A Proposal on Determine the Suitability of Cassava Starch as an Admixture in Cement Paste and Concrete

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. Hence, recommend a proper usage of cassava starch as a renewable organic admixture. With this end in sight, following specific objectives of this project will were 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 and mature cement paste, cement paste and concrete.
To study the durability parameters of concrete with starch 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

LITERATURE REVIEW

Admixture

Admixtures are used in concrete and cementitious material to attain a wide range of effects. There are set controlling, viscosity altering and water reducing admixtures among many. More detailed categories are accelerating admixtures, water reducing admixtures, retarding admixtures, air entraining admixtures etc. According to functions the classification is as follows: air-entraining admixtures, accelerating admixtures, hydration-control, corrosion inhibitors, shrinkage reducers, retarding admixtures, water- reducing admixtures, colouring admixtures, plasticizers, alkali- silica reactivity inhibitors, and miscellaneous admixtures such as workability and bonding admixtures, foaming, grouting, damp proofing and permeability reducing admixtures, gas-forming, anti-washout and pumping admixtures (Joseph et al., 2016). Different admixtures are blended together to achieve specific rheology requirements (Bessaies-Bey, 2016).

A high performance concrete cannot be imagined without the usage of good set of admixtures. These can alter one or more characteristic features of concrete and cement mortar. The effectiveness of admixtures depends on factors such as functional groups, chemical configuration and molecular weight of the added elements (Ouyang et al., 2009).

Chemical admixtures

In recent times, if more than ever, admixtures are used to enhance the workability, mechanical properties and durability of concrete. These admixtures can be of an impressive variety of molecules with very different chemical structures and physical properties. Superplasticizers are as high-range water reducer used to improved workability for concrete to a great extent at relatively low water to cement ratio, which leads to improvement of strength and permeability. It infused in the host material and reduces the yield stress and viscosity (Hot, 2014). Another commonly used admixture is air-entraining admixtures to impart resistance of freezing and thawing. Admixtures lead to reduction in water evaporation to mitigate shrinkage, and generate expansion to compensate shrinkage and prevent cracking. Bleeding and segregation can be reduced by introducing viscosity agents or stabilizers (Khayat & Mikanovic, 2012) or by enhanced of water retention capacity (Bulichen, 2012; Brumaud, 2013). Retarders delays the setting and hydration process (Plank, 2009) by increasing flowability retention (Perez, 2007; Li et al., 2012).

MATERIALS AND METHODS

Cement

Cement will be used as binding material for both cement paste and concrete casting in this study. From the array of different types of cement, CEM I (ASTM C 150) or ordinary Portland cement (OPC) will be used. It is said to be the general purpose cement for common use. However it is not prescribed to be used if the concrete is in contact with soil or ground water. Thus the concrete or mortar produced with OPC has some durability issues.

The composition of the cement is presented in Table 3.1. The relative amounts of the 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 the cement which will be converted to the weight fraction of each element in oxide form assuming that there is sufficient amount of oxygen charge balance the other elements all the time. The value of loss on ignition (LOI) will be found to be 1.8%. The relative percentage of components obtained from X-ray fluorescence (XRF) data will be normalized according to LOI in Table 3.1. Cement will be heated to 900 °C -1000 °C and the loss of weight will be measured after a constant weight will be obtained. At this elevated range of temperature, any water or CO₂ present in the cement specimen is driven off. Presence of water and CO₂ indicates prehydration and carbonation respectively. ASTM C 150 limits the maximum loss on ignition (LOI) to a value of 3.0%.

References

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