International Journal of Engineering Advanced Research (IJEAR) eISSN: 2710-7167 [Vol. 3 No. 1 March 2021]
Journal website: http://myjms.mohe.gov.my/index.php/ijear
THE PERFORMANCE OF INTERLOCKING COMPRESSED EARTH BRICK UNITS IN TERMS OF COMPRESSIVE
STRENGTH
Amira Ameer1*, Abdul Karim Mirasa2, Hidayati Asrah3, Nurmin Bolong4, Habib Musa Mohamad5 and Lim Chung Han6
1 2 3 4 5 6 Faculty of Engineering, Universiti Malaysia Sabah, Kota Kinabalu, MALAYSIA
*Corresponding author: [email protected], [email protected], [email protected]
Article Information:
Article history:
Received date : 5 March 2021 Revised date : 27 March 2021 Accepted date : 30 March 2021 Published date : 31 March 2021 To cite this document:
Ameer, A., Mirasa, A., Asrah, H., Bolong, N., Mohamad, H., & Lim, C.
(2021). THE PERFORMANCE OF INTERLOCKING COMPRESSED EARTH BRICK UNITS IN TERMS OF COMPRESSIVE STRENGTH.
International Journal Of Engineering Advanced Research, 3(1), 83-93.
Abstract: This study presents a compressive strength test of ICEB units with two different methods under five condition. The first method requires that the tongue be removed by grinding the surface of the samples until the top and bottom surface are parallel with a tolerance of 0.1 mm for every 100 mm and tested with mortar filling (condition i) and without mortar filling (condition ii). The second method used steel plate which capped both the bed surfaces of the samples in order to provide the same parallel planes prior to testing for air-drying (condition iii), wet (condition iv) and oven-drying tests (condition v).
The average compressive strength for the five conditions at 28 days is 5.11 N/mm2, 5.14 N/mm2, 5.66 N/mm2, 3.29 N/mm2 and 7.08 N/mm2 respectively. The ICEB units had compressive strength of more than 5 N/mm2 for all conditions, which is the minimum strength for the load- bearing brick, except for the wet condition. ICEB units tested using steel plate have a higher compressive strength compared to samples with the tongue removed. Whereas the compressive strength of ICEB units with tongue removed tested with mortar filling is 1% and 0.6% higher than that samples without mortar filling at 7 days and 28 days respectively. The ICEB units can therefore be used as load-bearing bricks and can be tested using steel plate without the need for tongue removed and mortar filling.
1. Introduction
Interlocking Compressed Earth Brick (ICEB) is one of the alternative methods for Industrialized Building System (IBS) that has been developed to comply with the green building construction standard. It is intended to replace the conventional fire clay brick method that requires intensive energy and high in CO2 emissions from fuel combustion alone (Han et al., 2018). The main materials used for the production of ICEB units are soil, stabilizers such as cement or lime, sand and water. Instead of using the firing method, ICEB is produced by using manual compaction machine or high-pressure hydraulic compaction machine, which indirectly contributes to its strength.
The current market worldwide demonstrates that ICEB varies in shape, size and material composition, but has the same method of construction that is dry stacked, also known as mortarless bricks (Tonduba, Mirasa, & Asrah, 2020). Since the ICEB can omit the installation and dismantling of beams and column’s formwork, the construction phase can be sped up indirectly.
In addition, the interlocking characteristic of the ICEB units with tongue and grooves allows steel to be inserted inside the bricks, making ICEB wall construction faster and easier. Dowels will interlock the ICEB units, and the wall will align vertically and horizontally automatically (Saari, Bakar, & Surip, 2017).
2. Compressive Strength of ICEB
The degree of compaction and the age of the ICEB samples both influence the compressive strength of the ICEB (Syaizul, Abdullah, Mirasa, & Lim, 2020) whereas according to Patankar, Gowda, & Td (2018), the factors affecting the compressive strength of the bricks are the materials, the method of manufacture of the brick and rate of loading. There is no standard test to determine the compressive strength of the ICEB units. The majority of researchers therefore determine the compressive strength of the ICEB unit according to ASTM C 67, BS EN 772-1, EN 1052-1 or BS 3921 standard. According to Hendry et al. (2014) in book of Design of Masonry Structures, the minimum average compressive strength of the load-bearing brick is 5 N/mm2 which comply with minimum requirement specified in BS EN 1998 and BS 3921. However, according to MS 76:
1972, the minimum compressive strength is 2.8 N/mm2 for bricks that is non-load bearing while 5.2 N/mm2 for load-bearing bricks used in one and two-storey dwelling houses.
Research conducted by Al-fakih et al., (2018) on the hollow and solid rubberized interlocking bricks shows that the Coefficient of Variation (CoV) of the compressive strength was 5.14% for hollow brick and 11.64% for solid brick. Meanwhile, Sasui, Jinwuth, & Hengrasmee (2017), found that CoV in the compressive strength of handmade adobe brick (sun dried brick) was 59.21%, which is higher than other research where CoV values are up to 28.51%.
Keywords: Interlocking Compressed Earth Brick, Compressive Strength, Wet Strength, Dry Strength, Oven Dry Strength, Mortar Filling, Without Mortar Filling.
The compressive strength of the ICEB unit is usually measured in both dry and wet conditions, with the wet condition indicating the worst case with the lowest compressive strength value (Syaizul et al., 2020). This is due to the liquefaction of unstabilized clay minerals and the formation of pore water pressures in the matrix of bricks (Riza, Abdul Rahman, & Ahmad Zaidi, 2011).
Study by Muntohar (2017) on the effect of lime and rice husk on the compressive strength of compressed stabilised earth brick under dry and wet conditions also found that the compressive strength of wet samples is generally lower than the sample with dry condition. This characteristic validates a loss of strength during the immersion.
Zakaria Che Muda, Al-Ademic, MohdSidek, & Nawfal S. Farhan (2013), studied soil-cement bricks by replacing the cement with pulverised fuel ash and removing the tongue and groove under two conditions that filled the frogs with mortar filling and without mortar filling. The study showed that the average of compressive strength without mortar fill for 0%, 10% 20% and 30% of PFA was 10.5, 7.72, 8.48 and 6.59 N/mm2, with mortar fill being 13.52, 9.42, 9.86 and 7.81 N/mm2 respectively. This shows that the mortar filling increases the strength of the soil-cement brick.
Mohammed (2016), investigated the mechanical properties of soil cement interlocking (SCI) bricks and found that the compressive strength of (SCI) bricks without mortar fill ranged from 7.73 to 12.33 N/mm2, while the compressive strength of (SCI) mortar-filled bricks ranged from 12.41 to 15.10 N/mm2.
The strength properties of ICEB units were studied using a steel plate at the top and bottom of the sample to create a flat surface prior to testing and the average compressive strength found to be 19.15 N/mm2 for wall brick (standard brick), beam brick 16.99 N/mm2, column brick 13.18 N/mm2 and half brick 11.79 N/mm2 (Saari et al., 2017). Whereas, M M Nasri, H Asrah, S Dullah, & A K Mirasa (2020), study the effect of moisture content and curing on the interlocking compressed brick’s properties. Steel plate was used to form a plane surface prior to testing and all ICB samples containing 18% of moisture surpassed the minimum compressive strength requirement (7 N/mm2) based on MS 76:1972. This study aims to investigate the compressive strength of standard ICEB units by using two different method with five different condition as stated in method section below.
3. Method
In this study, the compressive strength of the ICEB units was tested using BS EN 772-1 standard under two different test methods with five different conditions. The first method requires that the tongue to be removed and that the samples be tested under two conditions; (i) without mortar infill and (ii) with mortar infill. The second method was capped both sides of each samples with steel plates to ensure that the two bed surfaces had a flat surface for compression in three different conditions; (iii) air-dry condition, (iv) wet condition and (v) oven-dry condition.
3.1 Materials
Materials used to produce the ICEB have been attained locally such as cement, sand, soil, and water. Table 1 shows the physical properties of soil used in this study. The soil with 8% fines and classified as well-graded sand with clay (SW-SC) according to soil classification chart by Unified Soil Classification System (USCS) ASTM D 2487 free of organic material was dried and ground using a crushing machine. The maximum dry unit weight is 1687.88 Kg/m3, the optimum moisture content is 18.50%, the liquid limit is 38%, the plasticity index is 17.75% and the soil’s specific gravity is 2.86.
Table 1: Physical Properties of Soil Physical properties Value Maximum Dry Unit Weight
Optimum Moisture Content
% passing No. 200 sieve (75μm) Liquid Limit
Plasticity Index Specific Gravity USCS Soil Classification
1687.88 Kg/m3 18.50 %
8%
38%
18.75%
2.86 SW-SC
The river sand was prepared in accordance with the ASTM C778 standard. The type of cement used as binder in ICEB units and as a mortar filling in compressive strength test was Ordinary Portland Cement (OPC) and Table 2 and Table 3 shows the physical and chemical properties of the OPC.
Table 2: Physical Properties of OPC Physical
properties
Particle Size, d10 (μm)
Mean Particle Size, d50 (μm)
Particle Size, d90 (μm)
Specific gravity
OPC 0.08 1.59 32.25 3.05
Table 3: Chemical Oxides Properties of OPC Chemical
Properties (%)
SiO2 Al2O3 Fe2O3 CaO MgO LOI OPC 13.44 3.48 2.93 71.35 2.50 3.07
3.1.1 Samples
The ICEB units were manufactured and produced in Interlocking Brick Factory at Faculty of Engineering, Universiti Malaysia Sabah (UMS). The factory produces three types of ICEB units which are standard brick, half brick and U-brick. This study focuses on the standard ICEB unit with a dimension of 250mm x 125mm x 100mm (length x width x height). Figure 1 shows the standard ICEB unit with the surface of the tongue and groove bed. ICEB units were produced by mixing soil, sand and cement in dry conditions. Water was gradually added up to 13% range of moisture content achieved. The wet mixture was filled into the mould, compressed using hydraulic compression machine, and then cautiously removed from the compression mould. It was then placed in open area for moist curing process. The ICEB units were air dried for 24 hours and cured twice a day for 7 days. After that, the curing was reduced to twice a week for up to 28 days curing.
Subsequently, the ICEB units were divided into five groups of samples for two different test
methods with five different conditions, as indicated in the above-mentioned method. The sampling method was in accordance with the relevant part of EN 771, where the minimum number of samples for each test is six.
(a) (b)
Figure 1: Standard ICEB unit (a) surface with tongue; (b) surface with groove
3.1.2 Procedures
The compressive strength test was performed based on the specifications of the BS EN 772 -1.
The first method requires that the tongue to be removed by grinding the surface of the samples until the top and bottom surface are in parallel planes with a tolerance of 0.1 mm for every 100 mm. Samples were tested without a mortar fill for condition (i) and filled with 1:3 mortar, 24 hours prior to the compressive strength test for condition (ii). The second method used steel plate, which capped both the bed surfaces of the samples in order to provide the same parallel planes prior to the condition testing (iii), (iv) and (v). Figure 2 and Figure 3 show the condition of the sample for both methods.
(a) (b)
Figure 2: Standard ICEB unit after tongue removed (a) no mortar fill; (b) mortar fill.
(a) (b)
Figure 3: (a) Steel plate; (b) Steel plate capped both bed surface of standard ICEB unit
Air-dry condition samples were tested according to the procedure in which the samples were dried in the oven at 1050C ± 50C for at least 24-hour and cool at room temperature for at least four hours before testing. Wet-condition samples were tested by immersing the samples in water at temperature of 200C ± 50C for 24 hours and drained for 20 minutes before testing. While the oven- dry condition requires the samples to be dried in the oven at 1050C ± 50C until the constant mass is reached where the mass loss between two measurements is less than 0.2 % of the total mass at a 24-hour interval. The samples were then tested by Universal Testing Machine for compressive strength with a loading rate of 4 MPa/s.
3.2 Measurement
The compressive strength of each ICEB unit was calculated by dividing the maximum load achieved (N) by its loaded area (mm2). The net loaded area for condition (i) was calculated based on the smaller net loaded area of the two frogged bed face while the net loaded area for condition (ii), (iii), (iv) and (v) was calculated based on the basis of the gross area of the ICEB unit.
4. Results and Discussion
The ICEB units were tested for five conditions using a compressive strength test at 7 and 28 days of age. According to the standard specification, the top and bottom surface of the sample shall be in parallel and shall not depart from true plane surface with a tolerance of 0.1 mm for every 100 mm prior to the test. In addition, any tongue and grooves must be removed and the ICEB unit with frogs assessed as having a net loaded area of less than 35% of the bed face shall be tested by removing or filling the frogs (BS EN 772-1, 2011). However, in this study, the ICEB units had a frog with a net loaded area of more than 35%, which was 51%. The ICEB units can therefore be tested without removing or filling the frogs according to BS EN 772-1 standard. Previous researcher Sasui et al., (2017) stated that the CoV acceptable value is 28.51%. Therefore, based on this research, the CoV value shows in Table 4 ranging from 5.60% to 28.52% are acceptable.
Table 4: Compressive Strength at 28 days Method Test Condition Mortar
Fill
Average Strength (N/mm2)
Standard Deviation
CoV (%)
Range (N/mm2) Cut Tounge
Cut Tounge Steel plate Steel plate Steel plate
Air-dry Air-dry Air-Dry Wet Oven-Dry
No Yes No No No
5.11 5.14 5.66 3.29 7.08
0.90 0.29 0.71 0.94 1.41
17.56 5.60 12.50 28.52 19.95
3.41-5.83 4.82-5.37 5.10-6.73 2.52-4.72 5.89-9.39
4.1 Effect of Mortar Filling on Compressive Strength
The results of the compressive strength test are shown in Figure 4. From Figure 4, there is only a slight difference between the strength of ICEB units tested without mortar filling and with mortar filling. ICEB units tested at 7 days age without mortar filling is 2.98 N/mm2 and with mortar filling is 3.01 N/mm2 with 1% increase in strength while samples tested at 28 days increase 0.6% in strength from 5.11 N/mm2 for sample without mortar filling and 5.14 N/mm2 sample with mortar filling. Although there is an increase in compressive strength due to mortar filling, the percentage is pretty low.
Figure 4: Compressive Strength vs Sample Age
4.2 Effect of Testing Method (Cut Tongue vs Steel Plate)
Figure 5 shows the comparison between the compressive strength of the ICEB units tested under condition (i) and condition (iii) where condition (iii) gave a higher compressive strength of 3.64 N/mm2 and 5.66 N/mm2 compared to condition (i) which 2.98 N/mm2 and 5.11 N/mm2 for both sample ages. Testing the ICEB units by cutting the tongue before testing may reduce the strength of the brick due to physical damage and cracking during grinding. Therefore, capped both bed surface by using steel plate as shown in Figure 3 before testing could minimize the damage and cracking cause by grinding.
Figure 5: Compressive Strength Condition (i) and Condition (ii)
4.3 Effect of Moisture Content on ICEB Compressive Strength
In compliance with British Standard EN 772-1, the conditioning prior to testing of the ICEB units shall, as appropriate, use the prescribed moisture regime or the prescribed moisture condition. The conditioning method described in the above section of procedures and steel plate were used prior to testing. Figure 6 shows that the oven-dry condition has the highest compressive strength for both ages, followed by air-dry and wet conditions of 7.08 N/mm2, 5.66 N/mm2 and 3.29 N/mm2 for 28 days respectively.
According to this study, ICEB units have the lowest compressive strength value in wet conditions, which is comparable to research carried out by Abdullah, Razman, Noh, & Ibn Abd Wahid (2010) which stated that as moisture content increase, the compressive strenght will decrease due to the formation of pore water pressures and water cause the binder to soften. Since the average compressive strength in air and oven-dry conditions exceeds the minimum requirement of 5 N/mm2 of BS EN 1998 and BS 3921 standard specifications, the standard ICEB units can be used as load-bearing bricks.
Figure 6: Compressive Strength Condition (iii), Condition (iv) and Condition (v)
5. Conclusion
This article discusses the outcomes of the laboratory investigation's ICEB compressive strength tests. The conclusions to be drawn are as follows.
1. ICEB units which are capped before testing on both bed surface gives higher value compared to cutting the tongue of the samples to provide parallel planes prior to testing.
2. The compressive strength of ICEB units with tongue removal and mortar filling is 1% and 0.6% higher than that of tongue removal and without mortar filling at 7 days and 28 days respectively. The ICEB units can therefore be tested without mortar filling, as indicated in BS EN 772-1, as the net loading area of the sample with frogs is more than 35%.
3. The compressive strength of the standard ICEB units in oven-dry condition is higher than in air-dry and wet ICEB condition.
4. The standard ICEB units may be used as load bearing masonry walls as their lowest compressive strength under all conditions (with the exception of wet conditions) is 5.11 N/mm2 above the minimum requirement of 5 N/mm2.
6. Acknowledgement
The author would like to thank the Ministry of Higher Education Malaysia research grant (LRGS 0008-2017) and Universiti Malaysia Sabah, UMSGREAT, Grant no. GUG0394-2/2019 for their financial support.
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