reserved. EFFECT OF DATES NUCLEUS POWDER ON SOME ENGINERRING PROPERTIES OF CLAYEY SOIL IN COMPARISON TO

10.30772/qjes.v10i4.501 Abstract: Clayey soils are widely spread over the world. The clay soils are used and need to improve it’s engineering properties.Therefore, the treatment is considered one of the available solution for this purpose. Due to the nature of clay particles a trice plasticity,highly in surface area and the ion exchangaple ...etc. these properties encourage the idea of using pozzolanic materials, particularly the lime as pozzolana source.The alternative source of pozzolan is a metakaolin materials generated from burning the organic materials which are widely available in Iraq (i.e. Dates nucleus). The Dates nuclei is a waste material, so these additives can help in reducing the contamination and improving the environment. In this study, dates nuclei powder (DNP) was used after burning it at 900 o C for one hour and then mixed it with clayey soil in different by weight percentages. Hence, four percentages are selected (5%, 7.5%, 10%, and 15%) to study the effect of each addition on the shear strength of the clayey soil and the results are compared with the same soil that treated with lime. Many tests were conducted on ( the natural clay, clay-DNP and clay-lime) to evaluate the engineering characteristics and to explore best percentages that can used. Curing time (0, 7, 14, 28,90 and 180 days) was used to evaluate the effectiveness of pozzolanic reaction (emerges from DNP-soil mixture) with time. Interested results are found, the shear strength was increased to about six folds for 10%-DNP-soil at 180 days of curing. The liquid limit, plasticity index and the maximum dry density decreased in all percentages of DNP-Clay mixtures. On the other hand, the shear strength increment for DNP-Clay mixture after 180 days of curing is higher than that of Lime-Clay mixture for same period of curing. Forthermore, CBR results increased by six times for 10%DNP-Clay mixture for un-soaking conditions, while at soaking conditions, the increase was more than eleven times. The lime addition increase the CBR-value about three and eight times for unsoaking and soaking conditions,


INTRODUCTION
The speedy growing in population forced some clients to use bad soils quality in different construction projects due to the scarcity of soil in the urban areas. However, the engineers cannot use this type of soil without treatment before use. Therefore, different methods of soil treatment are used and the researchers trying to find the most cheaply and easy methods. The cement and the lime are oldest additive materials that used in soil improvement to increase the soil strength and decrease the compressibility by cementing agents (1). Chemical additives have been used in a wide range (i.e. SBR, Asphalt …etc) (2). Many researchers (i.e. 3,4) studied soil treatment using lime mixed with another additives to improve the workability and reduce the total cost. Pozzolanic reaction in clayey soil is activated due to the chemical behavior between clay particles and the alumina Al 2 O 3 .2SiO 2 leads to produce calcination effect on the soil system and this is the main effect of improvement (5). On the other hand, the physical soil properties (i.e. the plasticity) are strongly influenced by the pozzolanic reaction due to the agglomeration and flocculation effect on the fine soil particles and decrease the surface area (6). Many researchers are used several materials (like fibers, bottom ash, rice husk ash …etc) to improve engineering properties of soil, (7,8,1). The waste materials need tens of millions dollars annually to dispose off. Therefore, using the waste materials in soil improvement can produce two advantages: first, cleaning the environment with low cost and second is to develop new materials that improve soil properties. Today the recycle offal is a new science approach which named green technology. In this study, the date's nuclei powder was used as an additive to improve the shear strength of clayey soil. Increasing soil toughness by adding DNP are promising to use it for different layers if used, for example, in a road construction projects. On the other hand, the material used in this study is of no bad health effect on human or animals.

THE SOIL USED
The soil used in this study is clayey soil and was brought from Al-Hilla city around University of Babylon, the location coordinate is E442509.8, N322819.0 at 2.0 m below ground surface. The soil was then grinded to obtain homogenous soil mass. The soil was classified according to the Unified Soil Classification System ASTM D2487 (9) and found to be of fat clay with high plasticity (CH). Some soil properties are presented in Table 1, Figure 1 also shows grain size distribution curve.

LIME
The lime used in this study is a hydrate lime (Ca(OH) 2 and it was brought from the Nora factory in Karbala, Iraq. Table2 presented the chemical composition of lime used.    Figure 4 shows the results of the compaction tests, a decrease in maximum dry density with the increase in the optimum moisture content for sample treated with lime is observed. On the other hand, the samples treated with DNP shows an increase in the maximum dry density at 5%DNP then a decrease for other percentages. The decrease in maximum dry density with the increase in optimum moisture content can be attributed to the density of stabilizer which was less than the maximum density of the soil used. On the other hand, the small particle size of stabilizer caused an increase in total surface area of the mixture at the short time stage (before chemical reaction). This trend is noticed by other researchers (1,6,8,11).

EFFECT OF DNP ON CALIFORNIA BEARING RATIO (CBR) VALUES
CBR tests are performed for samples at different conditions. As shown in Figure 5, increasing in CBRvalue for both conditions (soaking and un-soaking) with curing time increasing are observed. In the case of un-soaking condition, the CBR-value increased about 1067% (from 3 for untreated soil to 35 for 10%DNP with soil). The soaking condition also shows an increase of about 1700 %( from 1.5 for untreated soil to 27 for 10% DNP with soil). Furthermore, the soil treated by lime also shows increasing in CBR of about 767% for un-soaking condition (from 3 for untreated soil to 26 for 3.8%lime with soil). The lime -clay soil mixture in soaking condition show an increase in CBR of about 1233% (from 1.5 to 20 for untreated soil and lime-clay mixture respectively). The results also revealed that the treated specimens by DNP was better than those treated by lime due to the increasing in the strength of about 300% of soil treated by lime to soil treated by DNP as discussed before.
The results obtained from CBR tests showed that the (untreated) soil was improved from increasing its strain characteristics. The results refer to modify the untreated soil to use in base and sub-base layer in road construction as recommended by Eren and Filize 2009 Figure 5 The change in shear strength (CBR) for treated specimens can be attributed to pozzolanic reaction that leads to agglomeration and flocculation of the clay particles and change the soil texture from highly plasticity clay to silty soil. The results also showed that the increase in CBR-values for DSP-Clay mixture are more than that for the lime-clay mixture for similar soaking conditions.

. Eren and Filize 2009 classified the soil according to its CBR number into five zones starting from bad if CBR is between 0 and 3 in the first zone and ends in a very well in zone five if soil has CBR of more than 50. The experimental results in this study shows that the modified specimens by 10%DNP lies in the fourth zone which has CBR of between 20 to 50 as shown in
The results obtained from this experimental work is correlated with the results presented by Amu et al., 2011, andMuthyalu et al., 2012. Examining the effect of using different chemical stabilizers on CBR, Rahman, 1986 found different behavior for the same type of soil.  This behavior may be attributed to the generated pozzolanic reaction of lime which may less than the quantity of alumina in clay particle, therefore, the soil has low strength. The shear strength also increased to about 577% for 180 days curing period for 10%DNP while the increasing in shear strength was about 244% for lime-clay mixture. Also the results showed about 97.5% increasing for 10%DNP more than the same soil treated by lime-clay mixture after 180 days of curing. Figure 7 shows the stabilizer agent percentages on shear strength of soil. The samples used in this figure are cured for 180 days. The results showed an increase in shear strength with increasing DNP percent till 10% then began to decrease after that. The increase in shear strength of 10%DNP was about 577% after 180 days curing period while the corresponding increase for lime -clay mixture was 243%. The results showed that the treated soil by DNP was better than the soil treated by lime for the same soil conditions.

CONCLUSIONS
From the results discussed earlier, the following conclusions may be drawn: 1-The addition of 10% DNP to the clayey soil has a significant effect in improving its shear strength. 2-Among the four percentages of DNP added to clay, the highest shear strength was achieved at 10%. 3-The percentage of DNP added to the clayey soils depended on the percent of clay particles such that the DNP effects increase as the clay particles increase.