Thermally Treated Clay as a Stabilizing Agent for Expansive Clayey Soil: Some Engineering Properties

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Values of free swelling and swelling pressure versus the combinations of soil and stabilisers (calcined clay and lime)_

Clay mixture	Soil 1		Soil 2		Soil 3
	Free swell (%)	Swelling pressure (kPa)	Free swell (%)	Swelling pressure (kPa)	Free swell (%)	Swelling pressure (kPa)
CC0L0	8.35	80	9.24	125	10.55	150
CC0L6	2.56	40	2.65	35	2.16	35
CC10L0	5.85	75	8.56	100	7.12	110
CC20L0	4.17	60	4.85	65	3.92	60
CC10L6	1.75	25	1.66	20	1.19	20
CC20L6	1.44	10	1.12	5	0.88	5

Clay mixtures used in the study_

Clay mixtured	Percentage
	Clay soil	Thermally treated clay	Lime
CC0L0 (control)	100	0	0
CC0L6	94	0	6
CC10L0	90	10	0
CC20L0	80	20	0
CC10L6	84	10	6
CC20L6	74	20	6

Some physical properties with chemical composition of quick lime_

Chemical composition(%)				Physical properties
CaO	MgO	Fe2O3	Sulphates (SO4)	Loss of ignition (%)	Specific gravity (g/cm3)	Blaine fineness (cm2/g)
93.5	0.53	0.47	1.2	3.9	2.2	4000

Basic properties of the studied clayey soils_

Soil	Depth(m)	Specific gravity, Ρ (g/cm3)	Clay particles, d<0.002 mm	Plasticity index (PI), %	Soil classification (USCS) [13]	Optimum water content, Wopt (%)	Maximum dry unit weight, γdmax(g/cm3)
S1	1	2.69	23	29	CH	25.5	1.42
S2	0.75	2.67	31.5	35	CH	23	1.38
S3	1.25	2.72	35	42	CH	26	1.30

Compressive strength of clay mortar cubes cured for 2, 7 and 28 days_

	Compressive strength (MPa)
Clay soils	2 days	7 days	28 days
Soil 1	2.64	6.73	11.93
Soil 2	2.80	5.23	8.45
Soil 3	2.35	5.36	9.86

Atterberg limits of the studied mixtures_

Soil mixture designation	PI (%)
	S1	S2	S3
CC0L0	29	35	42
CC0L6	9	6	7
CC10L0	19	21	19
CC20L0	14	17	16
CC10L6	7	5	6
CC20L6	4	3	4

Linear shrinkage values of the investigated clay mixtures_

Clay mixture	Linear shrinkage (LSI%)
	Soil 1	Soil 2	Soil 3
CC0L0	16.46	21.4	24.3
CC0L6	13.63	14.3	18.6
CC10L0	10.06	8.6	12.9
CC20L0	3.64	5.7	5.7
CC10L6	2.93	3.6	4.3
CC20L6	2.57	2.1	2.9

Maximum dry unit weight γdmax and optimum water content Wopt of the clay mixtures_

Clay mixture	γ(dmaxg/cm3)			Wopt (%)
	S1	S2	S3	S1	S2	S3
CC0L0	1.48	1.38	1.30	25.5	23	27
CC0L6	1.29	1.17	1.12	32.1	29.75	34.21
CC10L0	1.52	1.51	1.36	24.32	21.6	24.75
CC20L0	1.67	1.65	1.56	23.51	19.18	23.89
CC10L6	1.39	1.31	1.27	28.68	25.88	30.11
CC20L6	1.49	1.43	1.33	27.08	24.45	29.87