Maiduguri, Borno State. Nigeria 2 Department of Civil Engineering, Ahmadu Bello University Zaria, Maiduguri, Kaduna

Transcription

1 University of Maiduguri Faculty of Engineering Seminar Series Volume 9 number 1, July 2018 Compaction Characteristics of Heavy Metal Contaminated Soil Treated I.S. Muhammad 1, A.S. Muhammed 1*, A.M. Kundiri 1 and A.O. Eberemu 2 1 Department of Civil and Water Resources Engineering, University of Maiduguri, Maiduguri, Borno State. Nigeria 2 Department of Civil Engineering, Ahmadu Bello University Zaria, Maiduguri, Kaduna State. Nigeria sadiq4civil@yahoo.com; Abstract This paper presents compaction characteristics of heavy metals contaminated soil treated with Millet Husk Ash (MHA) admixed with Ordinary Portland Cement (OPC). The natural soil was classified as poorly graded sand (SP) and granular material (A-3) according to the Unified Soil Classification System (USCS) and Association of American State Highway and Transportation Officials (AASHTO) respectively. The soil was confirmed to have been contaminated based on the Atomic Absorption Spectrophotometry (AAS) laboratory analysis for heavy metals. The predominant heavy metals found in the soil were Iron, Lead, Chromium, Nickel and Zinc. The compaction characteristics of the soil treated with MHA and OPC as well as the soil treated with up to 16% MHA in stepwise increment of 4% admixed with up to 8% OPC in stepwise increment of 2% showed a decrease in Maximum Dry Density (MDD) and increase in Optimum Moisture Content (OMC). Keywords: Compaction, Contaminated soil and millet hush ash 1.0 Introduction Soil is a source of raw materials and plays a fundamental role in human activities and enhances the developmental aspect of living creatures (Petruzzelli et al., 2010). Despite this importance, soil has been degraded and deteriorated with several contaminants as a result of human activities. The recent advancement in urbanization due to population growth and industrial activities has no doubt brought about indiscriminate waste disposal which has adversely degraded our environment, thus, resulting to increase in the number of brownfields (Hong et al., 2014). The common among these contaminants are the heavy metals which have been classified as refractory and non-degradable (Jaishankar et al., 2014). These metals occur naturally at background concentrations that are often not considered toxic, however, the concentrations are further increased by anthropogenic activities (Vandana et al., 2011). Some engineering properties of these soils are affected by contaminants whose concentration exceeds the natural buffering capacity of the soil. High level of Na in soil causes dispersion, swelling and aggregate slaking in clay. According to Arpita (2014), the heavy metals negatively affects the geotechnical properties of soil and any slight change in these properties and soil strata behavior may lead to decrease in the bearing capacity as well as increase in total or differential settlement of foundation system. Therefore, for such soils to be suitable for engineering purposes, modification has to be done in order to achieve the desired engineering properties of the soil. Soil modification refers to the techniques employed with a view of altering some properties of the soil with a view to improving its engineering performance (Venkatramaiah, 2006). Seminar Series Volume 9(1), 2018 Page 37

2 Millets are cereal crops grown in the semi- arid zones of Africa and Asia mostly for food and fodder. Nigeria produces up to 40% of the millet produced in Africa due to low rainfall and adverse weather condition, northern part of the country produces more than 80% of the millet produced in the country (Obilana, 2003). Burning of millet husk under normal temperature and pressure produces Millet husk ash. This paper evaluates the compaction characteristic of heavy metals contaminated soil treated with Millet Husk Ash (MHA) admixed with Ordinary Portland Cement (OPC). 2.0 Materials and Methods 2.1 Materials The soil used in this study was collected at the Bulabulin scrap metal yard Maiduguri (latitude N and longitude E), Nigeria, using disturbed sampling method at a depth of 20 cm. The soil was air-dried and lumps were broken after which it was sieved through BS no. 4 sieve (4.75mm). The material passing this aperture size was used for the laboratory work. The Ordinary Portland cement (OPC) used in the research was purchased in an open market at Maiduguri. The Millet Husk Ash was generated by burning the husk, obtained from a farm after local milling, under normal temperature and pressure (open burning). The ash was sieved through BS sieve No. 200 (75µm) and the fraction passing the sieve was used throughout the study. 2.2 Methodology The index properties of the soil which include natural moisture content, sieve analysis and specific gravity for the natural and treated soil were conducted in the laboratory in accordance with British Standard BS 1377 (1990). The oxides composition for both OPC and MHA were determined using X-ray fluorescence (XRF) analysis. The heavy metals in the soil were determined using Atomic Absorption Spectrophotometer (AAS) analysis after digesting the sample with HNO3 followed by extraction with HCl (Ehi-Eromosele et al., 2012). Compaction of both natural and treated soils were carried out using British Standard Light (BSL) in accordance with BS 1337 part 2 of The soil was mixed with up to 16% MHA in stepwise increment of 4% and 8%OPC in stepwise increment of 2%. Air-dried soil sample passing BS sieve no. 4.75mm was used throughout the compaction. A cylindrical compaction mould with internal diameter of 105mm, internal height of 115mm and a volume of 1000 cm 3 was used. The mould was fitted with detachable baseplate and removable collar of 50mm height. The compaction was achieved by using a 2.5 kg rammer falling through 300 mm onto three layers, each receiving 27 uniformly distributed blows. 3.0 Results and Discussion 3.1 Index properties The index properties of the natural soil are presented in the Table 1. The preliminary test carried out on the natural soil shows that, it belongs to a group of poorly graded sand (SP) according to Unified Soil Classification System (ASTM, 1992) and A-3 soil according to AASHTO classification system (AASHTO, 1986). Seminar Series, Volume 9(1), 2018 Page 38

3 Table 1: Physical/Chemical Properties of Soil Properties Value Moisture content 4.37% Specific gravity 2.66 Coarse particles 20% Sand 76% % Passing 75µm sieve size 4.24 USCS SP AASHTO Classification A-3 CEC meq/100g The particle size analysis of the contaminated soil is presented in Figure one. Fig. 1: Particle size plot of the contaminated soil. It revealed that the percentage of particles passing through sieve with aperture size 0.075mm is 4.25% with a coefficient of Uniformity (Cu) of 2.55 and Coefficient of curvature (Cc) of Specific Gravity The variation of specific gravity of soil-opc-mha mixture is shown in figure 2. The soil has a specific gravity of The results obtained show an increase in the specific gravity value from for the various combinations of the binder with the exception of MHA alone which shows a decrease in the value from The reduction was due to the lower specific gravity (2.41) of the MHA, which gradually replaces the soil material. The decrease also indicated that the mineralogical alteration has not taken place with the MHA (Kumar, 2012). Seminar Series, Volume 9(1), 2018 Page 39

4 Specific gravity Muhammad et al.: Compaction Characteristics of Heavy Metal Contaminated Soil Treated Millet husk ash content (%) 0%OPC 2%OPC 4%OPC 6%OPC 8%OPC Fig. 2: Variation of specific gravity of soil-cement with millet husk ash content Similar trend was also reported when bagasse ash was used in treating foundry sand (Osinubi et al., 2011). The increase in the value of specific gravity value can be attributed to the higher specific gravity value of the cement (3.10) that partially substituted the soil. This is similar to the result obtained by (Moses and Afolayan, 2011). The two-way analysis of variance (ANOVA) carried out on the result of the specific gravity shows that the effect of OPC was statistically significant (Fcal= 6.93 Fcrit = 3.0) while MHA was not statistically significant (Fcal= 0.79 Fcrit = 3.0). 3.3 Properties of MHA and OPC The oxides compositions of Millet Husk Ash (MHA) and Ordinary Portland Cement (OPC) are presented in Table 2. Table 2: Oxides composition of MHA and OPC Chemical Oxides OPC Concentration (%) MHA Composition (%) SiO Al2O Fe2O CaO K2O MgO Na2O The chemical composition of both MHA and OPC summarized in Table 1 depict that the major chemical components of MHA are SiO2 (55.79), Al2O3 (19.24) and Fe2O3 (6.45). The summation of these oxides indicated that MHA has met the requirement set by the American Standard for Testing and Materials (ASTM C618, 2000) which stipulated that the total sum of these oxides should be greater than or equal to 70%. The MHA could also be Seminar Series, Volume 9(1), 2018 Page 40

5 classified as Class F pozzolana in accordance with the aforementioned standards. 3.4 Soil Contaminants The concentration of some identified heavy metals in the scrap yard soil were quantified and presented in Table 3. The result indicated that the concentrations of all the elements are far above the threshold value of heavy metals in soils (CCME, 2003). Table 3: Concentration of Heavy Metal in the contaminated soil Heavy Metal Concentration (g/l) Fe Pb 0.25 Cr 0.64 Ni 0.26 Zn 1.04 It could be the high level of refractory elements in the metal scrap yard soil could be attributed to the piling-up of different scrap yard metals at the site overtime. These contaminants found their way into the soil through leachate generated as a result of rain water. The high concentration of Fe could be attributed to the dominance of the scrap steel bar and other ferrous materials at the site. 3.5 Compaction Characteristics Maximum dry density The maximum dry density (MDD) generally decreased with higher content of OPC admixed with MHA. It decreased from 1.88 to 1.53Mg/m 3, 1.69 to 1.49 Mg/m 3, 1.59 to 1.37 Mg/m 3 and 1.55 to 1.32 Mg/m 3 for 0, 2, 4, 6 and 8 % cement treatment, respectively between 0 to 16% MHA admixtures. The variation of maximum dry density of soil-opc- MHA mixtures is shown in Fig. 3. Both cement and pozzolana treated soils showed a decreasing MDD that is in agreement with other findings (Moses et al., 2012). The decrease in MDD was due to the replacement of soil by the MHA in the mixture which have comparatively lower specific gravity of 2.41, as compared to that of the natural soil which is 2.66 as reported by similar researches (Eberemu, 2011). This could also be attributed to the coating of the soil by the MHA that produced particles with large voids and hence less density, as observed by (Uche and Ahmed 2013). Seminar Series, Volume 9(1), 2018 Page 41

6 Optimum Moisture Content (%) Maximum Dry Density (Mg/m 3 ) Muhammad et al.: Compaction Characteristics of Heavy Metal Contaminated Soil Treated Cement Content (%) 0% MHA 4% MHA 8% MHA 12% MHA 16% MHA Fig. 3: Variation of MDD with OPC-MHA treatment on the contaminated soil The two-way analysis of variance (ANOVA) test on the MDD result for BSL compaction shows that the effect of OPC and MHA on the soil were statistically significant (Fcal= 3.91 Fcrit = 3.0) for OPC and (Fcal= 4.0 Fcrit = 3.0) for MHA. Optimum moisture content The optimum moisture content (OMC) increases with higher OPC and MHA admixtures, it ranged from 8.93 to 14.03%, 9.41 to 15.34%, to 16.01% and to 17.23%, for 0, 2, 4, 6 and 8 % cement treatment, respectively between 0 to 16% MHA admixtures. The variation of OMC of soil-opc-mha is presented in Figure Cement Content %) 0% MHA 4% MHA 8% MHA 12% MHA 16% MHA Fig 4: Variation of OMC with OPC-MHA treatment on the contaminated soil Seminar Series, Volume 9(1), 2018 Page 42

7 The increase in OMC was due to the corresponding increase in the MHA which decreases the quantity of free silt and clay fraction, and coarser materials with larger surface areas were formed; this process is characterized with the phenomenon of water absorption (Eberemu, 2011; Umar et al., 2013 and Uche and Ahmed, 2013). The two-way analysis of variance (ANOVA) test on the OMC result for the BSL compaction shows that the effects of OPC and MHA on the soil were statistically significant (Fcal= Fcrit = 3.0) for OPC and (Fcal= Fcrit = 3.0) for MHA. 4.0 Conclusion The natural soil from the Bulabulin scrap metal yard belongs to the SP group in accordance with the Unified Soil Classification System (USCS) and A-3 as per AASHTO classification. The scrap metal site soil contains heavy metals at concentrations beyond the threshold values based on the metal composition analysis carried out. The predominant metals found in the soil were Iron (10.871g/l), Lead (0.246g/l), Chromium (0.64g/l), Nickel (0.260g/l) and Zinc (1.04g/l). The oxides composition of MHA which comprise of SiO2 (55.79%), Al2O3 (19.24%) and Fe2O3 (6.45%) is suitable for use as pozzolana. The MDD values of the soil decreased, while the OMC increased with the addition of Millet Husk Ash and Ordinary Portland Cement. The minimum MDD value recorded for the BSL compactive effort was 1.32 g/cm 3 at 8%OPC/16%MHA treatment. The OMC values increased from 8.93% for the natural soil to 17.23% at 8%OPC/16%MHA treatment. References AASHTO (1986). Standard Specification for Transportation, Material and Methods of Sampling and Testing. 14th ed. Washington, D.C.: Amsterdam Association of State Highway and Transportation Official. Arpita V. P. (2014). A study of Geotechnical Properties of Heavy Metak Contaminated Soil. Engineerin. 3(6) Ash AsHydraulic Barrier Material. Geo-Frontiers, ASTM (1992). Annual Book of Standards. Philadelphia: American Society for ASTM C618(2000). Specification for coal fly ash and raw calcined natural pozzolans for use in concrete. British Standard Institute. (1990). Methods of testing soils for civil engineering purposes. BS 1377, London. Canadian Council of Ministers of the Environment CCME(2003). Canadian Soil quality Guidelines for the protectionof environmental and human health. Summary of a Protocol for the Derivation of Environmental and Human Health Soil Quality Guidelines. Eberemu, O. A. (2011). Consolidation properties of compacted lateritic soil treated with rice husk ash. Geomaterials,1, Ehi-Eromosele, C.O; Adaramodu, A.A; Anake, W.U; Ajanaku, C.O. and Edobor-Osoh, A. (2012). Comparison of Three Methods of Digestion for Trace Metal Analysis in Surface Dust Collected from an EwasteRecycling Site. Nature and Science,10(10),42-47 Seminar Series, Volume 9(1), 2018 Page 43

8 Hong, A. H.; Puong Ling,L.; Selaman, O. S.(2014). Heavy metal concentration levels in soil at Lake Geriyoirrigation site, Yola, Adamawa state, North Eastern Nigeria. International Journal of Environmental Monitoring and Analysis. 2(2) Jaishankar M., Tseten, T., Anbalaban, N., Mathew B. B., Beeregowda, K. N. (2014). Toxicity mechanism, and health effects of some heavy metals. Interdiciplinary Toxicology, 7(2), Kumar, S.M.P (2012). Silica and Calcium effect on Geo-Technical Properties of ExpansiveSoil Extracted from Rice Husk Ash and Lime. International Conference on Environment Science and EngieeringIPCBEE vol.3 2, Moses G.; Saminu,A.; and Oriola, F.O.P.(2012). Influence of Compactive Efforts on Compacted Foundry Sand Treated With Cement Kiln Dust. Civil and Environmenta Research, 2(5), Moses, G. and Afolayan, J. O.(2011). Compacted Foundry Sand Treated with Cement Kiln Dust as Hydraulic BarrierMaterial.EJGE, Obilana, A. B(2003). Importance of millet in Africa, ICRISAT, Nairobi, Kenya, Osinubi, K.J. and Moses G. (2011). Compacted Foundry Sand Treated With Bagasse Osinubi, K.J., Yohanna, P. and Eberemu, A.O. (2015). Cement modification of tropical black clay using iron ore tailings as admixture. Elsevier, Transportation Geotechnics,5, Petruzzelli, G.; Grini, F.; Pezzarossa, B. and Pedro, F. (2010).The Fate of Pollutants in Soil. CNR, Institute of the Ecosystem Studies, Testing and Materials, vol Uche, O.A.U. and Ahmed, J. A (2013). Effect of Millet Husk Ash on the Properties of Marginal Lateritic Soil. Research Journal in Engineering and Applied Sciences 2(5), Umar, M.; Alhassan, H. M.; Abdulfatah, A.Y. and Idris, A. (2013). Beneficial use of Class- C Fly Ash in Improving Marginal Lateritic Soils for Road Construction. EJGE,18, Vandana, P.; Murthya, N.N. and Praveen, R.S. (2011). Assessment of heavy metal Venkatramaiah, C. (2006). Geotechnical engineering. New age international publishers. Third edition. Seminar Series, Volume 9(1), 2018 Page 44