A Proposal on Determine the Suitability of Cassava Starch as an Admixture in Cement Paste and Concrete
Objectives of study
The overall objective of the research work is to investigate the sustainability of cassava starch as admixtures cement paste and concrete.ย Hence,ย recommend a properย usage of cassava starch as a renewable organic admixture. With this end in sight, followingย specific objectivesย ofย thisย project willย wereย selected:
- To investigate whether cassava can be used as organic
- To study the characteristics of cassava starch like particle size distribution, fineness,
- To study the effect of cassava starch inclusion on various characteristics of fresh,hardened andย matureย cementย paste,ย cementย paste and concrete.
- To study the durability parameters of concrete with starchย ย Durability was assessed in terms of permeability of mature concrete by rapid chloride penetration test (RCPT), rapid migration test (RMT) and sorptivity test.
- To explore the effects of cassava starch admixture on micro structure level of mortar specimens by scanning electron microscopy (SEM) imaging
- To study the changes in the test parameters with variation of cassava starch content and determine optimum dose of cassava starch admixture for desired
LITERATUREย REVIEW
Admixture
Admixtures are used in concrete and cementitious material to attain a wide range ofย effects. There are set controlling, viscosity altering and water reducing admixturesย among many. More detailed categories are accelerating admixtures, water reducingย admixtures,ย retardingย admixtures,ย airย entrainingย admixturesย etc.ย Accordingย toย functionsย theย classificationย isย asย follows:ย air-entrainingย admixtures,ย acceleratingย admixtures,ย hydration-control,ย corrosionย inhibitors,ย shrinkageย reducers,ย retardingย admixtures, water- reducing admixtures, colouring admixtures, plasticizers, alkali-ย silica reactivity inhibitors,ย andย miscellaneous admixturesย such as workability andย bonding admixtures, foaming, grouting, damp proofing and permeability reducingย admixtures, gas-forming, anti-washout and pumping admixtures (Joseph et al., 2016).ย Different admixtures are blended together to achieve specific rheology requirementsย (Bessaies-Bey,ย 2016).
A high performance concrete cannot be imagined without the usage of good set ofย admixtures.ย Theseย canย alterย oneย orย moreย characteristicย featuresย ofย concreteย andย cementย mortar.ย Theย effectivenessย ofย admixturesย dependsย onย factorsย such asย functional groups, chemical configuration and molecular weight of the added elements (Ouyangย etย al.,ย 2009).
Chemicalย admixtures
In recent times, if more than ever, admixtures are used to enhance the workability,ย mechanical properties andย durability of concrete.ย Theseย admixturesย can beย of anย impressive variety of molecules with very different chemical structures and physicalย properties.ย Superplasticizersย areย asย high-rangeย waterย reducerย usedย toย improvedย workability for concrete to a great extentย at relatively low water to cement ratio,ย whichย leads toย improvementย of strength andย permeability.ย Itย infusedย in theย hostย material and reduces the yield stress and viscosity (Hot, 2014). Another commonlyย usedย admixtureย isย air-entrainingย admixturesย toย impartย resistanceย ofย freezingย andย thawing. Admixtures lead to reduction in water evaporation to mitigate shrinkage, andย generateย expansion toย compensateย shrinkageย andย preventย cracking.ย Bleedingย andย segregation can be reduced by introducing viscosity agents or stabilizers (Khayat &ย Mikanovic,ย 2012)ย orย byย enhancedย ofย waterย retentionย capacityย (Bulichen,ย 2012;ย Brumaud, 2013). Retarders delays the setting and hydration process (Plank, 2009) byย increasingย flowabilityย retention (Perez,ย 2007;ย Liย etย al.,ย 2012).
MATERIALSย ANDย METHODS
Cement
Cement will be used as binding material for both cement paste and concrete casting in thisย study. From the array of different types of cement, CEM I (ASTM C 150) or ordinaryย Portland cement (OPC) will be used. It is said to be the general purpose cement forย common use. However it is not prescribed to be used if the concrete is in contact withย soil or ground water. Thus the concrete or mortar produced with OPC has someย durabilityย issues.
The composition of the cement is presented in Table 3.1. The relative amounts of theย components have effects on the properties of cement and the products as cement paste and concrete. X-ray fluorescence (XRF) analysis gives relative amount of elements in theย cement which will be converted to the weight fraction of each element in oxide formย assuming that there is sufficient amount of oxygen charge balance the other elementsย all the time. The value of loss on ignition (LOI) will be found to be 1.8%. The relativeย percentageย ofย componentsย obtainedย fromย X-rayย fluorescenceย (XRF)ย dataย will beย normalized according to LOIย in Table 3.1. Cementย will be heated toย 900 ยฐC -1000 ยฐCย and the loss of weight will be measured after a constant weight will be obtained. At thisย elevated range of temperature, any water or CO2ย present in the cement specimen isย drivenย off.ย Presenceย ofย waterย andย CO2ย indicatesย prehydrationย andย carbonationย respectively. ASTM C 150 limits the maximum loss on ignition (LOI) to a value ofย 3.0%.
References
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