Effects of A Cationic Surfactant on

Acrylamide Grout and Grouted Sand

Maria Burton, REU Student

Shiva Sunder, Graduate Mentor

Dr. Cumaraswamy Vipulanandan, Faculty Advisor

Final Report

Department of Civil and Environmental Engineering

University of Houston

Houston, Texas

Sponsored by the National Science Foundation

May-July, 2009

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Abstract Grouting is one of the technologies that can be used to improve the strength and reduce the permeability

of in situ soils. Though grout has been used for decades, it is important to improve the formula, as some

soils are not able to utilize the grout mixes that are currently available. Research was done to find an

improved grout mix that is more acceptable in various environments. The addition of a cationic

surfactant to acrylamide grout was studied. When adding surfactant, things that were studied and

compared were: the viscosity with respect to time, the temperature with respect to time, the gelling time,

and the unconfined compressive strength. Various concentrations of acrylamide AV-100 grout were

tested with the addition of cetyl-trimethyl-ammonium bromide surfactant. Viscosity readings were

observed using a viscometer, and temperature was observed using a laser thermometer. Four different

sand samples were grouted and tested to observe the compressive strength. Introduction Grout is a material used in construction to fill voids, seal joints, embed rebar into masonry walls, connect

pre-cast concrete sections, or to inject into the ground for foundation stability. The general composition of

grout is water, cement, sand, and sometimes fine gravel (“Grout”). Other grouts consist of chemical

substances mixed in water, such as acrylamide grouts, which are used mainly for tunneling and sewer pipe

joint sealing to reduce infiltration into the system (Ozgurel and Vipulanandan, 2005).

The technology of grouting allows in-situ soils to improve in strength and reduce permeability. There are

several types of grouting technologies, but permeation grouting is where low viscous grouts are injected

into the soil to fill pores and enforce the behavior of in situ soil. The in situ soil is the soil already “in the

place.”

Foundation stability is an important use for grout in geotechnical engineering. When soils bear loads, such

as carrying the weight of new or existing buildings, the ground needs to remain in a stable condition.

Other requisites for foundation stability are: the in-depth impermeabilization of water bearing soils, in

tunnel construction, and to mitigate the movement of impacted soils and groundwater. For soils that are

not naturally stable, jet-grouting is performed to modify or improve the ground. Jet-grouting is a general

term that grouting contractors use to describe the different construction methods for ground modification

or improvement (“What is Jet-Grouting?”).

Jet-grouting was first seen in Japan in the 1970s. By the 1980s, North America was using the technique.

Permeation grouting varies with the type of soils being treated, however, jet-grouting can be applied to

almost any soil (Coulter and Martin 2006). Another grouting method is compaction grouting, which the

main objective is to densify the soil. In compaction grouting, a low mobility grout is injected through

preplaced casings into distinct soil zones at high pressures (Grouting: Compaction, Remediation and

Testing. 1997).

Chemical grouting is the most efficient and cost-effective technology for rehabilitation, like mending a

leaking sewer system. Acrylamide-based chemical grouts are close to being the ideal grout. They have

low initial viscosity, and then after they rapidly set, these grouts develop sufficient strength for majority

of applications. Acylamide grouts have been used in the United States since 1953 (Ozgurel and

Vipulanandan 2005).

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Grout pump-ability and the ability to fill voids and cracks depends on the grouts rheological properties.

This applies to various grouting applications such as: ground treatment, repair of concrete, reduction of

rock or soil permeability, environmental remediation, post-tensioning of concrete, rock anchors, sealing

radioactive waste repositories, and well completion. To improve the rheological, fresh, and durability

properties of grouts, chemical admixtures and mineral additives are often used (Sahmaran, M., et al.

2008).

Rheology is the science of dealing with the flow of materials. Examples are: the deformation of hardened

concrete, the handling and placing of freshly mixed concrete, and the behavior of slurries, pastes, and

grouts. The rheology of a grout can be characterized by three parameters: viscosity, cohesion, and internal

friction (Weaver, 2007).

The concept of viscosity is an important property of grout because the process of grouting transforms the

grout mix from a fluid to a solid. When grout enters a soil in liquid form, the resistance that the fluid

holds against deformation by shear stress is its viscosity, which changes with time as the grout solidifies.

Viscosity is a key property in lubricants and paints. For chemical engineers, surface tension determines

the quality of products (like coatings, paints, detergents, cosmetics and agrochemicals). In 1966, Pelofsky

introduced a linear relation between surface tension and viscosity (Queimada 2003).

Studies have been conducted to quantify the permeability and mechanical behavior of acrylamide grouted

sand, and the results have provided useful information. According to Ozurel and Vipulanandan (2005),

diluting acrylamide grout with water affects the mechanical properties of grouted sands, however diluting

grout with up to 50% of water does not affect the permeability of grouted sand. Further studies await to

improve the acrylamide grout. One idea that has not yet been explored is the effects of adding a surfactant

into the mix.

A Surfactant is a blend of surface acting agent. Surfactants are typically organic compounds that consist

of hydrophobic “tails” and hydrophilic “heads.” This makes them soluble in both organic solvents and

water. With surfactants, the surface tension of water gets reduced due to absorption at the liquid-gas

interface. The interfacial tension between oil and water is also reduced by adsorption at the liquid-liquid

interface. Everyday dishwashing liquid will promote water penetration in soil, but the effect would only

last a few days. One conflict is that many laundry detergent powders contain chemicals such as sodium

and boron, which can be harmful to plants and should not be applied to soils (“Surfactant”). Though this

may be true, there are certain types of surfactant not harmful to the environment, such as biosurfactants.

For now, the effect of surfactant is studied when added to acrylamide grout. Then, if the surfactant proves

any usefulness, methods will be determined on how to apply the surfactant with environmental

consideration.

Research has previously been done on the effect on the viscosity as surfactant is added to starches. The

final viscosity of cereal starch paste with surfactants was found to be higher than control; higher

surfactant concentration leads to higher final viscosity of cereal starch paste (Tomomi 2004). Now

surfactant is added to grout and observed.

Objectives Grout is a very important material for filling voids, sealing joints, or stabilizing the ground beneath

structures. Though the currently available grout has proved its worth over the years, it is important to

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continue to improve the formula, as some soils are not able to effectively utilize the current grout mixes.

Research must be done to try to improve the grout formula and make it more acceptable in various

environments.

For this research, the specific objectives were: (1) studying the viscosity, temperature, and gelling time of

acrylamide grout as it varied with time, (2) studying the viscosity, temperature, and gelling time of

acrylamide grout as it varied with time with surfactant added, (3) studying the compressive strength of

acrylamide grouted sand, and (4) studying the compressive strength of acrylamide grouted sand with

surfactant added. The final results were then compared and a conclusion was determined as to whether the

addition of surfactant provided any use.

Materials Grout AV-100 acrylamide chemical grout was used (figure 1). This grout was a crystal-like powder. It was

white in color and tended to clump up when dry but is dissolvable in water. AV-100 is a mixture of three

or more water-soluble chemicals that produce stiff gels when the solution is properly catalyzed. AV-100

also refers to the name of the base chemical in the mixture; a blend of Acrylamide Monomer (AM) and

Methylenebisacrylamide (MBA). Uses for AV-100 are: sewer joint sealing, sewer laterals, manhole

waterproofing, soil stabilization, and tunnels/dams water-stop. This chemical is not suitable for high water

flows or potable water applications (“AV-100 Chemical Grout (Powder Blend)”).

Fig. 1. AV-100 grout

Catalyst and Activator The catalyst used was called AV-102 catalyst AP (ammonium persulfate). It has a sugar/sand-like texture

and is white in color. AV-102 Catalyst AP is a material that is granular and is a strong oxidizing agent. It

is an initiator that triggers the reaction.

The activator used was called AV-101 catalyst T+. It is in liquid form, and the color is transparent. AV-

101 acts as a buffer and will appear to act as a catalyst in the AV-100 gel mix. The primary ingredient in

AV-101 is triethanolamine (TEA). Blending TEA with other additives creates a liquid that functions as an

activator for the reaction.

Surfactant Cetyltrimethylammonium bromide (CTAB) was the surfactant that was used. This chemical is a cationic

surfactant and has a fine powder texture. It is white in color and is considered harmful for the

environment. This substance should not be injected into the ground, as it could kill plant life.

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Sand Four types of sand were used. One was a standard sand called ASTM 20-30 sand, designated as sand #1.

Another was coarse sand, designated as sand #2. Fine sand was designated as sand #3. Sand #4 was a

mixture of 60% fine sand and 40% coarse sand. See figure 2 for the four types of sands used.

(a) (b) (c) (d)

Fig. 2. Sands (a) standard, (b) coarse, (c) fine, (d) 60% fine, 40% coarse

Methods

Grout AV 100 is a chemical used as a grout and was the substance used for this research. It is a salt-like

crystalline solid, and its proportions were varied with water and were tested and compared. The samples

were mixed with a chemical catalyst and activator, and the changes in viscosity and temperature were

measured with respect to time. Simultaneously, this chemical has a tendency to solidify due to

polymerization reaction, so the gelling time (solidifying time) of this chemical grout was also observed.

Grouted Sand Molds were filled with sand, and then grout was injected into the sand. The grouted sands were cured in

the molds till the time of testing. The unconfined compression test was performed to determine the

strength. The goal of this study was to characterize the grouts (AV 100 solutions with surfactant) using

standard properties and analyze their application in the process of grouting.

Preparation Before performing any actual testing, the viscometer had to be calibrated. The viscometer, see figure 3, is

a device used to calculate the viscosity of a liquid by inserting an attached spindle into the liquid and

measuring the resistance the liquid has as the spindle rotates at a given speed. When testing the

viscometer with standard liquids (standard 10 and standard 500), the readings were off from what they

should have been. To look into the problem in more depth, each viscometer spindle was tested, 5 runs for

each speed. This was done for each liquid standard, with standard 10 having a standard viscosity of 9.8

cP, and standard 500 having a standard viscosity of 445 cP. The results were graphed against their

allowable ranges of error with viscosity versus speed for each spindle of each standard. See figures 4 and

5 for the graphs.

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Fig. 3. Brookfield Dial Viscometer

(a) (b)

(c) (d)

Fig. 4. Calibration curves for standard 10: (a) spindle 1 results, (b) spindle 2 results, (c) spindle

3 results, and (d) spindle 4 results

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(a) (b)

(c) (d)

Fig. 5. Calibration curves for standard 500: (a) spindle 1 results, (b) spindle 2 results, (c) spindle 3

results, and (d) spindle 4 results

After graphing the calibration curves of the results, the final graphs for standard 10 revealed the test

averages to be within or near the ranges of error. The final graphs for standard 500 revealed the test

averages to be within or near the ranges of error except for spindle 1. This means that spindle 1 should

only be used for a fluid with a viscosity such as 9.8 cP for standard 10.

Testing Viscosity - Grout Mix (without surfactant) Once the viscometer was assured to be in working order, the acrylamide chemical grout called AV-100

was added to water for testing. As the grout concentration in the water varied, viscosities were noted.

Figure 6 shows the results for the viscosity versus the percent of AV-100 of the total weight. The graph

appears to be slightly linear in a positive direction. This means that as the percent of AV-100 increases,

the viscosity increases.

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Fig. 6. Variation of viscosity with varying percentage of AV-100 grout (without surfactant)

The next step was adding an activator to start the reaction and a catalyst to speed up the reaction. With

these, the grout mix would solidify (gel) at a higher rate. Several mixes were prepared with varying

concentrations of AV-100, catalyst, activator, and water; see table 1. The viscosities of these mixes were

observed with respect to time. Figures 7 and 8 show the results of mixes 1 and 5 respectively. Both graphs

show that the viscosity exponentially increases with respect to time.

Table 1. Grout mixes (without surfactant)

mix AV 100 (g) AV 101 - Catalyst (g) AV 102 - Activator (g) water (g) total (g)

1 10 0.5 0.5 89.0 100

2 10 1.0 1.0 88.0 100

3 10 1.5 1.5 87.0 100

5 10 0.2 0.2 89.6 100

10 10 0.4 0.4 89.2 100

11 10 0.3 0.3 89.4 100

12 15 0.5 0.5 84.0 100

13 12 0.2 0.2 87.6 100

Fig. 7. Variation of viscosity with time for grout mix 1 (without surfactant)

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Fig. 8. Variation of viscosity with time for grout mix 5 (without surfactant), reduced amount of catalyst

and activator

Temperature & Gelling Time - Grout Mix (without surfactant) More mixes that varied the proportions of grout, catalyst, activator, and water were prepared and placed

into the viscometer. As the solutions were continuously being stirred due to the rotation of the spindle in

the viscometer, temperatures were observed with respect to time. See figure 9 for the results of mixes 10,

11, and 12. The graph shows the relationships between time and temperature for each mix to be slightly

linear.

Fig. 9. Variation of temperature with time for grout mixes 10, 11, and 12 while in viscometer (without

surfactant)

Temperatures were observed with respect to time without the solution sitting in the viscometer and

without constant stirring. The results of mixes 1, 10, 11, and 13 are shown in figure 10. The graph shows

each to be an exponential relationship between temperature and time.

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Fig. 10. Variation of temperature with time for grout mixes 13, 11, 10, and 1 while sitting idle (without

surfactant)

Viscosity – Surfactant in Grout Mix

A new material, surfactant, was then added to the grout mix. A few mixes were made with AV-100 grout,

water, and an added surfactant called cetyltrimethylammonium bromide. Concentrations of the three were

varied, and the viscosity was observed for each mix. Results of the mixes are shown in figure 11. The

viscosity was affected by the addition of grout and surfactant. Addition of surfactant increased the

viscosity, while the addition of grout reduced the viscosity.

Fig. 11. Variation of viscosity with varying percentage of surfactant in grout mix

Temperature & Gelling Time – Surfactant in Grout Mix

To observe the characteristics of the surfactant-grout as it gels, the same activator and catalyst were added

to the mix as was to the grout mix without surfactant; see table 2 for the mixes When making the mixes,

they were split in half so that the catalyst was in one half of the solution and the activator was in the other

half of the solution. When testing time approached, the two halves would be combined, mixed, and the

reaction would start. Before combining the two halves of one mix, the halves were placed in a refrigerator

to cool to a common temperature. After being placed in the refrigerator however, the mixes started

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solidifying even without the catalyst and activator halves being mixed yet. When the mixes were taken

out of the refrigerator, they began solidifying more, having a foamy solid appearance.

Table 2. Surfactant-grout mixes

mix AV 100 (g) AV 101 - Catalyst (g) AV 102 - Activator (g) surfactant (g) water (g) total (g)

11i 10 0.3 0.3 1.0 88.4 100

11ii 10 0.3 0.3 2.5 86.9 100

11iii 10 0.3 0.3 5.0 84.4 100

11iv 10 0.3 0.3 7.5 81.9 100

When combined, each mix (surfactant, grout, catalyst, activator, and water) was observed and the

temperature was noted as it increased with respect to time. The gelling process was longer with the

surfactant than without. Each mix took at least one hour before the temperature stopped rising and started

to stabilize. Mix 11i took over one hour to stabilize in temperature. Mix 11ii was combined but not stirred

and took two hours before it stabilized in temperature. Mix 11iii was stirred and took over four hours to

stabilize in temperature. Mix 11iv was stirred and took over three hours to stabilize in temperature. See

figure 12 for the results of mixes 11i, 11ii, 11iii, and 11iv. The relationship between temperature and time

with surfactant addition appears to be slightly linear, and then it gradually stabilizes towards the end.

Fig. 12. Variation of temperature with time of surfactant-grout mixes 11i-11iv

All four mixes did not completely gel during the recorded temperature times. All except mix 11iii took

over two days to completely solidify. Mix 11iii never gelled, and this may have been caused by human

error during the experiment. The other three mixes gelled into a “jello” state after one day and then

solidified even further into a more crystal-like appearance after 2-3 days had passed. This crystal-like

appearance was the final outcome of all three mixes; see figure 13.

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(a) (b)

Fig. 13. (a) mix 11 ii and (b) mix 11 iv

Density – Surfactant in Grout Mix As the temperature was being observed with respect to time for mixes 11i –11iv, the change in density

was also being observed; see table 3 for the data and figure 14 for the plot. The overall trend was, as time

elapsed, temperature increased and density decreased.

Table 3. Temperature and density with respect to time for mix 11i, mix 11ii, mix 11iii, and mix 11iv

mix 11i mix 11ii

time (s) temp (F) density (g/mL) time (s) temp (F) density (g/mL)

0 45.5 0.996 0 35.5 1.184

3057 71.0 0.994 150 37.5 1.186

6000 84.5 0.992 480 54.0 1.184

3060 56.0 1.182

3960 63.0 1.180

4260 66.0 1.178

4980 69.5 1.176

6900 70.0 1.174

mix 11iii mix 11iv

time (s) temp (F) density (g/mL) time (s) temp (F) density (g/mL)

0 40.0 1.168 0 38.5 0.740

435 44.5 1.170 2325 58.5 0.738

1930 55.5 1.168 4075 64.5 0.736

3190 60.0 1.166 5862 67.5 0.734

5867 65.0 1.164 7445 69.0 0.732

8220 67.0 1.162 8955 69.5 0.730

11888 69.5 1.160 10350 70.0 0.728

12719 70.0 1.158

13885 70.0 1.156

15600 70.5 1.154

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Fig. 14. Density vs. time of surfactant-grout mixes 11i-11iv

Compressive Strength To observe properties of the grout in soil, a set-up was made to hold molds where grout was injected into

sand. A drill press was used to drill holes for filter pieces to prevent sand from leaving the mold set-up

and draining through the tubes. Once the grout was injected into the soil, the grouted soil was then

removed from the set-up and further tested via unconsolidated compression test.

Four types of sands were tested in the mold set-up. Sands that were used were: a standard sand called

ASTM 20-30 sand (sand #1), coarse sand (sand #2), fine sand (sand #3), and 60% fine, 40% coarse sand

(sand #4). See figure 15 below for the sieve analysis of these sands.

Fig. 15. Particle size distribution curves for sand 1, sand 2, sand 3, and sand 4 (s1, s2, s3, s4 respectively)

For grout injection, the molds that were set-up consisted of cylinders filled with sand enclosed by a filter

piece on each end to catch the sand from leaving the mold. The ends were attached to tubes that allowed

the grout to flow in from the bottom and exit the mold from the top. The grout was applied to a container

that used a pressurized chamber system to push the grout through the tubes and up into the sand. As the

grout exited the top of the mold, it was released out of a tube and disposed into a bucket. Once the grout

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had completely gelled, the grouted sand specimens were carefully taken out of the molds and used for

further testing. See figure 16 for the mold set-up.

Fig. 16. Grout injection mold set-up

The samples that were grouted were grouted with a grout, water, catalyst, and activator mix, mix 11, and

with a surfactant, grout, water, catalyst, and activator mix, mix 11ii. Both types of grouts were injected

into two sets of four types of sands each (a total of eight specimens for each grout mix); see tables 4 and 5

for details on each specimen. The gelling time for the surfactant-grout was longer than without the

surfactant.

Table 4. Soil types

soil # type soil

1 ASTM standard sand

2 coarse sand

3 fine sand

4 60% fine, 40% coarse sand

Table 5. Specimens grouted

specimen # soil # grouted with mix #

1 2 11 (regular grout)

2 2 11

3 1 11

4 1 11

5 3 11

6 3 11

7 4 11

8 4 11

9 2 11ii (surfactant-grout)

10 2 11ii

11 1 11ii

12 1 11ii

13 3 11ii

14 3 11ii

15 4 11ii

16 4 11ii

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The grouted sand specimens were coated at the ends with sulfur; see figure 17. The sulfur provides a level

surface for applying an evenly distributed loading to the top of the specimen via the tri-axial testing

machine. The tri-axial machine is shown in figure 18. The test performed with this machine was the

unconfined compression test.

Fig. 17. Grout-injected samples 1-8 (without surfactant) coated with sulfur on ends

Fig. 18. Tri-axial testing machine

The unconfined compression test is a test that determines unconfined compressive strength properties of

grouts and grouted sands. The experimental results are used to find the compressive stress-strain

relationship for the tested material. The relevant modulus can then be obtained using the stress-strain

relationship. The compression test provides data for specific purposes such as development, quality

control, and acceptance or rejection under specifications.

The test procedure followed for the unconfined compression test was the CIGMAT GR 2-04. The length,

diameter, and weight were measured for each specimen. Each specimen was coated with sulfur on the top

and bottom ends and was placed in the tri-axial machine. The machine applied a load until the specimen

failed; see figure 19 for the failed mix 11 grouted specimens. Specimens 1-8 all failed with a “v” shaped

crack down the middle of the specimen.

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Fig. 19. Samples 1-8 (from left to right respectively) after failure, grouted without surfactant

For each specimen tested, values of the applied load and vertical displacement were recorded with respect

to time. From this, the corresponding strain and stress values were calculated. Plots of the stress versus

strain values are shown in figure 20. Each plot shows the original graph (left) and then the corresponding

corrected graph (right). The graphs originally did not start out correctly at the origin so some adjustments

were made. This error may have been due to the fact that the sulfur coatings were not completely level on

some specimens. The correction for this was done by considered the R^2 value of the graph, and the error

was avoided considering the slope and the intercept. The curve was fitted such that it began from the

origin by giving approximate values.

Original Test Seating Correction

(a)

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(b)

(c)

(d)

18

(e)

(f)

(g)

19

(h)

Fig. 20. Stress versus strain for regular grout injected (a) specimen 1, (b) specimen 2, (c) specimen 3, (d)

specimen 4, (e) specimen 5, (f) specimen 6, (g) specimen 7, and (h) specimen 8. For each specimen, the

left graph is the original version of the plot, and the right graph is the corrected version.

From the graphs of figure 20, each peak shows where the maximum stress occurs, and that point is where

the specimen fails with the corresponding strain. See table 6 for values of maximum stress and

corresponding strain for each specimen. Figure 21 shows the variation in strength and variation in strain

with the mean grain diameter of the sand (d50). As the diameter increases, the strain decreases, and the

strength appears to show no distinct pattern.

Table 6. Maximum stress and corresponding strain values

soil sample strain max. stress (psi) Average Strain Average Stress (psi)

soil 2 - coarse 1 0.018 35.5 0.019 32.8

soil 2 - coarse 2 0.020 30.1

soil 1 - astm 3 0.025 32.7 0.022 24.5

soil 1 - astm 4 0.018 16.4

soil 3 - fine 5 0.066 46.3 0.064 39.0

soil 3 - fine 6 0.061 31.7

soil 4 - mix 7 0.054 40.8 0.046 41.5

soil 4 - mix 8 0.038 42.2

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(a) (b)

Fig. 21. (a)Variation in strength with d50 and (b) variation in strain with d50 for grouted sands without

surfactant

When the sand specimens were grouted with the surfactant-grout mix, gelling time took close to a full

week. As the specimens were taken out of their molds, they started to crumble; see figure 22. The

specimens were too soft to test for compressive strength.

Fig. 22. Specimens 9-16 after grouted with surfactant-grout mix

Conclusions This study was focused on investigating the effect of a cationic surfactant on the viscosity of acrylamide

grout, the setting temperature, the gelling time, and the compressive strength of acrylamide-grouted sand.

Based on this study, the following were observed with the addition of CTAB surfactant:

(1) the gelling time of acrylamide grout increased

(2) the viscosity increased

(3) the rate of temperature-increase with respect to time decreased

(4) the strength of the grouted sand decreased

The surfactant modified the grout properties. The change in the gelling time, viscosity, and temperature

could be useful properties of grout in various applications. Grouted sand properties were reduced (or

affected) by the addition of the surfactant. Because of the decrease in strength of the sand, CTAB

surfactant is not recommended for use in strengthening acrylamide grout, however, in some applications,

reducing the strength of the grout may be desired.

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Though surfactant has proved to be ineffective in strengthening acrylamide grout, it may increase the

strength in other types of grout. Research is always being done to improve the quality of different kinds of

grouts. Though surfactant is harmful to the environment, its ability to delay the gelling time may help in

certain situations, such as allowing the grout to seep into deeper areas of the ground if needed. If the

surfactant proves its use in another grout mix, research can be done to find a way to use this surfactant in

a way that doesn’t harm the environment around it. Biosurfactant is not harmful to the environment and

has similar properties to this surfactant. Another way to avoid the harmful effects of surfactants is to not

use it for ground injections but possibly for pipe sealing or crack sealing. Also, another chemical could be

added that would dilute the surfactants harmful properties.

Acknowledgment

The research study described herein was sponsored by the National Science Foundation under the Award

No. EEC-0649163. The opinions expressed in this study are those of the authors and do not necessarily

reflect the views of the sponsor.

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