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Influence of various densities and additives on mechanical properties of green foamed concrete.

INTRODUCTION

These days, demand and usage of foamed concrete as building material become privileged in construction industry due to its encouraging characteristics such as lighter weight, excellent thermal insulation and durable [1,2]. Foamed concrete is lighter than normal weight concrete due to artificial air bubbles trapped in its cement mortar by means of suitable foaming agent [3]. No utilization of coarse aggregate in fabrication of foamed concrete and fine aggregate (sand) can be partially of fully replaced by renewable materials such as pulverized fuel ash, silica fume, Coir fibres [4,5]. Moreover, foamed concrete has strong potential to be used as structural material with the minimum strength of 25 N/[mm.sup.2] [6]. Commonly, the strength value for foamed concrete of ranging densities between 800 kg/[m.sup.3] to 1000 kg/[m.sup.3] is from 1 N/[mm.sup.2] to 8 N/[mm.sup.2] respectively [7].

Density and porosity plays significant role in controlling the strength of foamed concrete [8]. Since early civilization, pozzolan materials has been practice to replace cement or sand in concrete either naturally or artificially [9]. Besides economic and environmental concerns, it has been proven to give enhancements to the strength of foamed concrete as its natural strength is low [10,11]. Mechanical properties has been one of the fundamental topic to be investigated but there is lack of knowledge in the effects of various types of additives on mechanical properties of foamed concrete [12].

Materials and Experimental Setup:

The samples of additives mentioned in the table 1 were prepared at the density of 1000 kg/[m.sup.3] because it has useful amount of mechanical properties and for comparison purpose. Totally 16 mixes were prepared and tested in the laboratory. Detailed explanations on the specifications of these additives are shown in the Table 1 below.

RESULTS AND DISCUSSION

This section presents detailed explanations on the investigations with different densities and various types and percentages of additives. Table 2 below shows clearly that density influences the mechanical properties due to pores production in foamed concrete. The strength of foamed concrete specimens is parallel with the ages. Low density consumed high dosage of foam, thus its density and value of strength were dropped [13]. High amount of pores induced will create weak cell structure between pores and matrix as there was insufficient surface area that connects pores and matrix. At low density, the pores will fuse close together and some of the bubbles merge with another and creates larger pores, thus cracks easily formed when external forces was applied on the concrete [14]. Compressive and flexural strength have similar strength development trend with tensile strength.

Table 3 above describes the changes in the compressive strength of each additives at different ages. Highest strength was produced with large inclusion of coir fibre as it has large diameter and high percentage of lignin. Also, it can provide a better compatibility between fibres and matrix due to its high failure strain. It did not cause the sample break apart but it will react as a micro crack agent. Next, both percentages of steel fibre have increased the strength of foamed concrete but does not show massive changes from age to age. high inclusion of fibers showed better compressive and flexural strength with some good additional effects because less amount of fibers are not evenly spread in the whole and later will lead to failure of the fiber where it unable to resist the load bearing at the very point of load [15]. Natural and synthetic fibres act as bridging component in foamed concrete during propagation of minor cracks [16]. 10% of silica fume (SLF-10) shows high early strength compared to other pozzolanic materials. It will improve the strength with the formation of discrete pores due to longer period of hydration process. Besides that, both PFA-15 and PFA-30 produced no improvement in the early strength but enormous improvement from 28 days to 180 days. Wood ash is a weak and unstable pozzolan, so that it was associated with PFA to avoid declining in concrete strength. Addition of wood ash must be lower to reach desired strength due to its high particle size. Ratio of silica/alumina will be increased due to the increasing percentage in POFA added and this will reduce the early strength development of foamed concrete [17].

Conclusion:

This study indicated that the mechanical properties of foamed concrete is primarily a function density and can be enhanced with the addition of various types of additives. Formation of larger size of pores and numbers of voids lead to weak bonding between matrix and pores, hence poor mechanical properties at low density. Among the additives, Coir fibre yield better enhancement of the mechanical properties. Short length coir fibres acts as reinforcement in foamed concrete and has high failure strain, thus it provides better compatibility between fibers and matrixes.

REFERENCES

[1] Kessler, H.G., 1998. Cellular lightweight concrete, Concr. Engineering International, pp: 56-60.

[2] Othuman Mydin, M.A., N. Md Sani, M. Taib, 2014. Industrialised Building System in Malaysia: A Review, Building Surveying and Technology MATEC Web of Conferences, 10: 01002.

[3] Othuman Mydin, M.A., 2011. Thin-walled steel enclosed lightweight foamcrete: A novel approach to fabricate sandwich composite. Australian J. of Basic & Applied Sciences, 5: 1727-1733.

[4] Othuman Mydin, M.A., N. Md Sani, A.F. Phius, 2014. Investigation of Industrialised Building System Performance in Comparison to Conventional Construction Method, MATEC Web of Conferences, 10: 04001.

[5] Jones, M.R., A. McCarthy, 2005. Preliminary views on the potential of foamed concrete as a structural material. Mag. Concr. Res., 57: 21-31.

[6] Othuman Mydin, M.A., Y.C. Wang, 2011. Structural Performance of Lightweight Steel-Foamed Concrete-Steel Composite Walling System under Compression. Journal of Thin-walled Structures, 49: 66-76.

[7] Othuman Mydin, M.A., N. Noordin, Z. Matori, N. Md Sani, N.F. Zahari, 2014. Experimental Investigation into Pull-Out Strength of Foamed Concrete Using Different Types of Screw, Building Surveying, MATEC Web of Conferences, 15: 01021.

[8] Mydin, M.A.O., A.F. Phius, N. Md Sani, N.M. Tawil, 2014. Potential of Green Construction in Malaysia: Industrialised Building System (IBS) vs Traditional Construction Method, E3S Web of Conferences, 3: 01009.

[9] Shankar Ganesan, Md Azree Othuman Mydin, Norazmawati Md. Sani, Adi Irfan Che Ani, 2014. Performance of Polymer Modified Mortar with Different Dosage of Polymeric Modifier, MATEC Web of Conferences, 15: 01019.

[10] M.A. Othuman Mydin, M.F. Mohamed Shajahan, S. Ganesan, N. Md. Sani, Laboratory Investigation on Compressive Strength and Micro-structural Features of Foamed Concrete with Addition of Wood Ash and Silica Fume as a Cement Replacement, MATEC Web of Conferences, 16 (2014) 01004

[11] Mydin, M.A., Y.C. Wang, 2012. Thermal and mechanical properties of Lightweight Foamed Concrete (LFC) at elevated temperatures. Magazine of Concrete Research, 64: 213-224.

[12] Soleimanzadeh, S., M.A. Othuman Mydin, 2013. Influence of High Temperatures on Flexural Strength of Foamed Concrete Containing Fly Ash and Polypropylene Fiber, Int. Journal of Engineering, 26: 365-374.

[13] Othuman Mydin, M.A., 2013. An Experimental Investigation on Thermal Conductivity of Lightweight Foamcrete for Thermal Insulation. Jurnal Teknologi, 63: 43-49.

[14] BCA Foamed concrete: Composition and properties. Report Ref. 46.042, Slough, 1994.

[15] Othuman Mydin, M.A., Y.C. Wang, 2011. Elevated-Temperature Thermal Properties of Lightweight Foamed Concrete. Journal of Construction & Building Materials, 25: 705-716.

[16] Mao, C.H., M.A. Othuman Mydin, X.B. Que, 2014. Analytical model to establish the thermal conductivity of porous structure, Jurnal Teknologi, 69: 103-111.

[17] Othuman Mydin, M.A., Y.C. Wang, 2012. Mechanical properties of foamed concrete exposed to high temperatures. Journal of Construction and Building Materials, 26: 638-654.

(1) M.A. Othuman Mydin, (1) S. Ganesan, (2) M. Y. Mohd Yunos

(1) School of Housing Building and Planning, Universiti Sains Malaysia, 11800, Penang, Malaysia

(2) Department of Landscape Architecture, Faculty of Design and Architecture, Universiti Putra Malaysia

ARTICLE INFO

Article history:

Received 12 October 2014

Received in revised form 26 December 2014

Accepted 1 January 2015

Available online 17 February 2015

Corresponding Author: Md Azree Othuman Mydin, School of Housing Building and Planning, Universiti Sains Malaysia, 11800, Penang, Malaysia

E-mail: azree@usm.my

Table 1: Materials and mix proportions of foamed concrete samples
with additives.

Materials                               Specifications
Cement                           Ordinary Portland cement CEM1
Sand                              River sand (5 mm sieve size)
Foaming Agent                Noraite PA-1 (1:33 with water volume)

Samples                      Remark     Mix ratio     Dry density
                                        (cement:     (Kg/[m.sup.3])
                                       sand:water)

Palm Oil Fuel Ash (25%)      POFA-25   1:1.5:0.45         1000
Palm Oil Fuel Ash (40%)      POFA-40   1:1.5:0.45         1000
Polypropylene Fiber (0.2%)   PF-0.2    1:1.5:0.45         1000
Polypropylene Fiber (0.4%)   PF-0.4    1:1.5:0.45         1000
Steel Fiber (0.25%)          SF-0.25   1:1.5:0.45         1000
Steel Fiber (0.4%)           SF-0.4    1:1.5:0.45         1000
Silica Fume (10%)            SLC-10    1:1.5:0.45         1000
Pulverized Fuel Ash (15%)    PFA-15    1:1.5:0.45         1000
Pulverized Fuel Ash (30%)    PFA-30    1:1.5:0.45         1000
Wood Ash (5%) & PFA (15%)    W5-P15    1:1.5:0.45         1000
Wood Ash (10%) & PFA (30%)   W10-P15   1:1.5:0.45         1000
Coir Fiber (0.2%)            CF-0.2    1:1.5:0.45         1000
Coir Fiber (0.4%)            CF-0.4    1:1.5:0.45         1000

Table 2: Mechanical properties of foamed concrete
samples with different densities

Sample             Mechanical Tests      Density       Ages of
                                      (kg/[m.sup.3])   Testing

                                                       7 days

Normal Foamed        Compressive           700           0.4
  Concrete--NFC1       Strength            1000          1.9
                    (N/[mm.sup.2])         1400          5.3
Normal Foamed          Flexural            700          0.27
  Concrete--NFC2       Strength            1000         0.85
                    (N/[mm.sup.2])         1400         2.01
Normal Foamed          Tensile             700          0.07
  Concrete--NFC3       Strength            1000         0.21
                    (N/[mm.sup.2])         1400         0.45

Sample             Ages of Testing

                   28 days   60 days   180 days

Normal Foamed        0.5       0.6       0.7
  Concrete--NFC1     2.1       2.2       2.2
                     7.1       9.4       9.9
Normal Foamed       0.34      0.40       0.40
  Concrete--NFC2    0.88      0.93       1.10
                    2.17      2.56       2.84
Normal Foamed       0.07      0.08       0.09
  Concrete--NFC3    0.22      0.25       0.25
                    0.58      0.75       0.78

Table 3: Mechanical properties of foamed concrete samples
with different types of additives.

Samples   Compressive Strength    Flexural Strength
          (N/[mm.sup.2])          (N/[mm.sup.2])

          Ages of                 Ages of
          Testing (days)          Testing (days)

           7    28    60    180    7      28     60    180
NFC-2     1.9   2.1   2.2   2.2   0.85   0.88   0.93   0.96
POFA-25   1.3   1.7   3.0   3.4   0.69   0.71   0.92   1.07
POFA-40   1.2   1.5   1.9   2.4   0.58   0.60   0.61   0.74
PF-0.2    1.8   2.1   2.5   3.1   0.84   1.11   1.19   1.25
PF-0.4    2.0   2.9   3.0   3.3   0.88   1.16   1.36   1.43
SF-0.25   2.0   2.5   2.5   2.7   0.83   0.88   0.90   0.98
SF-0.4    2.1   2.7   2.7   3.0   1.00   1.01   1.07   1.21
SLF-10    2.0   3.1   3.3   3.6   1.21   1.35   1.42   1.45
PFA-15    1.7   2.5   3.0   3.3   0.87   1.32   1.37   1.55
PFA-30    1.6   2.2   4.1   4.8   0.86   1.30   1.55   1.82
W5-P15    1.8   2.6   3.2   3.4   0.86   1.31   1.35   1.42
W10-P15   1.5   2.4   2.9   3.2   0.73   1.05   1.14   1.20
CF-0.2    2.2   2.7   3.2   3.3   1.24   1.39   1.52   1.55
CF-0.4    2.9   3.5   4.2   5.1   1.55   1.63   1.69   1.88

Samples   Tensile Strength
          (N/[mm.sup.2])

          Ages of
          Testing (days)

           7      28     60    180
NFC-2     0.21   0.22   0.25   0.25
POFA-25   0.18   0.28   0.29   0.30
POFA-40   0.13   0.14   0.15   0.16
PF-0.2    0.22   0.29   0.30   0.30
PF-0.4    0.26   0.36   0.36   0.37
SF-0.25   0.21   0.24   0.27   0.28
SF-0.4    0.25   0.28   0.30   0.33
SLF-10    0.25   0.29   0.34   0.35
PFA-15    0.19   0.29   0.32   0.36
PFA-30    0.18   0.27   0.39   0.42
W5-P15    0.20   0.27   0.29   0.34
W10-P15   0.17   0.21   0.23   0.31
CF-0.2    0.28   0.32   0.33   0.37
CF-0.4    0.30   0.41   0.41   0.42
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Article Details
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Author:Mydin, M.A. Othuman; Ganesan, S.; Yunos, M.Y. Mohd
Publication:Advances in Environmental Biology
Article Type:Report
Date:Mar 1, 2015
Words:2144
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