field and laboratory behaviour of fine-grained soil ...(2016a) among others. fundamentally, when...

Draft

Field and Laboratory Behaviour of Fine-Grained Soil Stabilised with Lime

Journal: Canadian Geotechnical Journal

Manuscript ID cgj-2019-0271.R1

Manuscript Type: Note

Date Submitted by the Author: 13-Jul-2019

Complete List of Authors: Consoli, Nilo Cesar; Universidade Federal do Rio Grande do SulBittar marin, Eduardo; University of Western AustraliaQuiñónez Samaniego, Rubén Alejandro; UFRGS, Graduate Program in Civil EngineeringScheuermann Filho, Hugo; Universidade Federal do Rio Grande do SulCristelo, Nuno; Universidade de Tras-os-Montes e Alto Douro

Keyword: Clay, Lime stabilization, field and laboratory tests, strength, porosity/lime index

Is the invited manuscript for consideration in a Special

Issue? :Not applicable (regular submission)

https://mc06.manuscriptcentral.com/cgj-pubs

Canadian Geotechnical Journal

Draft

1

Field and Laboratory Behaviour of Fine-Grained Soil Stabilised with Lime

Nilo Cesar Consoli1; Eduardo José Bittar Marin2; Rubén Alejandro Quiñónez

Samaniego3; Hugo Carlos Scheuermann Filho4; and Nuno Miguel Cordeiro

Cristelo5

ABSTRACT: Fine-grained soils, due to their high plasticity, possess great shrinkage potential

and high compressibility, and are responsible for very significant maintenance costs during the

service life of the associated infrastructures. Stabilisation of such soils with lime is one of the

most effective procedures to mitigate these undesirable characteristics and, at the same time, to

enhance their mechanical properties. Current research seeks, through field and laboratory tests,

to quantify the influence of calcitic hydrated lime on the strength and deflection characteristics

clayey soil from the Paraguayan region of Chaco. The influence of different dry unit weights,

lime amounts and curing periods on the strength and deflection of a Paraguayan clay stabilised

with lime was assessed. The present work shows, for the first time ever, that the porosity/lime

index is the proper parameter to be used in the field when dealing with the strength of clay-lime

bases of pavements. Hence, the results presented herein are a contribution to understanding the

conditions in which these soils can be stabilised in order to be used in infrastructural

applications.

Key words: Clay; lime stabilisation; strength; laboratory and field tests; porosity/lime index.

1 Professor of Civil Engineering, Graduate Programme in Civil Engineering, Universidade Federal do Rio Grande do Sul, Brazil. E-mail: [email protected] 2 Ph.D. Candidate, School of Civil, Environmental and Mining Engineering, The University of Western Australia, Australia. E-mail: [email protected] (formerly M.Sc. student at Universidade Federal of Rio Grande do Sul, Brazil)3 Ph.D. Candidate, Graduate Programme in Civil Engineering, Universidade Federal do Rio Grande do Sul, Brazil. E-mail: [email protected] 4 Ph.D. Candidate, Graduate Programme in Civil Engineering, Universidade Federal do Rio Grande do Sul, Brazil. E-mail: [email protected] 5 Lecturer, School of Engineering, Universidade de Trás-os-Montes e Alto Douro, Portugal. E-mail: [email protected]

Page 1 of 19



mailto:[email protected]





Draft

2

INTRODUCTION

Fine-grained soils tend to present high plasticity, great shrinkage and swelling potential, low

hydraulic conductivity and high compressibility (Mitchell 1981). Such features are related to

the amount and nature of the clay phase and may be disadvantageous for certain construction

purposes, such as dams and road embankments. However, clayey soils can have their

mechanical properties enhanced (i.e. soil stabilisation) through the addition of hydrated lime,

as previously shown by Umesha et al. (2009), Rajesh and Marimuthu (2015), Consoli et al.

(2016a) among others. Fundamentally, when hydrated lime is added to a fine-grained soil in the

presence of water the clay particles aggregate/flocculate in a short-term period which implies

the modification of the soil’ physical properties (e.g. grain size distribution). This is the

consequence owing to the cation exchange between the clay minerals and the calcium ions

(Ca2+) and the increase in the electrolyte content of the interstitial water (Herzog and Mitchell

1963; Transportation Research Board 1987). Besides, in a long-term period, the soil’ strength

and stiffness may be enhanced due to the precipitation of cementitious compounds resulting

from the pozzolanic reactions between the clay minerals and the calcium ions.

Previous findings on fine-grained soils–lime mixtures (e.g., Consoli et al. 2016a; 2016b)

have shown that their behaviour is complex and affected by many factors. Among those, the

following stand out: grain size distribution of the soil, lime type and content, moulding moisture

content, porosity of the mixed material, curing temperature and time of curing. In this sense,

Consoli et al. (2009) were pioneers in the establishment of a single dosage methodology based

on rational criteria where the porosity/lime index (/Liv) is the key feature in the evaluation of

the target unconfined compressive strength. Moreover, the same approach was successfully

applied by Consoli et al. (2011) in the assessment of the initial shear modulus (G0) of soil-lime

blends. Recently, Consoli et al. (2019) established efficaciously the influence of the amount of

lime and the porosity on the accumulated loss of mass (ALM) of fine-grained material-carbide

lime blends. Nonetheless, there are important subjects that still have to be elucidated.

Studies regarding the efficiency of the porosity/lime index in controlling the strength

and stiffness of compacted clay-lime blends are still restricted to laboratory settings. A question

that arises is if clay-lime specimens mixed and compacted in the laboratory depict the main

trends of specimens mixed and compacted with standard field equipments regarding the

unconfined compressive strength. Hence, the aim of the present research is the evaluation of

these tendencies in specimens mixed, compacted and cured under field conditions and in those

Page 2 of 19



Draft

3

mixed, compacted, cured and mixed under laboratory conditions. The positive results in the

present research, extrapolating field and laboratory strength results, considering specimens with

different percentages of lime and compacted specimens with different dry unit weights, enriches

the literature and open the scope for further exploration.

EXPERIMENTAL PROGRAM

Materials and Methods

The experimental program was divided in laboratory-based and field-based testing. The soil

and the lime were initially characterized in the laboratory. The minimum lime quantity needed

for the stabilisation of this soil was determined through the “initial consumption of lime” (ICL)

test, in accordance to the procedures stated by Rogers et al. (1997). Proctor tests on different

soil-lime blends followed, using standard compaction energy ASTM D698 (ASTM 2012), and

the results were then used to fabricate cylindrical specimens, with different lime contents, for

unconfined compressive strength (UCS) tests. The testing program was chosen in such a way

as to evaluate, separately, the influence of the lime content (L), the dry unit weight (d) and,

consequently, the porosity/lime index (/Liv).

The experimental field-testing was set up on the Paraguayan Chaco, a semi-arid region

located in the North-West of Paraguay. The local soil, which was collected and transported to

the laboratory for further tests was classified, according to ASTM D2487 (ASTM 2017) and

based on the characterization described in Table 1, as a lean clay (CL). The pH of the collected

soil was approximately 8.2. An X-ray diffraction test revealed the presence of the following

minerals: smectite, chlorite, kaolinite, illite and quartz. The soil’ specific gravity is 2.69.

Calcitic hydrated lime, with a specific gravity of 2.41, was used as the cementing agent

(ASTM 2011a). Stoichiometrically (based on a thermogravimetric analysis), the employed

calcitic hydrated lime has 81.0% of Ca(OH)2 and 9.40% of CaCO3. Distilled water was used

both for the characterization tests and for the fabrication of the mechanical tests’ specimens.

Preparation and Testing of Laboratory Specimens

The adapted ICL test used to establish the lime content (relative to the dry weight of soil) is

based on the pH variation of the soil-lime mixture as a function of the added lime. The pH value

of the mixture increases with increasing amounts of added lime, up until an asymptotic pH value

Page 3 of 19



Draft

4

is reached. Thus, the ICL is the lime content required to attain that threshold pH. Theoretically,

lime in excess of the ICL is utilized in the cementation process, through pozzolanic reactions,

which are responsible for the most significant portion of the strength increase. The results

showed that 4% lime (weight percentage of lime, relatively to the total soil+lime combination)

corresponds to the ICL of this particular soil. Therefore, this value was chosen for the

experimental plan, as well as the values of 6% and 8%, which were chosen considering previous

experience with lime treated soils (e.g., Ingles and Metcalf 1972; Mitchell 1981; Consoli et al.

2019).

A standard Proctor compaction test, performed on a soil-lime mixture with a 6% lime

content, revealed maximum dry unit weight and optimum moisture content values of 17.4

kN/m3 and 15%, respectively. A target dry unit weight for a given specimen was then

established through the total dry mass (soil+lime) divided by the total volume of the specimen.

All the specimens were moulded with moisture content of 15%. Three different dry unit weights

(14.5 kN/m3, 15.5 kN/m3 and 16.8 kN/m3 – mimicking field compaction conditions obtained in

present research), three lime contents (4%, 6% and 8%) and four curing periods (7, 28, 60 and

90 days of curing) were used in the fabrication of the UCS specimens. Cylindrical specimens

with 50 mm in diameter and 100 mm in height were used for the UCS tests.

Porosity () is defined as the ration between the volume of voids and the total volume

of the specimen (V). As shown in Eq. (1) (Consoli et al. 2011), porosity () can be related to

dry unit weight (d), hydrated lime (L) and soil content (S). Each material (soil and lime) has a

dry unit weight (sS and sL), which also needs to be considered for calculating porosity.

𝜂 = 100 ―

100 ∙ [((𝛾𝑑 ∙ 𝑉)

(1 + 𝐿/100)𝛾𝑆𝑠 ) + (

(𝛾𝑑 ∙ 𝑉 ∙ 𝐿)(100 + 𝐿)

𝛾𝑆𝐿 )]𝑉

(1)

The preparation of the specimens started by weighing the dry materials (clay and lime).

Next, they were mixed until they acquired visual homogeneity. Water was then added in order

to reach the target moisture content of 15%, continuing the mixing process until homogeneity

was again obtained. The specimen was then statically compacted in three layers, inside a

cylindrical lubricated split mould, targeting the previously specified dry unit weight. After the

moulding process, the specimen was immediately extracted from the split mould and its weight,

diameter and height were measured with accuracies of 0.01g and 0.1mm, respectively. The

specimens were cured in a humid room at 21º±2ºC and relative humidity above 95%.

Page 4 of 19



Draft

5

The UCS tests followed the recommendations stated by ASTM C39 (2010). Prior to the

tests, the samples were put underwater, for 24 hours, in order to increment the degree of

saturation and, hence, diminish possible suction effects (Consoli et al. 2011). The water

temperature was maintained at approximately 21ºC. The UCS tests were carried out under

strain-controlled conditions (axial displacement of 1.14 mm/min) and the maximum load was

recorded. Because of the typical data scatter usually associated with UCS tests, three specimens

were tested to determine the value in each mix design.

Construction of the experimental road pavement foundations

The first phase of the field experimental program was designed to evaluate the energy that could

be transmitted to each section by the compactor. Therefore, three preliminary 0.20 m thick

sections, with a surface area of 3.0 m x 3.0 m, were built using kneading compaction equipment

(Dynapac model CA25, with 95 kN working load and frequency of 33 Hz). Different lime

contents of 4%, 6% and 8% were assigned to each of these three sections. Due to possible lime

losses during field soil-lime blending, the lime content values in the field were increased by

10%, i.e. 4.4%, 6.6% and 8.8%. A levelled surface was previously prepared, and soil collected

nearby was transported and deposited on site. After screening, its moisture content was

measured, and water was added until the 15% target was reached. The lime was then included

and mixed with the wet soil (Figure 1a) using a motor grader and a tractor equipped with a disc

harrow. Next, the surface was regularized and the mixture was compacted (Figure 1b) using a

sheepsfoot drum roller to the target dry unit weight. After each passing of the compactor

equipment, the dry unit weight of the foundation was measured using a non-nuclear soil density

gauge.

The second phase of the field-testing program was the construction of three additional

experimental sections (with 30 m in length, 3 m wide and a thickness of 0.15 m) following the

same procedures described above. Each section was divided in three 10 m long subsections,

with different dry unit weight and lime content values (Table 2). In order to obtain the target

dry unit weight values of the Sections 1, 2 and 3, compactor passes equal to, respectively, 4, 8

and 16 were needed.

Right after construction finished (day 1) and on the following 3, 4, 14 and 28 days the

peak deflections of each subsection were assessed using a lightweight deflectometer in

accordance to the procedures stated by ASTM E2583 (ASTM 2011b). This test method can be

seen as a plate-bearing test in which the load is a force pulse deriving from a properly adjusted

falling mass. The impact of such mass results in the deflection of the surface, which is measured

Page 5 of 19



Draft

6

through suitable instrumentation. This peak deflection is related to the stiffness of the soil-lime

layer and, thus, is an indicative of the stabilisation performance along the curing period. That

is, a small deflection value suggests a higher stiffness than a great deflection value when layers

with the same height are compared. Additionally, cylindrical samples were retrieved from the

experimental sections after 182 days and were submitted to UCS tests. Those specimens

presented 50 mm in diameter and 100 mm in height.

RESULTS

Properties of the Field Layers

Figure 2 shows the variation of the dry unit weight of each of the preliminary soil-lime layers

(first phase of the field program) as a function of the number of passes of the compactor. It can

be observed that approximately the same dry unit weight is reached with any given number of

passes, regardless of the lime content. This indicates that the addition of lime (regarding the

quantities employed herein) has no influence on the density considering the compaction

technique used herein. Moreover, there is an asymptotic value for the dry unit weight, around

16.8 kN/m3, which is after 10 passes.

Results obtained with the lightweight deflectometer (LWD) are presented in Figure 3.

Three deflection measurements were performed nearly the center of each studied section for

every curing period. In general, a stiffness increase (smaller deflections) was observed for

greater curing periods. The 4% lime content was effective in every section for almost every

curing time. With the exception of Section 3, not much difference could be detected between

4%, 6% and 8% deflection values, in terms of effectiveness. Besides, extracted samples allowed

confirming that the experimental soil layers presented adequate homogeneity.

Unconfined Compressive Strength of Field and Laboratory Specimens

UCS tests were performed on samples extracted from the field layers, as well as on laboratory-

moulded specimens. The results, presented in Figure 4, show that an increase in lime content

does not have a major influence in the compressive strength of the laboratory specimens.

Likewise, the UCS results of the specimens collected from the field, after 182 days curing,

suggest that the variation in lime content has low influence on compressive strength, regardless

of the initial density. It is important to mention that the field samples were exposed to higher

Page 6 of 19



Draft

7

temperatures than the specimens cured in the laboratory due to the region’ climate. This

probably explains why the former appear to yield higher UCS values than those predicted by

the models fitted to the laboratory-specimens results.

On the other hand, the influence of porosity on the UCS of all mixtures appears to be

substantial in both field and laboratory conditions. Figure 5 shows that, in this case, the

porosity/lime index (/Livexp) controls the behaviour of the compressive strength. Indeed, unique

relationships were found between the UCS and this index, with high correlation values (R2) of

0.92, 0.92, 0.97, 0.94 and 0.98, for 7, 28, 60, 90 and 182 days, respectively. Furthermore,

although different compositions and curing times were used, a single adjustment exponent (exp)

of 0.12 was fitted to every case (from specimens moulded and cured in the field and in the

laboratory). This adjustment exponent (0.12) reflects the small influence of the lime content in

comparison with the porosity of the tested mixtures, as its value is relatively small.

In this sense, the correlation of the adjusted porosity/lime index and the compressive

strength of soils treated with lime has been shown by Consoli et al. (2011), in which the authors

have shown that the application of a power law, with an exponent of 0.12 (value estimated for

fine-grained soils), is required to create compatibility between the porosity and lime content

variations.

CONCLUSIONS

The present work was based on tests carried out on field and laboratory experimental specimens

of clay-lime mixtures. From the data presented in this technical note, the following conclusions

can be drawn:

The dry unit weight of each of the preliminary soil-lime layers (first phase of the

field program) was a function of the number of passes of the compactor. It was

observed that approximately the same dry unit weight is reached for a given

number of passes preliminary soil-lime layers, regardless of the lime content, thus

indicating that the addition of more or less lime (in the studied range) has no

influence on the field compaction process. Moreover, there is an asymptotic value

for the dry unit weight, around 16.8 kN/m3, which is after 10 passes;

Results obtained with the lightweight deflectometer (LWD) in all studied sections

have indicated that stiffness increase with time as the measured deflections

Page 7 of 19



Draft

8

decreased. The 4% lime content was effective in every section for almost every

curing time. With the exception of Section 3, not much difference could be

detected between 4%, 6% and 8% deflection values, in terms of effectiveness;

Unconfined compressive strength showed a high correlation with the adjusted

porosity/lime index (/Liv0.12). The present work also shows, for the first time ever,

that such parameter is the proper index to be used in the field when dealing with

pavement construction and field control of unconfined compressive strength.

ACKNOWLEDGEMENTS

The authors wish to explicit their appreciation to FAPERGS/CNPq 12/2014 – PRONEX (grant

# 16/2551-0000469-2), MCT-CNPq (INCT, Universal & Produtividade em Pesquisa) and

MEC-CAPES (PROEX) for the support to the research group.

REFERENCES

ASTM. 2006. Standard classification of soils for engineering purposes. ASTM standard D2487,

American Society for Testing and Materials, West Conshohocken, Philadelphia.

ASTM. 2007. Standard test method for pore water extraction and determination of the soluble

salt content of soils by Refractometer. ASTM standard D4542, American Society for Testing

and Materials, West Conshohocken, Philadelphia.

ASTM. 2010. Standard test method for compressive strength of cylindrical concrete specimens.

ASTM standard C39, American Society for Testing and Materials, West Conshohocken,

Philadelphia.

ASTM. 2011a. Standard specification for quicklime, hydrated lime, and limestone for

environmental uses. ASTM standard C1529, American Society for Testing and Materials,

West Conshohocken, Philadelphia.

Page 8 of 19



Draft

9

ASTM. 2011b. Standard test method for measuring deflections with a light weight

deflectometer (LWD). ASTM standard E2835, American Society for Testing and Materials,

West Conshohocken, Philadelphia.

ASTM. 2012. Standard test methods for laboratory compaction characteristics of soil using

standard effort (600 kN-m/m3). ASTM standard D698, American Society for Testing and

Materials, West Conshohocken, Philadelphia.

Consoli, N.C., Lopes Junior, L.S., Foppa, D., and Heineck, K.S. 2009. Key parameters

dictating strength control of lime/cement-treated soils. Proceedings of the Institute of

Civil Engineers – Geotechnical Engineering, 162(2): 111-118.

Consoli, N.C., Dalla Rosa, A., and Saldanha R.B. 2011. Variables governing strength of

compacted soil-fly ash-lime mixtures. Journal of Materials in Civil Engineering, 23(4): 432–

440.

Consoli, N.C., Quiñónez Samaniego, R.A., and Kanazawa Villalba, N.M. 2016a. Durability,

strength, and stiffness of dispersive clay–lime blends. Journal of Materials in Civil

Engineering, 28(11): 04016124.

Consoli, N.C., Quiñónez Samaniego, R.A., Marques, S.F.V., Venson, G.I., Pasche, E., and

González Velásquez, L.E. 2016b. Single model establishing strength of dispersive clay

treated with distinct binders. Canadian Geotechnical Journal, 53(12): 2072-2079.

Consoli, N.C., Saldanha, R.B., and Scheuermann Filho, H.C. 2019. Short and long-term effect

of sodium chloride on strength and durability of coal fly ash stabilized with lime. Canadian

Geotechnical Journal. doi: 10.1139/cgj-2018-0696.

Herzog, A., and Mitchell, J.K. 1963. Reactions accompanying stabilization of clay with cement.

Highway Research Record, 36, 146-171.

Ingles, O.G., and Metcalf, J.B. 1972. Soil stabilization principles and practice. Butterworth-

Heinemann Ltd, Oxford, UK.

Mitchell, J.K. 1981. Soil improvement – State-of-the-art report. In Proceedings of the 10th

International Conference on Soil Mechanics and Foundation Engineering, Stockholm,

Sweden, International Society of Soil Mechanics and Foundation Engineering, 4, pp. 509–

565.

Rajesh, T., and Marimuthu, A. 2015. Geotechnical characterization of dispersive soil stabilized

with lime and palm oil fuel ash. Journal of Civil Engineering and Environmental

Page 9 of 19



Draft

10

Technology, 2(8): 713-716.

Rogers, C.D.F., Glendinning, S., and Roff, T.E.J. 1997. Lime modification of clays for

construction expediency. Proceedings of the Institution of Civil Engineers – Geotechnical

Engineering, 125(4): 242-249.

Transportation Research Board. 1987. State of the Art Report 5. National Research Council,

Washington, D.C.

Umesha, T.S., Dinesh, S.V., and Sivapullaiah, P.V. 2009. Control of dispersivity of soil using

lime and cement. International Journal of Geology, 1(3), 8-16.

Page 10 of 19



Draft

11

NOTATION

L lime content (expressed in relation to mass of dry soil)

Liv volumetric lime content (expressed in relation to the total specimen volume)

qu unconfined compressive strength

R2 coefficient of determination

t curing time

V total volume of specimen

η porosity

η/Liv porosity/lime index

d dry unit weight

SL unit weight of lime grains

Ss unit weight of soil grains

w moisture content

LWD lightweight deflectometer

Page 11 of 19



Draft

12

Table 1. Physical properties of the soil sample.Parameter Value

Liquid limit (%) 33Plastic limit (%) 17Plastic index (%) 16Unit weight of the soil grains (kN/m3) 26.9Silt (0.002 mm < diameter < 0.075 mm) (%) 80Clay (diameter < 0.002 mm) (%) 20Mean particle diameter, D50 (mm) 0.0065Sodium Absorption Ratio (SAR) 14.1Soil Specific Surface (m2/g) 26.2USCS class (ASTM 2006) CL

Page 12 of 19



Draft

13

Table 2. Values of dry unit weight and moisture content for each experimental section.Section Parameter Subsection A Subsection B Subsection C Average

1 Lime content (%) 4 6 8 -Dry unit weight (kN/m3) 14.54 14.51 14.39 14.5Moisture content (%) 14.68 14.50 15.18 14.8



Page 13 of 19



Draft

14

Figure Captions

Figure 1. Construction of soil-lime layers: (a) mixing and (b) compaction.

Figure 2. Dry unit weight vs. number of compaction passes obtained during the first phase of

the field-testing.

Figure 3. Field measurements of deflections of the compacted layers, considering different dry

unit weight and lime content values.

Figure 4. Unconfined compressive strength (UCS) evolution with curing time of laboratory (7,

28, 60 and 90 days) and field (182 days) specimens prepared with dry unit weights of (a) 14.5

kN/m3; (b) 15.5 kN/m3 and (c) 16.8 kN/m3.

Figure 5. Variation of unconfined compressive strength (UCS) with the adjusted porosity/lime

index, for different curing periods (7d, 28d, 60d, 90d and 182d-field).

Page 14 of 19



Draft

Figure 1: Construction of soil-lime layers: (a) mixing and (b) compaction.

Page 15 of 19



Draft

Figure 2. Dry unit weight vs. number of compaction passes obtained during the first

phase of the field-testing.

Page 16 of 19



Draft

Figure 3. Field measurements of deflections of the compacted layers, considering

different dry unit weight and lime content values.

Page 17 of 19



Draft

Figure 4. Unconfined compressive strength (UCS) evolution with curing time of

laboratory (7, 28, 60 and 90 days) and field (182 days) specimens prepared with dry unit

weights of (a) 14.5 kN/m3; (b) 15.5 kN/m3 and (c) 16.8 kN/m3.

Page 18 of 19



Draft

Figure 5. Variation of unconfined compressive strength (UCS) with the adjusted

porosity/lime index, for different curing periods (7d, 28d, 60d, 90d and 182d-field).

Page 19 of 19



field and laboratory behaviour of fine-grained soil ...(2016a) among others. fundamentally, when...

Documents