSE CONSTRUCTION
Roadway Improvements, Madeira Beach, Florida GCTL Project No. 25279
October II, 2019 Report ofGeoteclmical £tploration Addendum No. I
1.0 INTRODUCTION
1.1 PROJECT CHARACTERISTICS
l11e subject project is located along within Madeira Beach in Pinellas County, Florida. Specifically,
the subject property is expected to include Johns Pass Avenue, Lillian Drive, Crystal Drive, East
Parsley Drive, West Parsley Drive, !29th A venue East, 131 51 A venue East, Pelican Lane, Marguerite
Drive, Village Boulevard, and 1291h Avenue West. These roadways are were observed to consist of
existing asphaltic concrete surfaced roadway areas with concrete curbing. This addendum is
understood to consist of evaluating the subsurface conditions encountered with anticipation of utilizing
a flexible pavement structure with a soil-cement base. The finished grades of the pavement areas are
expected to generally coincide with the existing grade levels.
1-1
Roadway Improvements, Madeira Beach. Florida GCTL Project No. 25279
October II, 2019 Report ofGeoteclmical &pi oration Addendum No. I
2.0 GENERALIZED SUBSURFACE CONDITIONS
2.1 SUBSURFACE CONDITIONS
2.1.1 Existing Pavement Structure
Based on these measured values, the average individual roadway pavement thicknesses have been
tabulated below.
Street Asphaltic Base Base Location Concrete Thickness Material
Thickness (Inch) (Inch)
Johns Pass Boulevard 2.5 6.6 Crushed Shell
Lillian Drive 2.0 8.0 Crushed Shell
Crystal Drive 1.8 6.4 Soil Cement
East Parsley Drive 2.5 4.7 Soil Cement/Crushed Concrete
West Parsley Drive 3.3 5.0 Soil Cement
1291h A venue East 1.4 6.9 Soil Cement
131 st A venue East 1.5 6.5 Soil Cement
Pelican Lane 2.2 4.0 Soil Cement
Marguerite Drive 2.5 6.0 Soil Cement
Village Boulevard 2.3 6.7 Soil Cement
1291h Avenue West 5.5 6.5 Crushed Shell
In this regard, based on our review, it is recommended the existing pavement section be considered as
follows:
Asphaltic Base Base Concrete Thickness Material Thickness (Inch)
(Inch) 2.2 6.1 Soil Cement
2-1
Roadway Improvements, Madeira Beach, Florida GCTL Project No. 25279
2.1.2 Subgrade Soils
October 11, 2019 Report of Geotechnical Exploration Addendum No. 1
Underlying the asphaltic concrete and pavement base materials, the subsurface materials encountered
generally consisted of a mixture of fine SAND (SP), slightly silty find SAND (SP-SM), silty SAND, and
marine shell fragments, with interbedded layers of SILT (ML) that extended to a depth of at least 5.2 feet
below the existing ground surface (soil boring termination). It is noted that the borings for DRI-13 and
DRI-16 encountered Peat at a depth range of 3.5 to 4.9 feet below the existing ground surface elevation.
2.1.3 Groundwater Conditions
As recorded during the time of our subsurface exploration the groundwater level was encountered at an
approximate depth range of 1.8 to 4.1 feet below the existing ground surfaces; the deeper groundwater
level measurements may have been artificially lower due to the silty material restricting groundwater
flow. It is estimated that the groundwater level will generally coincide with the adjacent intercostal
waterway. In this regard, it is estimated that the normal seasonal high groundwater level will be located
approximately one foot below the existing pavement surface elevations.
2-2
Roadway Improvements. Madeira Beach, Florida GCTL Project No. 25279
October II, 20I9 Report of Geotechnical Exploration Addendum No. I
3.0 EVALUATIONS AND DESIGN RECOMMENDATIONS
The following evaluations and recommendations have been developed on the basis of the previously
described project characteristics and subsurface conditions encountered during this exploration. The
subsurface data was evaluated utilizing correlations between the engineering performance
characteristics of similar subsurface conditions.
The following pavement recommendations presented in the following sections are considered
minimum for the site, soil and limited traffic conditions expected. The final pavement thickness
design should be determined by the project civil engineer using information obtained during the
subsurface exploration program and an analysis of anticipated traffic conditions.
3.1 GENERAL
Based on the results of the subsurface exploration, the near-surface soils encountered across the project
site consists of uncontrolled earthfill that predominately consists of very low permeable soils which
also have a shallow normal seasonal high groundwater level and a shallow aquitard ("confining")
layer. Structures constructed overlying this type of material tend to exhibit aesthetic and structural
distress, which was exhibited in the existing roadway structures.
Although the existing asphalt could be milled and repaved, it is believed this pavement would
experience similar distress in limited time durations. In this regard, in order to improve the existing
pavement, it is recommended that pavement reconstruction be performed. It is believed a semi
flexible pavement structure with a soil-cement base is considered the preferred pavement section for
the proposed roadway areas.
Soil-cement is a highly compacted mixture of soil/aggregate, cement, and water that is commonly
used as a pavement base for residential streets and commercial parking areas. The soil material in
soil-cement can be almost any combination of sand, silt, clay, gravel, or local granular materials,
such as slag, caliche, and limerock. In addition, a wide variety of waste materials including cinders
and fly ash can all be utilized as soil material. Old granular-base roads can also be reclaimed to
make great soil-cement.
3-1
Roadway Improvements, Madeira Beach, Florida GCTL Project No. 25279
In general, before construction
begins, laboratory tests establish the
cement content, compaction, and
water requirements of the soil
material to be used. During
construction, tests are made to
confirm that the requirements are
being attained. Soil-cement is
commonly mixed m a central
pugmill (see photograph). The
mixed soil-cement is then hauled to
October II, 2019 Report of Geotechnical Exploration Addendum No. I
the jobsite and spread on the prepared subgrade. the mixture is compacted to the specified dry
density and cured to prevent evaporation of water and assist in developing strength through cement
hydration.
3.2 SUBGRADE
Following removal of the existing pavement structure, including asphaltic concrete and underlying
base material, it is recommended the exposed soils be proofrolled with a non-vibratory drum roller,
having a static weight on the order of four tons, under the direction of a Geotechnical Engineer in order
to confirm the ability of the soils to properly support the expected roadway development. The
pavement subgrade should be compacted to a minimum depth of six inches to a density of at least 92
percent of the Modified Proctor maximum dry density (ASTM 01557).
Any fill used to elevate the cleared pavement areas to subgrade elevation should consist of "clean"
well-graded to fine sands having less than five percent finer than the No. 200 sieve, unifonnly
compacted to a density of at least 92 percent of the soil Modified Proctor maximum dry density.
One layer of a Geogrid stabilization material (such as Tensar Geogrid SS20, TriAx TXI40, Mirafi
BXG120, or approved equivalent) is expected to significantly improve the pavement stability. In this
regard, one layer of geogrid is recommended to be placed overlying the compacted and approved
pavement subgrade. Stabilized sub grade is not recommended with the use of Geogrid.
3-2
Roadway Improvements, Madeira Beach, Florida GCTL Project No. 25279
October II, 2019 Report of Geotechnical Exploration Addendum No. I
The Geogrid material should be placed in accordance with the manufacturers' recommendations. In
general, it is recommended that the Geogrid be placed as follows:
• Unroll the Geogrid, pull taut and stake.
• Overlap all end sections of the Geogrid approximately 18 inches.
• Dump, spread and compact approximately 4 to 6 inches of base material. Rubber-tired
vehicles and track-mounted vehicles should not operate on the Geogrid material prior to
placement of the base material.
3.3 BASE
A soil cement base (see
photograph) should be
designed according to FOOT
or PCA modified short cut
design procedure. A strength
of 300 to 400 psi should be
achieved on laboratory cured
compressive
specimens molded
strength
from
samples taken from the base
material as it is placed; higher
compressive strengths should
be avoided in order to limit shrinkage cracking. Before paving, the soil cement base should be
checked for soundness should be firm and true to line and grade prior to paving. As a guideline for
pavement design, we recommend that the soil cement base materials be a minimum of eight inches
thick in heavily traveled drives.
It is noted that soil cement pavements tend to develop aesthetic disruptions along the pavement surface
due to shrinkage cracking of the cement treated base material. In order to effectively reduce reflection
cracking and improve the aesthetic quality of the improved roadways, it is recommended that a
geosynthetic material, such as Mirafi MPV500 or approved equivalent, be placed in accordance with
the manufacture's recommendations between the asphaltic concrete and the soil cement base.
3-3
Roadway Improvements, Madeira Beach. Florida GCTL Project No. 25279
October II, 2019 Report of Geotechnical £"pi oration Addendum No. 1
3.4 ASPHALTIC CONCRETE
The asphaltic concrete structural course should consist of at least 2~ inches ofType SP-9.5 or SP-12.5
asphaltic concrete material. Type SP-9.5 or SP-12.5 should be utilized because of their durability
qualities. The asphaltic concrete should meet standard FOOT material requirements and placement
procedures as outlined in the current FOOT Standard Specifications for Road and Bridge Construction.
3.5 PAVEMENT THICKNESS DESIGN
The following pavement designs are based upon the design methods described in the FOOT "Flexible
Pavement Design Manual for New Construction and Pavement Rehabilitation" (Document No. 625-
0 10-002-b, dated April 1, 1993 ). These designs present the recommended range of IS-kip-equivalent
single axle loads for the "light duty", "moderate duty", and "heavy duty" pavement sections presented.
Based on the pavement conditions observed and the subsurface conditions encountered, the
evaluations were performed using the following parameters:
• Design Reliability = 85% at an overall standard deviation of 0.45 • Initial Serviceability= 4.2; Terminal Serviceability= 2.0; • Modulus of Resiliency, Mr = 8700 psi • Structural Coefficient for Asphaltic Concrete = 0.44 • Structural Coefficient for Soil Cement= 0.15 • Structural Coefficient for Compacted Subgrade = 0.04
Pavement Pavement Structural 18Kip Duty Structural Section Number Equivalent
Single Axle Loads
2.2" TypeS 6.1" 6" 2.1 70,000 Asphaltic Soil Cement Compacted
Existing Concrete Subgrade
2W' Type SP 8" 6" 2.9 600,000 Asphaltic Soil Cement Compacted
Moderate Concrete Geogrid Subgrade
2W'Type SP 10" 6" 3.3 1,800,000 Asphaltic Soil Cement Compacted
Heavy Concrete Geogrid Subgrade
3-4
Roadway Improvements, Jyfadeira Beach, Florida GCTL Project No. 25279
October 11, 2019 Report of Geotechnical £"Cploration Addendum No. I
4.0 CONSTRUCTION CONSIDERATIONS
4.1 Fill Placement and Subgrade Considerations
The following are our recommendations for overall site preparation and mechanical densification work
for construction of the proposed development, based on the anticipated construction and our boring
results. These recommendations, along with the Suggested Specifications for Soil-Cement Base
Course Construction presented in the Appendix of this report, should be used as a guideline for the
project general specifications prepared by the Design Engineer.
I. Prior to grading operations, the existing pavement structure should be removed. The
exposed materials should be evaluated by GCTL to confirm that all unsuitable materials,
if any, have been removed and that the soils are capable of supporting the proposed
pavement structures. Proofrolling should be performed with a self-propelled non
vibratory drum roller having a static drum weight on the order of four tons. Careful
observations should be made during proofrolling to help identify any areas of soft yielding
soils that may require over-excavation and replacement. It is noted that non-vibratory
compaction is recommended in order to avoid "pumping" conditions due to groundwater.
2. It is recommended that the natural ground be compacted to a dry density of at least 92
percent of the Modified Proctor Test maximum dry density (ASTM D-1557) to a
minimum depth of six inches below stripped grade within the pavement areas.
3. Following satisfactory completion of the proofrolling and compaction operations, the
proposed pavement subgrade area may be brought up to finished subgrade levels, if
required. It is recommended that off-site fill consist of soils having no more than five
percent passing the No. 200 sieve, and be free of rubble, organics, clay, debris and other
unsuitable material. Fill should be tested and approved by GCTL prior to acquisition.
Approved sand fill should be placed in loose lifts not exceeding six inches in thickness.
The fill soils should be compacted to a dry density of at least 92 percent of the Modified
Proctor Test maximum dry density within the pavement areas.
4-1
Roadway Improvements, Madeira Beach. Florida GCTL Project No. 25279
October II , 2019 Report of Geotechnical Exploration Addendum No. I
4. Soil moisture content may need to be controlled in order to facilitate proper compaction.
If additional moisture is necessary to achieve the compaction objectives of imported fill,
then water should be applied in such a way that will not cause erosion or removal of the
subgrade soils. A moisture content within two percentage points of the optimum
indicated by the Modified Proctor Test (ASTM D-1557) is recommended prior to
compaction ofthe natural ground and fill.
5. A representative from GCTL should be retained to provide on-site observation of
earthwork and ground modification activities. It is important that GCTL be retained to
observe that the subsurface conditions are as we have discussed and reported herein, and
that foundation construction, ground modification and fill placement are in accordance
with our recommendations.
4.2 GROUNDWATER CONTROL
Groundwater was encountered at a depth range of 1.8 to 4.1 feet below the existing ground surface
elevations. Groundwater levels should be detennined immediately prior to excavations and
construction. It is estimated that the groundwater level will generally coincide with the adjacent
intercostal waterway. In this regard, it is estimated that the normal seasonal high groundwater level
will be located approximately one foot below the existing pavement surface elevations. Groundwater
is expected to be satisfactorily controlled with a sump pump system for near-surface pavement
construction.
Soils exposed in the bases of all satisfactory excavations should be protected against any detrimental
change in conditions, such as physical disturbance or rain water. Surface runoff water should be
drained away from the excavations and not be allowed to pond.
4-2
Roadway Improvements, Madeira Beach. Florida GCTL Project No. 25279
October II, 2019 Report of Geotechnical Exploration Addendum No. I
5.0 BASIS FOR RECOMMENDATIONS
Our professional services have been performed, our findings obtained, and our recommendations
prepared in accordance with generally accepted geotechnical engineering principles and practices.
This company is not responsible for the conclusions, opinions or recommendations made by others
based on these data.
The scope of the exploration was intended to evaluate soil conditions within the primary influence of
the existing pavement and does not include an evaluation of potential deep soil conditions such as
sinkholes and/or compressible subsurface soils. The analysis and recommendations submitted in this
report are based upon the data obtained from the soil borings performed at the locations indicated.
Regardless of the thoroughness of a geotechnical exploration, there is always a possibility that
conditions between borings will be different from those at specific boring locations and that conditions
will not be as anticipated by the designers or contractors. In addition, the construction process may
itself alter soil conditions.
If any subsoil variations become evident during the course of this project, a re-evaluation of the
recommendations contained in this report will be necessary after we have had an opportunity to
observe the characteristics of the conditions encountered. The applicability of the report should also
be reviewed in the event significant changes occur in the design, nature or location of the proposed
facility.
The recommendations provided are based in part on project information provided to us and they only
apply to the specific project and site discussed in this report. If the project information is incorrect or if
additional information is available, the correct or additional information should be conveyed to us for
review. Our recommendations may then be modified, if necessary. Experienced geotechnical
personnel should observe and document the construction procedures used and the conditions
encountered. Unanticipated conditions and inadequate procedures should be reported to the design
team. We recommend that the owner retain GCTL to provide this service based upon our familiarity
with the project, the subsurface conditions, and the intent of the recommendations and design.
5-1
APPENDIX
SUGGESTED SPECIFICATIONS
FOR SOIL-CEMENT BASE COURSE CONSTRUCTION
rmm PORTLAND CEMENT ASSOCIATION
suaaested Specifications lor Soil-Cement Base course construction
1.GEnERAL 1.1 Description. Soil-cement shall consist of soil, portland cement,
and water proportioned, mixed, placed, compacted, and cured in
accordance with these specifications; and shall conform to the lines,
grades, thicknesses, and typical cross-sections shown in the plans.
These suggested specifications cover construction of soil-cement
base course, also referred to in some areas as cement-treated based,
cement-treated aggregate base, full depth recycling of flexible pave
ments, cement-recycled asphalt and base, and other names.
These specifications are intended to serve as a guide to format and
content for normal soil -cement construction. Most projects have
special features or requirements that should be incorporated in the
project documents.
2. MATERIALS 2.1 Soil. "Soil• may consist of ( 1) any combination of gravel, stone,
sand, silt, and clay; (2) miscellaneous material such as caliche,
scoria, slag, sand-shell, cinders, and ash; (3) waste material from
aggregate production plants; (4) high-quality crushed stone and
gravel base course aggregates; or (5) old flexible pavements, includ
ing the bituminous surface and stone or gravel base course.
The soi l shall not contain roots, topsoil, or any material deleterious
to its reaction with cement. The soil as processed for construction
shall not contain material retained on a 2-in. (50-mm) sieve except
for bituminous surface recycling work, which can contain up to 5%
of the total mixed material retained on a 2-in (50-mm) sieve.
2.2 Portland Cement. Portland cement shall comply with the latest
specifications for portland cement (ASTM C 150, ASTM C 1157,
CSA A-23.5, or AASHTO M 85) or blended hydraulic cements (ASTM
C 595, ASTM C 1157, CSA A-362, or AASHTO M 240).
<Cl 2001 Portland Cement Association All rights reserved.
2.3 Water. Water shall be free from substances deleterious to the
hardening of the soil-cement.
2.4 Pozzolans. If used, pozzolans including fly ash, slag, and silica
fume shall comply with the appropriate specifications (ASTM C 618,
AASHTO M 295 for fly ash; ASTM C 989, AASHTO M 302 for
slag; ASTM C 1240 for silica fume; or CSA A-23.5 for all).
2.5 Curing Compounds. Curing compounds shall comply with the
latest specifications for emulsified asphalt (ASTM D 9773) or liquid
membrane-forming compounds for curing concrete (ASTM C 309).
2.6 Sand Blotter. Sand used for the prevention of pickup of curing
materials shall be clean, dry, and non-plastic.
3. EQUIPMEnT 3.1 Description. Soil-cement may be constructed with any machine
or combination of machines or equipment that will produce com
pleted soil-cement meeting the requirements for soil pulverization,
cement and water application, mixing, transporting, placing, com
pacting, finishing, and curing as provided in these specifications.
3.2 Mixing Methods. Mixing shall be accomplished in a central
mixing plant or in place, using single-shaft or multiple-shaft mixers.
Agricultural disks or motor graders are not acceptable mixing
equipment.
3.3 Cement Proportioning. The cement meter for central-plant
mixing and the cement spreader for in-place mixing shall be capa
ble of uniformly distributing the cement at the specified rate.
Cement may be added in a dry or a slurry form. If applied in slurry
form, the slurry mixer and truck shall be capable of completely
dispersing the cement in the water to produce a uniform slurry,
and shall continuously agitate the slurry once mixed.
IITiiiJ SOIL-CEMENT INFORMATION
3.4 Application of Water. Water may be applied through the mixer
or with water trucks equipped with pressure-spray bars.
3.5 Compaction. Soil-cement shall be compacted with one or a com
bination of the following: tamping or grid roller, pneumatic-tire roller,
steel-wheel roller, vibratory roller, or vibrating-plate compactor.
4. GDnSTRUGTIDn REQUIREMEnTS 4.1 General
4.1.1 Preparation of Subgrade. Before soil-cement processing begins,
the area to be paved shall be graded and shaped to lines and grades
as shown in the plans or as directed by the engineer. During this
process any unsuitable soil or material shall be removed and replaced
with acceptable material. The subgrade shall be firm and able to sup
port without yielding or subsequent settlement the construction
equipment and the compaction of the soil-cement hereinafter speci
fied. Soft or yielding subgrade shall be corrected and made stable
before construction proceeds.
4.1.2 Mixing and Placing. Soil-cement shall not be mixed or placed
when the soil aggregate or subgrade is frozen, or when the air tem
perature is below 40• °F (4 °(). Moisture in the soil at the time of
cement application shall not exceed the quantity that will permit a
uniform and intimate mixture of the soil and cement during mixing
operations, and shall be within 2% of the optimum moisture content
for the soil-cement mixture at start of compaction.
The operation of cement application, mixing, spreading, compacting
and finishing shall be continuous and completed within 4 hours from
the start of mixing. Any soil-cement mixture that has not been com
pacted and finished shall not be left undisturbed for longer that 30
minutes.
4.2 Central-Plant-Mixed Method
4.2.1 Mixing. Soil-cement shall be central-plant mixed in an
approved continuous-flow or batch-type pugmill, or rotary-drum
mixer. The plant shall be equipped with metering and feeding devices
that will add the soil, cement, and water into the mixer in the speci
fied quantities. If necessary, a screening device shall be used to
remove oversized material greater than 2 in (SO mm) from the raw
soil feed prior to mixing. Soil and cement shall be mixed sufficiently
to prevent cement balls from forming when water is added. The max
imum plasticity index of the soil shall be eight.
The mixing time shall be that which is required to secure an intimate,
uniform mixture of the soil, cement, and water.
Free access to the plant must be provided to the engineer at all times
for inspection of the plant's operation and for sampling the soil-cement
mixture and its components. If the actual quantities of the mix vary
more than 3% by weight of the specified quantities, the engineer may
require such changes in the plant operation as will provide the
required accuracy.
4.2.2 Handling. The soil-cement mixture shall be transported from the
mixing plant to the paving area in trucks or other equipment having
2
beds that are smooth, clean, and tight. Truck bed covers shall be pro
vided and used at the engineer's discretion to protect the soil-cement
during transport from moisture variations due to weather conditions.
Any soil-cement wet excessively by rain, whether during transport or
after it has been spread, will be subject to rejection.
The total elapsed time between the addition of water to the mixture
and the start of compaction shall be the minimum possible. Haul time
shall not exceed 30 minutes, and compaction shall start as soon as
possible after spreading. In no case shall the total elapsed time exceed
45 minutes between the addition of water to the soil and cement and
the start of compaction.
The contractor shall take all necessary precautions to avoid damage
to completed soil-cement by the equipment.
4.2.3 Placing. Immediately prior to placement of the soil-cement, the
receiving surface shall be in a moist condition. The mixture shall be
placed without segregation at a quantity per linear foot (meter) that
will produce a uniformly compacted layer conforming to the required
grade and cross section. The mixture shall be spread by one or more
approved spreading devices. Not more than 60 minutes shall elapse
between placement of soil-cement in adjacent lanes at any location
except at longitudinal and transverse construction joints.
4.3 Mixed-in-Place Method
4.3.1 Preparation. The surface of the soil to be processed into soil
cement shall be at an elevation so that, when mixed with cement and
water and recompacted to the required density, the final elevation
will be as shown in the plans or as directed by the engineer. The
material in place and surface conditions shall be approved by the
engineer before the next phase of construction is begun.
4.3.2 Scarifying. Before cement is applied, the soil to be processed
may be scarified to the full depth of mixing. Scarification and pre
pulverization are required for the following conditions:
(1) For cohesive soils with a plasticity index greater than 20, the soil
shall be damp at the time of scarifying to reduce dust and aid in pul
verization.
(2) For full depth recycling of flexible pavements where the bitumi
nous surface is incorporated into the mixture, the pulverization to
final specified gradation, as noted in Section 4.3.4, shall be accom
plished prior to cement application.
(3) For slurry application of cement, initial scarification shall be done
to provide a method to uniformly distribute the slurry over the soil
without excessive runoff or ponding.
4.3.3 Application of Cement. The specified quantity of cement shall
be applied uniformly in a manner that minimizes dust and is satisfac
tory to the engineer. If cement is applied as a slurry, the time from first
contact of cement with water to application on the soil shall not
exceed 60 minutes. The time from slurry placement on the soil to
start of mixing shall not exceed 30 minutes.
4.3.4 Mixing. Mixing shall begin as soon as possible after the cement
has been spread and shall continue until a uniform mixture is produced.
The mixed material shall meet the following gradation conditions:
(1) For soils, 1 00% of the soil-cement mixture shall pass a 1-in.
(25-mm) sieve and a minimum of 80% shall pass a No. 4 (4.75-mm)
sieve, exclusive of any gravel or stone. Gravel or stone shall be no
more than 2-in. (50-mm) nominal maximum size.
(2) For full-depth recycling, the final mixture (bituminous
surface, granular base, and subgrade soil) shall be pulverized such
that 95% passes the 2-in. (50-mm) sieve and at least 55% passes the
No. 4 (4.75-mm) sieve. No more than 50% of the final mixed materi
al shall be made of the existing bituminous material unless approved
by the engineer and included in a mixture design. Additional material
may be added to the top or from the subgrade to improve the mixture
gradation, as long as this material was included in the mixture design.
The final pulverization test shall be made at the conclusion of mixing
operations. Mixing shall be continued until the product is uniform in
color, meets gradation requirements, and is at the required moisture
content throughout. The entire operation of cement spreading, water
application, and mixing shall result in a uniform soil, cement, and
water mixture for the full design depth and width.
4.4 Compaction. Soil-cement shall be uniformly compacted to a min
imum of 98% of maximum density based on a moving average of five
consecutive tests with no individual test below 96%. Field density of
compacted soil-cement can be determined by the 1) nuclear method
in the direct transmission mode (ASTM D 2922, MSHTO T 238); 2)
sand cone method (ASTM D 1556, AASHTO T 191 ); or rubber bal
loon method (ASTM D 2167 or MSHTO T 205). Optimum moisture
and maximum density shall be determined prior to start of construc
tion and also in the field during construction by a moisture density
test (ASTM D 558 or AASHTO T 134).
At the start of compaction whether central-plant mixed or mixed-in
place, the moisture content shall be within 2% of the specified optimum
moisture. No section shall be left undisturbed for longer than 30 minutes
during compaction operations. All compaction operations shall be com
pleted within 2 hours from the start of mixing.
4.5 Finishing. As compaction nears completion, the surface of the
soil-cement shall be shaped to the specified lines, grades, and cross
sections. If necessary or as required by the engineer, the surface shall
be lightly scarified or broom-dragged to remove imprints left by
equipment or to prevent compaction planes. Compaction shall then
be continued until uniform and adequate density is obtained. During
the finishing process the surface shall be kept moist by means of fog
type sprayers. Compaction and finishing shall be done in such a man
ner as to produce dense surface free of compaction planes, cracks,
ridges, or loose material. All finishing operations shall be completed
within 4 hours from start of mixing.
4.6 Curing. Finished portions of soil-cement that are traveled on by
equipment used in constructing an adjoining section shall be protect
ed in such a manner as to prevent equipment from marring or damag
ing completed work.
3
After completion of final finishing, the surface shall be cured by appli
cation of a bituminous or other approved sealing membrane, or by
being kept continuously moist for a period of 7 days with a fog-type
water spray that will not erode the surface of the soil-cement. If curing
material is used, it shall be applied as soon as possible, but not later
than 24 hours after completing finishing operations. The surface shall
be kept continuously moist prior to application of curing material.
For bituminous curing material, the soil-cement surface shall be
dense, free of all loose and extraneous materials, and shall contain
sufficient moisture to prevent excessive penetration of the bituminous
material. The bituminous material shall be uniformly applied to the
surface of the completed soil-cement. The exact rate and temperature
of application for complete coverage, without undue runoff, shall be
specified by the engineer.
Should it be necessary for construction equipment or other traffic to
use the bituminous-covered surface before the bituminous material
has dried sufficiently to prevent pickup, sufficient sand blotter cover
shall be applied before such use.
Sufficient protection from freezing shall be given the soil-cement for
at least 7 days after its construction or as approved by the engineer.
4.7 Construction Joints. At the end of each day's construction a
straight transverse construction joint shall be formed by cutting back
into the completed work to form a true vertical face.
Soil-cement for large, wide areas shall be built in a series of parallel
lanes of convenient length and width meeting approval of the engi
neer. Straight longitudinal joints shall be formed at the end of each
day's construction by cutting back into completed work to form a true
vertical face free of loose or shared material.
Special attention shall be given to joint construction to ensure a verti
cal joint, adequately mixed material, and compaction up against the
joint. On mixed-in-place construction using transverse shaft mixers, a
longitudinal joint constructed adjacent to partially hardened soil
cement built the preceding day may be formed by cutting back into
the previously constructed area during mixing operations. Guide
stakes shall be set for cement spreading and mixing.
4.8 Traffic. Completed portions of soil-cement can be opened imme
diately to low-speed local traffic and to construction equipment pro
vided the curing material or moist curing operations are not impaired,
and provided the soil-cement is sufficiently stable to withstand mar
ring or permanent deformation. The section can be opened up to all
traffic after the soil-cement has received a curing compound or subse
quent surface, and is sufficiently stable to withstand marring or per
manent deformation. If continuous moist curing is employed in lieu of
a curing compound, the soil-cement can be opened to all traffic after
the 7-day moist curing period, provided the soil-cement has hardened
sufficiently to prevent marring or permanent deformation.
4.9 Surfacing. Subsequent pavement layers (asphalt, chip-seal, or
concrete) can be placed any time after finishing, as long as the soil
cement is sufficiently stable to support the required construction
equipment without marring or permanent distortion of the surface.
I1Iilfl PORTLAND CEMENT ASSOCIATION
4.10 Maintenance. The contractor shall maintain the soil-cement in
good condition until all work is completed and accepted. Such main
tenance shall be done by the contractor at his own expense.
Maintenance shall include immediate repairs of any defects that may
occur. If it is necessary to replace any soil-cement, the replacement
shall be for the full depth, with vertical cuts, using either soil-cement
or concrete. No skin patches will be permitted.
5.1nSPEGTIDn AnD TESTinG 5.1 Description. The engineer, with the assistance and cooperation of
the contractor, shall make such inspections and tests as deemed neces
sary to ensure the conformance of the work to the contract documents.
These inspections and tests may include, but shall not be limited to, (1)
the taking of test samples of the soil-cement and its individual compo
nents at all stages of processing and after completion and (2) the close
observation of the operation of all equipment used on the work. Only
those materials, machines, and methods meeting the requirements of
the contract documents shall be approved by the engineer.
All testing of soil-cement or its individual components, unless otherwise
provided specifically in the contract documents, shall be in accordance
with the latest applicable ASTM, AASHTO, or CSA specifications in
effect as of the date of advertisement for bids on the project.
&. MEASUREMEnT AnD PAYMEnT 6.1 Measurement. This work will be measured (1) in square yards
(square meters) of completed and accepted soil-cement base course as
determined by the specified lines, grades, and cross sections shown on
the plans and (2) in tons (tonnes) or cwt of cement incorporated into
the soil-cement base course in accordance with the instructions of the
engineer.
6.2 Payment. This work will be paid for at the contract unit price per
square yard (square meter) of soil-cement base course and at the con
tract unit price per ton (tonne) or cwt of cement furnished, multiplied
by the quantities obtained in accordance with Section 6.1. Such pay
ment shall constitute full reimbursement for all work necessary to
complete the soil-cement, including watering, curing, inspection and
testing assistance, and all other incidental operations.
-------------------------------------------------1--------! I
KEYWORDS: compacting, curing, density, finishes, inspection, joints,
maintenance, measurement, soils, soil-cement, specifications, subgrades.
ABSTRACT: Specifies materials to use and construction methods needed
to produce soil-cement base courses. A resume of preparation; pulveriza
tion; cement application, mixing and spreading (mixed-in-place and cen
tral-plant-mixed methods); comapction; finishing; curing; jointing; main
tenance; measurements; and basis of payment for a soil-cement base
course.
REFERENCE: Suggested Specifications for Soil-Cement Base Course (SoilCement, Cement-Treated Base, Cement-Treated-Aggregate Base), 15008.11, Portland Cement Association, 2001.
CAUTION: Avoid prolonged contact between unhardened (wet) cement or cement-treated mixtures and skin surfaces. To prevent such contact, it is advisable to wear protective clothing. Skin areas that have been exposed to wet cement or cement-treated mixtures, either directly or indirectly or through saturated clothing, should be thoroughly washed with water.
This publication is based on the facts, tests, and authorities stated herein. It is intended for the use of professional personnel competent to evaluate the significance and limitations of the reported findings and who will accept responsibility for the application of the material it contains. The Portland Cement Association disclaims any and all responsibility for application of the stated principles or for the accuracy of any of the sources other than work performed or information developed by the Association.
I1IiilJ PORTLAND CEMENT ASSOCIATION
5420 Old Orchard Road Skokie, Illinois 60077-1 083 847.966.6200 www.portcement.org
An organization of cement companies to improve and extend the uses of portland cement and concrete through market development, engineering, research, education, and public affairs work.
18008.12