Soil stabilization has been practiced for quite some time by adding mixtures, such as cement, lime and fly ash. The additives of lime (L), natural pozzolana (NP) or a combination of both were investigated here on the impact on the temporal variation of geotechnical characteristics of two cohesive soils. Lime and natural pozzolana were added at the content of 0–8% and 0–20%, respectively. The soil specimens were cured for 1, 7, 28 and 90 days and then tested for shear strength. Our data show that a combination of lime with natural pozzolana causes the increase in the maximum dry density but the decrease in the optimum moisture content in the gray soil, and vice verse in the red soil. The shear stress of both cohesive soils stabilized with lime or with the combination of lime and natural pozzolana was found to increase with time. The cohesion and the internal friction angle in lime-added samples were demonstrated to increase with time. The combination of lime with natural pozzolana exhibits a significant effect on the enhancement of the cohesion and the internal friction angle at later stages. The lime-natural pozzolana combination appears to produce higher shear parameters than lime or natural pozzolana used alone.
Khelifa HARICHANE, Mohamed GHRICI, Hanifi MISSOUM.
Influence of natural pozzolana and lime additives on the temporal variation of soil compaction and shear strength.
Front. Earth Sci., 2011, 5(2): 162-169 DOI:10.1007/s11707-011-0166-1
Civil engineering projects located in areas with weak soils are one of the most common problems in the world. The conventional method of soil stabilization is to remove the weak soil and replace with a stronger material. The high cost of this method has driven researchers to look for alternative methods, and one of these methods is the process of soil stabilization.
Soil stabilization is a technique introduced many years ago with the main purpose to render the soils capable of meeting the requirements of the specific engineering projects (Kolias et al., 2005). In addition, when the soils at a site are poor or when they have undesirable property making them unsuitable for use in a geotechnical projects, they may have to be stabilized. In recent years, a variety of scientific techniques have been introduced for soil stabilization (Rogers et al., 1997). The techniques of soil stabilization often use the additives as cementing agents including cement, lime or industrial by-products, and extensive studies have been carried out on the stabilization of soils using various additives such as lime and cement (Basha et al., 2005).
However, limited researches have been conducted on the additive of natural pozzolana (NP) in soil stabilization. Hossain et al. (2007) utilized volcanic ash (VA) from natural resources of Papua New Guinea as an additive and investigated the resulted compaction, unconfined compressive strength and durability, but not the shear strength behavior.Natural pozzolana is found abundantly in extensive areas of Beni-Saf quarry in the West of Algeria (Ghrici et al., 2007). The use of natural pozzolana and its combination with lime as soil additives need to be investigated. As the soil is a good source of alumina, the effects of lime treatment can be enhanced to a great extent if the apparent shortage of silica can be adequately supplemented by the addition of natural pozzolana which is enriched in reactive silica. However, the literature indicates minimal studies on the stabilization of cohesive soils in Algeria.This paper presents the results of the effect of the curing time on the shear strength of two Algerian cohesive soils, stabilized with the combination of lime and natural pozzolana.
Experimental investigation
Materials used
The first soil used in this study was obtained from an embankment project site, and the second soil was obtained from a highway project site both near Chelif town in the West of Algeria. Previous soil investigations carried out at the sites indicated the presence of weak clays. These weak clays were encountered at a depth of about 4 to 5 m. The disturbed soil was excavated, placed in plastic bags, and transported to the laboratory for preparation and testing. Laboratory tests were carried out to classify each type of soil. The engineering properties of clayey soils are presented in Table 1.
The NP used in this investigation was collected from Beni-Saf in the West of Algeria. The NP was ground in a laboratory mill to the specific surface area of 420 m2/kg. The chemical composition of NP is presented in Table 2. The lime (L) used was a commercially available lime typically used for construction purposes. The chemical and physical properties of the lime are presented in Table 3.
Laboratory tests of compaction and shear strength
A series of laboratory tests of compaction and shear strength were conducted on the two clayey soils selected. Extensive combinations of natural pozzolana with lime were used to stabilize the two soils. The NP content was 0, 10% and 20%, and the lime content was 0, 4% and 8%. A total of 18 combinations based on soil 1 and soil 2 with single and mixed modes of stabilizers were studied (Table 4).
Proctor standard compaction test according to ASTM D698-00 (2000) was applied to determine the maximum dry density (MDD) and the optimum moisture content (OMC) of the soils. The soil mixtures, with and without additives, wait for 1 h to reach thorough equilibrium prior to compaction. The first series of compaction tests were aimed at determining the compaction properties of the unstabilized soils, and then carried out to determine the proctor compaction properties of the clay upon stabilization with varying amounts of lime and natural pozzolana.
The direct shear tests were performed following ASTM D6528-00 (2000), and were conducted on treated and untreated samples compacted at maximum dry density and optimum moisture content. Since the specimens were not saturated, excessive pore water pressure would not be expected in them. The direct shear test was unconsolidated and the load was applied at a rate of 1 mm/min. The normal stress was chosen to be 50, 100 and 200 kPa for all the specimens. Six specimens from each mixture were prepared for each curing period. To avoid excessive moisture loss, the specimens were wrapped up with a polyane film after demolding. The specimens were kept in the laboratory at the temperature of 25°C and the relative humidity of 50% until the test time (1, 7, 28 and 90 days).
Results and discussion
Compaction characteristics
The compaction test was to determine the effect of stabilizers on MDD and OMC. The MDD and OMC of soils mixed with lime, natural pozzolana or their combinations are reported in Figs. 1 and 2.
The results show that the OMC increases but the MDD decreases with the increase of lime addition. Similar behavior was observed before in lime stabilized clayey soils (Ola, 1977; Rahman, 1986; George et al., 1992; Bell, 1996; Gay and Schad, 2000; Hossain et al., 2007; Manasseh and Olufemi, 2008). The following reasons could explain this behavior; 1) the lime added causes the aggregation of the particles to occupy larger spaces and hence alters the effective grading of the soils, 2) the specific gravity of lime is generally lower than that of the soils tested, and 3) the pozzolanic reaction between the clay present in the soils and the lime is responsible for the increase in OMC.
Figures 1 and 2 show the effect of the NP content on both OMC and MDD. The OMC decreases and the MDD increases as the NP content increases from 0 to 20%. The increase in MDD is an indicator of the improvement of soil properties. Hossain et al. (2007) observed an increase in OMC and a decrease in MDD when the content of volcanic ash added increases from 0 to 20%. This is different from our study in NP.
The decrease in OMC observed in our study could apparently have resulted from the lower affinity of NP for water. In addition, the increase in MDD is probably attributed to the relatively higher specific gravity of the NP. The addition of a combination of lime with natural pozzolana to the gray soil decreases the OMC and increases the MDD. But for the red soil, the combination of lime with natural pozzolana increases the OMC and reduces the MDD, particularly at 20%NP content. Several researchers (Ola, 1977; Rahman, 1986; Basha et al., 2005) found that the change in MDD occurs due to the differences in both the particles size and specific gravity between the soil and stabilizers.
Recently, a power function model shown below (Eq. (1)) was developed to represent the optimum density-moisture relationship (Di Matteo et al., 2009), on the basis of 30 soil samples collected in central Italy and 41 soils described in the literature, all of which are tested in modified proctor.
The confrontation of our experimental results to those acquired by the model (Eq. (1)) was presented in Fig. 3. According to Fig. 3, we could note a good agreement between our results and those predicted by the model developed by Di Matteo et al. (2009). It appears that our soil stabilized samples follow the same behavior as those investigated by Di Matteo et al. (2009). Also, it should be noted that the slight overestimate of the model compared to our experimental results is explained by the modified proctor compaction used by Di Matteo et al. (2009).
Shear strength
Temporal variation of the shear stress
The effect of L, NP and their combinations on the temporal variation of the maximum shear stress of the gray and red soils was shown in Figs. 4 and 5, respectively.
The shear stress of both cohesive soils tested increases with the curing time. The addition of lime has a significant effect on the shear stress, particularly beyond 28 days, and in the samples containing 8% lime for both gray and red soils tested.The addition of natural pozzolana alone has a negligible effect on the temporal variation of the shear stress in gray soil, but leads to a marginal increase in the shear stress at later stages (90 days) in the red soil,
In the samples stabilized with the combination of lime and natural pozzolana, a considerable increase in the shear stress was observed beyond 7 days and particularly at later stages. In both soils, the combination of 20% NP and 8% L exhibits a high increase in the shear stress beyond 28 days. This trend was particularly noticeable in the red soil.
Temporal variation of shear parameters
The effect of L, NP and their combinations on the temporal variation of the shear parameters, cohesion and internal friction angle of the gray and red soils was shown in Figs. 6 and 7, respectively. In slope stability analysis, the maximum shear strength is generally of primary importance. For this reason only the shear parameters using the maximum shear stresses were calculated here.
The temporal variation of the cohesion of the gray and red soils was shown in Figs. 6(a) and 7(a). The addition of lime has a significant effect on the temporal variation of the cohesion. A considerable increase in cohesion was noticed at later stages and in the samples containing 8% lime. Similar behavior was found by Gay and Schad (2000). This behavior is probably due to the self-hardening effect related to the lime. Ola (1978) considered the increase in cohesion with the lime content, to be due to the bonding of particles to form larger aggregates so that the soil behaves as a coarse-grained, strongly bonded particulate material. Others (Lees et al., 1982; Bell, 1989) explained this behavior by the cementation and pozzolanic reactions which occur over time.
The addition of natural pozzolana alone has a marginal effect on the cohesion with increased curing time. This effect may be slightly pronounced in the gray soil at 90 days. In comparison, however, a considerable increase in cohesion was found at later stages in the samples stabilized with the combination of lime with natural pozzolana. In both soils, the combination of 20% NP with 8% L exhibits a high increase in the cohesion beyond 28 days. This trend is particularly noticeable in the gray soil.
It can be seen from Figs. 6(b) and 7(b) that in both stabilized soils, the internal friction angle increases with time as the lime content increases. However, in the gray soil there is a considerable increase in the internal friction angle beyond 28 days. Similar trend was found by Sezer et al. (2006). The latter used very high lime fly ash, and they concluded that this behavior is probably due to the fact that the internal friction angle of the fly ash is more than that of the soil.
On the other hand, the addition of natural pozzolana alone has a marginal effect on the internal friction angle with the curing time. In contrast, in the samples stabilized with the combination of lime and natural pozzolana, there is a significant increase in the internal friction angle at later stages. However, in the gray soil, the combination of 20% NP with 8% L has a negligible effect on the internal friction angle independent of the curing period.
The improvement in the cohesion and internal friction angle values may be due to the pozzolanic activity and self-cementitious characteristics of the mixed lime-natural pozzolana. This behavior is more pronounced beyond 28 days.
Conclusions
This paper presented the effect of curing time on the shear strength of cohesive soils stabilized with lime, natural pozzolana or a combination of both. On the basis of the test results from 18 stabilized soil mixtures, the following conclusions can be drawn.
The maximum dry density of lime-stabilized soils decreases with the increase in the lime content, in contrast with the natural pozzolana-stabilized soils. A combination of lime with natural pozzolana causes the maximum dry density increased in the gray soil but decreased in the red soil. The optimum moisture content of lime-stabilized soils increases with the increase in the lime content, in contrast with pozzolana-stabilized soils. A combination of lime with natural pozzolana causes the optimum moisture content decreased in the gray soil but increased in the red soil.
The shear stress of both cohesive soils stabilized with lime or with the combination of lime and natural pozzolana was found to increase with cure time. A considerable increase was particularly observed at later stages.
There is a considerable increase in the cohesion and the internal friction angle in the samples containing lime with the increase of curing period. The addition of natural pozzolana results in a marginal effect on the cohesion and the internal friction angle with the increase in the curing period. The combination of lime with natural pozzolana exhibits a significant effect on the enhancement of the cohesion and the internal friction angle at later stages. In both soils and particularly in the gray soil, the combination of 20%NP and 8%L exhibits a high increase in the cohesion beyond 28 days but has a negligible effect on the internal friction angle independent of the curing period. The results indicate the combination of lime with natural pozzolana produces higher shear parameters than lime or natural pozzolana used alone.
Al Hassan M, Mustapha A M (2007). Effect of rice husk ash on cement stabilized laterite. Leonardo Electronic Journal of Practices and Technologies, 11: 47-58
[2]
Al Rawas A A, Goosen M F A (2006). Expansive soils-Recent advances in characterization and treatment. London: Taylor & Francis group
[3]
Al Rawas A A, Hago A W, Al-Sarmi H (2005). Effect of lime, cement and sarooj (artificial pozzolan) on the swelling potential of an expansive soil from Oman. Build Environ, 40(5): 681-687
[4]
American Society for Testing and Materials (ASTM) (2000). Test Methods for Consolidated Undrained Direct Simple Shear Testing of Cohesive Soils (D6528-00). Annual book of ASTM Standards, Vol. 0408 USA
[5]
Bagherpour I, Choobbasti A J (2003). Stabilization of fine-grained soils by adding micro silica and lime or micro silica and cement. Electronic Journal of Geotechnical Engineering, 8(B): 1-10
[6]
Basha E A, Hashim R, Mahmud H B, Muntohar A S (2005). Stabilization of residual soil with rice husk ash and cement. Construct Build Mater, 19(6): 448-453
[7]
Basha E A, Hashim R, Muntohar A S (2003). Effect of the cement-rice husk ash on the plasticity and compaction of soil. Electronic Journal of Geotechnical Engineering, 8(A): 1-8
[8]
Bell F G (1989). Lime stabilization of clay soils. Bulletin of International Association of Engineering and Geology, 39(1): 67-74
[9]
Bell F G (1996). Lime stabilization of clay minerals and soils. Eng Geol, 42(4): 223-237
[10]
Choobbasti A J, Ghodrat H, Vahdatirad M J, Firouzian S, Barari A, Torabi M, Bagherian A (2010). Influence of using rice husk ash in soil stabilization method with lime. Front Earth Sci China, 4(4): 471-480
[11]
Di Matteo L, Bigotti F, Ricco R (2009). Best-fit models to estimate modified proctor properties of compacted soil. J Geotech Geoenviron Eng, 135(7): 992-996
[12]
Gay G, Schad H (2000). Influence of cement and lime additives on the compaction properties and shear parameters of fine grained soils. Otto-Graf Journal, 11: 19-31
[13]
George S Z, Ponniah D A, Little J A (1992). Effect of temperature on lime-soil stabilization. Construct Build Mater, 6(4): 247-252
[14]
Ghrici M, Kenai S, Said Mansour M (2007). Mechanical Properties and durability of mortar and concrete containing natural pozzolana and limestone blended cements. Cement Concr Compos, 29(7): 542-549
[15]
Goswami R K, Singh B (2005). Influence of fly ash and lime on plasticity characteristics of residual lateritic soil. Ground Improv, 9(4): 175-182
[16]
Hossain K M A, Lachemi M, Easa S (2007). Stabilized soils for construction applications incorporating natural resources of Papua New Guinea. Resour Conserv Recycling, 51(4): 711-731
[17]
Kalkan E (2009). Influence of silica fume on the desiccation cracks of compacted clayey soils. Appl Clay Sci, 43(3-4): 296-302
[18]
Kolias S, Kasselouri-Rigopoulou V, Karahalios A (2005). Stabilisation of clayey soils with high calcium fly ash and cement. Cement and Concrete Composites, 27: 301-313
[19]
Lees G, Abdelkader M O, Hamdani S K (1982). Effect of clay fraction on some mechanical properties of lime-soil mixtures. Journal of the Institution of Highway Engineers, 29: 209-220
[20]
Manasseh J, Olufemi A I (2008). Effect of lime on some geotechnical properties of Igumale shale. Electronic Journal of Geotechnical Engineering, 13(A): 1-12
[21]
Miller G A, Azad S (2000). Influence of soil type on stabilization with cement kiln dust. Construct Build Mater, 14(2): 89-97
[22]
Mu’Azu M A (2007). Influence of compactive effort on Bagasse ash with cement treated lateritic soil. Leonardo Electronic Journal of Practices and Technologies, 6(10): 79-92
[23]
Muntohar A S (2005). The influence of molding water content and lime content on the strength of stabilized soil with lime and rice husk ash. Civil Engineering Dimension, 7: 1-5
[24]
Muntohar A S, Hantoro G (2000). Influence of rice husk ash and lime on engineering properties of a clayey subgrade. Electronic Journal of Geotechnical Engineering, 5: 1-9
[25]
Okagbue C O, Yakubu J A (2000). Limestone ash waste as a substitute for lime in soil improvement for engineering construction. Bull Eng Geol Environ, 58(2): 107-113
[26]
Ola S A (1977). The potentials of lime stabilization of lateritic soils. Eng Geol, 11(4): 305-317
[27]
Ola S A (1978). Geotechnical properties and behaviour of some stabilized Nigerian laterite soils. Q J Eng Geol, 11(2): 145-160
[28]
Parsons R L, Kneebone E (2005). Field performance of fly ash stabilised subgrades. Ground Improv, 9(1): 33-38
[29]
Prabakar J, Dendorkar N, Morchhale R K (2004). Influence of fly ash on strength behavior of typical soils. Construct Build Mater, 18(4): 263-267
[30]
Rahman A M D (1986). The potentials of some stabilizers for the use of lateritic soil in construction. Build Environ, 21(1): 57-61
[31]
Rogers C D F, Glendinning S, Roff T E J (1997). Lime modification of clay soils for construction expediency. Geotech Eng, 125(4): 242-249
[32]
Senol A, Edil T B, Sazzad Bin-Shafique M D, Acosta H A, Benson C H (2006). Soft subgrades’ stabilization by using various fly ashes. Resour Conserv Recycling, 46(4): 365-376
[33]
Sezer A, Inan G, Yilmaz H R, Ramyar K (2006). Utilization of a very high lime fly ash for improvement of Izmir clay. Build Environ, 41(2): 150-155
RIGHTS & PERMISSIONS
Higher Education Press and Springer-Verlag Berlin Heidelberg
AI Summary 中Eng×
Note: Please be aware that the following content is generated by artificial intelligence. This website is not responsible for any consequences arising from the use of this content.
PDF
(423KB)
