Influence of soluble salts on the engineering properties of a granular soil used for highway and airport pavements

Dissertant

al-Doory, Firas Said

University

University of Technology

Faculty

-

Department

Department of Building and Construction Engineering

University Country

Iraq

Degree

Master

Degree Date

1998

English Abstract

The occurrence of salt-rich granular materials are a widely spread problem in highways and airports construction in Iraq and in many other countries especially in the Middle East and South Africa.

This study is performed to evaluate the influence of soluble salts on the engineering properties of a soil-aggregate material brought out from Al-Suddur quarry N-E Baghdad, Soluble salts, represented by sodium chloride (NaCI) ; sodium sulphate (Na2So4) ; and gypsum (CaSo4.

2H20), are added to the granular material by percentages ranging from zero to 15 % by weight of the dry soil.

The influence of soluble salts on the maximum dry density, obtained from modified AASHTO compaction test, is obtained and plotted, An equation is developed to clarify the effect of soluble salts on compactablity of the granular material.

Compactablity measurement are represented by a term named as "Absolute Dry Density".

Bowels definition of resilient modulus is utilized to determine the effect of soluble salts on lit is important parameter (MR).

Il is obtained from cyclic triaxiaI tests under three different bulk stresses.

The stress dependency nature of resilient modulus was evident.

Lover percentages (< 5 %) of highly soluble salts emphasize this dependency through its lubricating Consolidated Und rained tria \ ial tests indicate thai soluble salts may not negatively affect the main component of shear strength (ɸ) of the granular material.

California Bearing Ratio tests indicate that the existence of soluble salts in the granular material reduce the CBR value significantly especially when soaking period t \ cceds 15 days.

Apparently, physical effect of soluble salts depends mainly on their solubility and rate of dissolution in addition to the amount of water exists.

If the granular material is in partially saturated condition (O.

M.

C.), the maximum allowable soluble salts should be limited to 2.5 % or 5 % when only gypsum exist.

And the granular material should be conditioned under higher possible bulk stress 1o eliminate the lubricating effect of soluble salts on the resilient modulus.

For low traffic volume roads, the above limits of soluble salts may be exceeded Up to 10 % since it did not affect the main component of shear strength (ɸ) of the granular material.

Main Subjects

Civil Engineering

Topics

• Mechanics
• Soil physics
• Soil mechanics

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-306166