Indian Geotechnical Conference (December 18-20, 2003) s9

Index and Compaction Properties of Alkalies Treated Red Earth Contaminated with Acids IGC 2009, Guntur, INDIA

INDEX AND COMPACTION PROPERTIES OF ALKALIES TREATED RED EARTH CONTAMINATED WITH ACIDS

H.N. Ramesh Professor, Department of Civil Engineering, Soil Mechanics and Foundation Division, U.V.C.E., Bangalore University, Bangalore–560056, India. E-mail:[email protected] S.D. Venkataraja Mohan Assistant Professor, Department of Civil Engineering, Dr. Ambedkar Institute of Technology, Bangalore–560056, India. E-mail:[email protected]

ABSTRACT: In recent years attention has been given to the acidification and alkalization of the soils to understand physico- chemical and Engineering properties. The sources of acids and alkalis are acid rain, industrial effluents, ground water

contamination, leachate from land fills and chemical spillages. The effect of Sulphuric acid (H2SO4) and Orthophosphoric acid (H3PO4) with Calcium Carbonate (CaCO3) and Magnesium Carbonate (MgCO3) treated with Red Earth is studied. The Optimum percentages of CaCO3 and MgCO3 mix were 15% and 10 % respectively based on compaction test. Liquid limit with CaCO3 is decreased and with MgCO3 increased. Curing effect increased the liquid limit and Plastic limit. Shrinkage limit is increased with increase in CaCO3 and decreased with increase in MgCO3. Curing effect showed decrease in Shrinkage limit with CaCO3 and marginal increase with MgCO3. Maximum dry density is increased at optimum percentages of MgCO3 and CaCO3 mix with their optimum moisture content is increased and decreased respectively. Acidification of CaCO 3 and MgCO3 treated Red Earth showed decrease in maximum dry density and marginal decrease in optimum moisture content. However the negative effect of Sulphuric acid is more on index and compaction properties than that of Orthophosphoric acid.

1. INTRODUCTION Red earth covers large area in Indian subcontinent. These soils are mostly found in semi arid regions. The soil is a Modern construction requires not only profound preliminary typical non-expansive clayey soil containing kaolinite as its study of the foundation material, but also a thorough chief mineral constituent and acidification and alkalization of knowledge of the factors causing its changes in the life time this soil alters the Engineering properties of soil. of the structures supported by it. Behavior of any chemical or contaminant in the soil depends upon its properties and its interactivity with soil. The major sources of subsurface and 2. EXPERIMENTAL PROGRAM surface contamination are land disposal of industrial, mining, The Red Earth used for the present study has been obtained agricultural wastes and accidental spillage of chemicals. at a depth of 1.5 meters at a test pit dug for the proposed Bio- Results of some studies indicate that the detrimental effect of park at the Bangalore University campus, Jnanabharathi. It seepage of acids and bases into subsoil can cause severe was dried and sieved through a sieve of 4.75 mm to eliminate foundation failures. Extensive cracking damage to the floors, gravel fraction if any. pavements and foundations of light industrial building in a Index properties were determined as per IS-2720 part 5–6. fertilizer plant in Kerala State has reported by Sridharan et Various percentages of CaCO3 and MgCO3 additives are al. (1981). Severe damage occurred to the interconnecting mixed to Red Earth individually and acidification is done piping of a phosphoric acid storage tank in particular and with one normal Sulphuric acid (H2SO4) and Orthophosphoric also to the adjacent buildings due to differential movements acid (H3PO4) for optimum combination of Red Earth and between pump and acid tank foundations of a fertilizer plant Carbonates individually. Some of the important properties of in Calgory, Canada was reported by Joshi et al. (1994). A Red Earth studies are presented in Table 1. Chemicals used in

similar case of accidental spillage of highly concentrated study are Calcium Carbonate (CaCO3), Magnesium Carbonate caustic soda solution as a result of spillage from cracked (MgCO3), Sulphuric acid (H2SO4) and Orthophosporic acid drains in an industrial establishment in Tema, Ghana caused (H3PO4). These chemicals have been obtained from considerable structural damage to a light industrial building Qualigens Fine Chemicals and Sd Fine Chemicals Pvt. in the factory, in addition to localized subsidence of the area Limited, Mumbai India. The Calcium Carbonate and was reported by Kumapley & Ishola (1985). Magnesium Carbonate are in white powder form and insoluble in water but reacts with constituents of any soil.

16 Index and Compaction Properties of Alkalies Treated Red Earth Contaminated with Acids The strength of the acids was reduced to one normal solution.

Properties of CaCO3 and MgCO3 are given in Table 2. ) % (

t Table 1: Physical Properties of Red Earth i m i L

Color Brick Red d i

Specific gravity 2.39 u q i Grain size analysis L Fine sand 29% Silt 23% Clay 48% Curing in Days Atterberg’s limits Fig. 1: Variation of Liquid Limit with Different % Additives Liquid limit 45.5% at Different Curing Periods (contd.) Plastic limit 26.22% Plasticity Index 19.33% 3.1.2 Effect of Magnesium Carbonate

Shrinkage Limit 13.55% Magnesium Carbonate (MgCO3) increased the liquid limit of Optimum moisture Content 21.35% Red Earth from 45.5 percent to 50.7 at 10 percent MgCO3 Maximum dry density 16.5 kN/m3 and upto 54.5 percent due to cation exchange property of Magnesium ions. But with curing, the liquid limit for Red Unconfined Compressive strength 182 kPa Earth is decreases marginal for 7days and marginally Coefficient of permeability 2.48 × 10–7 cm/sec increased to 52 percent at 20 percent MgCO3 for 30 days curing due to increased cation exchange and enlarged double Table 2: Properties of Chemicals Used layer. (Fig. 2)

Properties CaCO3 MgCO3 Molecular Weight 100.1 84.3 54 RE ALONE RE+5%MgCO3

Color White White ) 52 ) % % (

RE+10%MgCO3 Crystal Symmetry Rhombic Trigonal ( 50

T t I i

M RE+15%MgCO3 I Refractive Index nD 1.681 1.51 m 48 i L

RE+20%MgCO3 D I

Density 2.71g/cc 2.05g/cc d 46 i U

u RE+15%MgCO3+1N H3PO4 ◦ ◦ Q I q

Melting Point 825 C 990 C i 44 L L RE+15%MgCO3+1N H2SO4 Solubility in 100 0.013g/100ml@ 0.01g/100ml@ 42 ◦ ◦ RE+1N H3PO4 parts solvent 20 C, soluble in 20 C, soluble in 40 acids acids 0 7 14 21 28 Curing in Days Assay 85% 95% CURING IN DAYS Fig. 2: Variation of Liquid Limit with Different % Additives 3. RESULTS AND DISCUSSIONS at Different Curing Periods 3.1 Liquid Limit 3.1.3 Effect of Sulphuric Acid 3.1.1 Effect of Calcium Carbonate Red Earth treated with optimum percentage of CaCO3 When Red Earth is treated with different percentage of increases liquid limit marginally with addition of 1N Calcium Carbonate liquid limit decreased from 45.5 percent Sulphuric acid. 1N Sulphuric acid increased the liquid limit to 39 percent. This is due to the reduction in thickness of to maximum 43.5 percent and for MgCO3 treated Red Earth diffused double layer of clay particles by exchange of the liquid limit decreased to 49.2 percent for 30 days curing monovalent cations by divalent calcium ions. However with respectively. curing (Fig. 1) the liquid limit for Red Earth increases slightly for 7 days due to flocculation of clay particle and 3.1.4 Effect of Ortho Phosphoric Acid increased upto 41.5 percent for 30 days curing. Optimum Normal Orthophosporic acid increased the liquid limit from decrease in liquid limit is found to be 37.5 percent at 15 38.9 percent to 46.5 percent for Red Earth treated with percent CaCO3. CaCO3 and also marginally decreased the liquid limit from 50.7 percent to 49.5 percent for MgCO3 treated Red Earth for immediate mixing. However, acidification of both optimum

17 Index and Compaction Properties of Alkalies Treated Red Earth Contaminated with Acids percent of CaCO3 and MgCO3 treated Red Earth showed However for Red Earth treated with optimum percentage of marginal increase in liquid limit when cured for 7 and 30 MgCO3 the Plastic limit decreases marginally. However for days (Fig. 2) Curing of CaCO3 and MgCO3 treated acidified Red Earth, to 7 and 30 days respectively, a decrease in plastic limit upto 3.2 Plastic Limit 14.2 percent is observed as shown in Figure 4.

With the addition of various percentages CaCO3 to Red Earth In both CaCO3 and MgCO3 treated Red Earth the plastic limit the plastic limit is decreased from 26.2 percent to 20.9 is slightly increased from 20.9 percent upto 23.5 percent and percent for immediate mixing. For 7 days and 30 days curing from 28.8 percent to 29.2 percent respectively on addition of plastic limit of CaCO3 treated Red Earth is found to have 1N H3PO4. For 7 and 30 days cured samples a marginal been increased marginally from 26.2 percent upto 28.3 increase in plastic limit is observed. percent (Fig. 3). This is due to flocculation of clay particle which hold the water during the curing period. 3.3 Shrinkage Limit

Shrinkage limit is increased from 13.5 percent to 20.1 30 RE ALONE percent for Red Earth treated with optimum percentages of 28 RE+5%CaCO3 CaCO . 26 3 ) ) RE+10%CaCO3

% 24 %

( With curing, the Shrinkage limit is decreased to 17.2 percent

T RE+15%CaCO3 t I i 22 for 7 days and further decreased to 15.5 for 30 days. M m I i 20 RE+20%CaCO3 L L

Addition of various percentages of MgCO3 decreases the C c RE+15%CaCO3+1N

I 18 i t

T H2SO4 s Shrinkage limit upto 11% with addition of 20% MgCO3.

a RE+15%CaCO3+1N l A H3PO4

P Further increase in Shrinkage limit is observed upon 7 days

L 14 RE+1N H2SO4 P 12 curing but a marginal decrease is observed for 30 days.

0 7 14 21 28 Addition of 1N H2SO4 to Red Earth alone increases the Curing in Days Shrinkage limit to 16.3%, with curing the same to 7 and 30 CURING IN DAYS days a marginal decrease in Shrinkage limit is found. An Fig. 3: Variation of Plastic Limit with Different Additives at increase in Shrinkage limit to 23.1 percent for acidification

Different Curing Period. (contd.) of CaCO3 treated and slight decrease to 12.5 percent for

acidification of MgCO3 treated Red Earth is observed. Various percentages of MgCO3 addition resulted in an increase in plastic limit values from 26.2 percent to 28.8 However curing effect showed decrease in Shrinkage limit percent at optimum percentage addition for immediate for both alkalies treated Red Earth. mixing. Addition of 1N H3PO4 to Red Earth alone increases the Shrinkage limit. However for 7 and 30 days of curing the Curing of MgCO3 treated Red Earth to 7 and 30 days respectively shown increase in Plastic limit upto 30.3 percent Shrinkage Limit increases marginally with optimum % of CaCO3 and with MgCO3 treated Red Earth. at 20 percent MgCO3 (Fig. 4).

24 RE ALONE 32

RE ALONE

t RE+5%CaCO3 i I ) M m )

30 i RE+5%MgCO3 I RE+10%CaCO3 % 20 L ( L %

( e T E

I RE+10%MgCO3 t 28 RE+15%CaCO3 i g 18 G M a I m i k RE+15%MgCO3 A RE+20%CaCO3 L L 26 n K i 16 r C c N I i h

RE+20%MgCO3 I RE+15%CaCO3+1N t T s 24 S R H2SO4 S 14 a l RE+15%MgCO3+1N H RE+155CaCO3+1N A P S L 22 H3PO4 12 H3PO4 P RE+15%MgCO3+1N 20 H2SO4 0 7 14 21 28 0 7 14 21 28 CURINGCuring IN in DAYS Days CURINGCuring inIN DaysDAYS Fig. 5: Variation of Shrinkage Limit with Different Additives Fig. 4: Variation of Plastic Limit with Different Additives at at Different Curing Periods (contd.) Different Curing Periods

Red Earth treated with optimum percentage of CaCO3 decreases Plastic limit with addition of 1N Sulphuric acid.

18 Index and Compaction Properties of Alkalies Treated Red Earth Contaminated with Acids

) RE ALONE 3 % % ( 17

RE+5%MgCO3 / T

i 16 N M

RE+10%MgCO3 k I m

i 15 L y

RE+15%MgCO3 i E

e 14 s G g n

a RE+20%MgCO3 e A 13 k D K

12 RE+15%MgCO3+1N y N r I r

h H3PO4 D R 11 S RE+15%MgCO3+1N H H2SO4

S 10 0 7 14 21 28 Water Content (%) CURINGCuring IN inDAYS Days Fig. 8: Variation of Dry Density with Water Content for Fig. 6: Variation of Shrinkage Limit with Different Additives Magnesium Carbonates and Acids Treated Red Earth at Different Curing Periods 4.3 Effect of Sulphuric Acid 4. COMPACTION Red Earth treated with optimum percentage of CaCO3 and 4.1 Effect of Calcium Carbonate MgCO3 marginally and respectively increased and decreased the dry density. Optimum moisture content respectively With the addition of various percentages CaCO to Red Earth 3 decreased and increased. the Maximum Dry density is increased with the decrease in optimum moisture to17.6% due to flocculation between soil 4.4 Effect of Orthoposphoric Acid and CaCO3 particles. The maximum dry density of 18.9 3 kN/m is at 15% optimum percent of CaCO3 content as Red Earth treated with optimum percentage of CaCO3 and shown in the Figure 7. MgCO3 slightly and respectively increased and decreased both dry density and optimum moisture content.

3 5. CONCLUSIONS m / N k

 The optimum percentage for CaCO3 and MgCO3 y t i additions to Red Earth is found to be 15% and 10% s n

e respectively based on compaction test. D  The negative effect of OrthoPhosphoric acid is less on y r

D index properties compared to Sulphuric acid effect, however with CaCO3 and MgCO3 some of the index properties were improved upon curing. Water Content (%)

Fig. 7: Variation of Dry Density with Water Content for REFERENCES Calcium Carbonates and Acids Treated Red Earth Joshi R.C., Pan X and Lohita P. (1994). “Volume Change in Calcareous Soils due to Phosphoric Acid Contamination,” 4.2 Effect of Magnesium Carbonate Proceedings of the XIII ICSMFE, New Delhi, Vol. 4, 1569–1574. Addition of various percentages of MgCO3 to Red Earth, the Maximum Dry density is increased to 17.7 kN/m3 with the Kumapley N.K and Ishola A. (1985). “The effect of increase in optimum moisture content to 30.9% due to Chemical Contamination on Soil Strength,” Proceedings flocculation and hydration between the soil and alkali of XI ICSMFE, Sanfransciso, Vol. 3, 1199–1201. particles as shown in the Figure 8. Sridharan A, Nagaraj T.S and Shivapullaiah P.V (1981). “Heaving of Soil due to Acid Contamination”, Proceedings of XI ICSMFE, Sanfransciso, Vol. 2, 383– 386.