Controlled Low Strength Materials (CLSM) Utilizing Fly Ash and Bottom Ash

Djwantoro Hardjito

Department of Civil Engineering Petra Christian University

Surabaya, Indonesia e-mail:

djwantoro.h@peter.petra.ac.id

Cheng Wee Chuan Department of Civil and

Construction Engineering Curtin University of Technology,

Sarawak Campus Miri, Sarawak, Malaysia

Jonie Tanijaya

Department of Civil Engineering Paulus Christian University

Indonesia Makassar, Indonesia

Abstract— Due to the increasing demand for electricity in Sarawak and the development of Sarawak Corridor of Renewable Energy (SCORE), Sarawak government had prompted to build more coal-fired power station as energy source. Thus, waste products of this energy source, such as fly ash and bottom ash have increased instantaneously. Disposal of these waste products will become very costly and may cause major environmental issues, such as land pollution. One of the ways to reduce these waste products is to utilize them as construction materials. This paper presents the results of parametric study on Controlled Low-Strength Materials (CLSM) utilizing fly ash and bottom ash from Sejingkat, Kuching. The properties of CLSM that had been investigated included hardening time, flowability, bleeding and segregation, density of hardened CLSM and unconfined compressive strength at CLSM age of 3 days, 7 days, 14 days, 28 days and 60 days. CLSM mixtures were designed by varying the proportion of cement, fly ash and bottom ash. CLSM mixtures were casted into cylinder moulds with the size of 39mm × 78mm (dia). From the experimental results, hardening time of CLSM was found to be in between 5 to 6.5 hours. In order to achieve good flowability, the water/ cement ratio used in CLSM was found to be very high, with the highest w/c ratio can be more than 8.0. With the increase of fillers, especially fly ash, bleeding and segregation condition of CLSM are improved. With various mixing proportion of CLSM, compressive strength of CLSM is controlled between 1.0MPa to 8.3MPa, in order to suit the requirement of different applications, such as excavatable backfill and structural backfill. With this range of strength, CLSM can be used as alternative material to solve the soft soil problems in Sarawak, especially in Northern Sarawak.

Keywords- Fly Ash; Bottom Ash; CLSM; Hardening Time; Flowability; Bleeding and Segregation; Density; Compressive Strength; Backfill; Soft Soil Problems

I. INTRODUCTION

A. Overview of Project Controlled Low Strength Materials (CLSM) is a self

compacted, cementitious materials used primarily as backfill in place of compacted fill. CLSMs are defined by ACI 229R

as materials that result in a compressive strength 8.3MPa or less [1]. It is also known as flowable fill, unshrinkable fill, controlled density fill and other various names.

In this project, bottom ash and Class F Fly Ash from Kuching Coal Fired Power Station in Sejingkat, Kuching are utilized in CLSM. The production of these by-products is increasing due to the development of coal-fired plants under the development of Sarawak Corridor of Renewable Energy (SCORE) to secure the electricity demand of Sarawak [2]. Disposal of these by-products will eventually become very costly and may cause major environmental issues, such as land pollution. Therefore, alternative methods of handling these by-products, such as utilizing them in concrete to produce CLSM, need to be thought of.

Northern part of Sarawak, like Miri and Brunei, has a major problem with soft soil. The soil is very soft and is not suitable for building foundation as it may cause structural failures, such as differential settlement of buildings, potholes and other problems [3]. To solve the problems, engineers have to replace the soft soil with better soil or have to treat the soil by mixing it with cement and then followed by compaction. However, these solutions might be very costly and tedious.

CLSM might be an alternative solution in the above problems because the materials can be easily obtained locally and sometimes can be more economical. This is because CLSM is generally made out of concrete materials mixed with by-products, which can be manufactured in batching plant. Furthermore, CLSM is flowable and self-compacted materials, so it does not require compaction after backfilling. This makes CLSM to be more economical.

However, due to by-product produced from different area may have different chemical composition and properties, it may have diverse effects on the properties of CLSM. Hence, it is important to carry out parametric study on CLSM utilizing the locally available by-products before its possible application in construction. This project is focused on the use of fly ash

and bottom ash from Kuching, and its effects on the properties of CLSM.

B. Objective of Research The main objectives of this research are to investigate the

hardening time of CLSM; to optimize the flowability of CLSM within the allowable range and to find out the water-cement ratio needed to achieved that flowability; to investigate bleeding and segregation condition of CLSM from various mixing proportion of CLSM and to find out the optimum proportion to minimize bleeding and segregation; to determine the density of hardened CLSM; and to elaborate the unconfined compressive strength of CLSM from various mixing proportion in order to find out suitable proportion for various applications.

C. Scope of Work This research is focused on the practical usage of fly ash

and bottom ash in CLSM for various purposes in construction industry. Properties of CLSM, such as hardening time, flowability, segregation, density of hardened CLSM, compressive strength and bleeding are investigated.

In this project, the materials used are cement, water, sand, fly ash and bottom ash from Sejingkat Kuching. The specimen moulds are self-constructed cylinders that have diameter of 39mm and height of 78mm. Research is carried out based on various mixing proportions by varying the percentage of cement (3%, 6%, 10% and 15% of total wet density) used and the percentages of fly ash and bottom ash (0%, 25%, 50%, 75%, and 100%).

II. LITERATURE REVIEW

A. Introduction on CLSM Controlled Low Strength Materials (CLSMs) is a self

compacted, cementitious material used primarily as backfill in place of compacted fill. CLSMs are defined by ACI 116R as materials that result in a compressive strength 8.3MPa or less [1]. It is also known as flowable fill, unshrinkable fill or plastic soil cement. Besides backfilling, other applications of CLSMs are void filling, bridge reclamation, conduit bedding and nuclear waste stabilization.

CLSMs can utilize the wastes or by-products such as fly ash, bottom ash, foundry sand, waste LCD glass, and quarry dust and glass cullet to reduce the use of cement and aggregates, and to improve the flowability of the fresh material. Among the by-products used, fly ash and bottom ash are the most commonly utilized in CLSMs [1]. Fly ash is actually one of the residues generated in the combustion of coal, whereas bottom ash is non-combustible constituents of coal with traces of combustible embedded in forming clinkers.

In the ACI Committee 229 (1999), the wet properties and dry properties of CLSMs are briefly stated. ACI stated that the wet density of the normal CLSM (containing fine aggregates) is approximately between 1840 to 2320kg/m3, whereas the dry density of CLSMs is roughly 1360 to 1760kg/m3 [1]. Besides that, wet CLSMs are described as flowable and self-

compacted. This means that it can be compacted by itself without any compacting work.

Generally, the compressive strength of CLSM is less than 8.3MPa. However, this strength has to be controlled to the desired strength based on the application. For example, ACI suggested the compressive strength range of 0.3 to 0.7 MPa for the applications that needs to be excavatable in the future [1]. This is because lower strength CLSMs can be easily excavated by hand tools or conventional excavation machinery, like backhoes or hydraulic excavators [4]. This is important to reduce the excavation cost in the future.

On the other hand, ACI suggested a relatively higher strength of more than 4.0 MPa for the applications such as structural fills whereby excavation is not likely to occur in the future [1]. Higher strength is required to support the structures above and to prevent itself from cracking and shrinking.

B. Materials of CLSM Conventional CLSM mixtures usually consist of water,

Portland cement, fly ash or other similar products, fine or coarse aggregates or both. It is not necessary to use the standardized materials set by ASTM or other standard requirements [1]. Selection of materials should base on availability, cost specific application, and necessary characteristics of mixture, such as strength, flowability, excavatability, and density.

1) Cement Cement is a binder material that holds all the other

materials together and contributes to the strength and cohesion for CLSM mixtures. Normally, in compliance with ASTM C 150, Type I or Type II Portland Cement will be used. Other types of cement can also be used in compliance with ASTM C 595 as long as the testing results are satisfactory.

2) Fly Ash Fly Ash is actually one of the residues generated in the

coal combustion. Fly Ash is used in CLSM to improve the flowability. Besides that, fly ash is also used to reduce bleeding, shrinkage and permeability as well as to increase the strength of CLSM [5].

Although fly ash has become an important construction material, especially in high strength concrete, approximately 70 to 75 percent of fly ash generated annually is still disposed in landfill as these fly ash does not meet the specification for use in Portland Cement concrete, due to high content of unburned carbon, as measured by the loss on ignition (LOI) test [6]. This is because higher unburned carbon contents increase water demand in concrete, causing water/ cement ratio to increase, thus reduce the strength of the concrete. Moreover, unburned carbon will also significantly increase chemical admixture demand, which will cause the total cost of concrete to increase. However, CLSM has no problem with the higher unburned carbon in the fly ash. Hence, CLSM is possibly the best solution to the environmental issues caused by fly ash landfill.

3) Bottom Ash

Bottom ash is another by-product material of coal combustion. Bottom ash is formed by large non-combustible particles that cannot be carried by the hot gases. These large non-combustible particles are put into crusher to reduce the particle size to approximately 75 microns to 25milimeters [6]. Since the size of bottom ash is similar to fine aggregates and it has relatively no cementitious properties compared to fly ash, it is used in CLSM as the fine aggregates.

Under the microscope, bottom ash particles are typically porous and angular in shape. Water will be absorbed and retained on the porous surface of bottom ash, while excessive water will be drained off [7]. Drained off water may cause the free water in CLSM to be excessive. This will actually cause bleeding condition in CLSM.

4) Water According to ACI Committee 229, water that is

acceptable for concrete mixtures is acceptable for CLSM mixtures. More information on water quality requirements can be obtained from ASTM C 94 standard.

5) Aggregates Aggregates are often the main part of CLSM mixtures.

The type, grading, and shape of aggregates can affect the physical properties of CLSM, such as flowability and compressive strength. Aggregates used in CLSM have to fulfill either one of the following specification:

a) ASTM C 33 specification aggregates within specified gradations;

b) Pea gravel with sand; c) 19mm minus aggregate with sand; d) Native sandy soils, with more than 10% passing a

75µm sieve; e) Quarry waste products, generally 10mm minus

aggregates [1].

III. EXPERIMENTAL PROGRAM

A. Mixing, Flowability Test, Casting, De-mould and Curing Before mixing, the materials were prepared in correct

amount according to proportion. This was done by measuring the mass of materials needed. After obtaining the correct amount of materials, all the materials except water were put into the Hobart mixer machine. Then, the partial of the water was placed into the mixer and start mixing for 1 minute. After that, the remaining water was placed into the mixer and the mixing was continued for 15 minutes. If the visual flowability of CLSM is too low, then additional water can be added. The additional amount of water used will be recorded.

After 15 minutes of mixing, the CLSM mixture was ready for flowability test. The equipments needed for this test were inverted slump cone, scoop, base plate and measuring tape. The CLSM mixture was loaded into the inverted slump cone until it was full. Then, the inverted slump cone was lifted up to allow the CLSM mixture to flow and form a circle. The diameter of the circle was measured with measuring tape. If

the diameter of the circle is within the range of 475mm and 750mm, flowability of the CLSM is acceptable [8].

After the flowability test, the CLSM mixture was filled into 15 fabricated cylinder moulds. No compaction is needed because CLSM is a self-compacted material. The filled CLSM mixture was left to harden indoor with room temperature of approximately 25 degree Celsius.

CLSM mixture hardened within 5 to 6.5 hours, but it could not be de-moulded within three days after casting. This is because hardened CLSM was still very fragile and could be easily crushed during de-moulding from the cylinder moulds. After three days, the hardened CLSM were de-moulded by using the Universal Testing Machine. Some of the hardened CLSM would be tested for 3 days compressive strength. The remaining of hardened CLSM would be cured by placing the hardened CLSM into the curing chambers.

B. Hardening Time Test Hardening time of CLSM was tested by using vicat

penetrometer. After mixing, the CLSM mixture was loaded in the penetrometer cast. Bleeding of the specimen had to be removed from the surface of specimen prior testing the specimen. Vicat needle was left to fall and the reading of penetration was recorded every 15 minutes. The CLSM mixture was considered hardened when the penetration of the vicat needle is less than 25mm.

C. Bleeding Test Bleeding test was measured by measuring the difference in

CLSM height due to water evaporation. In order to obtain the height reduction of the CLSM specimen, the new reduced height of CLSM specimens were measured on the third day after casting with Vernier Caliper.

The reduction of height over the total height of the CLSM specimen is considered as the percentage of bleeding. The percentage of bleeding can be calculated with the following expression:

% bleeding = (h1 – h2)/ h1 ×100 (1) Where,

h1 = initial height of CLSM specimens during casting

h2 = new measured height of hardened CLSM specimens after 3 days

D. Segregation Test There is no Standard Testing method for CLSM

segregation available. Thus, segregation of the CLSM specimen was tested visually. First of all, CLSM specimens were split into half after the compressive strength test. The split surface was then observed for obvious segregation condition. If there is any stratification exists, it is considered that there is segregation within the CLSM specimens.

E. Density of Hardened CLSM Density of hardened CLSM specimens was measured by

measuring the mass of the hardened CLSM, and then divided

by thCLSMThe dusing

F. CC

measare seloads1kN rstreng90 daspecithat tthe wobtainspeci

Thmachvalueaccorthe compdividspeci

G. MTh

paramamouof samixtuof thpropomass the cpercebotto75%

Prbleedstrengand bCLSMCLSMdemofrom and Discu

A. HH

3% cplottecan o

e volume of thM specimens wdiameter and tg Vernier Calip

Compressive StrCalifornia Bear

ure the unconfeveral rings av

s that the rings ring, 4.5kN ringth of CLSM ways. Prior to tmen had to be the loading of

whole surface oned reflects thmens.

he value obtahine does not de obtained has rding to respecload required

pressive strengtding the load

mens.

Mix Design andhe mixing pr

meters, such aunt of sand andand used was ure, whereas mhe total mass ortion was vari

of CLSM. Bycement, waterentage of masm ash (BA) band 100%.

IV. roperties of C

ding, segregatigth are discussbottom ash havM. Hence, the aM over fly aonstrate the ex

test results oftabulated into

ussions will be

Hardening TimeHardening time cement contented into graph, observed that h

he CLSM speciwas measured the height of thper.

rength Test ring Ratio (Cfined compressvailable for CBcan sustain ar

ng, 10kN ring was tested for testing, the cosmoothed and

f CBR machinof CLSM speche true compre

ained from thdirectly show th

to be comparctive load mead needed to th of CLSM sp

with the co

d Proportion roportion was as the total md the amount of

set to be 25mass of initial w

of CLSM. Aied from 3%, 6y subtracting thr and sand s was divided

by varying the

RESULTS AN

CLSM such as ion, density ased. From the ve significantlanalysis focuse

ash and bottomxperimental ref three sampleo tables and done based on

e of CLSM test has been ct and 6% cemas shown in Fhardening time

imens measureby using weig

he CLSM wer

CBR) machinesive strength ofBR machine.

re stated on theand 28kN ring3 days, 7 day

ontact surface d even. This wane was equallycimens and ensessive strength

he dial gauge he compressivered with the caasuring rings. A

make the specimen will bontact surface

designed by mass of CLSMf initial water u

5% of total mwater used wasAs for cemen6%, 10% and 1he total mass proportions, t

d between fly e ratio from 0%

D DISCUSSIONS

hardening timand unconfined

experimental ly affecting theed mainly on thm ash ratio. sults, each das. The data is

then plottedn the graphs plo

carried out for ment content. TFigure 1. Frome for 3% cem

ed. The mass ofghing machinere measured by

e was used tof CLSM. ThereThe maximume rings, such asg. Compressiveys, 28 days and

of the CLSMas to make surey distributed tosure the resultsh of the CLSM

on the CBRe strength. Thealibration charAfter obtainingspecimen faile calculated by

e area of the

fixing a fewM mixture, theused. The mass

mass of CLSMs set to be 15%nt content, the5% of the totaof CLSM withthe remainingash (FA) and

%, 25%, 50%

S me, flowabilityd compressiveresults, fly ashe properties ofhe properties ofTo effectively

ata is collectedthen averaged

d into graphsotted.

specimen withThe results are

m the graph, wement mix varies

f e. y

o e

m s e d

M e o s

M

R e rt g l, y e

w e s

M % e

al h g d

%,

y, e h f f y d d s.

h e e s

from 5 tcement mhardeningthese harrange. Ovwith the d

This mbottom asactually excessivespecimenbefore thwater traphardeningtime incre

Fig

Besidcontent inof CLSMof CLSMbinds agcement ahence theis the reacement co

B. FlowaFlowa

the flowaas showndiameter within thflowabilitexperimespecimen

Figureash: bottoResults sflowabilitBA ratio BA ratio.mixture, t

to 6.5 hours, mix varies frog time range srdening timesverall results sdecrease in fly

might be due sh particles. Thtrap water tha

e of free water n [7]. Althoughe hardening tipped in the porg time of the Ceases as the bo

gure 1: Hardening

des that, from n CLSM mixtu

M. As the cemenM is lower. Cggregates and added, the hyde strength gainason why the hontent is increa

ability of CLSMability is anothability test, resun in Figure 2.

of CLSM by he range of 4ty mixture for

ent, water contn in order to ach

e 2 also showom ash ratio foshow that the rty decreases gand increases

. It indicates ththe more water

whereas the om 4 to 6 houstated in ACI c

are reasonablshow that the hAsh: bottom A

to the unevenhe porous propat is released and eventually

gh water due ime testing, theres of bottom a

CLSM specimeottom ash conte

Time versus Fly A

Figure 1, it cure is also affent content is hement is a cefine particles

dration reactionn of the CLSMhardening timeased. 

M her important pults are collectAccording toinverted slum

75 to 750mmr most of the tent of CLSMhieve the requi

ws the water coor 3%, 6%, 10required water gradually fromdrastically fro

hat the higher Fr is needed to a

hardening timurs. Comparincommittee reply within the hardening timeAsh ratio by m

n surface and pperties of botto

during mixiny causing bleeto bleeding iere is still excash. This slowens. Hence, theent increased.

Ash: Bottom Ash R

can be seen thecting the hardigher, the hard

ementitious mas together. Wn will also in

M will also be fe of CLSM is

property of CLted and plotted Tripathi [8],

mp cone test nm in order to

field applicatiM was adjusted

ired flowability

ontent needed 0% and 15% ce

content to achm 0:100 to 25:om 25:75 to 10FA: BA ratio uachieve good f

me for 6% g with the ort (1999), acceptable e increases ass.

porosity of om ash will ng, causing eding to the s removed

cessive free ws down the e hardening

Ratio

hat cement dening time dening time aterial that With more ncrease and faster. This reduced as

LSM. From d into graph

the spread needs to be have good ion. In this d for every y.

versus fly ement mix. hieve good :75 of FA: 00:0 of FA: used in the flowability.

The eash c

ATangthat cin bosurfacmixtudecrewateradded

Balso dknowincreaout tmixtuthe flcarbobottoash aof unThusmoreCLSM

Inthe pbottoachiemixin

C. BFi

versuobser2.31%obtainfrom maximordinfill [5exper

explanation foontent causes t

According to ttermsirikul [7]

can retain and aottom ash is vece can help ture when bottoease of bottomr content in thd to maintain th

Figure 2: W

esides, more wdue to the incr

wn to have smasing flowabilihat fly ash mure due to the ply ash used [6]on has very pm ash. Due to

and the porositynburned carbon, the more fly water contentM.

n this experimeproportion of Cm ash is used

eve good flowng proportion,

leeding and Seigure 3 illustr

us fly ash: botrved that the b% to 7.25%. ned by Horigu1.5% to 6.8%

mum bleedingnary flowable f5]. Thus, the reriments are con

r this result isthe increase in

the research d], bottom ash hadsorb water. ery high, the wto decrease thom ash is adde

m ash will resuhe mixture andhe required flo

ater Content versu

water content rease of fly ashmooth and eveity of CLSM, b

may increase thpresent of high]. According toporous and units larger surf

y, the water nen in fly ash is ash with high t is needed to

ent, the optimuCLSM where d, due to the lewability. This

less friction am

egregation of Crates the bleettom ash ratiobleeding perce

Comparing tuchi, Okumura% , the results

ratio specifiedfill and 1 perceesults of bleednsidered to be v

s that the decrewater demand

done by Kasehas angular andTherefore, if th

water retained he demand fored to the mixtuult in the decr

d more water wowability.

us Fly Ash: Bottom

is needed for h content. Althen surface thabut recent resehe water demh content unbuo Kulaots et alneven surface

face area compeeded to lubriccomparativelyunburned carbachieve good

um water conte25% of fly aseast water conmay indicate

mong particles

CLSM ding percenta

o. From Figurentage of CLSMthe results wi, and Saeki [5]are quite sim

d in Japan is 3 ent for high qu

ding ratio obtaivery high.

ease of bottomd.

emchaisiri andd rough surfacehe initial wateron the uneven

r water in theure. Hence, therease of initiawill need to be

m Ash Ratio

mixtures mayhough fly ash isat will help inearch has found

mand in CLSMurned carbon in. [9], unburned

e just like thepared to bottomcant the surfacey much higherbon is used, thed flowability of

ent occurred ash and 75% ofntent needed to

that with thiswould occur.

ages of CLSMre 3, it can beM varies fromith the results], which varies

milar. Howeverpercent for theuality flowableined from both

m

d e r n e e

al e

y s n d

M n d e

m e r. e f

at f o s

M e

m s s r, e e h

From the contebottom asinitial mothe porescontent oamount oash may c

Besidis inversesame as Razak [1increase needed tincrease trequired decreasesthe free wfree wate

Fi

In thobservedused in particles voids, pexcessivesegregatiovery unlik

D. DensiFigure

versus flyhardenedash conteporosity specimenfurther inof the spebe decrea

From obtained ACI Combetween

the graph, bleent of bottom sh used indeedoisture contents of bottom asof CLSM mixtuof free water. Tcause bleeding

des that, the graely proportionthe condition 0]. The decreain aggregates

to lubricate ththe free water to hydrate cem

s as amount owater content ier is the cause o

igure 3: Bleeding P

his experiment. This is becauall the mixturhave smaller articles are l

e free water on of CLSM kely to happen

ity of Hardenede 4 shows the y ash: bottom

d CLSM at 28th

ent in the CLof bottom a

ns. Besides thatncrease the voiecimen increasased.

Figure 4, thevaries from 1

mmittee 22R 1360kg/m3 and

eding percentaash is increas

d has porous prt. The initial wsh will be addure, which evenThis is the reasg in CLSM.

aph also showsal to cement cof CLSM fo

ase of cementproportion. T

hese aggregatebetween parti

ment in order f cement usedin the CLSM mof bleeding.

Percentage versus F

t, there is nouse only fine ares instead of void between

less likely toexists or te

designed withn [1].

d CLSM density of haash ratio. Fro

h-day is directlLSM mixturesash that incrt, the uneven sd created in thses, the density

e density of C610kg/m3 to 1[1], the rang

d 1760kg/m3, w

age of CLSM insed. This showroperties and rwater content ded to the totantually ends upon that the use

s that bleeding content in CLSund by Nagan

t content will lhus, more waes and fillers,cles. Howeverto act as bon

d is reduced. Tmixture to incr

Fly Ash: Bottom A

o significant saggregates and

coarse aggregthe particles.

o be dislocateerrible bleedinh fine aggregat

ardened CLSMom the graph, ly proportiona. This is mainreases the vourface of botto

he specimens. Ay of hardened C

CLSM in this e1820kg/m3. Acge of CLSM whereas the res

ncreases as ws that the retains high

trapped in al moisture p with high e of bottom

percentage SM, which nathan and lead to the

ater will be , and thus r, the water nding agent This causes rease. This

Ash Ratio

segregation d fillers are gates. Fine With less ed. Unless ng occurs, tes only is

M at 28days density of

al to the fly nly due to

oid in the om ash will As the void CLSM will

experiment ccording to

density is sults found

by Hdensithose

F

E. UIn

speci60 dafollow3% ofor Cconte

Frquantcompmajoris usestrengthese can gbondewould[11].

Bto thconteCLSMthe vrequiused This preve

Futhe calso dthat iCalcilime betwethe grcomp

Horiguchi, Okuity varies frome results, the re

Figure 4: Density o

Unconfined Comn this experimmens was testeays. The data wed. Figure 5

of cement conteCLSM speciment in Figure 6,

rom all the ftity of cemenpressive strengr source of cemed to bond thegth of CLSM

particles. Thugenerate more ed together. Fud have higher

esides cementhe compressivent of fly ash M. This may bvoids betweenre cement pastas fillers, but actually impr

ents dislocation

urthermore, hicompressive strdue to the facts Silica Oxide ium Silicate Hreleased by theen aggregatesreater the bond

pressive strengt

umura, and Sam 1338kg/m3 tsults obtained

of CLSM at 28 day

mpressive Strenment, compreed for 3 days, was collected

shows the resuent. Similar pat

mens with 6%,, Figure 7 and F

figures, it cannt used will pgth. This is vementitous mate

e aggregates anis depending o

us, it is reasonstrength as p

urthermore, higstrength as it h

t, fly ash contee strength ofwill increase e due to fly ash

n larger particlte to fill [12]. Wmore on form

roves the bonn of particles d

igher fly ash crength of CLSt that fly ash h

(Si02), which ydrates (CSH)

he hydrated cems and fillers. Thding between pth of CLSM.

eki [5], the rato 2056kg/m3. seem to be ver

ys versus Fly Ash: B

ngth of CLSM essive strength7 days, 14 day

d and plotted ults of CLSM sttern of results, 10% and 15Figure 8.

n be concludeproduce CLSMery rational as erials within th

nd particles. Thon the bond fonable that morparticles are mgher cement conhas lower wate

ent also causesf CLSM specthe compressih that acts as fles, which woWith this, less

ming bonds betwnding betweendue to larger vo

content can slSM specimensas minor pozzcan be used to

) when it reactment [12]. CSHhus, the more Cparticles and th

ange of CLSMComparing to

ry similar.

Bottom Ash Ratio

h for all theys, 28 days andinto graphs as

specimens withs were obtained5% of cemen

ed that higherM with higher

cement is thehe mixture thahe compressiveormed betweenre cement used

more effectivelyntent of CLSM

er/ cement ratio

s minor effectsimens. Higherive strength offillers to reduceould otherwisecement will beween particles

n particles andoids.

ightly increases. This may beolanic materia

o produce morets with the freeH is the binderCSH producedhus increase the

M o

e d s h d

nt

r r e

at e n d y

M o

s r f e e e s. d

e e

al e e r

d, e

From cement isexcavatiowith 6% whereas structural

Fi

Fi

Fig

the experimens suitable for on purpose as i

cement is suCLSM mixtur

l backfill as it h

igure 5: Compressi

igure 6: Compressi

gure 7: Compressiv

nt results, CLgeneral purpoit has low com

uitable for roadre with 10% has higher com

ive Strength of CL

ive Strength of CL

ve Strength of CLS

LSM mixturesse backfilling

mpressive strengdway trench bcement is bes

mpressive stren

LSM with 3% Cem

LSM with 6% Cem

SM with 10% Cem

s with 3% and future

gth. CLSM backfilling; st used for

ngth [13].

ment Used

ment Used

ment Used

Bexper

1) botto

2) cemecontamoreof CL

3) waterash ra

4) occur75% to ach

5) increait is in

6) obser

7) fly asFigur

8) that propoBesidcompfly asthe lim

9) cemeexcavwith

Figure 8: Comp

ased on the rimental results

Hardening timm ash content,

From Figure ent has loweraining 3% cem cement conten

LSM will be.

From Figurer to achieve goatio increases.

Referring torred at the propof bottom ashhieve good flow

Figure 3 shases as the connversely propo

In this experrved.

Density of Hsh: bottom ashre 4.

From the comcement contenortional to thedes cement, flypressive strengsh will increasmit where fly a

From the expent is suitable vation purpose6% cement is

pressive Strength o

V. CONC

experiment cs, the following

me of CLSM i, as shown in F

1, it can be ser hardening

ment. Thus, itnt in CLSM, th

e 2, it can be ood flowability

o Figure 2, tportion of CLSh is used, as thwability.

hows that bleentent of bottomortional to cem

riment, there i

Hardened CLSMh ratio of CLS

mpressive strennt used in Ce compressive y ash content agth of CLSM sse the compresash: bottom ash

periment resulfor general pu as it has low cs suitable for

f CLSM with 15%

CLUSIONS conducted ang conclusions

increases with Figure 1.

en that CLSM time compar

t can be conche shorter the h

concluded thay increases as f

the optimum SM where 25%he least water c

eding percentam ash increased

ment content in

is no significa

M is directly pSM specimens

ngth test, it canLSM specimestrength of t

also has minorspecimens. Higssive strength oh ratio is 75: 2

lts, CLSM mixurpose backfillcompressive stroadway tren

% Cement Used

nd analysis ofare drawn:

the increase of

containing 6%ed to CLSM

cluded that thehardening time

at the requiredfly ash: bottom

water conten% of fly ash and

content needed

age of CLSMd. Besides thatCLSM.

ant segregation

proportional tos, as shown in

n be concludedens is directlythe specimensr effects on thegher content ofof CLSM unti5.

xtures with 3%ling and futuretrength. CLSMch backfilling

f

f

% M e e

d m

nt d d

M t,

n

o n

d y . e f l

% e

M ;

whereas structural

[1] ACIMat

[2] Sara200http

[3] KanBehEng

[4] The Spec

[5] HorOptof CSP-p. 3

[6] TrejDev

[7] Kasmethaggconc132

[8] TripLabTimInno(FloBaa

[9] Kulin FTestFly

[10] NagStreQuaACF

[11] Neved. E

[12] Dayand

[13] ConSep

CLSM mixturl backfill as it h

I Committee 2terial. America

awak Corridor9 Septem

p://www.sarawa

niraj, S.R. anhaviour of Orggineering, ed. C

European Gucification, Pro

riguchi, T., Htimization of CLClinker Ash an199. American07-325.

jo, D., K.J. Fvelopment using

semchaisiri, Rhod to determ

gregate for dcrete. Constru2-133.

pathi, H., et boratory Measme of Controvations in owable Fill), as, Editors. AST

aots, I., et al, 2Fly Ash and Det. in 2002 ConfAsh.

ganathan, S. anength Materialarry Dust, in TF/ VCA 2008. U

ville, A.M., 199Edinburgh Gat

y, K.W., 2006. d Specification.

ntrolled Low-Sttember]; Avail

re with 10% has higher com

REFERENCES

229R, 1999. Can Concrete Ins

r of Renewablmber 19];

akscore.com.m

nd R.R. Josepganic Soils of NC. Law. Taylor

uidelines for Seduction and Us

H. Okumura, CLSM Mix Propnd Fly Ash, in n Concrete Ins

olliard, and Lg Controlled L

R. and S. Tamine water retadesign and quuction and Bu

al., 2004. Msurement of Frolled Low-S

Controlled J.L. Hitch, ATM Internation

2002. Adsorptievelopment of aference on Unb

nd H.A. Razakl Using Incin

The 3rd ACF InUniversity of M

96. Properties te, Harlow: Lo

Concrete Mix3rd Edition ed

trength Materilable from: ww

cement is besmpressive stren

S Controlled Lostitute

le Energy. 20Available

my.

ph, 2007. GeNorth Sarawakr & Francis Gro

elf-CompactingUse. 2005. SCC

and N. Saekportion with CoACI Special P

stitute: Farmin

L. Du, 2004. SLow-Strength M

angtermsirikul,ainability of puality control

uilding Materia

Methods for Flowability an

Strength MatLow-Strength

A.K. Howard, nal: U.S.A.

ion on Unburnan Improved Fburned Carbon

k, 2008. Contrnerated Bottomnternational CoMalaysia.

of Concrete. 4ngman.

x Design, Quald. New York.

ial. 2008 [citeww.concrete.ne

st used for ngth.

w-Strength

007 [cited from:

eotechnical k. Soft Soil oup.

g Concrete C 028.

ki, 2001a. ombination Publication ngton Hills.

Sustainable Material.

, 2006. A porous fine l of fresh als 21 (6):

Field and nd Setting terials, in

Material and W.P.

ned Carbon Foam Index n on Utility

rolled Low-m Ash and onference -

4th Edition

lity Control

ed 2009 15 et.au.