10-07-2012, 02:44 PM
EXAMPLE PROBLEM ILLUSTRATING THE APPLICATION OF THE NATIONAL LIME ASSOCIATION MIXTURE DESIGN AND TESTING PROTOCOL
[attachment=27365]
INTRODUCTON
This design example is based on three Mississippi Department of Transportation
(MDOT) widening projects on state highways in Kemper, Lowndes, and Washington
counties. In all three, the lime-treated subgrade (LTS) layers are being evaluated as
structural components in the design. The design options considered are
using hot mix asphalt (HMA) directly over the LTS and
using HMA with a lime-fly ash stabilized base over the LTS.
Both options have previously been used successfully in other parts of the State.
In fact, MDOT has used lime stabilization in clay soils for over 30 years to
improve performance and as a platform for pavement structures.
OUTLINE OF MIXTURE DESIGN AND TESTING PROTOCOL (MDTP)
The MTDP (1,2) is designed to produce a mixture that possesses the desired
structural properties and durability in a pavement layer. The procedure measures
engineering properties that are critical to the performance of the lime-stabilized mixture
as a structural layer in a pavement system.
Compressive Strength Testing to Determine the Unconfined Compressive
Strength (UCS) of Lime-Soil Mixture
Unconfined compressive strength is determined using ASTM D 5102. UCS can
be used to approximate design parameters such as flexural strength, deformation potential
and stiffness (resilient modulus) when these data are not available:
Tensile strength can be conservatively estimated as 10 percent of the UCS,
and flexural strength can be conservatively estimated to be twice the tensile
strength or approximately 20 percent of UCS. (2)
Tube Suction Test (TST) to Evaluate Moisture Sensitivity
The dielectric value (DV), measured by a Tube Suction Test (6), is a measure of
how much moisture a base/subbase/subgrade will absorb through capillary rise and the
state of bonding of the absorbed moisture. Low dielectric values indicate the presence of
tightly absorbed and well-arranged water molecules. Scullion and Saarenketo (6) have
established DV selection criteria for subbase layers. The results of this test are used to
assess resistance of the stabilized material to moisture damage.
Eades and Grim pH Test
Dry soils are screened through a No. 40 sieve. All the soils are tested with 0, 2, 3,
4, 5, 6 and 7% of hydrated lime in accordance with ASTM D 6276. Special attention is
given to maintain the room temperature at 250C, as pH of lime-soil mixture is
temperature dependent.
[attachment=27365]
INTRODUCTON
This design example is based on three Mississippi Department of Transportation
(MDOT) widening projects on state highways in Kemper, Lowndes, and Washington
counties. In all three, the lime-treated subgrade (LTS) layers are being evaluated as
structural components in the design. The design options considered are
using hot mix asphalt (HMA) directly over the LTS and
using HMA with a lime-fly ash stabilized base over the LTS.
Both options have previously been used successfully in other parts of the State.
In fact, MDOT has used lime stabilization in clay soils for over 30 years to
improve performance and as a platform for pavement structures.
OUTLINE OF MIXTURE DESIGN AND TESTING PROTOCOL (MDTP)
The MTDP (1,2) is designed to produce a mixture that possesses the desired
structural properties and durability in a pavement layer. The procedure measures
engineering properties that are critical to the performance of the lime-stabilized mixture
as a structural layer in a pavement system.
Compressive Strength Testing to Determine the Unconfined Compressive
Strength (UCS) of Lime-Soil Mixture
Unconfined compressive strength is determined using ASTM D 5102. UCS can
be used to approximate design parameters such as flexural strength, deformation potential
and stiffness (resilient modulus) when these data are not available:
Tensile strength can be conservatively estimated as 10 percent of the UCS,
and flexural strength can be conservatively estimated to be twice the tensile
strength or approximately 20 percent of UCS. (2)
Tube Suction Test (TST) to Evaluate Moisture Sensitivity
The dielectric value (DV), measured by a Tube Suction Test (6), is a measure of
how much moisture a base/subbase/subgrade will absorb through capillary rise and the
state of bonding of the absorbed moisture. Low dielectric values indicate the presence of
tightly absorbed and well-arranged water molecules. Scullion and Saarenketo (6) have
established DV selection criteria for subbase layers. The results of this test are used to
assess resistance of the stabilized material to moisture damage.
Eades and Grim pH Test
Dry soils are screened through a No. 40 sieve. All the soils are tested with 0, 2, 3,
4, 5, 6 and 7% of hydrated lime in accordance with ASTM D 6276. Special attention is
given to maintain the room temperature at 250C, as pH of lime-soil mixture is
temperature dependent.