USE OF SOIL STABILIZERS ON HIGHWAY SHOULDERS

Background

General Assembly action:

VTRC shall study the use of soil stabilizers in highway s.houlders at one or more selected locations with the objective of finding a method of substantially reducing the occurrence of pavement/shoulder drop­ off at a reasonable cost

Research Plan

• Field study only
• No laboratory analysis involved
• Two locations
• Three stabilizers
• Test and Control Evaluation

Project Modifications

• One type of shoulder material (crushed stone).
• Two stabilizers
• Soiltac (vinyl acetate copolymer emulsion)
• Centrophase  AD (soy/lecithin emulsion)
• One location (Route 522, Powhatan Co.)

Before

After

Centrophase 9/14/2005

Soiltac 9/14/2005

Hypotheses

WORKING: The addition of stabilizers to the shoulder material did affect the strength of the material

NULL: The addition of stabilizers to the shoulder materi.al did not affect the strength of the material

As measured by its stiffness and bearing capacity

Performace Data

Low shoulders, Soiltac 9/21/2004

Low shoulders, Control 9/21/2004

Other Findings Visual Inspection

• 9/14 - 12/14, the surface of both test sections were firmer th.an the control section
• 2/8, the surface of both test sections were softer than the control section

Findings - Objective Tests

• Statistically speaking, on no occasion were test section data better than the control section data
• The 2/8/2005 data supports the visual inspection data
• Overall, the data supports the null hypothesis

Null Hypothesis

The addition of stabilizers to the shoulder material did not affect the strength of the materi.al as determined by measurement of its stiffness and bearing capacity

Entrance - Control Section 2/8/2005

DCP Penetration Readings for Sample Control-6, by Date

DCP Penetration Data - 2/8/2005

Conclusions

• Equipment normally used for road stabilization is not effective or efficient for stabilization of narrow shoulders.
• Soil stabilizers mixed with crusher run stone do not increase the stiffness or bearing strength.
• Soil stabilizers mixed with crusher run  stone do not prolong the period of optimum stiffness and bearing strength of the material.
• Insufficient evidence to determine if soil stabilizers   improve a shoulder's short-term resistance to erosion due to the action of water or traffic.
• The cost of using soil stabilizers as short-term surface stabilizers for crusher run stone shoulders is greater than the benefit received.

Recommendations

• Shoulders  should be designed for the anticipated traffic load.
• Soil stabilizers should not be used with, crushed  stone with the intent of improving or prolonging the CBR of shoulder material.
• Consider additional study of soil stabilizers as a short-term solution to shoulder erosion.

Project Limitations

• Project mandated : June 2004
• Report toi GA: January 1, 2005

Installation - 9/14/2004

Control 

GeoGauge measures stiffness

•  Defined as force over deflection
• The higher the stiffness reading the more resistant the material is to movement (e.g., rutting, corrugation)

The DCP measures penetration

• Inches/hammer  blow
• Correlates to CBR or bearing strength
• The less penetration per blow the more weight the material can carry per unit area.

2/5/2008 Soiltac - Centrophase - Control

Soiltac Section - 2/8/2005

Centrophase - 2/8/2005

DCP Penetration Readings for Sample Control-6, by Date

DCP Penetration Data 2/8/2005