Impact of Cement Replacement by Sawdust Ash on Workability

QUEST RESEARCH JOURNAL, VOL. 18, NO. 1, PP. 43–50, JAN–JUN, 2020 43

Impact of Cement Replacement by Sawdust Ash on Workability and Com-pressive Strength of Concrete

Aqib Munir*, Bashir Ahmed Memon, Mehboob OadDepartment of Civil Engineering, QUEST, Nawabsah*Corresponding author: [email protected]

Abstract

In this research paper, we analyze the effect of saw dust ash as cement replacement on compressive strength. Sawdustcollected from wood workshops of Nawabshah city was converted into ash by burning and grinding. Six concretemixes with ash dosage of 2.5% to 15% in the increment of 2.5% were developed. Also, a mix with conventionalingredients was developed as control mix. Workability by slump test shows a higher demand of water in the mix withsawdust ash, otherwise mechanical effort or admixtures will be needed to maintain the workability. Total 63 standardsize cylinders were cast using 1:2:4 mix and 0.5 water cement ratio. In each mix, 9 cylinders were cast, out of whichequal number of cylinders were cured for 7, 28 and 56 days. Weight of the specimen shows that sawdust ash ishelpful in developing light weight concrete. Increased dosage of the waste ash produces lighter concrete. Comparisonof compressive strength of the saw dust concrete mix with conventional concrete shows that 5% replacement ofcement with the waste ash is the optimum dosage. At this dosage, the decrease in compressive strength is 11.66%and reduction in weight is about 2%. Although, the elongated curing shows improvement in strength results, butat optimum dosage the reduction in compressive strength up to 12% was recorded as compared to 28-day curedspecimens.

Keywords—Green concrete, Saw dust ash, Compressive strength, Workability

F

1 Introduction

W ith the passage of time, concrete has proveditself as the most suitable material for con-

struction. It is a very strong and versatile constructionmaterial. However, concrete has an excellent resistanceto compression (crushing), yet it is very poor in tension(stretching). To give it a good load bearing capabilityin tension also, it must be reinforced with steel bars(rebar), polymer strands or fiber. There are many by-products which can be used as partial or full replace-ment with different ingredients of concrete. Sawdust(wooden shavings) is a by-product or waste productof woodworking operations such as sawing, milling,planning, routing, drilling and sanding. Not manypeople realize it, but there are hundreds of ways thatsawdust can be used as a by-product in the modernworld. Normally the waste is used as plant food, messcleaner, fake snow, weed killer and fire maker. Pakistangenerates about 48 million tons of solid waste everyyear [19] with about 20 to 25 million tons in metropoli-tan cities [20], which has been increasing more than

ISSN: 2523-0379 (Online), ISSN: 1605-8607 (Print)

2 percent annually. Like other developing countries,Pakistan lacks waste management infrastructure, cre-ating serious environmental problems. Most municipalwaste is either burned, dumped or buried on vacantlots, threatening the environment, health and welfareof the general population.On the other hand, consumption of ingredients ofconcrete, to meet the modern development style andaccommodation needs, has increased drastically. As aresult, cement industry is working round the clock toyield cement as per with the consumption requirement.Also, quarrying of natural aggregates causes seriousproblems to environment. From another perspective, ifthe use of the natural aggregates is analyzed, it revealsthat natural sources of the aggregates are depletingquickly. Therefore, to save the natural aggregates andsave the environment from quarrying of aggregatesand impact of cement industry, search of alternativeingredients of concrete has become an active area ofresearch.Several alternative materials have been used by schol-ars around the world as partial or full replacement of


ingredients of concrete. But the scatter in results showsthat still there is a need of more work in the fieldto develop awareness for using such material. In thispaper, partial replacement of cement with sawdust ashis proposed. Sawdust ash is used in different dosages.Compressive and tensile strength of concrete speci-mens is evaluated to check the impact of the sawdustash as partial replacement of cement.

2 Literature ReviewVarious alternative materials such as jute, glass, fiber,polythene, etc. and waste materials like bricks, rubber,tires, debris, etc. have been used by different scholarsaround the world as a replacement of one or otheringredient of concrete. Full or partial replacement ofthe ingredients has also been studied. However, thescatter in results is a potential hurdle in preparingthe code or standard of their use. Sawdust is a wastematerial which has been used by several scholars inits original form as an alternative of fine aggregateor by converting it into ash as alternative materialfor cement. In this regard, Abdullahi et. al. [1] usedsaw dust as replacement of sand in five dosages from10% to 50%. The compressive strength results of stan-dard size cubes (150 mm) prepared for the purposeshowed 10% as optimum dosage at which the strengthfalls in the range specified by BS code. However,the authors concluded that the concrete cannot beused for structural purposes as it causes fluctuationand reduction in strength. Oyedepo et. al. [2] alsomade similar attempt to partially replace the sandbut with dosage up to 100% in increment of 25%. Theuniformity and curvature coefficients of the sand were1.049 and 1.324 respectively, which confirms a goodgrading of the material as per BS standards. Also,the average crushing value of the sand confirmed thestandard requirement of BS code. Test results showedthat the workability of the concrete reduced withincrease in the dosage of the dust, whereas, concretestrength at dosage above 25% did not confirm thestrength specified for light weight concrete. Therefore,the authors concluded that beyond 25% replacement,concrete had a decremental pattern for workability andstrength. In another attempt by Narayanan et. al.[3],the authors used sawdust as a partial replacement ofsand in definite quantities and studied density andstrength of the concrete. The authors recorded lowerspecific gravity (0.27) and higher water absorption(2) in comparison to the conventional sand. Theyobserved from the test results of M20 grade concrete(w/c=0.5) that both density and strength decreasedwith the increase in sawdust quantity. Therefore, they

concluded that it may be used in both normal and lightweight non-structural elements. Similar conclusion isalso made by Velmurugan and Jose [4] for mortarblock of M30 grade concrete based on the laboratoryinvestigations of density, workability and compressivestrength of the concrete. They also argued that the useof waste is not only eco-friendly, but is also economical.In addition, it shows a positive effect in developinglight-weight concrete with optimum dosage up to 20%.Dixson et. al. [5] used sawdust from rice mills toconvert into ash. The same was used as a replacementof fine aggregate from 5% to 15% to develop M25concrete. From the test results of 7, 14 and 28 daycured samples, the authors observed that light-weightconcrete using sawdust ash may be developed if thepercentage replacement is limited to 5%. Gosh [6] alsoused sawdust in concrete, replacing the natural fineaggregates up to 40%. From the test results of mortarand concrete specimen, the authors recommended areplacement dosage of 10%-20% which is higher thanearlier recommendation of the same. Geeta el al. [7]used binary blending of sawdust and quarry dust asreplacement of fine aggregates. They used sawdustin the dosage of 5% to 15%, and quarry dust from35% to 50%. From the test results, they observedthat 5% of saw dust and 45% of quarry dust resultin almost the same strength as that of conventionalconcrete. On the other hand, Sawant et. al. [8] usedcement replacement from 5% to 25% by sawdust ash toprepare 150 mm side cubes, 150mm diameter cylindersand 550mm x 100mm x 100mm prisms to test compres-sive, tensile and flexural strength of concrete. Theyalso used Metakaolin as bonding admixture. Basedon their experimental work, the authors recommended5% replacement of fine aggregate with sawdust andMetakaolin as admixture to ensure concrete strengthat par with conventional concrete.Workability, unit weight and strength of concrete withfine aggregates replaced by teak wood dust from 0%-30% were studied by Lakshmi and Dilip [9]. Theauthors observed a decrease in workability and anincrease in water absorption with the increase indosage of wood dust. The strength results were foundto be higher than that of conventional concrete. Thesimilar dosage of teak wood dust as replacement offine aggregates to produce M20 grade concrete wasattempted by Tiwari et. al. [10]. Unlike Lakshmi andDilip [9], the authors observed a decrease in strength ofthe samples containing teak wood dust in comparisonto conventional concrete. Mageshwari and Vidivelli[11] used sawdust ash as a partial replacement of riversand from 5% to 30% with increment of 5%. Alongwith basic properties of the aggregates, the authors


evaluated compressive, tensile and flexural strengthof the standard specimens used for the purpose andcured for 180 days. From the experimental results, theauthors observed that the strength increased with theincrease in curing age, but decreased with the increasein the dosage of the ash. They also observed that thewater requirement of the concrete increased with theincrease in the replacement level. The authors con-cluded their work with remarks that ash has potentialto be used as river sand replacement only if used inthe optimum dosage of 10%-20%. In another work bySuliman et. al. [12] to minimize environmental issuesand construction cost, the authors used sawdust ashas a replacement of river sand. But unlike Mageshwariand Vidivelli [11], they used sawdust ash dosage up to15% by volume and tested concrete cubes of standardsize. The authors also tested the cubes with respect toenvironmental hazards of using the ash. From the com-pressive strength results, the authors recommended10% replacement of river sand as optimum dosage.Also, they concluded that the use of ash is free fromany harmful contamination for health.Another way of using sawdust is by converting it intoash. The burnt product is grinded and sieved. Then,it may be used as a partial replacement of cement. Tothis end, Mangi et. al. [13] published review a paperdiscussing the use of the product in fresh concrete. Ma-lik et. al. [14] used the product to replace the cementby 5%-20%. The test results of M25 grade concrete fordensity, water absorption and strength showed a 10%replacement as optimum. The work was extended byRaheem et. al. [15] to prepare concrete specimens usingcement replacement up to 25%. Also, the specimenswere cured up to 90 days. The authors stated thatalthough strength gain of the proposed concrete isslow at early age, but it increases significantly ascuring age is extended up to 90 days. They concludedthat 5% replacement is the optimum. Lone et. al.[16] on other hand recommended 8% as the optimumdosage. Marthong [17] also used the material up to40% to study water absorption, shrinkage, durabilityand compressive strength. Based on the laboratorytests results, the author suggested 10% as the optimumdosage of the material.Kumar et. al. [18] used sawdust as a replacement offine aggregates with respect to low cost constructionmaterial. 10%, 15% and 20% of the sand was replacedwith sawdust, whereas other ingredients of conven-tional concrete were used as per standard requirement.Based on the tests conducted in the research program,the authors argued that the unit weight of the concreteblocks reduced with increase in dosage of the sawdust.Also, the cost of the resulting blocks is smaller than

Fig. 1: Saw dust

the conventional mortar or concrete blocks. Therefore,it can be conveniently used as low-cost material inconstruction.From the literature review, it is evident that a plethoraof work is done by different scholars on developing thegreen concrete and to study its properties. However,various research gaps may still needed to be addressed.Therefore, in this research study, locally availablesawdust is utilized to develop the sawdust ash to beused as cement replacement to prepare green concrete.Laboratory investigations are carried out to check theworkability and strength of sawdust ash concrete.

3 Materials & TestingIn the following, details of the materials used for theproposed research are given.

3.1 SawdustSaw dust used in this research work was collectedfrom the woodwork shops in and around Nawabshahcity. The material in its original form (Figure 1) wasbrought to the laboratory and sorted for unwanted de-bris. Then, the material was burnt followed by grindingto fine powder (Figure 2). The sieving of the materialwas done to ensure its fineness equal to the fineness ofthe cement.

3.2 Conventional Concrete IngredientsOrdinary Portland cement under brand name PakLand obtained from local market was used in ourresearch. Hill sand as fine aggregates and crush ofmaximum size equal to 25 mm were also obtained fromthe approved source of the aggregates. Both aggregateswere sieved in accordance with the relevant ASTMstandard before using in the concrete mix. The waterused for concreting was potable water with pH value6.8.


Fig. 2: Sawdust ash

3.3 Concrete Mix and Slump TestThe sawdust ash was used as the cement replacementby weight. The material was used in the dosage of2.%, 5%, 7.5%, 10%, 12.5% and 15%. Altogether,six concrete mixes were prepared with saw dust ash.Additionally, one mix was prepared without using thewaste material ash. The mix was used to check theresults of the proposed concrete. In all mixes, a 1:2:4mix with 0.5 water cement ratio was used. The mixwas selected as it is commonly used in the industry.Table 1 gives the details of the material quantitiesused in all batches of the concrete along with detailsof the cylinders cast for the evaluation of compressivestrength.The concrete ingredients were weighed and mixedthoroughly followed by adding required quantity ofwater in mixer. The slump test for each batch ofthe concrete was performed in standard fashion. Theobtained values of the slump for all mixes are given inTable 2.

3.4 Casting and Testing of the SpecimensTotal 63 cylinders of standard size were preparedwith 9 specimens from each concrete mix. The castingof the specimens was done in accordance with thestandard procedure. After 24 hours, the specimenswere demolded and left to air dry (Figure 4). Fromeach batch, 3 specimens were cured for 7-, 28- and 56-day respectively by fully immersing in potable water.The curing method is opted as is commonly used onconstruction sites. After the elapse of respective curingtime, the dry weight of the specimens was evaluatedfollowed by the testing for compressive strength in auniversal testing machine under gradually increasingload till failure (Figure 5). The automatic testingmachine applied the load on specimen using hydraulicsystem at the rate of 0.5 kN/sec. The obtained results

Fig. 3: Slump test

Fig. 4: The specimens

of weight and compressive strength of all specimensare listed in Table 3.

4 Results & DiscussionIt is observed that the slump values obtained fromslump test decrease with the increase in the dosage ofsawdust ash. The decrease in slump is attributed to thefineness of the ash due to which the gap between theaggregates is filled to a maximum extent. As a result,

Fig. 5: Testing


# Saw DustAsh (%)

No ofCylinders

Cement(Kg)

Fine Aggregates(Kg)

Coarse Aggregates(Kg)

Saw DustAsh (Kg)

Water(Kg)

1 0.0 9 17.30 34.59 69.21 0.00 8.642 2.5 9 16.87 34.59 69.21 0.432 8.643 5.0 9 16.44 34.59 69.21 0.864 8.644 7.5 9 16.00 34.59 69.21 1.296 8.645 10.0 9 15.57 34.59 69.21 1.728 8.646 12.5 9 15.12 34.59 69.21 2.163 8.647 15.0 9 14.70 34.59 69.21 2.592 8.64

TABLE 1: Material quantities

No Saw Dust Ash (%) Slump (mm)1 0.0 162 2.5 153 5.0 134 7.5 105 10.0 96 12.5 77 15.0 3

TABLE 2: Slump values

Fig. 6: Comparison of slump values

aggregates become attached to each other with ash andslump decreases. The slump results are compared withconventional concrete in Figure 6.It is further observed that slump is less than requiredrange for the mix. This shows that the use of sawdustash requires more water in concrete, otherwise moreeffort in the shape of mechanical equipment or ad-mixtures will be required to maintain the workability.Average values of weight and compressive strength

of the specimens in each dosage of sawdust ash andcuring age are given in Table 4. The comparison ofweight of the specimens of the proposed concrete withthe weight of the conventional concrete shows thatthe reduction in the the weight of the specimens isobtained with the increase in the dosage of sawdustash. Thus, the waste ash helps in developing light-weight concrete.A maximum decrease of 7.87% in the weight is ob-

Fig. 7: Percentile reduction in weight

served at the sawdust ash dosage of 15%. However,strength checking before finalizing the dosage of thewaste ash should be made. Details of the percentilereduction in the weight with respect to control spec-imens at relevant curing age are shown in Figure 7.Average compressive strength of all concrete mixesof the proposed concrete versus average compressivestrength of conventional concrete is shown in Figure8-10. Figure 11 shows the percentile reduction in com-pressive strength within respective curing age. It maybe observed that the early strength (7-Day curing)observed a fluctuating behavior, whereas, both 28- and56-day cured concrete observed a reduction in com-pressive strength except for 2.5% dosage. At 5% dosageof the waste ash, 28-day cured specimens observeda minimum reduction in compressive strength. Elon-gated curing shows an increasing pattern in strengthcompared to 28-day cured samples, but the sampleswith 5% dosage of the waste ash showed a decrease inthe strength. Also, the elongated curing is not commonin the field. Therefore, considering the 28-day curing asthe standard curing age, a minimum reduction equalto 11.66% optimum dosage of sawdust ash is concludedto be equal to 5%. At this dosage level, the reduction inweight of concrete is observed to be equal to 2%. Theresults showed that sawdust ash has good cementitiousproperties and can be used in concrete without much


# Saw DustAsh (%)

7-Day Curing 28-Day Curing 56-Day CuringWeight

(Kg)Comp. Str.

(MPa) Weight (Kg) Comp. Str.(MPa) Weight (Kg) Comp. Str.

(MPa)1

0.013.33 19.99 13.48 24.60 13.36 18.09

2 13.39 21.46 13.51 29.19 13.29 21.343 13.31 20.39 13.52 26.77 13.33 19.864

2.513.32 19.06 13.54 16.99 12.91 19.14

5 13.10 20.88 13.49 17.57 13.24 19.706 13.22 20.51 13.56 16.85 13.01 20.627

5.013.21 17.22 13.36 21.11 13.26 21.82

8 13.12 16.25 13.17 22.70 12.88 20.749 13.06 15.48 13.24 27.35 13.16 20.0310

7.512.98 15.77 13.60 18.51 12.83 22.83

11 12.91 15.90 13.19 16.10 12.94 21.4112 12.80 17.96 13.32 16.90 12.87 20.6213

10.012.77 12.44 13.05 15.68 13.09 24.70

14 12.69 14.14 12.88 19.88 13.18 20.9515 12.74 14.48 12.99 16.07 12.81 22.2116

12.512.52 13.77 12.84 13.50 13.03 20.99

17 12.44 10.76 12.91 13.02 13.00 22.4818 12.57 11.45 12.77 12.44 12.77 20.8319

15.012.35 13.00 12.40 11.73 12.65 14.53

20 12.22 10.07 12.66 12.27 12.71 16.9021 12.31 10.73 12.59 11.45 12.53 16.40

TABLE 3: Weight and compressive strength of all specimens

# Saw DustAsh (%)

Average Weight (kg) Compressive Strength (MPa)7-Day 28-Day 56-Day 7-Day 28-Day 56-Day

1 0.0 13.34 13.50 13.33 20.61 26.85 29.652 2.5 13.21 13.53 13.05 20.15 17.14 19.823 5.0 13.13 13.26 13.10 16.32 23.72 20.874 7.5 12.90 13.37 12.88 16.54 17.17 21.625 10.0 12.73 12.97 13.03 13.69 17.21 22.626 12.5 12.51 12.84 12.93 11.99 12.99 21.447 15.0 12.29 12.55 12.63 11.27 11.82 15.94

TABLE 4: Average weight and compressive strength of the specimens

Fig. 8: 7-Days curing

loss of compressive strength. However, the observed re-duction must be considered before deciding the use ofconcrete in structural members. Concrete may initiallybe used in low load areas.


5 ConclusionBased on the obtained results from laboratory investi-gations for the proposed concrete, it is concluded that:

a) The workability of concrete with sawdust ashreduces with the increase in the dosage of the ash.



Fig. 11: Percentile reduction

b) Higher water demand of the concrete should beaddressed while selecting the w/c ratio, otherwisemechanical effort or admixture will be required tomaintain the workability.

c) Introduction of sawdust ash in concrete helpsin producing light-weight concrete. A maximumdecrease of 7.87% in the weight is observed atsawdust ash dosage of 15%.

d) Compressive strength results show reduction of11.66% at 5% replacement of cement with saw-dust ash for 28-day cured specimens. Hence, 5%replacement is concluded as the optimum.

e) Although, elongated curing shows improvementin compressive strength results, but in comparisonto 28-day cured specimens the percentile reduc-tion is higher.

It is concluded that waste ash has good cementitiousproperties and a 5% dosage may be used in new con-crete. However, reduction in strength must be consid-ered before deciding its specific structural component.

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Impact of Cement Replacement by Sawdust Ash on Workability