Effects of A Cationic Surfactant on Acrylamide Grout and ...

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

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. AV101 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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