ASR

ALKALI SILICA REACTION (ASR)

CHAPTER 1 INTRODUCTION

As one of the internal crumbles of concrete durability, Alkali-Aggregate Reaction (AAR) is

formed from the reaction between the alkali (K2O, Na2O) in concrete pore solution with the

active component of concrete aggregate. This results in expansion or swelling of the concrete,

thus leading to cracking, followed by concrete structural damages. As propose by Stanton in

early 1940s, there are 3 types of Alkali-Aggregate Reaction (AAR), namely:

Alkali-Silicon Reaction (ASR): Reaction between alkali in concrete and active silicon dioxide

in aggregate

Alkali-Silica Reaction (ASR): Reaction between alkali in concrete and silicate in aggregate

Alkali-Carbonate Reaction (ACR): Reaction between alkali in concrete and carbonate in

aggregate

Alkali-silica reaction (ASR) is an issue to be inhibited in concrete structure and Portland cement

concrete pavement which resulted from the reaction between highly alkaline solution with

certain aggregate with silica in Portland cement concrete. Alkaline solution is formed from the

hydration of Portland cement having high alkali (potassium and sodium) content. The outcome

of this reaction is the formation of an alkali-silica gel (often reffered as “reaction rim”) which

would swell in the presence of moisture, hence leading to the expansion and then cracking of

the concrete.

In Malaysia, alkali-silica reaction has been one of the major distresses to the construction

materials such as granite or microgranite, which is vastly use as concrete aggregate. Due to its

threat to the concrete structure, this concern affected the import of local aggregates to country

such as Singapore. This is because the local aggregates or concrete structure may be subjected

to potential high risk due to the reaction of the component containing silicon dioxide with the

presence of sufficient alkali.

As an overview, this paper introduces and discusses on the alkali-silica reaction about the

causes and effects of this reaction, i.e. various crack patterns in concrete structure and

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pavement. Following these come with the problems faced in Malaysia due to ASR and

mitigation measures taken to resolve the issues.

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CHAPTER 2 CAUSES OF ASR

2.1 Factors Causing Alkali Silica Reaction (ASR)

Alkali silica reaction is reaction between the hydroxyl ions in the pore water of concrete and

certain forms of silica which occasionally occur in significant quantities in the aggregate. Three

components, reactive silica from the aggregates, sufficient alkalis and sufficient moisture, are

required in order for ASR to cause damage to concrete structures. However, factors governing

ASR are as below.

1. Influence Portland cement characteristics on alkali silica reactivity

The sodium and potassium in cement are present as sulphate phases or contained within the

aluminates and silicate phases of the anhydrous cement. Higher concentrations of alkali in the

pore water solution encourage greater swelling capacities in the gel. The concentration of

sodium and potassium compounds and hydroxyl ions is dependent on the quantity of sodium

and potassium compounds in the anhydrous Portland cement. The hydroxyl ion concentration

in the pore solution of concrete made with high alkali cement might be ten times as that made

with low alkali cement.

2. Aggregate

Generally, alkali aggregate reaction involves two main types of aggregates, which are rapid and

slow/late alkali reactive aggregates. Rapid alkali reaction aggregates will react by dissolution to

form alkali silica gel at both surfaces of the reactive particles and inside the particles. For

slow/late alkali reactive aggregates, the reaction initiates at original cracks, inhomogeneities or

grain boundaries, which act as pathways for the alkaline pore solution. Therefore, only certain

parts of reactive particles should be considered as alkali reactive and minimal gel formation is

produced. However, the gels are capable of separating the grain boundaries and leading to

expansion and cracking of aggregate, and the resulting cracks will appear more marked, longer

and more defined.

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Besides that, smaller particles will have a much higher specific surface area compared to

coarser particles. Hence, smaller particles will react quicker. However, the alkali reaction is

most damaging for certain rock types when the reactive rocks occur in a particular size range.

Both natural aggregates, eroded to present size by natural agents, and crushed aggregates,

obtained by a deliberated fragmentation of rocks are used in concrete. The physical factors and

chemical factors might to a certain degree, differ between these types of aggregates. This also

will introduce some possible in differences the alkali reactivity of these distinctive types of

aggregates.

3. Moisture and environment

Moisture must be sufficiently available in the concrete to permit expansive ASR to occur.

Laboratory data indicate that relative humidity values in the concrete must exceed about 80%

referenced to 23 ± 1°C before expansion due to ASR can develop. This condition is easily met

outdoor slab-on-grade concrete regardless of climate. Interior portions of elevated concrete

members, such as support columns and girders, also exceed the 80% relative humidity level at

least on a cyclic basis. Except for near-surface concrete in elevated structures, concrete climate

can be expected to be sufficiently damp to support expansive ASR on an almost continuous

basis. Near-surface concrete experiences major relative humidity fluctuations that support

expansive ASR on an intermittent basis, regardless of climate. Where high water-cement ratios

are used, residual mixing water may be sufficient to support expansive ASR in mass concrete,

even in interior air-conditioned exposures.

4. Temperature

Like any other chemical reactions, the rate of alkali silica reactions is accelerated by high

temperatures, in the range of 10 to 38°C. When concrete dries, evaporating water is brought to

the surface together with the alkalis. Under hot and dry conditions, the rate and amount of

evaporating water is increased, thus enhancing alkali silica reactions.

(Praestholm, 2010) carried out an experiment to determine the effects of temperature on the

expansion of concrete due to alkali silica reactions (ASR). Identical samples were placed both

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under varying temperatures and constant temperature. Expansions of the samples under both

conditions were recorded. It was concluded that under varying temperatures, concrete expands

slower compared to when it is exposed to constant temperature. In addition, the expansion

also follows a more constant rate if the temperature is varying.

5. Alkalis from other sources

Certain types of aggregates within an alkaline medium such as concrete, may release sodium

and potassium ions into the pore solution. Grain size strongly influences the release of alkalies.

The rate of removal of alkali is also dependent on the state and type of aggregates, with fine,

freshly crushed material rapidly giving up alkalies. Leaching of alkalies in aggregate pore

solution interaction from concrete during curing and weathering can be significant.

Sea water/dredged aggregates will also contribute alkali. When sodium chloride is

present in the aggregate or mix water, the tricalcium aluminates in Portland cement may react

with the chloride taking some of the chloride out of the solution with the separation of sodium

ions in solution. Similar enhancement of alkalies has also been found to occur for sulphates and

nitrates.

Alkali ions might also enter concrete from the outside, commonly on the coast and on roads

and bridges where de-icing salts are employed.

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CHAPTER 3 EFFECTS OF ASR

3.1 Introduction

ASR is a major cause of the deterioration of highway structures and pavements. The Strategic

Highway Research Program (SHRP) in United States has addressed this problem through Project

C-315. SHRP C-315 revised the ASR in bridge structures and pavements.

3.2 ASR in Bridge Structures

3.2.1 Cracking related with ASR at mid-span in bridge deck

Predominant cracks are:

Oriented longitudinal with respect to deck

Interconnected by short/ tight micro-cracks that extend transversely or randomly

between longitudinal cracks

Cracking may be more severe over grids. In addition, there are no consistent relationship

between steel in top reinforcing mat and location of cracks.

Figure 3.1 Cracking related with ASR at mid-span in bridge deck

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3.2.2 Cracking associated with ASR in the corner of bridge deck

These cracks tend to curve from transverse orientation at the end of bridge deck to longitudinal

orientation toward middle span of the bridge deck.

Figure 3.2 Cracking associated with ASR in the corner of bridge deck

The crack pattern is due to restraint by steel reinforcement and other concrete members

around the deck. Furthermore, the rain water flows or collects on a deck can show more severe

cracking.

3.2.3 Cracking associated with ASR in end block of concrete guard rail on bridge deck

These cracks could be results from freezing and thawing. ASR is the main cause of cracking

during initial frost-free climates. However, this type of cracking does not interpreted as

confirming evidence of ASR in freezing and thawing areas.

The initial cracking is due to ASR and hence leads to faster progression of freeze-thaw damage

by creating a pathway for moisture to enter into the concrete mass expanding the cracks upon

freezing.

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Figure 3.3 Cracking associated with ASR in end block of concrete guard rail on bridge deck

3.2.4 Cracking associated with ASR in bridge column

Predominant cracks are

oriented longitudinally

connected in irregular shape by short transverse cracks

by fine random micro cracks

Cracking patterns are related to the configuration of the embedded steel reinforcement. Drying

shrinkage can enlarge the cracks.

Figure 3.4 Cracking associated with ASR in bridge column

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3.2.5 Cracking associated with ASR in wing wall of bridge structure

Majority of these cracks are

Sub-horizontal orientation

More strongly developed at lower levels

However, the humidity and moisture are at the highest level due to wicking effects from soil

and shielding from solar drying. These cracks may results from frost action and assign ASR as a

cause. In climates that are essentially frost-free, thus ASR is probably a cause.

Figure 3.5 Cracking associated with ASR in wing wall of bridge structure

3.3 ASR in Pavements

3.3.1 A well-defined crack pattern associated with ASR in highway pavement

These cracks pattern are commonly defined as mop-cracking or pattern-cracking. The

orientation of predominant cracks is longitudinal. These cracks pattern is basically developed

uniformly across the width of the pavement although the cracks in wheel path are more

apparent due to infiltration of dirt as show in Figure 3.6. Furthermore, the crack pattern is

similar to jointed and continuously reinforced concrete pavement (CRCP).

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Figure 3.6 A well-defined crack pattern associated with ASR in highway pavement

3.3.2 Cracking associated with ASR in jointed pavement

These cracks are transversely across jointed pavement. The orientation of predominant cracks

is longitudinal (left to right); interconnecting cracks are randomly oriented. These cracks are

open and do not fill with secondary deposits at the surface. The severity of cracking increasing

due to severe desert drying occurs in this region.

Figure 3.7 Cracking associated with ASR in jointed pavement

3.3.3 Cracking associated with ASR in continuously reinforced concrete pavement (CRCP)

The cracks for CRCP are

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Most frequently oriented longitudinal direction of pavement (top to bottom)

Interconnected by finer transverse or random cracks

Thus, it produces a generally rectilinear pattern. In addition, the wearing surface is relatively

smooth, in contrast to grooved and textured surface, enhances appearance of crack which

show in Figure 3.8

Figure 3.8 Cracking associated with ASR in continuously reinforced concrete pavement (CRCP)

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CHAPTER 4 PROBLEMS OF ASR IN MALAYSIA4.1 Introduction

In Malaysia, the problems related to ASR in local aggregates or concrete structures are not well

documented. However, the risk for ASR occurs is still potentially high. This chapter discusses

about problems of ASR encountered in several cases in Malaysia, i.e. Sg. Pontian in Pahang and

Tamparuli Bridge in Sabah;

4.2 Case Studies

Case problem for bridge structure in Malaysia

1) Sg. Pontian in Kuala Pontian, Pahang

In West Malaysia, one the ASR case was reported happened at the pile head of bridge in Sg.

Pontian in Kuala Pontian, Pahang as shown in Figure 4.1, Kuala Pontian is a small fishing village

situated at the west coast of Pahang with geographical coordinates of 2° 46' 0" North, 103° 32'

0" East. Its original name (with diacritics) is Kampong Kuala Pontian. The stream of Sg. Pontian

is a body of running water moving to a lower channel on land. The stream of water will move to

a stream mouth in Kuala Pontian where the stream discharges into a lagoon before the water

go into the South China Sea.

Figure 4.1: Location of Sg. Pontian in Kuala Pontian, Pahang

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Study area


Random map-like crack formed due to ASR is one common type of intrinsic cracks happened in

Malaysia. The diagnosis of alkali-silica reaction (ASR) in a concrete structure requires a

combination of recognition of the visual symptoms of ASR, appropriate testing to verify the

presence of ASR gel, and deterioration of the concrete in the structure. Typical visual symptoms

include unusual expansion of the concrete evidenced by longitudinal cracks, map cracking

(random cracking pattern), closed joints, spalled surfaces, displacement of adjacent structural

components, pop outs, efflorescence, or discoloration (darkened or blotchy areas). If site

inspections reveal one or more of these visual symptoms it may be appropriate to sample and

test the concrete to verify the presence of ASR gel. In addition, the source of any other

deterioration mechanisms should be noted and the structure should be evaluated for

soundness.

In this case, the full analysis was carried out by Dr. Hashim of University of Malaya and followed

by JICA department who confirmed the presence of ASR. The visual symptom at this particular

bridge is the map cracking type which the cracking pattern is random as shown in Figure 4.2.

Figure 4.2: Close up look at the random map cracking of bridge in Sg. Pontian in Kuala Pontian,

Pahang

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2) Location of Tamparuli Bridge in Sabah

There are other similar cases happened in East Malaysia. For example the Tamparuli suspension

bridge located in Tamparuli in Sabah with geographical coordinated of 6°8 0″North′

116°16 0″E′ ast. Tamparuli is a small town and sub-district of Tuaran on the west coast of Sabah,

Malaysia.The Tamparuli Bridge is a suspension pedestrian bridge which connects local citizens

to Tamparuli market.

Figure 4.3: Location of Tamparuli Bridge in Sabah

Typical indicators of ASR are random map cracking and, in advanced cases, closed joints and

attendant spalled concrete. The cracking due to ASR appeared in Tamparuli Bridge due to

frequent supply of moisture from the river water, in this case is happened at the bridge

abutment which subject to wicking action. Petrography examination (ASTM C295) can

conclusively identify ASR in on this bridge.

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Study area


Figure 4.4a): Tamparuli Bridge in Sabah

4.4b): The random map cracking at the abutment of the bridge

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CHAPTER 5 SOLUTIONS OF ASR IN MALAYSIA

5.1 Solution for the Alkali-Silica Reaction Problem in the Malaysian Context

High Slag Blastfurnace Cement (HSBFC)

High Slag Blastfurnace Cement (HSBFC) is high performance specialty cement. It is formed by

homogeneous blend of Ordinary Portland cement (OPC) and Ground Granulated Blastfurnace

Slag (GGBS/GGBFS) complying with BS 4246 and ASTM C595. It is well established in the

construction industry in producing durable concrete. HSBFC is designed to ensure consistent

slag content and to enhance concrete performance. It is also acknowledged as ‘Eco friendly

building material’. The using of HSBFC can eliminate the risk of damage caused by Alkali-silica

Reaction (ASR) in concrete thus improve the long term strength development of concrete.

HSBFC possesses other features such as good workability, prolonged slump retention, higher

ultimate compressive strength and higher flexural strength. The more aesthetically pleasing

appearance of lighter colour in HSBFC concrete can soften the visual impact of large structures.

HSBFC is highly recommended for use in the following areas:

• Marine structures

• Basement or sub-structure works

• Dams, reservoirs and hydro-electric projects

• Sewerage treatment plant

• Foundation such as piles in soils containing sulphates/chlorides

•Underground pre-cast/in-situ-placing concrete structures such as

tunnels

• Bigger concrete structures such as transfer beams

• Pre-cast sewerage pipes

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Palm Oil Fuel Ash

Research on various aspects of durability of concrete utilising palm oil fuel ash (POFA), a

recently identified pozzolanic material, as a partial replacement of ordinary Portland cement

(OPC) has been in progress in Malaysia since the 1990s.

Palm oil fuel ash is a waste material obtained by burning of palm oil husk and shell as fuel in

palm oil mill boilers. At present, some 200 palm oil mills are in operation in Malaysia where

thousands of tons of ash are produced annually and are simply disposed of without any

commercial return. However, it has been found that this ash has pozzolanic properties that not

only enable the replacement of cement but also play an active role in making strong and

durable concrete. A pozzolanic material exhibits cementitious properties when combined with

Calcium Hydroxide.

Like other fly ashes, palm oil fuel ash is greyish in colour, becoming dark with increasing

proportions of unburnt carbon. Table 1 shows the physical properties and chemical analysis of

POFA. One of the most important properties that is to be noted is the fineness of the ash.

Fineness, as measured in specific surface area, shows that POFA is much finer than OPC. The

chemical analysis suggests that this ash, in general, satisfies the requirement to be pozzolanic,

and may be grouped in between Class C and Class F pozzolana as specified in the American

Society for Testing and Materials (ASTM) standard C618-92a.

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Table 5.1: Physical properties and chemical analysis of OPC and POFA (A.S.M. Abdul Awal, 1997)

Over the years, there have been several reports of occurrences of alkali-silica reactivity in

Malaysia where the most reactive aggregates identified so far are andesite, rhyolite, tuff and

quartzite.

The maximum expansion due to alkali-silica reaction depends on a certain proportion of the

reactive material in the aggregate known as ‘pessimum’ content. Figure 5.1 reveals that the

larger the amount of tuff, the higher was the expansion at all ages.

Figure 5.1: Effect of aggregate content on expansion (A.S.M. Abdul Awal, 1997)

Figure

2:

Influence of Palm-Oil Fuel Figure 5.2: Ash on expansion (A.S.M. Abdul Awal, 1997)

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Figure 5.2 illustrates the graphs of expansion of mortar bars, plotted against time, in which OPC

was replaced with various amounts of POFA. It is evident from the figure that a reduction in

expansion occurred with an increase in the amount of ash content. It is exhibited that 50%

replacement showed substantial reduction in expansion and a slower onset of expansion. The

higher replacement value of 50% PFOA may affect the development of strength of the concrete

as reduction in compressive strength is recorded for more than 40% of additives. Careful design

with adequate amount of ash can be chosen by long-term laboratory tests.

Table 5.2: Alkali content of POFA and OPC (A.S.M. Abdul Awal, 1997)

Table 5.2 presents the alkali content of POFA and OPC. It can be seen that POFA has a much

higher initial alkaline content. Despite this, POFA is more effective in reducing expansion. This is

due to the POFA particles reacting actively with cement particles due to its reactive nature and

fineness, hence leaving little unreacted alkali for reaction with aggregate.

Ground Granulated Blast Furnace Slag (GGBS)

(Bashah, 2006) reported that slag in excess of 40% has successfully been applied in projects in

Johor, Malaysia hence reducing the amount of expansion to amounts that are unlikely to cause

distress. The application of ground granulated blast furnace slag (GGBS) was conducted

subsequent from the report from the Ministry of Works in 1988 that found evidence of alkali

silica reaction in the city. GGBS is well recognized in reducing the potential alkali silica reaction.

Figure 5.3 exhibits the protection offered by GGBS against alkali silica reaction.

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Figure 5.3: Protection against Alkali-Silica Reaction with GBS. (Bashah, 2006)

The usage of blended cements containing slag in Malaysia is quick recent compared to other

developed countries. Its use in Malaysia began in the mid and late 90’s when the Malaysian

Standards for slag cement were developed. Table 5.3 indicate the used of blended cements

containing GGBS in several projects in Malaysia. GGBS can be used as an alternative to OPC in

most cases. Additionally, the enhanced properties will enable it to be used in certain

applications where OPC would be inadequate. GGBS in Malaysia conforms to Malaysian

Standard MS 1388: 1995 “Specification for High Slag Blast furnace Cement” and MS 1389 : 1995

“ Specification for Portland Blast furnace Cement”. While MS 1389 permits slag content up from

6 to 65% of the total cementitious content, MS 1388 allow even higher slag content of up to 85

% for special applications.

GGBS is a non-metallic mineral byproduct formed when iron is produced in a blast furnace. It

does not come from steel or non-ferrous material production. It is produced simultaneously

with iron at around 15000C. Rapid quenching with water produces a solid, glassy material

which, when ground, results in a product that possesses latent hydraulicity similar to OPC. The

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end product is a complex material consisting mainly of calcium silicates and calcium aluminates.

GGBS also adds to the cementitious properties and contributes better chemical resistance.

Table 5.3: Major Projects in Malaysia using GGBS (YTL Cement Sdn Bhd)

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Rice Husk Ash

(Md. Saffiudin, 2006) reported on the capability of Rice Husk Ash (RHA) as a supplementary

cementing material for concrete production. Addition of RHA imparts excellent resistance to

cope with alkali-silica reactivity. RHA is produced from incinerating the husks of rice paddy. Rice

husk is a by-product of rice milling industry. Controlled incineration of rice husks with a

temperature between 500 0 C and 700 0 C produces non-crystalline amorphous rice husk ash.

The particles of rice husk ash occur in cellular structure with a very high surface fineness. They

have a high content of amorphous silica (up to 90% to 95%), which originally comes from the

surfaces of the husk. Due to high silica content, rice husk ash possesses excellent pozzolanic

activity. Although RHA is yet to be widely applied in Malaysia, it is seen as a suitable alternative

as due to the abundance of paddy crop in Malaysia.

RHA helps to reduce the supply of alkali from cement. The RHA competes with the slow reactive

aggregate and consumes the alkali from the cement due to its greater reactivity. Further, it

absorbs the surrounding water and refines the pore structure. This further hinders the diffusion

of alkali ions to the surface of aggregate by microporous rice husk ash.

Figure 5.4: Reduction of alkali-silica expansion according to ASTM standards. (Chandra, 1997)

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Demolition Wastes (clay based)

The application of using fired clay bricks (FCB) as coarse aggregates in the production of

concrete has been reported by (Kalsum, 2008). Fired clay brick (FCB) can be categorized as one

of the demolition wastes as most of the unwanted FCB from buildings or houses renovation are

being illegally disposed off in most places. The utilization of this type of clay based waste

materials would replace the natural aggregates in concrete mixture.

The coarse aggregates were replaced with 20 -100% of crushed FCB and strengths of more than

35 N/mm2 was monitored. Results showed that not only does substituting 40% of clay brick

aggregates after 28 days curing produced higher mechanical strength compared to the

reference natural aggregates, resistance to alkali-silica reaction was also observed. FCBs are

common construction wastes that are easily available and are in abundance in Malaysia.

Silica Fume

Silica fume or mircrosilica is a byproduct of the reduction of high-purity quartz with coal in

electric furnaces during the production of silicon and ferrosilicon alloys. Besides, silica fume is

also byproduct of other silicon alloys such as ferrochromium, ferrromagnesium. Silica fume

consists of very fine vitreous particles with a surface area ranging from 60,000 to 150,000 ft2/lb

(measured by nitrogen absorption techniques). Due to its fineness and high silica content, it is

suitable in mixing concrete to improve its properties. Silica fume improves compressive

strength, bond strength, and abrasion resistance, reduces permeability, and helps in preventing

reinforce bar from corrosion.

During mixing, silica fume has been used as an addition to concrete up to 15% by weight of

cement. With an addition of 15%, the concrete will require high demand in water while the

concrete might become very strong and brittle. However, dosage rate of less than 5 percent will

not require a water reducer, while in another way, water reducer will be require for high

replacement rates.

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The first national standard for silica fume in concrete was created by AASHTO in year 1990

(AASHTO Designation M 307-90). ). The AASHTO discovers silica fume to use as a mineral

admixture in mortar to fill small voids in concrete. It provides the chemical and physical

requirements and specific acceptance tests.

Silica Fume is available in dry and wet condition. The dry silica stored in silos and hoppers, can

be produced with or without dry admixtures. On the other hand, the silica fume slurry

containing chemical admixtures is stored in tanks of capacities ranging from a few thousand to

400,000 gallons (1,510 m3).

Lithium Compound

The use of lithium compounds in controlling expansion due to ASR was first adopted by McCoy

and Caldwell (1950). They conducted some investigation on the potential material use of

chemical admixtures to prevent or reduce ASR expansion or damage. 0ver 100 different

compounds were included in this investigation and it can be concluded that lithium compounds

such as lithium silicate and lithium sulfate is the most suitable material to reduce ASR

expansion.

For specifications for using lithium to control ASR in concrete, BRE (2002) has provided

guidance on using lithium compounds in new concrete. BRE has considered the aggregate

reactivity, fly ash dosage, type of lithium compound, and total alkali content of the concrete

mixture. The table below has shown the guidelines recently for using lithium admixtures in

concrete.

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Aggregate

Type

Lithium

Compound

Fly Ash, %(by mass

of cementitious

materials)

Lithium Dosage

Mass

Addition(kg

per kg of

Na2Oe)

Volume Addition(L

of Solution

Admixture per kg

of Na2Oe)

Molar

Ratio Li:

(Na + K)

High

Reactivity

LiOH•H2O

(solid)

0-14 1.30 - 0.96

15-25 1.00 - 0.74

LiNO3 (30%

solution)

0-14 5.95 5.00 0.80

15-25 5.20 4.40 0.71

Normal

Reactivity

LiOH•H2O

(solid)0-25 0.75 - 0.56

LiNO3 (30%

solution)0-25 3.75 3.15 0.51

Table 5.4 Guideline for using lithium in concrete (http://www.fhwa.dot.gov)

There are several mechanisms have been proposed to describe the effect of lithium, the

mechanisms are shown below:

i. Lithium may alter the ASR product composition

ii. Lithium may reduce silica dissolution

iii. Lithium may decrease the repolymerization of silica

iv. Lithium may reduce repulsive forces between colloidal ASR gel particles.

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Innerseal DPS

Innerseal DPS is a sealant which applicable for curing concrete, strengthening concrete, dust proofs, and

creates permanent internal moisture vapor barrier below the surface. Since the majority of failure of

concrete is due to moisture problem and alkali attack from beneath the surface. Innearseal DPS creates

a surface for adhesion and internal barrier to prevent moisture and alkali from the reaching the coated

surface. Innerseal DPS can also be used to enhance, protect and strengthen masonry applications such

as manufactured stone. Innerseal DPS can stop moisture intrusion and eliminate mold problems. Besides

that, Innerseal DPS permanent sealer can be used interior or exterior concrete, precast construction and

etc.

Innerseal CBE

Innerseal CBE is an advanced blend of technology that offers the absolute ultimate in protection

for concrete and cementious surfaces. Innerseal CBE is applicable in strengthening concrete,

waterproofs, protects against the elements while also creating a permanent internal barrier.

Besides that, Innerseal CBE can be used on most porous unsealed concrete and cementious

surfaces such as concrete and mortar. Applications include; Driveways, Sidewalks, Bridges, Aqua

ducts, Pre cast & Tilt Up Construction, Swimming Pool decks and Parking Garages.

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Alkali Absorption Agent

The alkali absorption agent can absorbed the Na+ and K+ from cement concrete, and the alkali

precipitation from the aggregate. The agent will be inhibited once it done its job. Besides that, the agent

will also absorb the Na+ from deicing salt or seawater by reducing the expansion pressure caused by salt

crystals to prevent freezing damage. In order to obtain alkali ion adsorbent or NH+4 zeolite, fine

powder of natural zeolite NH4Cl solution have to go through heating, mixing, filtration, washing, drying.

The agent will change the concentration of low alkali solution and high alkali solution of the concrete.

The table below showed the effect of the agent on the concentration of concrete.

Time 1h 3h 1h 2h 3h 7h 10h 14h

Initial

Alkali

mol/l

0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.35

FZ 0.22 0.20 0.15 0.1 0.07 0.04 0.025 0

NZ 0.30 0.29 0.23 0.20 0.20 0.16 0.15 0.16

Table 5.5 Effect of Alkali Absorption Agent

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CHAPTER 6 CONCLUSIONIn conclusion, ASR occurs only in the presence of sufficient alkalis in cement to react with the

reactive silica in aggregates. Thus, the main purposes of the solutions proposed are to restrict

the quantity of alkalis available per unit area, so that less alkali-silica gel is produced, and to

keep the concrete dry in the extent that the suction exceeds the expansion pressure produced

from ASR. The proposed solution in 5.2 may not be practical enough as justification for the

employment of those solutions would have to be judged in terms of economical aspects. This is

due to the higher cost of the proposed new construction materials compared to the

conventional Portland cement concrete and local aggregates available in Malaysia. Apart from

using alternative cementing materials, alkali absorption agent can be used which is formulated

by ion exchange of natural Zeolite superfine powder. The alkali absorption agent could be a

more practical and cheaper option for effective prevention of ASR or Alkali-aggregate Reaction

(AAR).

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REFERENCES

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Bashah, A. S. (2006). Effect of Silica Fume to the strength and permeability of high performance ground granulated blast furnace slag concrete. Johore: University Teknologi Malaysia.

Chandra, S. (1997). Waste materials used in concrete manufacturing. New Jersey: Noyes Publications.

Government of Malaysia, Final Report: The Study on the Maintenance and Rehabilitation of bridges in Malaysia, JICA, December 1992.

Kalsum, e. a. (2008). RECYCLING OF CLAY BASED DEMOLITION WASTES FOR THE PRODUCTION OF CONCRETE BLOCK . International Conference on Environment , 1-5.

Md. Saffiudin, M. Z. (2006). Supplementary Cementing Materials for High Performance Concrete. BRAC University Journal Vol III , 47-57.

Ng, See King, Leow Choon Heng and Ku Mohammad Sani Ku Mahamud, “A National Guide on Bridge Inspection,” Presentation in 4th Malaysian Road Congress, Kuala Lumpur, October 2000.

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Wakefield Manufacturing. (n.d.). Retrieved April 2011, from http://wakefieldmfg.com/index.html

http://www.engro-global.com/pdts_building_materials.html

http://leadstates.transportation.org/asr/library/C315/c315c.stm

http://leadstates.transportation.org/asr/library/C315/c315b.stm

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http://leadstates.transportation.org/asr/library/C315/c315b.stm

http://leadstates.transportation.org/asr/library/C315/c315c.stm

http://www.engro-global.com/pdts_building_materials.html

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