This study examined the relationship between soil physico-chemical parameters and unconfined strength in various fine-grained soils when mixed with chemical additives. To be considered effective, the soil-additive mixture must exhibit a strength increase of at least 345 kPa (50 psi). The research focused on AASHTO Soil Group Classifications falling under the fine-grained soil category (A-4 to A-7). Additive amounts are given for Fly Ash (FA), Cement Kiln Dust (CKD), and Lime (hydrated and quick lime). The results of this study suggest that the surface area is perhaps the most important factor in determining if a chemical additive will be effective for stabilization. Out of the eight tested soils, the seven soils with surface areas lower than 150 m 2 /g reached the 345 kPa strength gain with the different additives. However, the one soil with a surface area higher than 150 m 2 /g never reached the strength gain with any of the additives used at any of the tested percentages.

An assessment of soil parameters governing soil strength increases with chemical additives.

Additions of byproduct chemicals, such as fly ash or cement kiln dust, have been shown to increase the unconfined compression strength (UCS) of soils. To be considered effective, the soil must exhibit a strength increase of at least 50 psi. Many current design methods base chemical additive percentage recommendations on the results of Atterberg Limit tests which do not always properly characterize the soil stabilization response. For example, Atterberg limit tests may reveal the same AASHTO classification of soil at two different sites, but one site may require more than twice the additive percentage of a chemical to achieve the desired UCS increase. This study examined the relationship between soil physico-chemical parameters and unconfined compression strength in various fine-grained soils to determine if other soil parameters have significant effects on predicting the strength of a soil treated with a given additive and additive content. The results of this study suggest that the surface area and shrinkage properties of the soil, combined with the Atterberg limit results, present a better picture of a given soil and will allow for better predictions of the amount of chemical stabilizer needed to adequately stabilize the soil.

Validation and Refinement of Chemical Stabilization Procedures for Pavement Subgrade Soils in Oklahoma - Volume I

Stabilization by lime, which is frequently carried out to improve the mechanical properties of soils, results from the formation and development of cementitious calcium silicate aluminate hydrate gel. The gel produces interlocking and bonding of the soil particles, hence increasing the strength and abrasion resistance. The proposed method to assess the compressive strength of the existing structure of lime stabilized soil using a simple mechanical abrasion technique, provides an alternative means by which the strength characteristics can be assessed. The advantages of employing the abrasion method are (1) the relative ease of specimen collection and preparation as the test is not particularly sensitive to specimen size and shape and (2) the ease of application to existing structures as large-scale mechanical testing equipment would not be required once a calibration chart has been esablished, and testing could be carried out on site.

Technical note. assessment of the unconfined compressive strength of a lime stabilized soil by an abrasion test

Stabilization by lime, which is frequently carried out to improve the mechanical properties of soils, results from the formation and development of cementitious calcium silicate aluminate hydrate gel. The gel produces interlocking and bonding of the soil particles, hence increasing the strength and abrasion resistance. The proposed method to assess the compressive strength of the existing structure of lime stabilized soil using a simple mechanical abrasion technique, provides an alternative means by which the strength characteristics can be assessed. The advantages of employing the abrasion method are (1) the relative ease of specimen collection and preparation as the test is not particularly sensitive to specimen size and shape and (2) the ease of application to existing structures as large-scale mechanical testing equipment would not be required once a calibration chart has been established, and testing could be carried out on site.

S Wild

Papers

Technical note. assessment of the unconfined compressive strength of a lime stabilized soil by an abrasion test

Assessment of the Unconfined Compressive Strength of a Lime Stabilized Soil by an Abrasion Test