EFFECT OF CEREAL FLOURS ON THE PROPERTIES OF CONCRETE
In hot weather retarding admixture are added to prolong the chemical process of hydration so that concrete remain plastic and workable for longer period of time which will gives room to high volume placements. The goal of the research is to investigate the effect of cereal flours made from maize and sorghum on the properties of concrete; this is with a view to establishing the efficacy of the selected cereals as retarder in concrete. The objectives of this research are to; determine the physical and chemical properties of cereal flour made from sorghum and maize flour, establish appropriate dosages of admixture (cereal flour) required for concrete mixes in terms of compression and tension strength, assess the effects of the cereals flour on the fresh properties of concrete, assess the effects of the cereals flour on the hardened properties of concrete. The mix used for the research was calculated using the BRE method and the water cement ratio of 0.6 was used. The mix ratio of 1:1.13:3.40 was used. Trial test was conducted with maize, sorghum, wheat and millet. The cereal was ground, sieved and added in various percentages by weight to the cement, mix and cast in a cube of 100 by 100 by100mmmould left in the mould for 24 hours then demould and immersed in water for seven days. After seven days it was tested for compressive strength, the sorghum and maizegave the highest and higher values of compressive strength respectively and therefore used for the main work. The same procedure was used for the main workthe samples used were produced in three different batches. The first sets of batches were the control samples which also served as source of comparison. The second and the third batches had various percentages of maize and sorghum flour added respectively. The curing was done by complete immersion for 1, 3, 7, 28 and 56 days for all the samples. The compressive strength and tensile strength increase from 1% to 3% dosage of the cereal flour added by weight of the cement. The compressive strength and tensile strength increase as the age of curing increases. Sorghum flour had higher values of compression and tension strength than maize flour. The result of the water absorption test of hardened concrete for maize flour showed that at 28 days 4% and 5% dosage of maize flour added by weight of cement conform to water absorption test for hardened concrete. 1% to 3% dosage of the maize flour do not conform to water absorption test for hardened concrete, at 56 days 1% and 2% of maize flour dosage do not conform to water absorption test while 3% to 5% dosage of maize flour conform to water absorption test. For sorghum flour at 28 days 1% and 2% dosage do not conform to water absorption test for hardened concrete, 3% to 5% dosage conform to water absorption for hardened concrete. At 56 days all the specimens conform to water absorption test for hardened concrete. For the results of the abrasion resistance it was observed that the abrasion resistance decreases with increase in curing period. It was also observed that the maize flour has higher abrasion resistance than sorghum flour. The optimum compressive and tensile strength of the test specimen is achieved at 3% dosage of maize and sorghum flour added to the cement. Maize and sorghum flour delay the setting time of cement, for sorghum flour added to cement the setting time is achieHow to Write a Final Year Project and Research Thesis in Nigeriaved at 410 minutes while for maize is 248 minutes. Maize flour and sorghum flour are good retarding admixtures as they delay the setting time of cement.
1.1 Background of the Study
Concrete is a very important material widely used in construction of many structures such as buildings, roads, and underground structures. It is a man-made building material that looks like stone. The word concrete is derived from the latin word concretus, meaning “to grow together”. According to Bells (2015) in 1756 British engineer John Smeaton made the first modern concrete (hydraulic cement) by adding pebbles as a coarse aggregate and mixing powdered brick into the cement.
Bells (2015) also emphasized that Concrete is a material used in building construction consisting of a hard chemically inert substance known as aggregate (usually made from different types/sizes of sand and gravel) that is bonded together by cement and water. Also, Lyons (2007) maintained that concrete is a mixture of cement, aggregates and water, with any other admixtures which may be added to modify the placing and curing processes or the ultimate physical properties.
Garba (2014) described concrete as a composite material that consists essentially of a binding medium in which are embedded particles or fragments of aggregates. Concrete is a relatively new construction material when compared to earth, stone, timber and steel. However it is now the most widely used material for building and civil engineering construction. The simplest definition of concrete as suggested by Zongjin (2011) is just a constipation of filler and binder (Concrete = Filler + Binder).
Cement and water constituents of the concrete chemically react to form a binding medium (binder); this binding medium holds the aggregates (filler) together (Portland Cement Association, 2015). According to Zongjin (2011) depending on the kind of binder used, concrete can be named in different ways. For instance, if a concrete is made with non-hydraulic cement, it is called non-hydraulic cement concrete; if a concrete made of hydraulic cement, it is called hydraulic cement concrete; if a concrete is made of asphalt, it is called asphalt concrete; if a concrete is made of polymer, it is called polymer concrete.
Non-hydraulic cement cannot gain strength in water, while hydraulic cement does. (Stulz and Mukerji, 1998) The Assyrians and Babylonians used clay as a bonding substance or cement. The Egyptians used lime and gypsum cement, these are examples of non-hydraulic cement (Duggal, 2008).
Ordinary Portland cement (OPC) is the most used type of cement (Bells, 2015). According to Shetty (2005) prior to 1987, there is only one grade of OPC which was governed by IS 269 – (1989). After 1987, higher grade of cement was introduced in India. The OPC was classified into three grades, namely 33 grade, 43 grade and 53 grade depending upon the strength of the cement at 28 days when tested as per IS 4031part 6 – (1988). Garba (2014) opined that Portland cement is the most produced and used cement types in the construction industry. Portland cement is used in the manufacture of precast products, buildings, bridges, hydraulic engineering structures, etc. All Portland cements have the same chemical components although in varying proportions. The variations in proportion of the componentsof Portland cement determine its characteristics and type.
The major part of concrete beside the cement is the aggregate (Neville and Brooks, 2010). Aggregates include sand, crushed stone, gravel, slag, burnt shale and burnt clay. Concrete that included imbedded metal (usually steel) is called reinforced concrete or ferroconcrete (El – Reedy, 2009). According to Bells (2015) reinforced concrete was invented in 1849 by Joseph Monier who received a patent in1867. Joseph Monier was a gardener who made garden pots and tubs of concrete reinforced with an iron mesh. Reinforced concrete combines the tensile or bendable strength of metal and the compression strength of concrete to withstand heavy loads. Joseph Monier exhibited his invention at the Paris exposition of 1867, besides his pots and tubs, he promoted reinforced concrete for use in railway, pipes, floors, arches and bridges.
The properties of concrete depend on the quantities and qualities of its components. (U.S Department of Transportation, FHWA, 2015). Cement durability, strength and relatively low cost make it the backbone of building and infrastructure worldwide. Concrete as the most produced materials on earth will only be more demanded, for example, developing nations become increasingly urban, extreme weather events necessitate more durable building materials and the price of other infrastructure materials continues to rise (Portland Cement Association, 2015). The durability and other properties of concrete are highly variable and sometimes unpredictable.
However, concrete properties can be improved upon in terms of workability, water-cement ratios, setting time, segregation, pumpability, increase strength, early strength development, durability and permeability potentials and compensation of poor aggregate properties (Garba, 2014).
Introduction of admixtures in a concrete helps in improving both fresh and hardened properties of concrete (Zongjin, 2011). When admixtures are applied in a concrete it gives a workable, well compacted, and more durable concrete which may not be possible without admixture. This is because some admixtures reduce the water content of concrete as well as the void and pores presence to give a better concrete. Strength and other properties of concrete depend on the dosage of admixtures present in the concrete (Rixomand Mailvaganam, 1999).
Admixtures can be organic or inorganic materials added in small quantities to modify the properties of mortar in the fresh/hardened state (BS EN 998 – 1: 2010). Admixtures are substances introduced into batch of concrete, during or immediately before mixing in order to altar or improves the properties of the fresh or hardened concrete or both. According to Neil and Ravindra(1996), numerous benefits are available through the use of admixtures such as: improved quality, acceleration or retardation of setting time, coloring, greater concrete strength, increased flow for the same water – to – cement ratio, enhanced frost and sulfate resistance, improved fire resistance, cracking control, lower density, improved workability and enhanced finished concrete.
According to Okafor (2008), several compounds have been found to exhibit retarding action in concrete and their performance is covered in the British standard BS 5075: Part 1 (1982). Some of these compounds include soluble zinc, salt, borates, sugar and carbohydrate derivatives.
Cereal crops are very rich in carbohydrates, relatively cheap, produced locally in very large quantities and the production of flour from their grains does not require any complicated technology. In 2012, the top 5 cereals in the world ranked on the basis of production tonnage are maize (corn), rice (paddy), wheat, barley and sorghum. These crops are also among the top 50 agricultural commodities in the world with maize ranking second next to sugarcane. Rice (paddy) ranks third, wheat – fourth, barley –twelfth and sorghum thirteen while millet ranks number forty – two (FAOSat, 2014). According to Chapman and Carter (1976), cereal is generally defined as a grass grown for its small edible seeds. They also explained that all cereals are angiosperms, monocots, and member of the grass family Gramineae.
Lantican (2001) defines cereals or grains crops as agronomic crops belonging to the grass family Graminea which are utilized staples; the word cereal is derived from the most important grain deity, the Roman Goddess Ceres. Baraja (2015) opted that the seed and grain are not exactly the same despite their interchangeable use. In rice, the grain consists of the brown rice and the enveloping rice hull. The brown rice is the plant‟s true fruit (a type of fruit called Caryopsis) and consists of a seed and the surrounding fruit wall. The fruit wall (pericarp) consists of several thin layer of tissues which are fused together and inseparable from the seed coat. In indica rice, the hull consists of the lemma, palea, sterile lemmas and rachilla. The grain, or kernel of corn (maize) is likewise a Caryopsis.
Okafor (2008), observed that cassava flour considerably improved the workability of the fresh concrete and delayed the setting time of cement by up to 6 hours. Cassava reduced the early strength of concrete but the long term strength will be improved. According to Otoko (2014), a small quantity of cassava powder (0.05% by weight of cement) has the potential of increasing the workability as well as the long term strength of concrete. Also Abalaka (2011) observed that the compressive strength of sugar as admixture is at peak at 0.05% of sugar concentration. He also ascertained that the maximum strength of cassava powder as admixture is at 0.05% of cassava starch concentration. For the purpose of this research the researcher intends to investigate the impact of two cereal flours namely maize and sorghum on the properties of Portland cement concrete.
1.2 Statement of Research Problem
Due to high temperature when concrete is mixed freshly the water demand for adequate workability is high, other problems associated with this high temperature are increase in concrete shrink loss, difficulties in placing concrete as a result of high rate of setting, increased tendency of plastic shrinkage cracking (Khan and Muhammad, 2004). The hot weather also has tendencies of increasing the temperature of fresh concrete resulting in lower ultimate strength and thermal cracking(Otoko, 2014). As a result of the above mentioned problems associated with fresh concrete due to hot weather retarders are introduced in producing concrete in hot climate so that concrete remain plastic during mixing, transporting, placing, compacting and finishing. These conventional retarding admixtures are rare to find thereby making search for alternative materials to be necessary.
The importance of the use of retarder for producing concrete in hot climate cannot be over emphasis as set retarding concrete admixtures delay the chemical reaction that takes place when concrete starts the setting process (Mihai and Rosca, 2008). Retarders as admixture in concrete a lot of initial setting problem could be solved. The main problem associated with conventional retarder is that they are imported and expensive (Alibaba, 2017), thereby affecting the overall cost of producing concrete and these makes their usage low in construction practices in Nigeria.
The production of Conventional retarding admixtures involves industrial processes which emit carbon monoxide to the atmosphere thereby affecting the ecosystem. The research intends to use cereal flour (maize and sorghum) as conventional retarding admixture in concrete.
1.3 Justification of the Study
Cereal crops are widely available in the world and can be afforded by everyone which will not affect the cost of the project. Cereals are carbohydrates which could be good retarders. Retarders have the properties of slowing down the chemical process of hydration so that concrete remains plastic and workable for longer time than concrete without retarder (Shetty, 2005). The slowing down of heat of hydration will leads to reduction in thermal cracks.
Using cereal flour will avail more opportunities for the farmers in terms of increase in income from the sale or yield from their farms, this will also create more job opportunities that will increase the standard of living.
Concrete containing organic admixture is used for good performance and for ecological and economic reasons. The most common organic admixtures are sugar and carbohydrate derivatives (cassava and cereal).
1.4 Aim and Objectives
The study aims at investigating the effect of cereal flours made from maize and sorghum on the properties of concrete; this is with a view to establishing the efficacy of the selected cereals as retarders in concrete.
The objectives of this research are to;
Determine the physical and chemical properties of cereal flours made from sorghum and maize flour. Establish appropriate dosages of admixture (cereal flour) required for concrete mixes.Assess the effects of the cereal flour on the fresh properties of concrete. Assess the effects of the cereal flour on the hardened properties of concrete.
1.5 Scope and Limitations
The research assessed the properties of cereal flour and its effects on the setting time of cement and properties of concrete. The major properties of concrete evaluated were compressive strength, tensile strength, water absorption, and abrasion resistance. The cereal flours used are maize flours and sorghum flours. Tests such as soundness test, setting time test and slump test was carried out on fresh concrete. Cost analysis of retarders was not carried out in this research.
Tests such as flexural strength, creeps, and shrinkage were not conducted, due to the unavailability of machines and equipment.
EFFECT OF CEREAL FLOURS ON THE PROPERTIES OF CONCRETE
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