International Research Journal on Engineering Vol. 2(1), pp. 001-007, January, 2014 Available online at http://www.apexjournal.org

©2014 Apex Journal International

Full Length Research

Strength characteristics of earth bricks and their application in construction

Mbereyaho Léopold1*, Twubahimana Joseph Désiré2 and Mureramanzi Germain3

1Institution: University of Rwanda, College of Science and Technology (COSTECH) Postal address: BP 3900 Kigali,

Rwanda. 2Institution: Saint Joseph Integrated Technical College, P.O. Box 1330 Kigali, Rwanda.

3Kicukiro College of Technology; IPRC/Kigali. Rwanda.

Accepted 17 December, 2013

Worldwide, technology is facing the great challenge which is “environmental destruction” through various factors among which high consumption of some natural resources contributes significantly. The foresight of this research paper is to search for alternative solution to the high consumption of valley clay as main material during bricks production by providing and supplying burnt earthen bricks which will firstly serve as “Environmental friendly “in fact that it will enhance local technical skills and rely on available local raw materials, secondly will be” Economical based “in fact that it will be marketable within local context at reasonable cost and finally the product will offer sufficient compressive strength to be accepted as Engineering material reflecting sustainability in modernity construction. The main objective of this work is to find out an alternative material to the ordinary burnt valley clay brick by replacing them as raw material basing on comparative analysis of compressive strength characteristics between finished mud brick and ordinary burnt valley clay brick and techniques to apply on that material so that the finished made brick offers significant required strength. The research is based on soil sampling from different areas in the country. These samples are tested and results analysis for identification of the type of soils present. Then these soils were used in bricks preparation for which strength characteristics were finally identified. It was concluded from the results that the mud brick can be used for some simple buildings in which their strength characteristics could depends on the type of the soils used. Key words: Mud, earth, clay-silt soils, brick, heating, compressive, strength, bricks.

INTRODUCTION A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar. Bricks were often used for reasons of speed and economy, even in areas where stone was available.

Bricks may be made from clay, shale, soft slate, calcium silicate, concrete, or shaped from quarried stone.

Clay is the most common material, with modern clay bricks formed in one of three processes - soft mud, dry press, or extruded. Clay is highly needed for its mere-ly properties of plasticity which contributes in resisting against cracking during the process of firing the bricks.

Normally, brick contains the following ingredients (Duggal, 2008; http://www.answers.com/topic/fly-ash; *Corresponding author. Email: mbermalu@yahoo.fr

http://en.wikipedia.org/wiki/brick) 1. Silica (sand) - 50% to 60% by weight 2. Alumina (clay) - 20% to 30% by weight 3. Lime - 2 to 5% by weight 4. Iron oxide - 5 to 6% (not greater than 7%) by weight 5. Magnesia - less than 1% by weight

The clay brick has been used as a construction and architectural materials for several millennia. And as the time went on, various improvements have been made on clay bricks, whereby some additives such as shale and broken brick fragments have been used to improve both strength and durability, additives of chopped straw to the wet clay to improve structural strength of the product. And to reduce the energy demand for firing of raw bricks, the calorific value of several organic substances, generally

002 Int. Res. J. Eng. regarded as waste products e.g. sawdust, coal dust and waste oil, has been utilized by adding them to clay. Many other solutions have been adopted to improve the quality of clay brick for instance by utilization of sewage sludge in the manufacture of clay bricks. As the technology was stepped forwarding, clay bricks won the ground worldwide and become successful over other construction materials.

In Rwanda, clay brick has became more and more desirable and essential in construction to a great extent to builders while thinking about suitable building materials, the bricks come first in their minds. According to the survey conducted, about 75 percent of buildings in Rwanda cities and towns are constructed using clay bricks. The high demand of the clay bricks causes destruction of valleys which has a great impact on the environment destruction. Furthermore, the cost of transport is increasing as valley‘s clay is not found everywhere. Finally, the time delaying due to long appointments given by some brick factories for supplying clay bricks to their customers, are other factors (Chandigarh, 1992; Glanville, 1992)

It is with that regards this study was conducted with purpose of assessing the strength characteristics of earth burnt bricks to see if they can be an alternative to burnt clay bricks. These would firstly serve as “Environmental friendly “in fact that it will not require any excavation works conducting to the environment destruction, and oppositely will rely on available local raw materials, secondly would be more accessible in fact that it will be marketable within local context at reasonable cost. However, the product should offer sufficient compressive strength to be accepted as building material reflecting sustainability in modern construction.

This study will first establish the type of soils to be used as there is a clear influence of its mineralogical composition to strength characteristics of the bricks. The study also assess the strength characteristics of unburnt earth bricks, as these were being used in most of rural construction, before the apparition in construction of hydraform bricks and blocks still date with insufficient of the respective machines. The environment can’t wait until the complete stoppage of use of trees in burning will happen (MURERAMANZI Germain GS 20060376, 2010).

METHODOLOGY

The following methodology was used:

i. Sampling with various types of the soil from some areas in Rwanda ii. Field test, Visual test, Touch test and LABORATORY TEST to determine the name of the soil for the proposed new material iii. Burning of different types of bricks iv. Laboratory tests for compressive strength.

v. Comparative Analysis of compressive strength charac-teristics of earth bricks with other types of bricks for which these characteristics are already known

Soil sampling

The two samples were taken arbitrarily from Kabarondo region in eastern province, where the type of soil concerned in this study, is found in abundance. The two samples (A and B) were taken at approximately one meter deep from the top soil to avoid the presence of organic portions in the study sample; and the distance of approximately 100 meters between the two samples was considered. The soil is, by naked eye, blown red in color (Figure 1). This region is at 1°

C57

″ 33´S latitude and at 30°

C36″ 53´E longitude, the temperature of the region is at approximately 21°C. By eyes, the great area of this region is made of this type of soil. This type of soil can also be found in different places in Rwanda. Determination of type of the soil for the new material The following types of test were conducted based on (MURERAMANZI Germain GS 20060376, 2010) in order to determine the type of the soil:

Field, visual and touch tests

The aim of field test is to approach as far as possible the reality of the characteristics of the concerned new raw material that will give the new type of burnt mud brick.

By examining the soil with a naked eye it can be seen that the proportion of fine fractions is high and the proportion of sand in this soil is too low.

When crumble it by rubbing it between the fingers or palm of the hand. The sensation of this soil in hand, depending on the moisture content which reflects the cohesion of the soil, indicates that the soil is silt-clay.

Laboratory test

A Sieve analysis: Sieve analysis is carried out to determine the percentage of various sizes of particles in a given dry soil sample. It is termed as mechanical analysis. The sieves used for analysis of collected soil samples were as follows:

4.75mm, 2.36mm, 1.18mm, 600 µm, 425 µm, 300 µm,150 µm, 75 µm.

Representative sample is taken by considering a well mixed dry soil sample of 1000g and get a represent-tative sample of 50g by riffling (using riffle box). The sample should be put in the oven and dry it completely to avoid the moisture content before measuring that testing sample of 50g. The sample had to be soaked for

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Figure 1. Soil sample

Figure 2. Result of plot sample A

24 hours in order to allow all particles to absorb water properly and be able to separate different size of particle. Then after soaking, the sample is washed on a 75 µm sieve and make sure that retained particles remain very clean, they are dried in the oven during 12 hours. Those retained particles are subjected to sieve analysis.

As usual, sieving is performed by arranging the various sieves one over the other in order of their mesh openings, the largest sieve being kept at the top and the smallest aperture sieve at the bottom and receiver placed at the bottom and top cover placed at the top. The sample is put

on the top sieve and the whole assemble is placed on the shaking machine for 5 minutes and the soil retained on each sieve is weighed (MURERAMANZI Germain GS 20060376, 2010; Apparao and Rao, 1995; http://theiceindia.file.wordpress.com/2008/09/10171) Sample A: Mass of dry soil (Ms) =50g Meniscus correction (Cm) =0.5 The results obtained from dry sieve analysis and hydro-meter analysis as seen in Figure 2 is as follows: Sand:

004 Int. Res. J. Eng.

Figure 3. Result of plot sample B.

2%; Silt: 22% and Clay: 74% . Therefore the soil is named: clay-silt Sample B: Mass of dry soil (Ms) =50g Meniscus correction (Cm) =0.5 The results obtained from dry sieve analysis and hydrometer analysis as seen in Figure 3 is as follows: Sand: 5%, Silt: 20% and Clay: 72%. Therefore the soil is named: clay-silt.

The results prove that the selected soil for this research is: CLAY-SILT This soil is used for the preparation of the bricks under question in this study. Preparation and firing of different types of bricks (MURERAMANZI Germain GS 20060376, 2010)

Forming of raw brick and drying process The two samples (A and B) were mixed with water of approximately 17% of total weight of the brick, the mixing of water and the soil should take enough time from approximately 3 to 5 minutes to be sure that the mixture is well mixed. Then they were put in the forms where three pieces were formed from each sample.

The drying period has taken 15 days and it was necessary to make sure that every side of the brick was exposed on the sun and a distance of approximately 10mm minimum between bricks was respected.

Firing process After the drying period, the bricks were put in the furnace for burning (Figure 4). The period of burning the bricks in the furnace took 4 days.

After being cooled, the six bricks were taken to be tested for their compression strength in National Laboratory. All those 6 pieces are shown in Figures 5 and 6.

Laboratory tests for compressive strength

The recommendation of application of earth burnt bricks in construction has to be based on its strength characteristics comparing to other types of bricks already used in construction. Therefore, in this research the following types of bricks were also tested:

i. 3 Finished clay bricks taken from Ruliba factory, as this factory is known to offer bricks of high quality. ii. 3 burnt clay bricks from Rwinkwavu valley as many people are used to extract clay and make bricks. Also people from Kabarondo use to go at Rwinkwavu to get bricks for construction. iii. 3 clay-silt burnt Bricks From Kabarondo iv. 3 pieces of unburnt mud bricks from Rukarakara, which is in the same region of Kabarondo. This is used for comparison between burning effect and use without burning.

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Figure 4. Furnace to burn bricks. Source: MURERAMANZI Germain GS 20060376 (2010)

Figure 5. Burnt bricks from sample A. Source: MURERAMANZI Germain GS 20060376 (2010)

v. Improved clay-silt bricks with addition of grasses in the content It was noted that as the format of all given bricks were different, the comparison all results were recalculated assuming the same working section (242 cm

2).

RESULTS AND DISCUSSION Summary of results from compression tests for various

types of bricks are presented in Table 1. Comparison of results to maximum compressive strength as it is given in some standards As a reference, Indian Standards were used. According to Indian standard IS 3495, the maximum of compression strength of clay brick is of 30 MPA. Therefore the com-parison of results from the aforementioned tests with that maximum value is presented in the Figure 7.

006 Int. Res. J. Eng.

Figure 6. Burnt bricks from sample B. Source: MURERAMANZI Germain GS 20060376 (2010)

Table 1. Summary result from compression test

Types of bricks compression Average weight of the brick (Kg) Strength (MPa)

Finished clay bricks taken from Ruliba factory 2.890 23.00

Clay burnt bricks from Rwinkwavu clay valley 2.683 15.00

Clay-silt burnt Bricks From Kabarondo 5.12 4.00

Unburnt clay-silt bricks made from Kabarondo 6.132 1.14

Improved clay-silt bricks with addition of grasses in the content 6.20 1.70

Figure 6. Comparison diagram for various bricks. Source: MURERAMANZI Germain GS 20060376 (2010)

The afore results can also be compared with the Stabilized Compressed Earth Blocks which are having around 2-4 MPa or with the hydrafom brick with 4- 10 MPa, as these are two technologies lastly used to make bricks and blocks which are more environmental and economical friendly.

The results also confirm the importance of heating the brick as it increase the compressive strength up to around 72%. Another important observation is the proof supporting people practice of adding glasses in mud bricks. It was confirmed that with this practice the compressive strength of bricks is increased by around 30%.

Further, it is important to note that the compressive strength of all bricks is mainly depending on the percentage of clay soil particles contained in their raw materials.

Finally, it is established that the compressive strength of ordinary clay burnt bricks is around 3 - 4 times greater than the same one for clay-silt burnt Bricks. Also, it is clear that clay-silt burnt bricks have quite the same compressive strength as for hydrafom bricks. Conclusion

Considering the fact that the required minimum compressive strength is 4MPa for bricks used in simple building and 7MPa for story buildings, the clay - silt burnt bricks can be used for simple buildings.

Further, it is clear that the hydrafom bricks may be more preferred than the heating of clay - silt soils as this will, not only offer the same strength but also will be a more environmental friendly material.

Finally, it was established that the quality of burnt bricks depends on the percentage of clay particles present in the soil.

Recommendations

Based on the afore results it is important to recommend the following: i. The use of earth unburnt bricks, as it had been the case in Rwandan rural areas is not advised. ii. Earth burnt bricks can still be used in construction of simple buildings, iii. The research should continue with other types of soils to see if still some soils can offer the needed strength characteristics.

Léopold et al 007 iv. It is recommended to consider the application of the burnt clay-silt bricks for instance in the case of construction of agglomerations or settlements (IMIDUGUDU) and other similar houses which do not carry a heavy load during their service live. v. While research continues, for more important building, it is advised to apply hydraform bricks as an only good alternative for burnt clay brick to keep the safe environment. REFERENCES Apparao, K.V.S., Rao, V.C.S. (1995). Soil testing,

laxmipublications (P) Ltd New Delhi. Chandigarh, (1992). Civil Engineering Materials, Tata Mc

Graw-Hill Publishing Company limited New Delhi. Duggal. S. K. (2008). Motilal Nehru Institute of Technology

Allahabad (U.P.). Building materials (third revised edition). New Age International (p) Limited, Publisher.

Glanville, J.I. (1992). P. Eng. Faculty of Engineering, University of Manitoba at Winnipeg. Evaluation Report On Fired Bricks - October 1992

http://theiceindia.file.wordpress.com/2008/09/10171. Engineering properties of soils based on laboratory testing prof.Krishna Reddy, UIC

http://www.answers.com/topic/fly-ash, 3 may and http://en.wikipedia.org/wiki/brick

Keneth, C.B. (1987). Engineering materials, 5th edition, MC TAT, New Delhi.

Mureramanzi Germain GS 20060376 (2010). Comparative study of compressive strength characteristics between specific burnt mud bricks and ordinary burnt clay bricks. Final year project under supervision of Dr Leopold Mbereyaho. KIST.