Maturity period and curing as important quality control parameters

International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 2, March - April (2013), © IAEME
393
MATURITY PERIOD AND CURING AS IMPORTANT QUALITY
CONTROL PARAMETERS FOR LIME STABILIZED CLAY
SUBGRADES
Dr. K.V.Krishna Reddy1
, Mr.K.P.Reddy2
1
Professor & Principal, Chilkur Balaji Institute of Technology, Hyderabad-75, AP, India
2
Maintenance Engineer, Vasavi College of Engineering, Hyderabad-75, AP, India
ABSTRACT
With rapid industrialization and the need for rural road development, it has become
imperative to use poor subgrades for road formation. Poor subgrades, especially clayey soils
need stabilization for effective performance. Though undesirable, most of the times insitu
conditions does not go in hand with the strict quality control measures with regard to the
delay in compaction (maturity period) and curing in road formation works.
The object of the present study is to determine the effect of delayed compaction on
California bearing strength and curing period on the California bearing strength (CBR) and
unconfined compressive strength (UCC) of clay-lime mixes. The results highlight the
importance of the maturity period and curing as important quality control parameters.
Key Words: Maturity Period, Delay in compaction, Curing of lime stabilized subgrades,
Lime stabilization.
1. INTRODUCTION
Rural Road Connectivity is not only a key component of Rural Development by
promoting access to economic and social services and thereby generating increased
agricultural incomes and productive employment opportunities in India, It is well known that
even where connectivity has been provided, the roads constructed are of such quality (due to
poor construction or maintenance techniques) that they cannot always be categorized as All-
weather roads. In the process of connecting various parts of the country, it has become
necessary to use all the types of subgrades for highway formation and clayey soils are no
exception.
INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND
TECHNOLOGY (IJCIET)
ISSN 0976 – 6308 (Print)
ISSN 0976 – 6316(Online)
Volume 4, Issue 2, March - April (2013), pp. 393-401
© IAEME: www.iaeme.com/ijciet.asp
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394
Clayey subgrades stabilized with lime, cement or chemicals have come to stay as a
standard engineering material for high way construction. During recent years, there has been
an extensive use or lime for the stabilization or clayey soils, which have many advantages
over the other types of stabilization, however due to minor negligence in parameters like
maturity period and curing of the stabilized mixes a lot of strength loss occurs which is
irreparable and need a lot of maintenance after construction
2. LITERATURE REVIEW
Dumblet observed that the delay in wet mixing and subsequent compaction has little
significance. Mitchell working with an organic expansive clay mixed with 4 percent dolomite
hydrated lime gathered that a delay of 24 hours between wet mixing and compaction can
result in loss in maximum dry density and a loss the compressive strength.
To investigate the effect of elapsed time between mixing and compaction of a dune
sand and montmorillonitic clay with flyash and a high Calcium hydrated lime, Davidson,
inferred that a delay of 24 hours had negligible effect on the density and strength in case of
dune sand, but in case of clay, the delay in mixing and compaction caused appreciable
decrease in dry density and strength or the mixes.
An evaluation of the effect of delay between mixing was investigated upon by cocka
et al. Samples of soil mixed with lime and cement were compacted at different delay periods.
Results indicated that the dry density or the samples showed a slight decrease irrespective of
the addition of lime to the soil. Strength values also showed a decrease, though the decrease
was minimized by the addition or lime.
Fly ash is one of the most plentiful and versatile of the industrial by-products (Collins,
1992). It is classified into two classes based on the chemical composition of the flyash. Class
‘F’ flyash is produced from burning anthracite and bituminous coals and contains small
amount of lime (CaO). (Cockrell, 1970; Chu and Kao 1993) This flyash has siliceous and
aluminous material (pozzolans), which itself possesses little or no cementitious value but in
the presence of moisture, chemically reacts with lime at ordinary temperature to form
cementitious compounds. Class ‘C’ flyash is produced from lignite and sub-bituminous coals
and usually contain significant amount of lime along with pozzolanic materials. The
pozzolanic reactivity of the flyash is not represented by any chemical or physical property of
the flyash. Cementious calcium silicate and calcium aluminosilicate hydrates are formed
when flyash reacts with water and lime, (Hausmann, 1990). Fly ash produced in the
combustion of sub bituminous coals exhibits self-cementing characteristics that can be
adapted to a wide range of stabilisation applications. Ash treatment can effectively reduce the
swell potential of fat clay soils and increase subgrade support capacity of pavement
subgrades. Ash hydration occurs rapidly and must be addressed by the construction
procedures to obtain maximum potential benefit from the ash treatment. This can be accom-
plished by limiting the delay between incorporation of the ash and final compaction to less
than 2 hours. Hydration chemistry can differ significantly between specific sources and
design mixes must be based on the specific ash to be used. Compressive strengths of ash
treated materials are dependent upon moisture content at time of compaction and strict
moisture control is required during construction (Katti, 1970; Churchill, 1999; Ferguson,
1993 and Thomas, 2002). An optimum content of 15% of flyash and lime in ratio of 1:4
could be used to obtain best stabilizing effect on alluvial soil (Ghosh, 1973). Addition of lime

395
to the soil-flyash mixture results in increased friction angle, cohesive intercept, and average
modulus (Consoli, 2001).
3. RESEARCH METHODOLOGY
The percentage of lime to be added to low plastic clay soils for stabilization has been
varied from 0 to 4 % as literature review shows that the same has no effect beyond 4%. The
optimum moisture content and maximum dry density of the soil and the soil lime mixes is
determined to find the OMC and MDD values at which the samples have to be compacted for
strength tests, namely California bearing Ratio (CBR) and Unconfined compressive strength
(UCC) of the clay and clay lime mixes.
Delay in compaction is studied on California bearing ratio of clay lime mixes at 0, 2
and 4% of lime at respective OMC and MDD for compaction after maturity period of 30
minutes, 12 hours, 24 hours and 48 hours respectively.
The California bearing ratio is determined for all the clay lime mixes with varying the
curing period on maturity of 30 minutes and after 7days, 28 days and 40 days followed by 4
day soaking in all the cases.
Unconfined compressive test of the clay lime mixes is done with varying curing
periods of 7 days, 28 days and 40 days. Results have been analyzed to determine the effect of
delay in compaction and curing period.
4. DATA ANALYSIS
The experimental results are tabulated from the plots drawn for the respective
laboratory experiments. Table I shows the properties of clay and lime used for
experimentation. Table 2 represent the optimum moisture content and maximum dry density
of the clay lime mixes at various percentages of lime. Table 3 represent the effect of delayed
compaction on optimum moisture content, maximum dry density and the California bearing
ratio value (CBR) of the clay lime mixes. Table 4 and 5 depict the effect of curing on the
CBR value and unconfined compression strength (UCC) of the clay lime mixes respectively.
Table 1 Properties of clay and lime used for experimentation
S. No. Property Value
1 Grain Size Distribution
1.18mm
75 micron
%
99
83
2 Atterberg Limits
Liquid Limit (%)
Plastic Limit (%)
Plasticity Index
29
18
11
3 Compaction properties
Optimum moisture content (%)
Maximum Dry Density (g/cc)
14.6
1.84
4 Soaked CBR (%) 6.0
S.
No.
Property Clay
1 Calcium hydroxide
95%
2 Chloride 0.01%
3 Sulphate 0.2%
4
Aluminium Iron
and insoluble
matter
1.0%
5 Arsonic 0.0004%
6 Lead 0.001%

396
Table 2 Compaction test results
S.no Mix OMC (%) MDD( g/cc)
1 Clay +0% lime 14.6 1.84
2 Clay +1% lime 14.7 1.85
3 Clay +2% lime 15.0 1.88
4 Clay +3% lime 15.0 1.88
5 Clay +4% lime 15.2 1.91
Table 3 Properties for delay in compaction on clay -lime mixes
Clay +0% lime
S.no Property On Maturity 12 hours 24hours 48 hours
1 OMC(%) 14.6 13.6 12.8 12.0
2 MDD (g/cc) 1.84 1.82 1.78 1.72
3 CBR (%) 6 5.2 4.8 4
Clay +1% lime
1 OMC(%) 14.7 13.9 13.4 12.6
2 MDD (g/cc) 1.85 1.83 1.76 1.73
3 CBR (%) 6.5 5.7 4.5 4.2
Clay +2% lime
1 OMC (%) 14.8 14.6 14.2 14.0
2 MDD(g/cc) 1.86 1.84 1.78 1.74
3 CBR (%) 15 12 11 11
Clay +3% lime
1 OMC (%) 15.0 14.6 14.4 14.1
2 MDD(g/cc) 1.88 1.86 1.79 1.73
3 CBR (%) 15.6 13 11.1 10.8
Clay +4% lime
1 OMC (%) 15.2 14.8 14.6 14.2
2 MDD (g/cc) 1.91 1.87 1.84 1.78
3 CBR (%) 20 18 17 16

397
Table 4 CBR values on clay- lime mixes soil with curing and soaking
S.no Mix CBR
4 D
soaking
CBR
7Dcuring &
4D soaking
CBR
28D curing &
4D soaking
CBR
40D curing &
4D soaking
1 Clay +1%
lime
12% 25% 30% 32%
2 Clay +2%
lime
15% 30% 32% 35%
3 Clay +3%
lime
18% 31% 34% 38%
4 Clay +4%
lime
20% 27% 36% 40%
Table 5 UCC values on clay- lime mixes depicting effect of curing
S.no Mix UCC
7D Curing
(Kg/cm2
)
UCC
28D Curing
(Kg/cm2
)
UCC
40DCuring
(Kg/cm2
)
1 Clay +0% lime 1.3 - -
2 Clay +1% lime 2 3.8 3.9
3 Clay +2% lime 4 5.2 6
4 Clay +3% lime 4.1 5.15 6.3
5 Clay +4% lime 3.8 6 8
5. RESULTS
The results and plots thereof are interpreted to observe the effect of delay in compaction
on CBR of the clay lime mixes and that of curing on UCC and CBR strength of clay lime
mixes. The same are depicted vide plots 1 to 3. Plot 1 shows the effect of delay in
compaction on the clay lime mixes and Plots 2 and 3 show the effect of curing on CBR
and UCC of the clay lime mixes respectively

398
0.00 10.00 20.00 30.00 40.00 50.00
No of hours of dealy in Compaction
4.00
8.00
12.00
16.00
20.00
CaliforniaBearingRatio%
Clay + 0% Lime
Clay + 1% Lime
Clay + 2% Lime
Clay + 3% Lime
Clay + 4% Lime
.
Plot 1 Effect of Delay in compaction on CBR of clay –lime Mixes
0.00 10.00 20.00 30.00 40.00
No of Days of Curing
10.00
20.00
30.00
40.00
CaliforniaBearingRatio%
0 Days Curing + 4 Day Soaking
7Days Curing + 4 Day Soaking
Plot 2 Effect of curing period on CBR of clay –lime Mixes

399
0.00 10.00 20.00 30.00 40.00
No. of Days of Curing
2.00
4.00
6.00
8.00
UuconfinedCompressiveStrengthkg/sqcm
Clay + 1% Lime
Clay + 2% Lime
Clay + 3% Lime
Clay + 4% Lime
Plot 3 Effect of curing period on UCC of clay –lime Mixes
6. ACKNOWLEDGEMENT
At the outset the authors would thank the Head, CED at Vasavi Engineering College
and Head Transportation Division and professors at JNTUH for their valuable guidance and
encouragement during experimentation.
7. CONCLUSION
1. The OMC and MDD values decreased with delay in compaction. The decrease was
significant with OMC decreasing from 15.2% to 14.2% and MDD decreasing from 1.91
g/cc to 1.78 g/cc. for 4% lime mixed clay soil.
2. The CBR values decreased from 20% to 16% as the delay in compaction increased to 48
hours for 4% lime mixed clay soil. This has a lot of effect on the strength of the
subgrades.
3. The CBR and UCC values increased significantly for 7 day cured and 28 day cured
samples. Curing up to 7 days showed increase in the CBR and UCC values, which
increased till 28 day strength and further the effect was insignificant.
4. The CBR strength achieved with 2% of lime was almost achieved with 1% lime mixed
clay soil with 7 days curing.
5. UCC value with 2% lime mixing with no curing is found to be 4 kg/cm2
and the same for
1% lime mixed soils with 7 days curing is found to be 3.8 kg/cm2
6. Clay- Lime mixes should be compacted immediately after maturity of 30 minutes. There
should not be any delay in compaction after mixing clay with lime and water. Delay in
compaction leads to substantial decrease in the CBR values.
7. It is recommended that all the clay lime mixes should be cured at least for 7 days and for
a maximum of 28 days.

400
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Maturity period and curing as important quality control parameters

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