sludge-to-cement conversion

7/25/2019 Sludge-to-cement conversion

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A REVIEW OF RELATED LITERATURE AND STUDIES

Overview

This research study investigates on the utilization of alum sludge from

wastewater treatment as a clay substitute in Portland cement production. This chapter

presents a summary of the relevant studies carried out in the area of conversion

wastewater sludge into construction material. Moreover, this chapter highlights the

effect of sludge-cement ratio to the mechanical properties of the Portland cement.

The Review

3.1 Sludge used as c!s"ruc"i! #a"erial

3.1.1 Sludge as ce#e!"$li%e #a"erial&

The potential of utilizing dewatered sludge to produce cementitious materials is one

aspect of using sludge as new material resource. Tay and Show (!!" concluded that

digested and dewatered sludge could be used to produce cement li#e material. $n

preparing cement specimens, the sludge was dried and mi%ed with limestone powder.

The resulted mi%ture was ground and incinerated. The sludge cement was found to

have high water demand and &uic# setting compared with ordinary cement. 'valuation

of mortar cube strength showed that it was possible to produce masonry binder made of

cement sludge that would satisfy the strength re&uirements of the STM standard for

masonry cement. )urther studies were needed to evaluate long term properties such as

durability prior to acceptance as a suitable masonry binder. Sewage sludge pellets

(SSP" is used as substituting material in raw mi% formulation in manufacturing process

of Portland cement. Monzo (!!*" replaced ++ of cement clin#er dry weight by (SSP"


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without any problem or larger differences comparing to cement made with normal

clin#er contents. oh et al. +/0 used pulverized sludge ash blended with cement in

concrete mi%. The sewage sludge treated at 11! !2 to remove organic materials for

using as filler in concrete. The presented ash was collected and pulverized to finer than

+1!3m, then incorporated into the cement. The results indicated that concrete

wor#ability was improved as sludge ash content 2hapter 4 sludge as construction

materials 4-1 increased. The /-day compressive strength of concrete cubes with +!

sludge ash in cement was about the same of ordinary concrete, but when sludge ash

increase up to *!, the strength drops by 1! +/0. Sewage sludge ash (SS" was

used as replacement of cement at +1 and 4! by weight in mortar. ccording to

Monzo, the mortar containing +1 of (SS" as replacement of cement has a

compressive strength similar to reference mortar. 5hen (SS" content increased up to

4!, a significant decrease was observed. oncalves (!!*" tried to use sewage

sludge treated at different temperature as replacement material of cement in mortar

preparation. dry sludge at +!1 !2 was used as replacement of cement by ! of dry

weight. The result showed that there was no setting occurred. nother trial was done

but by using treated sludge at *1!!2, 6!!!2, /1!!2 as replacement of 1 and +! of

cement weight. The results indicated that the presence of any #ind of previous treated

sludge caused decreasing in mortar compressive strength.

3.'.( Sludge i! c!cre"e #i)"ures

The possibility of using dry sludge as additive materials to concrete has been

investigated by 7alls (!!1". The sewage sludge was passed through a drying process

to reduce its humidity to a certain limit and #illing microorganisms8 this allowed adding


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dry sludge to concrete mi% without large change in mi%. 9ry sludge was added to

concrete mi% as fine sand at percent various from !-+!. The use of sludge in concrete

was beneficial in that when sludge reacts with cement and comes to form of binding

matri%, the sludge components were stabilized and &uantity of laechable heavy ions

was reduced compared to free dry sludge. The results obtained by 7alls showed that

the compressive strength of concrete decreased as the sludge content increased.

Sludge content of +! or more cannot be used because the setting time was delayed

and the concrete mechanical properties were reduced significantly. durability test was

carried out on samples with sludge as additive to concrete to evaluate long term

performance. sample was sub:ected to accelerated attac#. These attac#s involved a

combined wet-dry cycles using fresh and sea water, accelerated aging in an autoclave

and accelerated carbonation. The results indicated by 7alls and ;a&ue (!!1" showed

that sludge concrete has durability similar to reference concrete. 2hapter 4 sludge as

construction materials 4-< Sewage sludge was also used in manufacturing of concrete

for pavement but as replacement of sand. replacement of


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3.'.* Sludge i! cera#ic a!d glass +rduc"i!

2eramic industry is a high consumer of silicate which consider as the basic raw material

of ceramic. The main components of sludge ash are silicate (Si> ", this ma#e sludge

ash applicable to use as raw material in ceramic production. Suzu#i (!!6" produce

ceramic samples by adding limestone to sewage sludge incinerated ash. The sludge

ash is presented as fine dust, so it can be directly mi%ed with other ceramic paste

components. 2eramic samples containing 1! sludge ash showed strength, acid

resistance, and absorption coefficient within the normal range for ceramic. ccording to

)erriera (!!4", the leaching test results of ceramic containing sludge ash showed

minimum diffusion values of heavy metals. $n other application, sludge ash is converted

into glassli#e material. melting of sludge ash components converted ash into glass.

The melting process is #nown by verification process has a temperature above +4!! o2.

sludge-to-cement conversion

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