Feasibility of Using Sea Shells Ash as Admixtures for Concrete

Journal of Environmental Science and Engineering A 1 (2012) 121-127 Formerly part of Journal of Environmental Science and Engineering, ISSN 1934-8932

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Feasibility of Using Sea Shells Ash as Admixtures for Concrete Benjamin R. Etuk1, Idongesit F. Etuk1 and Linus O. Asuquo2 1. Department of Chemical and Petroleum Engineering, University of Uyo, Uyo 52001, Nigeria 2. Department of Mechanical Engineering, University of Uyo, Uyo 52001, Nigeria Received: June 24, 2011 / Accepted: August 2, 2011 / Published: January 20, 2012. Abstract: This research aims at producing pozzolanic admixtures from waste shells of periwinkle, oyster and snail. The clean shells were ashed at 800 °C and analysed for chemical composition. The results show that they are pozzolanic in nature. The effect of using the shells ash as admixtures on the setting time and compressive strength of cement paste and mortar were investigated using varying percentages of 0%, 5%, 10%, 15%, 20%, 25% and 30% by weight of each of the shell ashes. The results show that the water consistency, initial, and final setting times of each of the cement blends were increasing with increase in percentage replacement of cement with each of the shell ashes. The optimum compressive strength with percentage replacement level of 10% for periwinkle shell ash (PSA), 15% for oyster shell ash (OSA), and 20% for snail shell ash (SSA) were obtained with ashes produced. Key words: Sea shell ash, concrete, admixtures, waste utilization.

1. Introduction Housing delivery in Nigeria in the rural, semi-urban and urban areas is still a serious problem due partly to the high cost of some essential materials, especially cement (a major material in the construction industry) whose cost has increased over the years and may soon be out of reach of the ordinary citizens. Recently, to arrest the escalating cost of cement, the Federal government directed local manufacturers to evolve strategies to bring down the price of the commodity to avoid a review of the existing policy on cement which gave 2013 as the deadline for the country to be self-sufficient in cement production [1]. Concrete is an essential construction material composed of cement, aggregate (gravel or granite and sand) and water. In order to reduce the construction, researchers have been exploring the possibility of using pozzolanic admixtures produced from locally Corresponding author: Benjamin R. Etuk, associate professor, Ph.D., main research fields: separation processes, particulate systems, food processing, waste control and utilization. E-mail: [email protected].

available and/or waste materials to partially or fully replace the costly conventional materials. An admixture is a material other than cement, water and aggregates that is used as an ingredient of concrete and is added to the batch immediately before or during mixing [2]. According to Michael [3], admixtures in concrete can improve its workability, hardening, or strength characteristics and generally result in a reduction in the cost of concrete construction [4]. For instance, activated kaolin clay, fly ash, silica fume, baryte powder and oil shale ash had been used as components of blended binders for mortars with good results in terms of their pozzalinic activity [5]. The use of cassava starch [6], rice husk ash [7-10], rice straw ash [11], and wood waste ash [12] to partially replace different types of cement in concrete had also been reported. The use of these agricultural materials helped to reduce waste as well as improve the strength properties of the concrete. However, the strength reduced with time due to microbial activity. In Nigeria, the intensity of fishing activities in the

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Feasibility of Using Sea Shells Ash as Admixtures for Concrete

riverine areas has resulted in the production and accumulation of large quantities of sea shells as wastes along the coastal regions, market areas and dump sites. Usually, the fleshes of the species are processed for consumption while the inedible hard shells are dumped at open sites thereby causing environmental pollution. Periwinkle, snail, oyster and all marine animals belonging to phylum mollusca and class gastropoda [13]. They belong to the group of exoskeleton animals. The exoskeletons contain rigid and resistant components that fulfill a set of functional roles including protection, excretion, support, feeding, acting, etc.. They contain chitin and when calcium carbonate is added, the exoskeleton grows in strength and hardness [14]. An exploratory study on the suitability of sea shells, such as periwinkle shells, as partial or full replacement for granite in concrete work had been reported with satisfactory compressive test results at appropriate concrete mix ratios [15]. Using the ash of the sea shell, investigation had shown that up to 50% replacement of cement in sandcrete blocks and 5% replacement in laterite blocks were possible with good results in terms of compressive strength [16, 17]. In this paper, the utilization of the ash of waste shells of periwinkle (PSA), snail (SSA) and oyster (OSA) as partial replacement for cement in the construction industry is reported. The concentrations of the ash from the different shells in finely divided form are evaluated to determine the optimum needed that will not compromise the workability, hardening and strength properties of the concrete produced. The effective utilization of these sea shell wastes which are available almost free of cost and in abundance will not only reduce their pollution tendency but will help in reducing the amount of cement used in concrete work.

used were UNICEM® Ordinary Portland Cement (OPCEM), water and sand. The periwinkle, snail and oyster shells were obtained from Akpan Andem market in Uyo, a dump site at Okpoedu, Itu, and Issiet in Itu and Uruan Local Government Areas respectively, all in Akwa Ibom State, Nigeria.

2. Materials and Methods

2.3 Determination of Specific Gravity

The materials used in carrying out the research were periwinkle, snail and oyster shells. Other materials

The specific gravity of the ash samples was determined in accordance with BS method [20]. The

2.1 Production of Pozzolanic Admixture The three different shell samples were each washed thoroughly to remove dirt and mud and then sun-dried for three days. The samples were then placed in a furnace and ashed at temperatures of 800 °C for a period of four hours. The ash samples were then ground into a powdered form using metallic mortar and pestle, sieved through a sieve mesh size of 63 microns, and kept in tight containers for analyses. 2.2 Chemical Analyses The shell ashes were analysed to determine their composition at the Quality Control Laboratory of Ashakacem, Gombe, State, in accordance with Nigerian Industrial Standard (NIS) method [18]. In the method, stearic acid (0.4 g) and 20.0 g of each of the three different shell ashes obtained at temperatures of 800 °C were measured and were put in a grinding pot and ground for 60 seconds using the Herzog grinding machine. The aluminum cup was filled half way with stearic acid and then filled up with the samples. The cup was carefully inserted into the pellet making machine (Herzog pressing machine). The pellet produced was then placed in the cement X-ray spectrophotometer and the programme to which the samples were analysed was selected, that is, the program OPCEM (ordinary Portland cement), and the start key was clicked so that within 2-3 minutes the results were obtained [19].


empty density bottle with stopper was weighed as W1 and then filled with shell ash to about three quarter of the bottle. This was measured as W2. The bottle containing the shell ash was then filled up with water and a stopper used to cover it. This was measured as W3. The content of the density bottle were then poured out and the bottle rinsed with water. The bottle was thereafter filled with water and the stopper inserted. This was measured as W4. The specific gravity for each of the shell ashes was determined, using the formula: W2 – W1 (1) Sp gr = (W2 – W1) – (W3 – W4) 2.4 Determination of Consistency of Cement Pastes Four hundred and ninety grams of the OPCEM was weighed and placed on a non-absorbent metallic tray. By trial mixtures, the required water content which produced the cement paste of desired standard consistency of between 26 and 33 (expressed as a percentage by mass of the dry cement) was chosen. The measured water was then added to the weighed cement, thoroughly mixed and finely ground together with a hand-trowel for four to five minutes to form a neat cement paste. The neat cement paste was then placed in a special metallic mould and the consistency of the neat cement paste was then determined by lowering the plunger which is attached to the Vicat® apparatus and allowed to make contact with the top surface of the paste before it was finally released. Under the action of its weight, the plunger was allowed to penetrate the paste and the depth of penetration for a standard and consistent cement paste was to a point 5 mm to 7 mm from the bottom of the mould. This test meets the requirement stated in BS [21]. 2.5 Determination of Initial and Final Setting Times The plunger used for consistency test was replaced with a round needle with a cross-sectional area of 1 mm2 used as the initial set needle. The process of

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making the needle penetrate the paste of standard consistency was repeated at intervals of 5 minutes, until the paste was stiffed enough for the initial set needle to penetrate only to a point 10 mm to 20 mm from the bottom of the mould. The initial setting time was recorded as the time that elapsed from when the paste was made to when it set [21]. The initial set needle was then replaced with the final set needle with a 1 mm square needle having a circular cutting edge of 5mm in diameter. The final set needle was made to penetrate the paste in the mould, so that it left a circular cutting edge of 5 mm in diameter and set 0.5 mm behind the tip of the needle. The process of allowing the needle penetrate the paste was repeated at intervals of 5 minutes, and the final set was said to have taken place when the needle which was gently lowered to the surface of the paste made an impression on it but the circular cutting edge failed to penetrate [6]. 2.6 Production of the Mortar Cubes The moulds of size 50 × 50 × 50 mm were used for all the casting of the mortar cubes. The moulds were cleaned and oiled to enhance easy removal of the cubes after setting and prevent damage of the test cubes. A mixture of 0.27 kg of cement, 0.81 kg of sand, and 0.135 kg of water, all in a mix ratio of (1:3:0.5) was measured. The mixture was mixed thoroughly by means of a trowel on a non-absorbent metallic tray to obtain a homogenous mixture. This was used as a reference sample (i.e 0% replacement). The mix was then transferred into the mould of 50 × 50 × 50 mm and filled in three equal layers. Each of the layers was compacted 25 times using a rod of three quarter diameter and allowed for twenty four (24) hours before removing

it and then cured in water for

7 days. This process was repeated with cement replaced by each of the shell ashes by weight at varied concentrations of 5, 10, 15, 20, 25 and 30 percent. The cubes were put into a curing tank containing

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water. This was done to maintain satisfactory moisture content as that hydration of the cementious material continues long enough to achieve the required strength, durability and reduce shrinkage induced cracking in the cube [22]. 2.7 Compressive Strength Test This test was done in accordance with BS EN method [23] and used by Oymael [24]. The cubes were removed from the curing tank at the end of the curing period (7 days) and then weighed, before compressive strength was conducted. Three cubes each for the different replacement levels were crushed at 7 days using a manual compressive machine, with capacity of 1000 kN. The test was carried out in the Building Department Laboratory, University of Uyo, Uyo.

3. Results and Discussion 3.1 Chemical Analyses The chemical composition of the OPCEM used and the shell ashes are shown in Table 1. The results show the cement to have the four major compounds, namely, CaO, SiO2, Al2O3, and Fe2O3, with high percentages of CaO and SiO2 which accounts for its strength. Also the results for each of the shell ashes show that they contain the main chemical compounds of cement namely, CaO, SiO2, Al2O3, and Fe2O3, and the similarity in most of the chemical composition in the OPCEM and the latter make the partial replacement of cement by each of the shell ashes to be feasible. From the data presented, the amount of sulphur trioxide (SO3) present in each of the shell ashes lies within the optimum range of not more than 3.0% recommended by ASTM [25]. However, the results show that PSA contains more SO3 followed by OSA and SSA. 3.2 Specific Gravity Test Table 2 shows the results of the specific gravity for cement, periwinkle shell ash, snail shell ash and oyster shell ash obtained. From the data, it is clear that the specific gravity of the ashes are all lower than that of

cement used. Nevertheless, they are in accordance with BS [20]. 3.3 Consistency/Setting Time Test Fig. 1 shows the results of water consistency of cement paste blended with PSA, OSA and SSA produced at temperature of 800 °C. The water consistency of the blended cement paste increases with increase in percentage replacement in the following trend of PSA > OSA > SSA. The reason for this trend may be attributed to the high silica contents in PSA compared to OSA and SSA. For SSA the lowest water consistency could also be as a result of high lime content. The results of initial and final setting times of cement paste blended with PSA, OSA and SSA obtained at 800 oC are presented in Figs. 2 and 3. The results show that the initial and final setting times increase with increase in the percentage replacement of each of the shell ash. This may be due to the increase in the required mix water, as well as retarded hydration caused by having more of the shell ashes than cement in the mix. Table 1 Chemical composition of OPCEM and the sea shells ash obtained at 800 °C. Component SiO2 Al2O3 Fe2O3 CaO MgO SO3 K2O Na2O P2O5 MnO3 TiO2 Table 2

OPCEM 20.06 5.85 3.05 61.44 0.93 2.71 0.97 0.14 0.17 0.20 0.28

Composition (wt %) PSA SSA OSA 26.26 10.20 13.41 8.79 4.81 4.95 4.82 3.15 3.80 55.53 61.95 57.95 0.4 0.18 0.19 0.18 0.03 0.12 0.20 0.05 0.02 0.25 0.04 0.22 0.05 0.01 0.01 0.07 0.01 0.01 0.05 0.01 0.01

Specific gravity.

Material Cement Periwinkle shell ash Oyster shell ash Snail shell ash

Specific gravity 3.10 2.50 2.33 2.44


Fig. 1

Water consistency with percentage replacement of cement with sea shell ash in concrete.

Fig. 2

Initial setting time with percentage replacement of cement with sea shell ash.

Fig. 3

Final setting time with percentage replacement of cement with sea shell ash.

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Fig. 4

Compressive strength with varying percentage replacement of cement with sea shell ash.

3.4 Compressive Strength The results of the compressive strength of the mortar cubes produced from cement blended with each of the shell ashes are shown in Fig. 4. The figure shows the plots of the 7 days compressive strength against percentage replacement of PSA, OSA and SSA obtained at temperatures of 800 °C. The results show that at first the compressive strength of each of the mixes is low compared to that of the control mix. This is so, because the pozzolanic activity is slow as it

(3) The initial and final setting times of the blended cement pastes were found to increase with increasing percentage replacement of each of the shell ashes; (4) The compressive strength of the mortar cubes decreases with increase in the amount of the shell ash in the cement paste; (5) The cement can be replaced partially by up to 10% by weight of periwinkle shell ash (PSA), 15% by weight of oyster shell ash (OSA), and 20% by weight of snail shell ash (SSA) in making of mortar cubes without the strength being affected.

allows for the hydration of cement, but later increases with increases in percentage replacement up to 10%

Acknowledgments

by weight of PSA, 15% for OSA and 20% for SSA, shell ash increases.

The authors are deeply thankful to Ashaka Cement Company, Gombe State for their help in the chemical analyses of the ash samples.

4. Conclusions

References

Based on the results of this study, the following conclusions are drawn: (1) Periwinkle shell ash (PSA), oyster shell ash (OSA) and snail shell ash (SSA) are pozzolanic in nature and satisfies the requirements of ASTM [25]. Therefore, it can be used as a cement replacement material; (2) The water consistency increases with increase in the percentage replacement of each of the shell ashes;

[1]

and then decreases as the percentage for each of the

[2]

[3]

[4]

R. Badmus, Cement: Manufacturers fine-tune strategies to meet ultimatum, The Punch Newspaper (Nigeria), May 20, 2011, p. 32. M.S. Shetty, Concrete Technology, Theory and Practice, revised ed., S. Chand and Company Ltd., Ram Nagar, New Delhi, 2005, pp. 124-217. R.L. Michael, Civil Engineering Reference Manual, 6th ed., Professional Publications, Inc., Belmont, CA, USA, 1992, pp. 142-144. C. Piper, Why Use an Admixture with Concrete? [Online],


[5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13] [14]

http://www.ehow.com/info_8761265_use-admixture-con crete.html. A. Shvarzman, K. Kovler, I. Schamban, G. Grader, G. Shter, Influence of chemical and phase composition of mineral admixtures on their pozzolanic activity, Advances in Cement Research 13 (2001) 1-7. O.E. Alutu, T.O. Ehondor, The setting time of portland cement pastes dosed with cassava starch admixtures, Nigerian Journal of Industrial & Systems Studies 4 (2005) 24-31. D.C. Okpala, Rice husk ash (rha) as partial replacement of cement in concrete, in: Proceeding of the Annual Conference of the Nigerian Society of Engineers, Port Harcourt, Nigeria, 1987, pp. 20-25. J.I.C. Mbachu, J.O. Kolawole, Shrinkage and elastic moduli of ordinary portland cement (opc) and rice husk ash (rha) concrete made with different coarse aggregate types, J. Envir. Sci. 1 (1998) 35-40. K. Sakr, Effects of silica fume and rice husk ash on the properties of heavy weight concrete, J. Mater. Civ. Eng. 18 (2006) 367-376. E.B. Oyetola, M. Abdullahi, The use of rice husk ash in low-cost sandcrete block production, Leornardo Electronic Journal of Practices and Technologies 5 (2006) 58-70. M.A. El-Sayed, T.M. El-Samni, Physical and chemical properties of rice straw ash and its effect on the cement paste produced from different cement types, J. King Saud. Univ. Eng. Sci. 19 (2006) 21-30. F.F. Udoeyo, H. Inyang, D.T. Young, E.E. Paradu, Potential of wood waste ash as an additive in concrete, J. Mater. Civ. Eng. 18 (2004) 605-611. C. Peter, E. Michael, Marine Biology, 15th ed., Mc Graw-Hill Companies, New York, 2005, pp. 167-225. B. Nicholas, Exceptional fossil preservation and the combian explosion, Integrative and Comparative Biology

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43 (2003) 166-177. [15] A.P. Adewuyi, T. Adegoke, Exploratory study of periwinkle shells as coarse aggregates in concrete works, Journal of Applied Sciences Research 4 (2008) 1678-1681. [16] A.A. Umoh, I.A. Odesola, The effects of periwinkle shell filler on the compressive strength developments of lateritic blocks, Intern. J. Eng. 2 (2008) 1-11. [17] O.F. Job, A.A. Umoh, S.C. Nsikak, Engineering properties of sandcrete blocks containing periwinkle shell ash and ordinary Portland cement, Inter. J. Envir. Sci. 1 (2009) 18-24. [18] Nigeria Industrial Standard, NIS 412, Standards for Cement, Standard Organization of Nigeria, Abuja, Nigeria, 2009, pp. 9-15. [19] M. Abdulfattah, Determination of chemical analysis using pellets, in: A laboratory Manual of Quality Control, Ashakacem Plc., Gombe State, 2001, pp. 1-12. [20] Methods for Sampling and Testing of Mineral Aggregates, Sands and Fillers, British Standard Institution, London, 1975. [21] Specification for Ordinary and Rapid Hardening of Portland Cement, British Standard Institution, London, 2000. [22] A.M. Neville, Properties of Concrete, 5th eds., Ritman Limited, New York, 2000, p. 900. [23] Cement, Composition, Specifications and Conformity criteria for Common Cements, British Standards Institution, London, 1997. [24] S. Oymael, Suitability of oil shale ash as a constituent of cement, Oil Shale Journal 24 (2007) 45-58. [25] Specification for Fly Ash and Raw or Calcined Natural Pozzolanas for Use as Mineral Admixture in Portland Cement Concrete, American Society for Testing and Materials Standards, Philadelphia, USA, 2008.

Feasibility of Using Sea Shells Ash as Admixtures for Concrete

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