EXPERIMENTAL STUDY OF FLEXURAL STRENGTH
(OUT OF PLANE) ON WALL PANEL BY USING AUTOCLAVED AERATED CONCRETE AND BAMBOO REINFORCEMENT
Miftakhul Jannah
1, Sri Murni Dewi
2, Hendro Suseno
21
Student, Magister of Structural Engineering, Departement of Civil Engineering, Faculty of Civil Engineering, Brawijaya of University
2
Lecturer, Departement of Civil Engineering, Faculty of Engineering, Brawijaya of University
*Corresponding Author: [email protected]
ABSTRACT
The use of wall panels in the construction sector is tremendously familiar, because the implementation process is faster and more efficient. However, concrete wall panels are considered quite heavy, so that in this research will be discussed to learn more about wall panels by utilizing AAC lightweight bricks and bamboo reinforcement to reduce the panel's own weight without reducing its structural strength. In this present study, the specimen was made with a scale model to be tested for flexural capacity when receiving out of plane loads. Based on the research results, there were differences in the characteristics between AAC panels and ordinary reinforced concrete panels so that the flexural strength test with out of plane loading, AAC panels have increased flexural capacity more than ordinary reinforced concrete panels.
Keywords: Lightweight Brick, Autoclaved Aerated Concrete, Bamboo, Flexural Capacity, Out of Plane
1. INTRODUCTION
Nowadays, the construction sector is required to be done quickly and efficiently.
One of the methods considered fast and efficient at the present is building works by using pre-cast method. One of the examples of precast products that are widely used in Indonesia is wall panel.
Wall panel is a concrete product that has a typical shape and strength. Materials for making pre-cast concrete panels include: water, cement, fines aggregate, coarse aggregate, admixture, and reinforcement as a concrete binder. Concrete panels can be used as partitions of house walls, high rise buildings, commercial buildings, basement wall coverings, ground retaining cover on underpass and flyover buildings, guardrail on toll roads, and so forth.
The use of wall panels in the construction sector is tremendously familiar.
However, concrete wall panels in the market are considered quite heavy, so to anticipate this, it began planned a wall panel by using AAC as
a panel filler and bamboo as reinforcement.
Referring to the explanation above, it identified problems that would arise from the replacement of panel material that should have been made from ordinary reinforced concrete.
This research is the part of a grant research that examines concrete panels with AAC fillers and is restrained by bamboo reinforcement. The variation given is in the type of panel loading.
Loading was done by in-plane loading, out of plane loading, and cyclic loading. The writing of this scientific paper was focused on discussing panels that were loaded by out of plane.
The objective of this research is to analyze the flexural capacity and behavior of load (P) and deflection (Δ) correlation on AAC concrete panels and ordinary reinforced concrete panels when receiving out of plane loads.
2. LITERATURE REVIEW 2.1 Wall Panel
Wall is one of the elements that has
important roles. The functions of the wall are as follows [1]:
1. Function as a load bearer on it;
2. Function as a cover or room divider, both visual and aquatic;
3. Facing the outside and indoor space.
The panel wall is a sheet of material that is usually formed or cut into rectangles, which function as a decorative wall, sound dampening, heat retardant and can be combined with other supporting materials to maintain uniformity and appearance. Although there is no size limit specified for the material that fulfills the intended panel functions, the maximum practical size for wall panels has been suggested to be 24 inches by 8 feet, to enable transportation process [2].
The use of wall panels can reduce construction costs by giving a consistent appearance on the panel surface so that application of paint or other finishing materials is not needed. Wall panels also allow finishing to be done on one side only [2].
2.2 Concrete
Concrete compressive strength is the magnitude of load per unit area, which causes the concrete test specimen to disintegrate when it is loaded with a certain compressive force, which is produced by a press machine (Compression Testing Machine)[3].
(N/mm2) (1) Where :
σstress = Concrete compressive stress (N/mm2)
P = Testing load (N)
A = Plane cross-sectional area (mm2) 2.3 Autoclaved aerated concrete (AAC)
AAC lightweight brick is a cellular concrete in which air bubbles are caused by chemical reactions, AAC dough is generally composed of quartz sand, cement, chalk, a little gypsum, water, and aluminum paste as an improver (chemical air filler) [4]. AAC with lightweight brick compressive strength produced by PT. Surya Indogreen Perkasa used in this study has a compressive strength of 4 MPa.
2.4 Bamboo
The reason for using bamboo as an alternative reinforcement is because its tensile
strength is so great that it almost matches the tensile strength of steel which can even reach 370 MPa [5].
The strength of a bamboo to resist tensile forces depends on the part of the stem used.
The tip has a strength of tensile force of 12%
lower than the base [6].
Figure 1. Test Results of Bamboo and Steel Tensile Strength [5]
In Figure 1, it can be seen than in the testing results of bamboo tensile strength, it obtained the testing results of original bamboo tensile strength which is quite high, namely almost 5000 kg/cm.
2.5 Wiremesh
Wiremesh is a high melting voltage fabricated iron fabric consisting of two layers of steel that are crossed perpendicular to each other. Each crossing point is welded automatically into one, producing a homo- geneous cross section, without losing strength and cross-sectional area consistently [7].
2.6 Panel loading
For this study, loading is done by out of plane loading. The out of plane loading it self is a long structure (relatively long compared to the latitude dimension) where the load works along the structure in the direction of the X-Y plane, (and both ends of the structure are in practical conditions which cannot move). In this condition, the displacement component or displacement in the z direction, i.e. ω, , the magnitude of 0 (zero), and other displacement components respectively i.e. u and v, are functions of x and y only. This condition resulted εz=0; γxz=0; γyz=0 [8].
Figure 2. Out of Plan Load Modeling 2.7 Deflection of reinforced concrete beams
Deflection in structural rods is the function of the length of the placement span or condition of the edges, the type of loading and flexural stiffness of the EI of the element. The flexural stiffness of EI beams can be estimated by using concrete modulus of elasticity, and the moment of inertia of the cross section of crackless reinforced concrete [9]. For normal concrete, the concrete modulus of elasticity can be taken of:
(in MPa) (2) Where:
Ec = Concrete modulus of elasticity (MPa)
= Concrete quality (MPa)
Deflection of the beam occurs due to the strain that arises caused by external loads. In a simple beam, the maximum deflection with a centralized load can be calculated by the equation:
(3) Where:
= Deflection of the beam (mm) P = load (N)
L = length of span on the beam (mm) E = modulus of elasticity (MPa) I = moment of inertia on the beam (mm4) 2.8 Ductility
Ductility is the ability of a material or structural element or structural system in a complex way in experiencing large deformations and in some cycles of deformation between post yields (elastic limit) and still maintain strength without a significant decrease [10].
Ductility can be formulated as a comparison between deformation at the time of the ultimate and deformation at the time of the first yield. Meanwhile, the determination of the yield point value is shown in Figure 3. From several alternatives suggested in determining the yield point, many researchers have used the D option or yield point determination based on the equivalence of the melting point at the time of elasto-plastic.
Figure 3. Yield Point Determination Alternative [10]
2.9 Modulus of Elasticity
Modulus of elasticity is a number used to measure an object or material resistance in experiencing elastic deformation when force is applied to the object [10].
The modulus of elasticity in the panel is obtained from the test results in the laboratory.
The reading results on the dial gauge will be compared with deflection reading. Afterwards, the results on the dial gauge reading will be converted into voltage data working on the panel. Meanwhile, the deflection readings in LVDT will be processed into strain data on the outer fibers of the tensile concrete section.
Thus, we can obtain the Modulus of Elasticity of AAC concrete panels from the results of experiments in the laboratory.
3. METHODOLOGY 3.1 Research Parameter
The design parameters used in this study are as follows:
1. Wall panels with a size of 40 cm x 80 cm x 3.5 cm and 60 cm x 120 cm x 5 cm using bamboo reinforcement and with and without using Autoclaved Aerated Concrete (AAC) material.
2. Concrete and mortar quality of f’c = 5 Mpa 3. Bamboo main reinforced uses 5D10
4. The tensile stress of the bamboo reinforcement is in accordance with the tensile test following the regulations/
testing standards for steel reinforcement based on Indonesian National Standard.
5. Testing is done after the age of the wall panel reaches 28 days.
6. Testing will be carried out with a simple roll pins and by loading 1 point in the middle of the span to facilitate the calculation analysis.
Table 1. Specimen Specification
Figure 4. Specimen Detail 3.2 Flexural Strength Test
Some of the research activities carried out in laboratory tests are as follows:
1. Taking test specimen from the care place after 28 days;
2. Placing test specimen on the Loading Frame centrically;
3. Applying dial gauge and LVDT at the specified location then setting the readings;
4. Starting the test by giving axial vertical load on the hydraulic jack constantly;
5. Recording the deformation of each loading and strain that occurs in the reading of the data logger tool;
6. Performing the steps above in accordance with the number of test items that will be examined.
7. After all data was collected, then an analysis of the research results was carried out.
Experimental analysis was then compared to theoretical analysis. Afterwards, conclusions and general research suggestions were made.
Specimen code Dimension (cm)
Number
(Unit) Remarks
DBR 1 1D DBR 2 1D DBR 3 1D
40 x 80 x 3.5 cm 3 unit Small AAC specimen
TBR 1 1D 40 x 80 x 3.5 cm 1 unit Control specimen
DBR 1 2D DBR 2 2D DBR 3 2D
60 x 120 x 5 cm 3 unit Large AAC specimen
TBR 1 2D 60 x 120 x 5 cm 1 unit Control specimen
(a) AAC panel size 40 x 80 cm and 60 x 120 cm
(b) Panel control size 40 x 80 cm and 60 x 120 cm
Figure 5. Sketch of Tool Setting and Flexural Strength Testing
4. RESULTS & DISCUSSION 4.1 Panel Specimen
The average weight of AAC wall panels measuring 40 x 80 x 3.5 cm is 18.23 kg or 4.42 kg lighter than normal concrete panels of the same size which weighs 22.65 kg. Meanwhile, for AAC walls, the size of 60 x 120 x 5 cm is 46.45 kg or 14.55 kg lighter than normal
concrete panels of the same size that weighs 61 kg. The detail of the weight panel properties test results can be seen in Table 2. Below is the result of weight measurement on the wall panel with the following details:
Table 2. Panel Test Specimen Weight Test Results
4.2 Panel Flexural Capacity Analysis The calculation for this composite concrete panel is carried out with an approach to equalize the value of each material modulus of elasticity. Thus, some of the materials used as composers of concrete panels have the same modulus of elasticity but have changes in area.
After obtaining the modulus of elasticity of the composite panel, the data is processed to obtain
the value of inertia which is then used to analyze the value of the crack moment, and is converted to the value of the crack load on the panel. Following are the theoretical calculation results of each panel type which will be compared to the experimental panel test results in the laboratory
Table 3. Panel Flexural Capacity Calculation Results
No Code Dimension
(cm) Cast Date Weight
(Kg) Remarks
1 TBR 1 TL 40 x 80 01 July 2019 22.65 Panel control 2 DBR 1 TL 40 x 80 09 July 2019 19.20 Panel AAC 3 DBR 2 TL 40 x 80 08 July 2019 17.95 Panel AAC 4 DBR 3 TL 40 x 80 02 July 2019 17.55 Panel AAC 5 TBR 1 TL 60 x 120 07 July 2019 61.00 Panel control 6 DBR 1 TL 60 x 120 06 July 2019 45.15 Panel AAC 7 DBR 2 TL 60 x 120 08 July 2019 46.60 Panel AAC 8 DBR 3 TL 60 x 120 04 July 2019 47.60 Panel AAC
Specimen (kg.m) (kg)
Panel without AAC (40 x 80 cm) 0,129 64,9
Panel without AAC (60 x 120 cm) 0,388 129,2
Panel AAC (40 x 80 cm) 0,293 146,6
Panel AAC (60 x 120 cm) 0,956 318,8
4.3 Panel Flexural Strength Test Results Panel testing is carried out by giving a uniform load. Meanwhile, the two columns that curb the panel will be held by using roll pins.
By applying force in the middle of the span, the support of the roll pins or commonly referred to as the three point flexural test will occur. The test results that have been carried out can be seen in Figure 7.
Figure 7. The Test Results of Out of Plane Loading on The Panel Measuring 40 x 80 cm From Figure 7, it can be seen that in
the testing of panel measuring 40 x 80 cm, ordinary reinforced concrete panels with TBR 1 TL 2B specimen code are able to accept crack loads of 50 kg; meanwhile concrete panels using AAC with DBR 1 TL 2B specimen code, DBR 2 TL 2B, and DBR 3 TL 2B are able to accept crack loads of 100 kg, 75 kg and 75 kg, respectively,
so that the average flexural capacity test results on AAC wall panels measuring 40 x 80 cm is 83.33 kg . This shows that the flexural capacity of the wall panels using AAC and bamboo reinforcement is higher than the wall panels with the ordinary reinforced concrete with bamboo reinforcement composition or with an increase in percentage reaching 66.67%
Figure 8. The Test Results of Out of Plane Loading on The Panel Measuring 60 x 120cm
Load (kg) Load (kg) Load (kg)
Load (kg) Load (kg)
Deflection(mm) Deflection(mm)
Deflection(mm) Deflection(mm)
Load (kg) Load (kg) Load (kg)Load (kg)
Deflection(mm) Deflection(mm)
Deflection(mm) Deflection(mm)
In Figure 8, it can be seen the results of panel flexural capacity measuring 60 x 120 cm, ordinary reinforced concrete panels with TBR1 TL 1B specimen code is able to accept crack loads of 100 kg; meanwhile concrete panels using AAC with DBR 1 TL 1B, DBR 2 TL 1B, and DBR 3 TL 1B specimen code are able to accept crack loads of 125 kg, 100 kg and 100 kg, respectively, so that the average flexural capacity test results on AAC wall panels measuring 60 x 120 cm is 108.33 kg.
This shows the capacity of the wall panels using AAC and bamboo reinforcement on panels measuring 60 x 120 cm also experiences increased flexural capacity in the crack load, ie with a percentage increase of 8.33% of the wall panels with ordinary reinforced concrete with bamboo reinforcement with the same size.
4.4 Analysis of calculation and testing results
The test results in the laboratory will be used as a comparison on the results of an analytical panel calculation. The difference between the test results and the calculation results in an analysis will be used as a multiplier coefficient given the variety of materials used and the adhesion between the materials that exist in the composite concrete panel.
The summary of the results of the testing series that have been carried out and the results of the calculation of the crack capacity of the concrete panel can be seen in Table 4
Table 4. Summary of Test Results and Crack Load Analysis (Pcr) Specimen
Pcr Percentage of tests
against theoretical analysis Analysis
(Kg)
Testing (Kg)
Panel without AAC (40 x 80 cm) 64.90 50.00 77%
Panel without AAC (60 x 120 cm) 129.23 100.00 77%
Panel AAC (40 x 80 cm) 146.64 83.33 57%
Panel AAC (60 x 120 cm) 318.79 108.33 34%
From Table 4, it can be concluded that the results of the testing in the laboratory are smaller than the results of the Analysis calculation. The test results on wall panels with ordinary reinforced concrete with bamboo reinforcement showed a consistent amount of analysis results of 77% either in panels with dimensions of 40 x 80 cm or 60 x 120 cm.
Whereas on the wall panel with the composition of AAC and bamboo reinforcement with dimensions of 40 x 80 cm and 60 x 120 cm respectively, they were only able to withstand crack loads of 57% and 34%
of the crack load calculation analysis results theoretically. The difference in capacity between bamboo reinforced wall panels without AAC and with AAC showed that adding AAC to the center of the cross section makes the panel to e non-monolithic. From the
test results in the laboratory, it revealed that a horizontal crack occurred. These horizontal cracks indicated that the panel slipped between each material.
4.5 Correlation between Load and Deflection
Load given to the panel in stages will make the panel deflected in the direction of the given load. In this study, it is assumed that the work load is the load caused by the wind that will hit the wall. The purpose of this lab test, in addition to knowing the capacity of the panel that gets out of plane load, is to study the behavior of the physical form changes from the panel when experiencing loading. In the following Table 5, it represents the amount of deflection that occurs on a wall panel when given out of plane load.
Table 5. Wall Panel Deflection at The Time of P Crack and P Ultimate Load
(Kg)
Deflection (mm)
Panel 40 x 80 cm Panel 60 x 120 cm
TBR DBR 1 DBR 2 DBR 3 TBR DBR 1 DBR 2 DBR 3
0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
25 0.18 0.44 0.19 0.10 0.18 0.24 0.20 0.10
50 *0.39 0.45 0.39 0.43 0.41 0.42 0.55 0.27
75 0.62 0.58 *0.61 *0.74 0.50 0.75 0.57 0.31
100 2.42 *0.74 1.92 1.32 *1.08 0.93 *0.95 *0.80
125 3.94 1.33 *3.69 2.52 4.07 *0.93 2.60 0.80
130 4.73 2.23 *3.01 4.68 1.22 2.97 0.81
150 7.86 5.79 7.14 *2.38 4.48 0.85
175 12.11 2.67 *11.30 6.72 1.31
200 *20.03 *16.09 *11.05 *2.71
*) Deflection at the time of Pcr and Pu
On wall panel measuring 40 x 80 cm, panels with AAC composition obtained an average crack load (Pcr) that occurred when the panel was loaded with 75-100 kg, and experienced an average deflection of 0.60 - 0.74 mm; whereas, on panels measuring 60 x 120 cm, the average panel experienced cracking when receiving loads of of 100-125 kg with a magnitude of deflection from 0.80 to 0.95 mm. Thus, it can be concluded that in a larger plane, the panel can receive a greater load to achieve its crack.
The specimens made in this study were found that the AAC wall panels experienced slippage, or not working between the materials simultaneously. This can be seen by the inconsistency of the ultimate capacity of the panel and also the inconsistency of deflection value that occurred when reaching the ultimate point.
Physically, it can be seen the side of the panel experienced horizontal crack. Horizontal cracks that occurred were right in the middle (h) of the panel where the bamboo reinforcement was located. It can be seen in Figure 9.
Figure 9. Differences in the shape of cracks between wall panels with AAC and without AAC
In Figure 9., it showed that when the ultimate crack occurred, in addition to experiencing a crack in the tensile area, the panel also experienced horizontal crack on the side of the panel. This horizontal crack occurred on the panel with the AAC composition. Whereas on panels with ordinary reinforced concrete, it did not have horizontal cracks. Therefore, it can be concluded and henceforth to be input in the next research is that it needs an additional anchor to unite the tensile and compressive sides to avoid horizontal cracks or slippage between materials.
5. CONCLUDING AND SUGGESTION
5.1 Conclusion
Based on the results of the research that has been done, the conclusion is as follows:
1. Characteristics differences of the weight of ordinary reinforced concrete wall panels and AAC panels both on wall panels with a size of 40 x 80 x 3.5 cm and a size of 60 x 120 x 5 cm have a considerable difference;
2. There is a difference in the flexural capacity caused by out of plane flexural load in ordinary reinforced concrete panels and AAC panels. From the test results in the laboratory, both AAC panels on panels with dimensions of 40 x 80 x 3.5 cm and 60 x 120 x 5 cm have both increased flexural capacity compared to ordinary reinforced concrete panels. However, the enlargement of dimensions in AAC
concrete panels is not directly proportional to the increase in its flexural capacity;
3. From the observations in the laboratory, the panel with AAC has an average value of deflection at crack loads (Pcr) which is greater than that of ordinary reinforced concrete panels, both on wall panels measuring 40 x 80 x 3.5 cm or panels measuring 60 x 120 x 5 cm; thus, it can be concluded that the panels with AAC are more ductile than ordinary reinforced concrete panels.
5.2 Suggestion
Based on the research that has been done, there are several suggestions that can improve or develop this research further. The suggestions are as follows:
1. It is necessary to conduct studies and further researches on the form of connection (interlocking) between panels so that these wall panels are ready to be produced and marketed en masse;
2. To observe changes in the flexural moment that occur, it is better to add the strain reader parameters. It is recommended to apply a reinforcement bamboo strain sensor and also to apply a concrete strain sensor in the outer tensile concrete. Thus, it will get the form of strain diagram and flecural moments that are more specific;
3. The loading interval should also be minimized in order to get more detailed results;
4. It needs additional adhesive or anchor to unite the flexural side and the compressive side so
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