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Physical and mechanical properties of chemically grouted sand
Tunnelling and Underground Space Technology 26 (2011) 718–724
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Tunnelling and Underground Space Technology journal homepage: www.elsevier.com/locate/tust
Physical and mechanical properties of chemically grouted sand C.A. Anagnostopoulos a,⇑, T. Papaliangas a, S. Manolopoulou b, T. Dimopoulos a a b
Department of Civil Infrastructure Engineering, Technological Educational Institution of Thessaloniki, 574 00 Thessaloniki, Greece Department of Civil Engineering, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece
a r t i c l e
i n f o
Article history: Received 22 December 2009 Received in revised form 20 April 2011 Accepted 4 May 2011 Available online 31 May 2011 Keywords: Epoxy resin Grout Compressive strength Triaxial test Fine sand
a b s t r a c t It is generally accepted that only chemical grouts or solutions are available to penetrate and fill narrow joints or soils with very small pore size. Over the last 30 years a few hundreds of different compounds have been used for this purpose showing a wide spectrum of properties. Epoxy resins are among the compounds that are commonly used in building restoration because of their high strength and durability against mechanical or physical erosion. The purpose of this paper is to investigate the improvement of the physical properties (water permeability, porosity and dry unit weight) and mechanical properties (compressive strength, elastic modulus, splitting tensile strength and strength under triaxial stress conditions) of fine sand mixed with a water-soluble two component epoxy resin is, since there is not any published data about the efficiency of such high strength material in ground improvement. The experiments were carried out using different solutions of epoxy resin, which had epoxy resin/water (ER/W) ratio of 2.0, 1.5, 1.0 and 0.5. Cylindrical specimens were prepared by mixing fine sand with an adequate quantity of epoxy resin and were used for compression, splitting tensile and triaxial strength tests. Development of compressive and splitting tensile strength was evaluated from tests at the ages of 3, 7 and 28 days whereas strength under triaxial conditions was determined on specimens cured for 28 days. The results of this study indicate that the epoxy resin solutions, especially the solutions with low water content resulted in higher strength, lower porosity and lower water permeability of the sand, improving significantly the physical and mechanical properties of the fine sand. Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction Materials utilized for grouting purposes can be classified in two general categories, cement suspensions and chemical solutions. Cement grouts are used successfully in granular soils with large voids or in fractured rock with wide crack openings, because they fulfill the following requirements (Widmann, 1996): (a) (b) (c) (d) (e)
They penetrate easily into soil pores. They propagate a large distance under low pressure. They fill the voids completely. They maintain the required properties in the hardened state. Their cost is low, particularly when compared with chemical grouts.
Table 1, reproduced from Perret et al. (2000) summarizes the different injectability criteria needed for the cement grouting of fractured rock. Fig. 1 depicts the penetrability limits of cement and chemical grouts, such as calcium chloride in combination with sodium silicate (joosten process) and sodium silicate with formamide as a reactant to form silica gel, based on the grain size ⇑ Corresponding author. Tel./fax: +30 2310 810481. E-mail address: [email protected] (C.A. Anagnostopoulos). 0886-7798/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.tust.2011.05.006
distribution of the soil. Fig. 2 shows the relationship between the water permeability of the soil and the average diameter d50 of the grout particle (Cambefort, 1977). According to this relationship and the previous experience, micro fine cement is expected to flow sufficiently through soils with water permeability greater than 105 m/s. As a result, the use of chemical grouts is restricted to soils with very small void size or rock mass with narrow joints, where cement suspensions cannot be injectable or their penetration is very limited. Various materials are used for chemical grouting depending on the purpose of grouting and the properties of the ground. The most common are sodium silicate, acrylate, lignin, urethane and resin grouts. Particularly, one of the principal resins, which are used for grouting, is epoxy resin. Epoxy grouts generally consist of two components. Epoxy components (A-component) are mixed with amine components (B-component) to obtain epoxy resins. The final product is characterized by high strength in compression, tension, bond, durability, high resistance to acids, alkalis and organic chemicals and low shrinkage when cured. Also, some epoxies may be diluted with water up to twice their volume to provide a low cost product, but as a consequence their strength decreases. This reduction of strength is proportional to the amount of mixing water. Although, numerous studies have been conducted concerning the application of epoxy grouts for structural repair or in fractured
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C.A. Anagnostopoulos et al. / Tunnelling and Underground Space Technology 26 (2011) 718–724 Table 1 Injectability criteria for injection into fractured rock according to the minimum crack opening or to the ratio between the maximum diameter (Dmax) of cement particles and the joint aperture. Authors
Minimum crack opening
Kennedy Morozov and Goncharov Ruiz and Leone Sinclair Cambefort Houlsby Littlejohn Bruce and Millmore
3 Dmax 4 to 5 Dmax 0.2–0.4 mm 0.1–0.5 mm 0.15 mm 0.5 mm 0.16 mm 0.16 mm
properties (compressive strength, elastic modulus, splitting tensile strength and shear strength parameters) of a fine sand. 2. Materials used Axios river fine sand with grain size distribution ranging from 0.074 mm to 2 mm sieves (Table 2) with uniformity coefficient of Cu = 2.5, dry unit weight of cd = 16 kN/m3, saturated unit weight of csat = 20.2 KN/m3 and porosity of n = 0.42 was used. The permeability coefficient k of fine sand with a relative density of Dr = 0.95 is 1.58 104 m/s and was determined by using the method of constant head (ASTM D 5084-03). The epoxy resin used is a commercial product with trading name RESICOLOR 440 provided from Resimix co. It is water-soluble and comprises two components. The mixture ratio by weight of the two components A (epoxy resin) and B (hardener) is A:B = 0.5. According to the manufacturer, epoxy resin, without any addition of water, gains its final strength after 7 days. Compressive strength reaches the value of 70 MPa, whereas flexural and adhesive strength are in excess of 35 MPa and 3 MPa, correspondingly. 3. Laboratory procedure
Fig. 1. Penetrability limits of grouts based on the particle-size distribution of the soil.
Fig. 2. Penetrability limits of grouts based on the permeability of soil.
concrete (Issa and Debs, 2007; Au et al., 2003), there is not any published data about the efficacy of epoxy resin grouts on soil or rock strengthening and especially of low cost water soluble epoxy resin grouts. The main objective of this laboratory project was to investigate the use of two-component water-soluble epoxy resin grouts, with different resin to water ratios, for the improvement of physical (water permeability, porosity, dry unit weight) and mechanical
Grouts were prepared with epoxy resin/water (ER/W) ratios (by weight) of 2.0, 1.5, 1.0 and 0.5. Preparation of all grouts was accomplished using a high speed rotating stirrer. Grouting of sand was carried out by mixing sand with an adequate quantity (about 50% of the dry weight of the sand being treated) of epoxy grout hence the intergranular voids be completely filled. Mix was performed by using a three blade paddle mixer suggested by ASTM C938-80 specifications. Afterwards, grouted sand was poured in cylindrical molds 5.43 cm in diameter and 11 cm high and compacted in equal layers of 2 cm thickness, so that specimens would be as consistent as possible. These cylindrical specimens having a height to diameter ratio of 2 (ISRM, 1981) were subjected to compressive strength tests at the ages of 3, 7 and 28 days and for triaxial tests at the age of 28 days. Compression and triaxial tests were carried out under a constant strain rate of 1%/min. Compression tests were performed according to ASTM D 4219-02. The elastic modulus E was determined from the linear part of the compressive stress–strain curve. Splitting tensile tests were conducted, in accordance with the instructions of ASTM D 3967–95a, on specimens with a thickness to diameter ratio (t/D) of 2.0/5.43 cm = 0.37. For the purpose of studying the strength of grouted sand under triaxial loading, a triaxial testing apparatus was designed (see Fig. 3) based on standard triaxial conditions, which comprised the following parts: (a) Hoek triaxial cell in which the specimens were placed and subjected to the different confining pressures. (b) A manual pump connected with Hoek triaxial cell in order to apply the desired constant confining pressure for each test. (c) A commercially available compression testing device (TRITECH 50 KN/WYKEHAM FARRANCE) for the application of the vertical load, with linearly variable differential transformer (LVDT) linked to a data logger–computer for the recording of stress–strain during the test. Table 2 Grain size distribution of the fine sand. Sieve
No 8
No 10
No 20
No 40
No 100
No 200
Aperture (mm) Cumulative percentage passing (%)
2.38 100
2.00 95
0.84 90
0.42 60
0.149 5
0.074 0
720
C.A. Anagnostopoulos et al. / Tunnelling and Underground Space Technology 26 (2011) 718–724
Compressive stress (kPa)
1000 900 800 700 ER/W = 1.5/1
600
ER/W = 2/1
500 400 300 200 100 0
0
1
2
3
4
5
6
Strain (%)
(a)
Fig. 3. Triaxial testing system.
Compressive stress (kPa)
7000 6000 5000 4000 3000 2000
ER/W = 1.5/1
4. Results and discussion Fig. 4a–c depicts the stress–strain relation of mixed fine sand specimens with epoxy resin grouts of different proportions at 3, 7 and 28 days of curing. Fig. 5a–c shows the development of compressive strength, splitting tensile strength and elastic modulus related with curing time. The results reveal the adverse influence of water on the strength development of grouted sand at all ER/W ratios. Strength values, for all ages tested, decrease with the increase of water content. The water content had a more pronounced effect on the retardation and reduction of the final strength of grouted sand in the case of grouts with ER/W ratio of 1.0 and 0.5. The
ER/W = 2/1
1000 0
0
1
2
3
4
Strain (%)
(b) 14000
Compressive stress (kPa)
Triaxial tests were performed under confining pressures r3 of 67.5, 110, 157 and 225 kPa. Specimens of the same size as those used for the compressive and triaxial strength tests, aged 28 days, were used for the evaluation of water permeability according to ASTM D 5084-03 and dry unit weight according to ASTM C 29/29M-91a. Porosity n was calculated according to the method referred to by Perret et al. (2000). It should be mentioned that a classical laboratory method for determining strength or physical parameters of chemically grouted soil specimens, adopted by many researchers, is the one proposed by ASTM D 4320-04. This method is very important for the estimation of strength of cement grouted soils, which appears to be decreased as the distance from injection point increases because of clogging mechanism domination during the injection process. On the other hand, epoxy resin grouts can penetrate easily and uniformly, without clogging, into the soil voids resulting in the development of isotropic strength along the injection distance (Anagnostopoulos and Hadjispyrou, 2004). Consequently, the method of ASTM was considered as not appropriate in this case and the simplest method of mixing for making epoxy resin grouted sand specimens was chosen by the authors. Each of the reported values for physical and mechanical parameters represents the average value of three or four specimens.
ER/W = 1/1
12000 10000 8000 6000 ER/W = 1/2
4000
ER/W = 1/1 ER/W = 1.5/1
2000 0
ER/W = 2/1
0
1
2
3
4
5
6
Strain (%)
(c) Fig. 4. Typical stress–strain curves of grouted fine sand with different epoxy resin grouts: (a) 3 days; (b) 7 days; (c) 28 days.
retarding phenomenon may be attributed to the amount of water that is retained by the hydrophilic parts of the epoxy resin, inhibiting to some extent its chemical reaction with the hardener, and thus the development of strength. The reduction of the final strength, even after the evaporation of water, is owed to the formation of a weaker epoxy resin polymer membrane-sand matrix, because of the high dispersion of chemical substances which happens in the high diluted epoxy grouts. Particularly, in the case of epoxy resin grouting with ER/W ratio of 1.0 and 0.5, no strength development was observed at the age of 3 days, whereas for ER/W ratio of 1.5 the strength parameters were generally low. Grouted samples with ER/W ratio of 2.0 appeared to have much higher strength with mean values for compressive strength, splitting tensile strength and elastic modulus of 920 kPa, 348 kPa and 161 MPa, respectively.
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14
Deviatoric stress (MPa)
Compressive strength (kPa)
14000 12000 10000
3 Days 7 Days 28 Days
8000 6000 4000 2000 0
12 10 8
1.5
1
67.5 kPa 110 kPa
4
157 kPa 225kPa
2 0
0.5
0 kPa
6
0
2
4
6
ER/W
Deviatoric stress (MPa)
Splitting tensile strength (kPa)
3 Days 7 Days 28 Days
1000
0.5
1.5
1
400 3 Days 7 Days 28 Days
200 150
67.5 kPa 110 kPa
5
157 kPa
0
2
4
6
8
10
(b)
100
20 15 0 kPa
10
67.5 kPa 110 kPa 157 kPa
5 0
50 0
0 kPa
25
Deviatoric stress (MPa)
Elastic modulus (MPa)
10
2
450
250
15
Strain (%)
(b)
300
20
0
ER/W
350
14
225 kPa
500 0
12
25
2500
1500
10
(a)
(a)
2000
8
Strain (%)
2
225 kPa
0
2
4
6
8
10
12
Strain (%) 0.5
1
1.5
(c)
2
ER/W
30
Fig. 5. (a) Compressive strength; (b) Splitting tensile strength; (c) Elastic modulus development of grouted fine sand with different epoxy resin grouts.
Nevertheless, strengths exhibited were noted to increase over time, resulting in significantly higher 7 and 28 day strength values. This tendency was strongly dependent on ER/W ratio. For example, grouted samples with ER/W ratio of 0.5 did not gain any strength even after 7 days of curing, whereas grouted samples with ER/W ratio of 2.0 at the same time interval showed a noticeable strength development with mean values for compressive strength, splitting tensile strength and elastic modulus of 6480 kPa, 888 kPa and 245 MPa, respectively. Additionally, grouted samples with thick epoxy grouts (ER/W = 2.0, 1.5) appeared to have strength enhancement significantly higher than that of the grouted samples with thinner epoxy grouts for all curing ages. The lowest final strength values at 28 days of curing were observed for grouting with ER/
Deviatoric stress (MPa)
(c) 25 20 15 0 kPa 67.5 kPa
10
110 kPa 157 kPa 225 kPa
5 0
0
2
4
6
8
10
12
Strain (%)
(d) Fig. 6. Typical deviatoric stress–strain curves of fine sand grouted with ER/W ratio of (a) 0.5; (b) 1.0; (c) 1.5; (d) 2.0 at different confining pressures.
C.A. Anagnostopoulos et al. / Tunnelling and Underground Space Technology 26 (2011) 718–724
Dry unit weight (KN/m 3 )
17.4 17.2 17 16.8 16.6 16.4 16.2 16 15.8 0
0.5
1
1.5
2
ER/W Fig. 8. Dry unit weight of grouted fine sand with different epoxy resin grouts.
45 40
Porosity (%)
W ratio of 0.5, which were equal to 960 kPa for compressive strength, 40 MPa for elastic modulus and 84 kPa for splitting tensile strength. On the contrary, grouting with ER/W ratio of 2.0 resulted in compressive strength of 12,961 kPa, elastic modulus of 395 MPa and splitting tensile strength of 2017 kPa. Inspection of the diagrams representing the relation between compressive stress–strain reveals an extended plastic zone that occurs before and after fracture for all ER/W grouted samples. Especially, grouted samples with ER/W ratio of 1.5 and 2.0 did not fail at the end of test, but were continuously deforming, up to a strain of at least 3.5%, where the test was stopped. This is an indication of the strong adhesion between the formed polymer film and sand grains. It also demonstrates the domination of the elastoplastic behavior of epoxy resin to the mechanical response of the whole mixture. Typical trends in deviatoric stress (r1–r3)-strain obtained in triaxial tests are shown in Fig. 6a–d. These results illustrate the beneficial effect that epoxy grouts have on the strength and on the stiffness of the sand. As expected, peak strength and initial stiffness strongly increased with an increase in ER content and confining pressure. For example, the application of 225 kPa confining pressure on grouted specimens with ER/W ratio of 0.5 caused a deviator increment of 1150%, compared to the unconfined test. Generally, the degree of post-peak strength loss tends to decrease with increasing confining pressure and ER/W ratio resulting in a relatively constant peak strength. The strain at which the peak stress was achieved generally increased with increasing confining pressure and ER/W ratio, although some scatter was observed. The lowest deviatoric stress value obtained at confining pressure of 67.5 kPa is 6.7 MPa for grouted sand with ER/W ratio of 0.5 and the highest one obtained at confining pressure of 225 kPa is 26.57 MPa for grouted sand with ER/W ratio of 2.0. The effect of confining pressure and ER content on the enhancement of max deviatoric stress is clearly seen in Fig. 7. A remarkable extension of plastic zone for all grouted samples with the different ER/W ratios is observed, a fact that was reflected in the failure mode of the samples. Generally, no strain localization with inclined shear bands occurred, and the failure was associated with a fairly uniform strong expansion of the specimen. This observation supports the hypothesis that grouted specimens failed because of indirect tensile development and not because of shearing. The physical parameters of grouted fine sand are depicted in Figs 8–10. As for the mechanical properties, the improvement of physical properties was also dependent directly on ER/W ratio. In the case of grouting with thick grouts, permeability test results confirm the formation of a dense polymer film-sand matrix by which a large number of pores are filled or sealed resulting in
35 30 25 20 15 0
0.5
1
1.5
2
ER/W Fig. 9. Porosity of grouted fine sand with different epoxy resin grouts.
ER/W Permeability coefficient (m/s)
722
1.0E-03
0
0.5
1
1.5
2
1.0E-04 1.0E-05 1.0E-06 1.0E-07 1.0E-08 1.0E-09
Fig. 10. Permeability coefficient of grouted fine sand with different epoxy resin grouts.
Max deviatoric stress (MPa)
30
ER/W = 1/2 ER/W = 1/1
25
ER/W = 1.5/1 ER/W = 2/1
20 15 10 5 0
0
50
100
150
200
250
Confining pressure (kPa) Fig. 7. Confining pressure – deviatoric stress relation of grouted fine sand with different epoxy resin grouts.
the significant reduction of water permeability. Permeability coefficient k decreased almost five orders of magnitude for ER/W ratio of 2.0 and about four orders of magnitude for ER/W ratio of 1.5. Despite the weakening of the polymer membrane-sand matrix in the case of grouting with thin grouts, a noticeable decrease of water permeability was obtained. k values were 5.7 107 m/s for ER/ W ratio of 1.0 and 1.0 105 m/s for ER/W ratio of 0.5. Porosity and dry unit weight values confirm the above mentioned observations about the influence of ER/W ratio or the adverse impact of water when existing in high amounts in grout composition. The observed improvement of physical and mechanical properties for the grouted sand can further be manifested by the examination of scanning electron micrographs. Fig. 11 shows a
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Compressive strength (kPa)
18000 Experimental 3 days
16000
Experimental 7 days
14000
Experimental 28 days
12000
Model for 7 days
Model for 3 days Model for 28 days
10000 8000 6000 4000 2000 0 0
0,5
1
1,5
2
2,5
1,5
2
2,5
1,5
2
2,5
ER/W
Splitting tensile strength (kPa)
(a)
Fig. 11. A scanning electron micrograph of untreated sand.
3000 Experimental 3 days Experimental 7 days
2500
Experimental 28 days Model for 3 days
2000
Model for 7 days Model for 28 days
1500 1000 500 0
0
0,5
1
ER/W
(b) 600
Fig. 12. A scanning electron micrograph of fracture surface of grouted sand with ER/W ratio of 2.0.
micrograph of an untreated sand specimen where the sand particles appear almost unconnected with large voids existing around their periphery. In contrast, Fig. 12 shows a micrograph of the view perpendicular to the failure surface of a grouted sand specimen with ER/W ratio of 2.0. It is clearly seen that a large number of voids are infilled with polymer patches which act as adhesive ties to the sand grains forming a dense impermeable high strength structure. 5. Regression models Based on the laboratory results and using SPSS 16.0 statistic program a non-linear regression analysis was performed in order to correlate the compressive strength, splitting tensile strength and elastic modulus of grouted sand to the ER/W ratio and curing time, which were taken as a descriptor variables. Permeability coefficient was also correlated but only to the ER/W ratio, since previous research has shown its independence from curing time (Anagnostopoulos and Hadjispyrou, 2004). The model that gives the best correlation concerning the mechanical parameters has the following form: b
y ¼ a ðER=WÞ lnðAGE=cÞ
ð1Þ
Elastic modulus (MPa)
Experimental 3 days
500
Experimental 7 days Experimental 28 days Model for 3 days
400
Model for 7 days Model for 28 days
300 200 100 0
0
0,5
1
ER/W
(c) Fig. 13. Experimental results vs. computed values from the regression equations: (a) compressive strength; (b) splitting tensile strength; (c) elastic modulus.
where y is the dependent variable corresponding to the desired mechanical property, a, b and c are coefficients calculated from the regression analysis. The equations and the corresponding correlation coefficients R2 obtained from the regression analysis are as follows: a. Compressive strength (C.S.)
C:S:ðkPaÞ ¼ 1416:77ðER=WÞ1:988 lnðAGE=2:5Þ; R2 ¼ 0:98
ð2Þ
b. Splitting tensile strength (T.S.)
T:S:ðkPaÞ ¼ 243:17ðER=WÞ1:853 lnðAGE=2:5Þ; R2 ¼ 0:97
ð3Þ
c. Elastic modulus (E.M.)
E:M:ðMPaÞ ¼ 26:84ðER=WÞ2:2 lnðAGEÞ; R2 ¼ 0:98
ð4Þ
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Permeability coefficient (m/s)
ER/W 1,00E-04
0
0,5
1
1,5
2
2,5
1,00E-05 1,00E-06 1,00E-07 1,00E-08 1,00E-09
and ER/W ratio. A remarkable extension of plastic zone is obtained and the difference between peak strength and ultimate strength is negligible. The failure mode of the specimens indicates that fracture probably occurs due to the development of indirect tensile strength. A further investigation should be carried out to determine the mechanical behavior of grouted sand under a wide range of confining pressures. 3. The reliability and accuracy of the produced non-linear regression models were checked by comparing predicted output from these models to the measured values and found to be satisfactorily consistent. 4. In general, it can be concluded that epoxy resin grouts can be used for grouting purposes to provide suitable solutions for the strengthening of the foundation material.
Fig. 14. Measured permeability coefficient vs. computed values from the regression equation.
References The above relations for the mechanical properties of the grouted specimens at any age (days) and ER/W ratio were found to fit satisfactorily the experimental data, as shown in Fig. 13a–c. The model that gives the best correlation concerning the permeability coefficient is the following:
kðm=sÞ ¼ 0:0002e5:52ðER=WÞ ; R2 ¼ 0:99
ð5Þ
Fig. 14 illustrates the correlation of the measured permeability coefficient to the computed values from the regression analysis. 6. Conclusions Experimental results showed that the use of water soluble epoxy resin has a considerable effect on improving the physical and mechanical properties of the fine sand. Particularly, the following conclusions can de drawn: 1. Compressive strength, tensile strength and elastic modulus development of the grouted fine sand depends directly on the water content of the epoxy resin solution. Grouts with ER/W ratio of 2.0 and 1.5 result in significantly high strength and low permeability. Despite the weakening of the polymer membrane-sand matrix, in the case of high diluted grouts, the 28 day mechanical properties and permeability appear to be satisfactorily improved. 2. Under triaxial stress conditions, the peak strength and stiffness of all grouted specimens with different ER/W ratio increase significantly. This increment depends on the confining pressure
Anagnostopoulos, CA., Hadjispyrou, S., 2004. Laboratory study of an epoxy resin grouted sand. Ground Improvement 8, 39–45. ASTM Standard C 29/C 29M-91a, 1993. Standard test method for unit weight and voids in aggregate. In: Annual Book of ASTM Standards. ASTM International, West Conshohocken, PA, USA. ASTM Standard C 938-80, 1993. Standard practice for proportioning grout mixtures for preplaced-aggregate concrete. In: Annual Book of ASTM Standards. ASTM International, West Conshohocken, PA, USA. ASTM Standard D 3967-95a, 2005. standard test method for splitting tensile strength of intact rock core specimens. In: Annual Book of ASTM Standards. ASTM International, West Conshohocken, PA, USA. ASTM Standard D 4219-02, 2005. Standard test method for unconfined compressive strength index of chemical – grouted soils. In: Annual Book of ASTM Standards. ASTM International, West Conshohocken, PA, USA. ASTM Standard D 4320-04, 2005. Standard practice for laboratory preparation of chemically grouted soil specimens for obtaining design strength parameters. In: Annual Book of ASTM Standards. ASTM International, West Conshohocken, PA, USA. ASTM Standard D 5084-03, 2005. Standard test methods for measurement of hydraulic conductivity of saturated porous materials using a flexible wall permeameter. In: Annual Book of ASTM Standards. ASTM International, West Conshohocken, PA, USA. Au, S.K.A., Soga, K., Jafari, M.R., Bolton, M.D., Komiya, K., 2003. Factors affecting longterm efficiency of compensation grouting in clays. J. Geotech. Geoenvir. Eng. 129 (3), 254–262. Cambefort, H., 1977. The principles and applications of grouting. Q. J. Eng. Geol. 10, 57–95. Issa, C.A., Debs, P., 2007. Experimental study of epoxy repairing of cracks in concrete. Construction and Building Materials 21 (1), 157–163. Perret, S., Khayat, K.H., Ballivy, G., 2000. The effect of degree of saturation on sand groutability: experimental simulation. Ground Improve. 4, 13–22. RM, I.S., 1981. Suggested methods for determining the strength of rock materials in triaxial compression. In: Brown, E.T. (Ed.), International Society of Rock Meckanics, ISRM Suggested Methods. Pergamon Press, NJ. Widmann, R., 1996. International commission for rock mechanics. Commission on rock grouting. Int. J. Rock Mech. Mining Sci. Geomech. Abstracts 33 (8), 803– 847.
Contents lists available at ScienceDirect
Tunnelling and Underground Space Technology journal homepage: www.elsevier.com/locate/tust
Physical and mechanical properties of chemically grouted sand C.A. Anagnostopoulos a,⇑, T. Papaliangas a, S. Manolopoulou b, T. Dimopoulos a a b
Department of Civil Infrastructure Engineering, Technological Educational Institution of Thessaloniki, 574 00 Thessaloniki, Greece Department of Civil Engineering, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece
a r t i c l e
i n f o
Article history: Received 22 December 2009 Received in revised form 20 April 2011 Accepted 4 May 2011 Available online 31 May 2011 Keywords: Epoxy resin Grout Compressive strength Triaxial test Fine sand
a b s t r a c t It is generally accepted that only chemical grouts or solutions are available to penetrate and fill narrow joints or soils with very small pore size. Over the last 30 years a few hundreds of different compounds have been used for this purpose showing a wide spectrum of properties. Epoxy resins are among the compounds that are commonly used in building restoration because of their high strength and durability against mechanical or physical erosion. The purpose of this paper is to investigate the improvement of the physical properties (water permeability, porosity and dry unit weight) and mechanical properties (compressive strength, elastic modulus, splitting tensile strength and strength under triaxial stress conditions) of fine sand mixed with a water-soluble two component epoxy resin is, since there is not any published data about the efficiency of such high strength material in ground improvement. The experiments were carried out using different solutions of epoxy resin, which had epoxy resin/water (ER/W) ratio of 2.0, 1.5, 1.0 and 0.5. Cylindrical specimens were prepared by mixing fine sand with an adequate quantity of epoxy resin and were used for compression, splitting tensile and triaxial strength tests. Development of compressive and splitting tensile strength was evaluated from tests at the ages of 3, 7 and 28 days whereas strength under triaxial conditions was determined on specimens cured for 28 days. The results of this study indicate that the epoxy resin solutions, especially the solutions with low water content resulted in higher strength, lower porosity and lower water permeability of the sand, improving significantly the physical and mechanical properties of the fine sand. Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction Materials utilized for grouting purposes can be classified in two general categories, cement suspensions and chemical solutions. Cement grouts are used successfully in granular soils with large voids or in fractured rock with wide crack openings, because they fulfill the following requirements (Widmann, 1996): (a) (b) (c) (d) (e)
They penetrate easily into soil pores. They propagate a large distance under low pressure. They fill the voids completely. They maintain the required properties in the hardened state. Their cost is low, particularly when compared with chemical grouts.
Table 1, reproduced from Perret et al. (2000) summarizes the different injectability criteria needed for the cement grouting of fractured rock. Fig. 1 depicts the penetrability limits of cement and chemical grouts, such as calcium chloride in combination with sodium silicate (joosten process) and sodium silicate with formamide as a reactant to form silica gel, based on the grain size ⇑ Corresponding author. Tel./fax: +30 2310 810481. E-mail address: [email protected] (C.A. Anagnostopoulos). 0886-7798/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.tust.2011.05.006
distribution of the soil. Fig. 2 shows the relationship between the water permeability of the soil and the average diameter d50 of the grout particle (Cambefort, 1977). According to this relationship and the previous experience, micro fine cement is expected to flow sufficiently through soils with water permeability greater than 105 m/s. As a result, the use of chemical grouts is restricted to soils with very small void size or rock mass with narrow joints, where cement suspensions cannot be injectable or their penetration is very limited. Various materials are used for chemical grouting depending on the purpose of grouting and the properties of the ground. The most common are sodium silicate, acrylate, lignin, urethane and resin grouts. Particularly, one of the principal resins, which are used for grouting, is epoxy resin. Epoxy grouts generally consist of two components. Epoxy components (A-component) are mixed with amine components (B-component) to obtain epoxy resins. The final product is characterized by high strength in compression, tension, bond, durability, high resistance to acids, alkalis and organic chemicals and low shrinkage when cured. Also, some epoxies may be diluted with water up to twice their volume to provide a low cost product, but as a consequence their strength decreases. This reduction of strength is proportional to the amount of mixing water. Although, numerous studies have been conducted concerning the application of epoxy grouts for structural repair or in fractured
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Minimum crack opening
Kennedy Morozov and Goncharov Ruiz and Leone Sinclair Cambefort Houlsby Littlejohn Bruce and Millmore
3 Dmax 4 to 5 Dmax 0.2–0.4 mm 0.1–0.5 mm 0.15 mm 0.5 mm 0.16 mm 0.16 mm
properties (compressive strength, elastic modulus, splitting tensile strength and shear strength parameters) of a fine sand. 2. Materials used Axios river fine sand with grain size distribution ranging from 0.074 mm to 2 mm sieves (Table 2) with uniformity coefficient of Cu = 2.5, dry unit weight of cd = 16 kN/m3, saturated unit weight of csat = 20.2 KN/m3 and porosity of n = 0.42 was used. The permeability coefficient k of fine sand with a relative density of Dr = 0.95 is 1.58 104 m/s and was determined by using the method of constant head (ASTM D 5084-03). The epoxy resin used is a commercial product with trading name RESICOLOR 440 provided from Resimix co. It is water-soluble and comprises two components. The mixture ratio by weight of the two components A (epoxy resin) and B (hardener) is A:B = 0.5. According to the manufacturer, epoxy resin, without any addition of water, gains its final strength after 7 days. Compressive strength reaches the value of 70 MPa, whereas flexural and adhesive strength are in excess of 35 MPa and 3 MPa, correspondingly. 3. Laboratory procedure
Fig. 1. Penetrability limits of grouts based on the particle-size distribution of the soil.
Fig. 2. Penetrability limits of grouts based on the permeability of soil.
concrete (Issa and Debs, 2007; Au et al., 2003), there is not any published data about the efficacy of epoxy resin grouts on soil or rock strengthening and especially of low cost water soluble epoxy resin grouts. The main objective of this laboratory project was to investigate the use of two-component water-soluble epoxy resin grouts, with different resin to water ratios, for the improvement of physical (water permeability, porosity, dry unit weight) and mechanical
Grouts were prepared with epoxy resin/water (ER/W) ratios (by weight) of 2.0, 1.5, 1.0 and 0.5. Preparation of all grouts was accomplished using a high speed rotating stirrer. Grouting of sand was carried out by mixing sand with an adequate quantity (about 50% of the dry weight of the sand being treated) of epoxy grout hence the intergranular voids be completely filled. Mix was performed by using a three blade paddle mixer suggested by ASTM C938-80 specifications. Afterwards, grouted sand was poured in cylindrical molds 5.43 cm in diameter and 11 cm high and compacted in equal layers of 2 cm thickness, so that specimens would be as consistent as possible. These cylindrical specimens having a height to diameter ratio of 2 (ISRM, 1981) were subjected to compressive strength tests at the ages of 3, 7 and 28 days and for triaxial tests at the age of 28 days. Compression and triaxial tests were carried out under a constant strain rate of 1%/min. Compression tests were performed according to ASTM D 4219-02. The elastic modulus E was determined from the linear part of the compressive stress–strain curve. Splitting tensile tests were conducted, in accordance with the instructions of ASTM D 3967–95a, on specimens with a thickness to diameter ratio (t/D) of 2.0/5.43 cm = 0.37. For the purpose of studying the strength of grouted sand under triaxial loading, a triaxial testing apparatus was designed (see Fig. 3) based on standard triaxial conditions, which comprised the following parts: (a) Hoek triaxial cell in which the specimens were placed and subjected to the different confining pressures. (b) A manual pump connected with Hoek triaxial cell in order to apply the desired constant confining pressure for each test. (c) A commercially available compression testing device (TRITECH 50 KN/WYKEHAM FARRANCE) for the application of the vertical load, with linearly variable differential transformer (LVDT) linked to a data logger–computer for the recording of stress–strain during the test. Table 2 Grain size distribution of the fine sand. Sieve
No 8
No 10
No 20
No 40
No 100
No 200
Aperture (mm) Cumulative percentage passing (%)
2.38 100
2.00 95
0.84 90
0.42 60
0.149 5
0.074 0
720
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Compressive stress (kPa)
1000 900 800 700 ER/W = 1.5/1
600
ER/W = 2/1
500 400 300 200 100 0
0
1
2
3
4
5
6
Strain (%)
(a)
Fig. 3. Triaxial testing system.
Compressive stress (kPa)
7000 6000 5000 4000 3000 2000
ER/W = 1.5/1
4. Results and discussion Fig. 4a–c depicts the stress–strain relation of mixed fine sand specimens with epoxy resin grouts of different proportions at 3, 7 and 28 days of curing. Fig. 5a–c shows the development of compressive strength, splitting tensile strength and elastic modulus related with curing time. The results reveal the adverse influence of water on the strength development of grouted sand at all ER/W ratios. Strength values, for all ages tested, decrease with the increase of water content. The water content had a more pronounced effect on the retardation and reduction of the final strength of grouted sand in the case of grouts with ER/W ratio of 1.0 and 0.5. The
ER/W = 2/1
1000 0
0
1
2
3
4
Strain (%)
(b) 14000
Compressive stress (kPa)
Triaxial tests were performed under confining pressures r3 of 67.5, 110, 157 and 225 kPa. Specimens of the same size as those used for the compressive and triaxial strength tests, aged 28 days, were used for the evaluation of water permeability according to ASTM D 5084-03 and dry unit weight according to ASTM C 29/29M-91a. Porosity n was calculated according to the method referred to by Perret et al. (2000). It should be mentioned that a classical laboratory method for determining strength or physical parameters of chemically grouted soil specimens, adopted by many researchers, is the one proposed by ASTM D 4320-04. This method is very important for the estimation of strength of cement grouted soils, which appears to be decreased as the distance from injection point increases because of clogging mechanism domination during the injection process. On the other hand, epoxy resin grouts can penetrate easily and uniformly, without clogging, into the soil voids resulting in the development of isotropic strength along the injection distance (Anagnostopoulos and Hadjispyrou, 2004). Consequently, the method of ASTM was considered as not appropriate in this case and the simplest method of mixing for making epoxy resin grouted sand specimens was chosen by the authors. Each of the reported values for physical and mechanical parameters represents the average value of three or four specimens.
ER/W = 1/1
12000 10000 8000 6000 ER/W = 1/2
4000
ER/W = 1/1 ER/W = 1.5/1
2000 0
ER/W = 2/1
0
1
2
3
4
5
6
Strain (%)
(c) Fig. 4. Typical stress–strain curves of grouted fine sand with different epoxy resin grouts: (a) 3 days; (b) 7 days; (c) 28 days.
retarding phenomenon may be attributed to the amount of water that is retained by the hydrophilic parts of the epoxy resin, inhibiting to some extent its chemical reaction with the hardener, and thus the development of strength. The reduction of the final strength, even after the evaporation of water, is owed to the formation of a weaker epoxy resin polymer membrane-sand matrix, because of the high dispersion of chemical substances which happens in the high diluted epoxy grouts. Particularly, in the case of epoxy resin grouting with ER/W ratio of 1.0 and 0.5, no strength development was observed at the age of 3 days, whereas for ER/W ratio of 1.5 the strength parameters were generally low. Grouted samples with ER/W ratio of 2.0 appeared to have much higher strength with mean values for compressive strength, splitting tensile strength and elastic modulus of 920 kPa, 348 kPa and 161 MPa, respectively.
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14
Deviatoric stress (MPa)
Compressive strength (kPa)
14000 12000 10000
3 Days 7 Days 28 Days
8000 6000 4000 2000 0
12 10 8
1.5
1
67.5 kPa 110 kPa
4
157 kPa 225kPa
2 0
0.5
0 kPa
6
0
2
4
6
ER/W
Deviatoric stress (MPa)
Splitting tensile strength (kPa)
3 Days 7 Days 28 Days
1000
0.5
1.5
1
400 3 Days 7 Days 28 Days
200 150
67.5 kPa 110 kPa
5
157 kPa
0
2
4
6
8
10
(b)
100
20 15 0 kPa
10
67.5 kPa 110 kPa 157 kPa
5 0
50 0
0 kPa
25
Deviatoric stress (MPa)
Elastic modulus (MPa)
10
2
450
250
15
Strain (%)
(b)
300
20
0
ER/W
350
14
225 kPa
500 0
12
25
2500
1500
10
(a)
(a)
2000
8
Strain (%)
2
225 kPa
0
2
4
6
8
10
12
Strain (%) 0.5
1
1.5
(c)
2
ER/W
30
Fig. 5. (a) Compressive strength; (b) Splitting tensile strength; (c) Elastic modulus development of grouted fine sand with different epoxy resin grouts.
Nevertheless, strengths exhibited were noted to increase over time, resulting in significantly higher 7 and 28 day strength values. This tendency was strongly dependent on ER/W ratio. For example, grouted samples with ER/W ratio of 0.5 did not gain any strength even after 7 days of curing, whereas grouted samples with ER/W ratio of 2.0 at the same time interval showed a noticeable strength development with mean values for compressive strength, splitting tensile strength and elastic modulus of 6480 kPa, 888 kPa and 245 MPa, respectively. Additionally, grouted samples with thick epoxy grouts (ER/W = 2.0, 1.5) appeared to have strength enhancement significantly higher than that of the grouted samples with thinner epoxy grouts for all curing ages. The lowest final strength values at 28 days of curing were observed for grouting with ER/
Deviatoric stress (MPa)
(c) 25 20 15 0 kPa 67.5 kPa
10
110 kPa 157 kPa 225 kPa
5 0
0
2
4
6
8
10
12
Strain (%)
(d) Fig. 6. Typical deviatoric stress–strain curves of fine sand grouted with ER/W ratio of (a) 0.5; (b) 1.0; (c) 1.5; (d) 2.0 at different confining pressures.
C.A. Anagnostopoulos et al. / Tunnelling and Underground Space Technology 26 (2011) 718–724
Dry unit weight (KN/m 3 )
17.4 17.2 17 16.8 16.6 16.4 16.2 16 15.8 0
0.5
1
1.5
2
ER/W Fig. 8. Dry unit weight of grouted fine sand with different epoxy resin grouts.
45 40
Porosity (%)
W ratio of 0.5, which were equal to 960 kPa for compressive strength, 40 MPa for elastic modulus and 84 kPa for splitting tensile strength. On the contrary, grouting with ER/W ratio of 2.0 resulted in compressive strength of 12,961 kPa, elastic modulus of 395 MPa and splitting tensile strength of 2017 kPa. Inspection of the diagrams representing the relation between compressive stress–strain reveals an extended plastic zone that occurs before and after fracture for all ER/W grouted samples. Especially, grouted samples with ER/W ratio of 1.5 and 2.0 did not fail at the end of test, but were continuously deforming, up to a strain of at least 3.5%, where the test was stopped. This is an indication of the strong adhesion between the formed polymer film and sand grains. It also demonstrates the domination of the elastoplastic behavior of epoxy resin to the mechanical response of the whole mixture. Typical trends in deviatoric stress (r1–r3)-strain obtained in triaxial tests are shown in Fig. 6a–d. These results illustrate the beneficial effect that epoxy grouts have on the strength and on the stiffness of the sand. As expected, peak strength and initial stiffness strongly increased with an increase in ER content and confining pressure. For example, the application of 225 kPa confining pressure on grouted specimens with ER/W ratio of 0.5 caused a deviator increment of 1150%, compared to the unconfined test. Generally, the degree of post-peak strength loss tends to decrease with increasing confining pressure and ER/W ratio resulting in a relatively constant peak strength. The strain at which the peak stress was achieved generally increased with increasing confining pressure and ER/W ratio, although some scatter was observed. The lowest deviatoric stress value obtained at confining pressure of 67.5 kPa is 6.7 MPa for grouted sand with ER/W ratio of 0.5 and the highest one obtained at confining pressure of 225 kPa is 26.57 MPa for grouted sand with ER/W ratio of 2.0. The effect of confining pressure and ER content on the enhancement of max deviatoric stress is clearly seen in Fig. 7. A remarkable extension of plastic zone for all grouted samples with the different ER/W ratios is observed, a fact that was reflected in the failure mode of the samples. Generally, no strain localization with inclined shear bands occurred, and the failure was associated with a fairly uniform strong expansion of the specimen. This observation supports the hypothesis that grouted specimens failed because of indirect tensile development and not because of shearing. The physical parameters of grouted fine sand are depicted in Figs 8–10. As for the mechanical properties, the improvement of physical properties was also dependent directly on ER/W ratio. In the case of grouting with thick grouts, permeability test results confirm the formation of a dense polymer film-sand matrix by which a large number of pores are filled or sealed resulting in
35 30 25 20 15 0
0.5
1
1.5
2
ER/W Fig. 9. Porosity of grouted fine sand with different epoxy resin grouts.
ER/W Permeability coefficient (m/s)
722
1.0E-03
0
0.5
1
1.5
2
1.0E-04 1.0E-05 1.0E-06 1.0E-07 1.0E-08 1.0E-09
Fig. 10. Permeability coefficient of grouted fine sand with different epoxy resin grouts.
Max deviatoric stress (MPa)
30
ER/W = 1/2 ER/W = 1/1
25
ER/W = 1.5/1 ER/W = 2/1
20 15 10 5 0
0
50
100
150
200
250
Confining pressure (kPa) Fig. 7. Confining pressure – deviatoric stress relation of grouted fine sand with different epoxy resin grouts.
the significant reduction of water permeability. Permeability coefficient k decreased almost five orders of magnitude for ER/W ratio of 2.0 and about four orders of magnitude for ER/W ratio of 1.5. Despite the weakening of the polymer membrane-sand matrix in the case of grouting with thin grouts, a noticeable decrease of water permeability was obtained. k values were 5.7 107 m/s for ER/ W ratio of 1.0 and 1.0 105 m/s for ER/W ratio of 0.5. Porosity and dry unit weight values confirm the above mentioned observations about the influence of ER/W ratio or the adverse impact of water when existing in high amounts in grout composition. The observed improvement of physical and mechanical properties for the grouted sand can further be manifested by the examination of scanning electron micrographs. Fig. 11 shows a
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Compressive strength (kPa)
18000 Experimental 3 days
16000
Experimental 7 days
14000
Experimental 28 days
12000
Model for 7 days
Model for 3 days Model for 28 days
10000 8000 6000 4000 2000 0 0
0,5
1
1,5
2
2,5
1,5
2
2,5
1,5
2
2,5
ER/W
Splitting tensile strength (kPa)
(a)
Fig. 11. A scanning electron micrograph of untreated sand.
3000 Experimental 3 days Experimental 7 days
2500
Experimental 28 days Model for 3 days
2000
Model for 7 days Model for 28 days
1500 1000 500 0
0
0,5
1
ER/W
(b) 600
Fig. 12. A scanning electron micrograph of fracture surface of grouted sand with ER/W ratio of 2.0.
micrograph of an untreated sand specimen where the sand particles appear almost unconnected with large voids existing around their periphery. In contrast, Fig. 12 shows a micrograph of the view perpendicular to the failure surface of a grouted sand specimen with ER/W ratio of 2.0. It is clearly seen that a large number of voids are infilled with polymer patches which act as adhesive ties to the sand grains forming a dense impermeable high strength structure. 5. Regression models Based on the laboratory results and using SPSS 16.0 statistic program a non-linear regression analysis was performed in order to correlate the compressive strength, splitting tensile strength and elastic modulus of grouted sand to the ER/W ratio and curing time, which were taken as a descriptor variables. Permeability coefficient was also correlated but only to the ER/W ratio, since previous research has shown its independence from curing time (Anagnostopoulos and Hadjispyrou, 2004). The model that gives the best correlation concerning the mechanical parameters has the following form: b
y ¼ a ðER=WÞ lnðAGE=cÞ
ð1Þ
Elastic modulus (MPa)
Experimental 3 days
500
Experimental 7 days Experimental 28 days Model for 3 days
400
Model for 7 days Model for 28 days
300 200 100 0
0
0,5
1
ER/W
(c) Fig. 13. Experimental results vs. computed values from the regression equations: (a) compressive strength; (b) splitting tensile strength; (c) elastic modulus.
where y is the dependent variable corresponding to the desired mechanical property, a, b and c are coefficients calculated from the regression analysis. The equations and the corresponding correlation coefficients R2 obtained from the regression analysis are as follows: a. Compressive strength (C.S.)
C:S:ðkPaÞ ¼ 1416:77ðER=WÞ1:988 lnðAGE=2:5Þ; R2 ¼ 0:98
ð2Þ
b. Splitting tensile strength (T.S.)
T:S:ðkPaÞ ¼ 243:17ðER=WÞ1:853 lnðAGE=2:5Þ; R2 ¼ 0:97
ð3Þ
c. Elastic modulus (E.M.)
E:M:ðMPaÞ ¼ 26:84ðER=WÞ2:2 lnðAGEÞ; R2 ¼ 0:98
ð4Þ
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Permeability coefficient (m/s)
ER/W 1,00E-04
0
0,5
1
1,5
2
2,5
1,00E-05 1,00E-06 1,00E-07 1,00E-08 1,00E-09
and ER/W ratio. A remarkable extension of plastic zone is obtained and the difference between peak strength and ultimate strength is negligible. The failure mode of the specimens indicates that fracture probably occurs due to the development of indirect tensile strength. A further investigation should be carried out to determine the mechanical behavior of grouted sand under a wide range of confining pressures. 3. The reliability and accuracy of the produced non-linear regression models were checked by comparing predicted output from these models to the measured values and found to be satisfactorily consistent. 4. In general, it can be concluded that epoxy resin grouts can be used for grouting purposes to provide suitable solutions for the strengthening of the foundation material.
Fig. 14. Measured permeability coefficient vs. computed values from the regression equation.
References The above relations for the mechanical properties of the grouted specimens at any age (days) and ER/W ratio were found to fit satisfactorily the experimental data, as shown in Fig. 13a–c. The model that gives the best correlation concerning the permeability coefficient is the following:
kðm=sÞ ¼ 0:0002e5:52ðER=WÞ ; R2 ¼ 0:99
ð5Þ
Fig. 14 illustrates the correlation of the measured permeability coefficient to the computed values from the regression analysis. 6. Conclusions Experimental results showed that the use of water soluble epoxy resin has a considerable effect on improving the physical and mechanical properties of the fine sand. Particularly, the following conclusions can de drawn: 1. Compressive strength, tensile strength and elastic modulus development of the grouted fine sand depends directly on the water content of the epoxy resin solution. Grouts with ER/W ratio of 2.0 and 1.5 result in significantly high strength and low permeability. Despite the weakening of the polymer membrane-sand matrix, in the case of high diluted grouts, the 28 day mechanical properties and permeability appear to be satisfactorily improved. 2. Under triaxial stress conditions, the peak strength and stiffness of all grouted specimens with different ER/W ratio increase significantly. This increment depends on the confining pressure
Anagnostopoulos, CA., Hadjispyrou, S., 2004. Laboratory study of an epoxy resin grouted sand. Ground Improvement 8, 39–45. ASTM Standard C 29/C 29M-91a, 1993. Standard test method for unit weight and voids in aggregate. In: Annual Book of ASTM Standards. ASTM International, West Conshohocken, PA, USA. ASTM Standard C 938-80, 1993. Standard practice for proportioning grout mixtures for preplaced-aggregate concrete. In: Annual Book of ASTM Standards. ASTM International, West Conshohocken, PA, USA. ASTM Standard D 3967-95a, 2005. standard test method for splitting tensile strength of intact rock core specimens. In: Annual Book of ASTM Standards. ASTM International, West Conshohocken, PA, USA. ASTM Standard D 4219-02, 2005. Standard test method for unconfined compressive strength index of chemical – grouted soils. In: Annual Book of ASTM Standards. ASTM International, West Conshohocken, PA, USA. ASTM Standard D 4320-04, 2005. Standard practice for laboratory preparation of chemically grouted soil specimens for obtaining design strength parameters. In: Annual Book of ASTM Standards. ASTM International, West Conshohocken, PA, USA. ASTM Standard D 5084-03, 2005. Standard test methods for measurement of hydraulic conductivity of saturated porous materials using a flexible wall permeameter. In: Annual Book of ASTM Standards. ASTM International, West Conshohocken, PA, USA. Au, S.K.A., Soga, K., Jafari, M.R., Bolton, M.D., Komiya, K., 2003. Factors affecting longterm efficiency of compensation grouting in clays. J. Geotech. Geoenvir. Eng. 129 (3), 254–262. Cambefort, H., 1977. The principles and applications of grouting. Q. J. Eng. Geol. 10, 57–95. Issa, C.A., Debs, P., 2007. Experimental study of epoxy repairing of cracks in concrete. Construction and Building Materials 21 (1), 157–163. Perret, S., Khayat, K.H., Ballivy, G., 2000. The effect of degree of saturation on sand groutability: experimental simulation. Ground Improve. 4, 13–22. RM, I.S., 1981. Suggested methods for determining the strength of rock materials in triaxial compression. In: Brown, E.T. (Ed.), International Society of Rock Meckanics, ISRM Suggested Methods. Pergamon Press, NJ. Widmann, R., 1996. International commission for rock mechanics. Commission on rock grouting. Int. J. Rock Mech. Mining Sci. Geomech. Abstracts 33 (8), 803– 847.