بررسی عامل زمان و درصد مخلوط آهک و خاکستر بادی بر خواص فیزیکی و مکانیکی خاک ریزدانه

Abstract:
A geotechnical engineer may sometimes encounter fine-grained clay soils. Improvement of
the engineering properties of those soils is necessary in order to achieve suitable construction
sites. One of the methods for soil modification is to use additives, which are economically
justifiable as well as being abundantly produced and accessible. Lime is one of the additives
that results in reinforcement of the soil through Pozzolanic reactions. But in case that the soil
consists of sulfate ions or when a stabilized soil becomes prone to sulfate water, then the
presence of lime not only doesnot decrease the swelling of the stabilized layer, but also it acts
to the contrary and causes the increase in swelling and reduces the strength. Addition of fly
ashes reduces the destructive effects of the sulfates (such as bulk increase and cracking) and
increases the abatement of carbonation in a soil stabilized by lime or cement while rising the
PH level of the aggregate and calcium ion, which results in expedient pozzolanic reaction.
This article discusses the impact of fly ash addition on the geotechnical properties of soil and
lime aggregate.
The ML soil was used in this study with various percentages of fly ash and a given percentage
of lime. Then the effect of fly ash on lime and soil aggregate was studied through shear
strength and Atterberg limits tests. These tests were performed for 7-day and 28-day saturated
specimens of different percentages so that a set of diverse fly ash and lime aggregates would
be tested. The results represent the extraordinary impact of fly ash on the shear strength as the
28-day samples showed a 138% increase while the 7-day samples had a 90% rise. Also the
cohesion parameter was increased up to 700% in the 28 –day samples while it showed a 600%
rise in the 7-day samples. The internal friction angle also showed a significant increase,
especially since the low price of fly ash makes it economically advantageous. This article
would at least be useful for rehabilitation of problematic soils and for application of novel
results and technologies in the geotechnical engineering.