الفهرس 
Aim and Objectives of StudyOnly 14 pages are availabe for public view
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Abstract
Many Egyptian cities outside the Nile Valley have experienced active urbanization during the last thirty years. These areas are considerably encompassing with problematic expansive clayey soils that impose frequent notable damages for the engineering structures built on them due to their high volume change potential. The present work aims at improving the volume change behavior of some Egyptian expansive clays soils using the calcined carbonate powder waste and sodium chloride. Hence, an intensive experimental work was conducted to achieve a full characterization for the studied clayey soils before and after treatment as well as for the carbonate waste.
The soil samples were treated with different doses of the waste lime (1.25– 12.5%) and sodium chloride (2.5 – 12.5%) for 1 hour, 1 day and some selected mixtures for 14 and 90 day of curing at the room temperature. Three water amounts (80%, 50% and 20% by L.L.) were used in the treatment process to evaluate the impact of water quantity on the performance of the additives. A significant reduction of (73.5 – 86.5%) and (52 – 90%), (74.5 –
88%) and (50 – 89.8%), (60 – 73.8%) and (57.6 – 88.1%) in the free
swelling, swelling potential and plasticity index; respectively, was achieved by 2.5% lime and by 10% NaCl; respectively, after 1 day curing.
It is found that the gained improvement by lime treatment is attributed to the alteration of the highly expansive Na-montmorillonite mineral to the almost non-expansive Ca-montmorillonite mineral due to calcium replacements in the short term cation exchange reaction, whereas that gained by NaCl treatment is ascribed to the complete destruction of Na-montmorillonite mineral as a result of sodium replacements. Both Hydrocalumite and sodium aluminate hydrate compounds are the newly formed cementaceous phases of the lime and NaCl-treated clayey soils; respectively. The results showed that the higher the water amount used in the treatment by the two stabilizers, the higher the achieved improvement in the swelling and plasticity of the studied soils. The gained significant improvement in the geotechnical properties of the studied expansive soils indicates the high performance of the two additives in reducing their swelling and plasticity, even though the calcined carbonate waste showed higher efficiency than the sodium chloride.
Key Words: Expansive soil, geotechnical properties, soil stabilization, calcined carbonate waste and sodium chloride.