EFFECTS OF GROUNDNUT HUSK ASH (GHA) IN CEMENT PASTE AND MORTAR

Transcription

1 INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND TECHNOLOGY (IJCIET) International Journal of Civil Engineering and Technology (IJCIET), ISSN (Print), ISSN (Print) ISSN (Online) Volume 5, Issue 1, October (214), pp IAEME: Journal Impact Factor (214): (Calculated by GISI) IJCIET IAEME EFFECTS OF GROUNDNUT HUSK ASH (GHA) IN CEMENT PASTE AND MORTAR Egbe-Ngu Ntui Ogork 1, Okorie Austine Uche 2 1, 2 (Department of Civil Engineering, Bayero University, PMB 311 Kano, Nigeria) ABSTRACT This paper presents the findings of an investigation on the effects of Groundnut Husk Ash (GHA) in cement paste and Mortar as a supplementary cementing material. The GHA used was obtained by controlled burning of groundnut husk to a temperature of 6 o C and sieved through 75 µm sieve after allowing cooling, and characterized. The effects of GHA on cement paste and mortar were investigated at replacement levels of, 5, 1, 2, 3 and 4 %, respectively by weight of cement. A total of ninety 4 mm x 4 mm x 16 mm GHA-Mortar prisms made with 1 : 3 (cement : sand) and.5 water-cement ratio were tested for flexural and compressive strengths at 3, 7, 28, 6 and 9 days of curing. The results of the investigations showed that GHA was of low reactivity, with a combined SiO 2, Al 2 O 3 and Fe 2 O 3 content of 26.6 %. The drying shrinkage decreased, while consistency, initial and final setting times of cement paste increased with increase in GHA content, where as the flexural and compressive strengths of Mortar decreased with increase in GHA content. However, 1 % GHA replacement was considered as optimum for structural mortar. Keywords: Cement, Effect, GHA, Mortar, Replacement. 1. INTRODUCTION The construction industry is heavily reliant on the use of cement-based products (mortar and concrete) as major materials for buildings and other civil engineering works. The strength of mortar or concrete depends on the cohesion of the cement paste, its adhesion to the aggregate particles and to a certain extent on the strength of the aggregates [1]. This therefore indicates the very importance of cement in mortar or concrete production. However, in many developing countries, ordinary Portland cement is an expensive and sometimes scarce commodity and this has contributed to limit the construction of adequate housing in most of these countries. Reference [2] attributed the high cost of ordinary Portland cement to be largely due to the high cost of plant and high energy required in the production, and suggested that a viable means of reducing the cost of cement based 88

2 construction is by either reducing the energy costs in the burning of clinker or by increasing the production of pozzolanic cement and pozzolanas for the partial replacement of cement. The development of supplementary cementitious materials is fundamental to advancing low cost construction materials to be used in the production of self-sufficient shelter especially in developing countries. The use of various ashes as potential replacement of cement in mortar and concrete production has attracted the attention of researchers because of its potential to reduce or totally eliminate the classification of ashes as waste materials polluting the environment and also reduce the quantity and consequently the cost of cement applied in concrete works [3]. According to [1], apart from the cost benefit of use of pozzolanas with Ordinary Portland cement, they enhance the properties of mortar and concrete. Groundnut husk is a waste from agricultural product which is usually burnt, dumped or left to decay naturally. It constitutes about 25 % of the total pod (husk and seeds) mass [4]. However, [5] and [6] have earlier reported the use of Groundnut Husk Ash (GHA) as a supplementary cementing material in concrete. They indicated that GHA has a low silicon dioxide content, and the combined content of oxides of Silicon, Aluminium and iron was less than the minimum of 7 % required of a good pozzolana [7]. They also suggested that up to 1 % GHA content could be used as a partial substitute of cement in structural concrete. It is on this premise that this research sets out to further investigate the effects of GHA in cement paste and Mortar as a supplementary cementing material. 2. MATERIALS AND METHODS 2.1 Materials Ordinary Portland cement manufactured in Nigeria as Dangote brand, with a specific gravity of 3.14 was used. The oxide composition of the cement is shown in TABLE 1. Sharp sand from river Challawa, Kano, Nigeria, with a specific gravity of 2.62, bulk density of kg/m 3 and moisture content of 2.5 % was used. The particle size distribution of the sand shown in Fig. 1, indicate that the sand used was classified as zone -1 based on [8] grading limits for fine aggregates. Groundnut husk was sourced from Yakasai village, Kano State, Nigeria. The Groundnut Husk Ash (GHA) was obtained by a two-step burning method [9], where the groundnut husk was burnt to ash and further heating the ash to a temperature of about 6 o C in a kiln and controlling the firing at that temperature for about two hours and the ash was allowed to cool before sieving through a 75 µm sieve. The GHA is of specific gravity of 2.12, bulk density of 835 kg/m 3, moisture content of 1.6 % and grain size distribution is also shown in Fig. 1. A chemical composition analysis of the GHA was conducted using X-Ray Flouresence (XRF) analytical method and also shown in TABLE 1. Table 1: Oxide Composition of OPC (Dangote Brand) and GHA Oxide (%) SiO 2 Al 2 O 3 Fe 2 O 3 CaO MgO K 2 O Na 2 O SO 3 TiO 2 MnO BaO OPC GHA Oxide (%) V 2 O 5 P 2 O 5 ZnO Cr 2 O 3 NiO CuO SrO ZrO 2 Cl L.o.I OPC GHA

3 % Passing Zone 1 UpperLimit F.A Fine Agregates GHA Passing.75mm Sieve Zone 1 Lower Limit F.A Sieve Metric Size (mm) Figure 1: Particle Size Distribution of GHA and River Sand 2.2 Methods Tests on Cement Paste. Six mixes were used for the determination of Consistency, Setting Times and drying linear shrinkage of GHA-Cement in accordance with [1]. MP- is the control mix ( % GHA) and MP-5, MP-1, MP-2, MP-3 and MP-4 are mixes containing GHA at replacement levels of 5, 1, 2, 3, and 4 %, respectively. Three readings were taken and an average found. The behavior is shown in Fig Tests on Groundnut Husk Ash (GHA)-Mortar Mortar of 1: 3 (GHA-Cement: Sand) mix with a water-cement ratio of.5 was used to prepare 4 mm x 4 mm x 16 mm prism specimens to determine the Flexural and Compressive Strengths of GHA-Mortar cured in water for 3, 7, 28, 6 and 9 days. Six mixes were used, M- is the control mix and M-5, M-1, M-2, M-3 and M-4 are mixes containing GHA at replacement levels of 5, 1, 2, 3, and 4 %, respectively. The Flexural Strength test was conducted in accordance with [11]. A total of ninety (9) prisms were cast and three prisms tested for an average for each curing regime using the Avery Denison Universal Testing Machine of 6 kn load capacity at a rate of loading of (5 ± 1) N/s. Samples of 4 mm x 4 mm x 4 mm were prepared from the crushed samples (half prisms) from the flexural strength test and tested for compressive strength using the Avery Denison Universal Testing Machine. The flexural strength and compressive strength are shown in Fig. 5 and 6, respectively. The 28 day pozzolanic activity index of GHA-Mortar was determined and a pozzolanic index of 62.8 % was obtained. 9

4 3. ANALYSIS AND DISCUSSION OF RESULTS 3.1 Groundnut Husk Ash (GHA) The physical properties of GHA showed that it has a specific gravity of 2.12 and a Loss on Ignition (LoI) value of 8.2 %, which is within [7] acceptable limit of 1 % for Class N pozzolana. This therefore indicated that the GHA was properly burnt. However, the chemical composition of GHA indicate a combined SiO 2 Al 2 O 3 and Fe 2 O 3 content of 26.6 %, which is much lower than the minimum value of 7 % in [7] for a good pozzolana, and would therefore be of low reactivity. This is further confirmed by the low 28 day pozzolanic index of GHA-Mortar of 62.8 %. The chemical composition of GHA also indicated a high K 2 O content of 38.8 %, which is far higher than 1.2 % limit recommended in cement [12]. The high K 2 O content may be a source of disruption in GHA- Mortar and concrete. GHA also showed a CaO content of %, which indicates that it has some self cementing properties. 3.2 Groundnut Husk Ash (GHA)-Cement Paste The consistency of GHA-Cement Paste shown in Fig. 2 indicated that water requirement increases with increase in GHA content. The normal consistency of cement paste was 3. % while that of GHA-Cement Pastes ranged from %, depending on GHA content. The increase in water requirement with increase in GHA content may be due to high porosity as well as high LoI of GHA, consistent with [13] report on rice husk ash-calcium carbide residue as supplementary cementing materials. It may also be due to lower specific gravity of GHA than cement, that is, higher volume of GHA compared to OPC of same weight would require more water to form paste. CONSISTENCY (%) GHA CONTENT (%) Figure 2: Consistency of GHA-Cement Paste The setting times of GHA-Cement pastes shown in Fig. 3 showed increase in setting times with increase in GHA content. The initial and final setting times of the cement paste were 46 and 554 minutes, respectively, while that of GHA-Cement pastes ranged from 46 and 6 minutes to 81 and 643 minutes, respectively, with the least and longest times occurring in paste with 5 % and 4 % GHA content, respectively. The results suggested that GHA retards the setting times of cement, and this would be suitable for use in hot weather concreting, as well as in mass concreting and long haulage of ready mix concrete. The delay in setting times of GHA-Cement paste was due to the 91

5 dilution of cement with GHA and slower pozzolanic reaction of GHA. This is consistent with early works by [14] and [15]. SETTING TIME (MINUTES) INITIAL SETTING TIME FINAL SETTING TIME GHA CONTENT (%) Figure 3: Setting times of GHA-Cement Paste The drying shrinkage of GHA-Cement Paste shown in Fig. 4 indicated that the shrinkage of GHA-Cement Paste with GHA content up to 1 % was same as that of control paste, but the shrinkage of GHA-Cement pastes at replacement levels from 2 % and above decreased with increase in GHA content. The decrease in shrinkage may be due to high porosity of GHA particles which absorb more water than cement, leading to reduced shrinkage [16] and [17]. This suggests that GHA-Cement would not be subject to higher movement when put into use compared with control paste. DRYING SHRINKAGE (%) MP- MP-5 MP-1 MP-2 MP-3 MP-4 MIX NUMBER Figure 4: Drying Shrinkage of GHA-Cement Paste 3.3 Flexural Strength and Compressive Strength of GHA-Mortar The flexural strength of GHA-Mortar shown in Fig. 5 indicated that flexural strength of mortar increased with age of curing but decreased with increase in GHA content. However, the optimum 28 days flexural strength was obtained at 5 % GHA content, and the flexural strength of GHA-Mortar at 1 % GHA content was same as that of control at 9 days curing. A similar 92

6 behaviour was observed with compressive strength of GHA-Mortar shown in Fig. 6. However, GHA content of 1 % cement replacement by weight was considered as optimum for structural mortar. The increase in strength with age of curing is due to hydration of cement and pozzolanic reaction of GHA. The decrease in strength with increase in GHA replacement could be due to the reaction mechanism of GHA, in which dilution of cement and slower strength development from the pozzolanic reaction would be responsible for the reduction in strength [18]. Furthermore, for constant water/binder ratio, the reduction in flow of mortar with increase in GHA content reduced compaction of mortar which may result in reduction in strength of the mortar. However, higher flexural and compressive strengths of mix containing 5 % GHA over control mix at 28 days curing and beyond is due to pozzolanic reaction where dilution effect is not significant and the secondary C- S-H compliment the strength from the hydration products. 8 7 Flexural Strength (N/mm2) % GHA 5 % GHA 1 % GHA 2 % GHA 3 % GHA 4 % GHA Curing Age (Days) Figure 5: Flexural strength development of GHA- Mortar 4 Compressive Strength (N/mm2) % GHA 5 % GHA 1 % GHA 2 % GHA 3 % GHA 4 % GHA Curing Age (Days) Figure 6: Compressive strength of GHA-Mortar 93

7 4. CONCLUSION i) The GHA is of low reactivity, with a combined SiO 2, Al 2 O 3 and Fe 2 O 3 content of 26.6 % which indicate that it does not satisfy the minimum value of 7 % (ASTM C618, 28) for a good pozzolana. ii) The drying linear shrinkage decreased, while consistency, initial and final setting times of cement increased with increase in GHA content. Therefore GHA can be used as a retarder, suitable for use in hot weather concreting, as well as in mass concreting and long haulage of ready mix concrete. iii) The compressive and flexural strengths of GHA-Mortar decreased with increase in GHA content. However, 1 % GHA is optimum content recommended for production of structural mortar, while GHA content of 2 % and above is recommended for non structural mortar. REFERENCES [1] A.M. Neville, Properties of concrete (Singapore: Fourth edition, Pearson Education, 23). [2] B.A. Alabadan, M.A. Olutoye, M.S. Abolarin and M. Zakariya, Partial replacement of ordinary Portland cement (OPC) with Bambara groundnut shell ash (BGSA) in concrete, Leonardo Electronic Journal of Practices and Technologies, 6, 25, [3] B.J. Olawuyi and K.O. Olusola, Compressive strength of volcanic ash/ ordinary Portland cement laterized concrete, Civil Engineering Dimension, 12(1), 21, [4] F. Singh and B. Diwakar, Nutritive value and uses of pigeon pea and groundnut, Skill development series, 14, 1993, Human resources development program, International Crop Research Institute for the semi arid tropics, Patancheru, Andhra Pradesh, India. [5] A.U. Elinwa and A. Awari, Groundnut-husk ash concrete, Nigeria journal of Engineering Management, 2(1), 21, [6] B.A. Alabadan, C.F. Njoku and M.O. Yusuf, The Potentials of Groundnut Shell Ash as Concrete Admixture, Agricultural Engineering International, The CIGR Ejournal, VIII, 26, 1-8. [7] ASTM C 618, Specification for coal fly ash and raw or calcined natural pozzolanas for use as mineral admixtures in Ordinary Portland Cement Concrete (West Conshecken, U.S.A: Annual book of ASTM standards, 28) [8] BS 882, Part 2, Grading limits for fine aggregates (London: British Standard Institution, 1992) [9] S. Sugita, On the Economical Production of large Quantities of Active RHA, International Symposium on Innovative World of Concrete, 2, 1993, [1] BS EN 196, Part 3, Methods of testing cement: Determination of setting time and soundness (London: British Standard Institution, 1995) [11] BS EN 196, Part 1, Methods of testing cement: Determination of strength (London: British Standard Institution, 1994) [12] BS EN 197, Part 1, Composition, Specification and Conformity Criteria for Common Cements (London: British Standard Institution, 2). [13] C. Jaturapitakkul and B. Roongreung, Cementing Material from Calcium Carbide Residue- Rice Husk Ash, Journal of Materials in Civil Engineering, 15(5), 23, [14] M. Gesoglu and O.E. Erdogan, Effect of mineral admixtures on fresh and hardened properties of self-compacting concretes, Binary, ternary and quaternary systems, Material Structures, 4, 27, [15] K. Ezziane, E.H. Kadri, A. Hallal and R. Duval, Effect of mineral additives on the setting of blended cement by maturity method. Materials and Structures, 43, 21,

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