Development of light weight bricks using red clay and rice-husk
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Date
2015
Journal Title
Journal ISSN
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Publisher
Uva Wellassa University of Sri Lanka
Abstract
Bricks are one of the oldest building materials that can be made at relatively low cost. They have
been in continual use for more than 5000 years and still used in Sri Lanka, because of their many
advantages (El-Mahllawy et al., 2013). Mud bricks, burned bricks and cement bricks are types of
bricks using in construction purposes (Society of Civil Engineers, 1996). The composition of red clay
minerals used in brick production is SiO2 (60.67%), Al2O3 (15.18%) and Fe2O3 (7.61%) (Hettiarachchi
et al., 2010). Certain admixtures such as rice-husks, sawdust, etc. are added to brick raw mixtures to
produce different effects such as color, high strength, or low weight in the finished product.
Admixtures consists of organic matter are burned out when bricks undergo firing. Cons equently,
porous bricks are produced. This permits the control of the bulk density of brick products and help in
producing lighter bricks with low material cost. In this research work, bricks are made using red clay
and 5 wt. % of rice-husk or 5 wt. % of rice-husk ash as admixtures. The fabricated bricks were
analyzed to measure material properties such as compressive strength, weight, volume, density, water
absorption, and color changes during firing process. Results are then compared with the values
obtained from commercial bricks.
Methodology
Preparation of prototype bricks
The dimensions of the bricks studied in this project were 25% of the commercial brick dimensions.
Accordingly, length.41/4” (10.79 cm) x width 23/4” (6.98 cm) x height 11/4” (3.17 cm) mold was
used to make prototype bricks. Bricks were made with both premixed clay (obtained from brick
makers) and dried clay with rice husk.
Procedure 1 (Premixed Clay)
The amount of water added to the clay material was unknown as it was obtained as a wet sample
from the brick makers. The purpose of making bricks with this premix is to set standards for tensile
strength and weight of the bricks similar to market quality bricks. Accordingly, five brick blocks
were made with premixed clay (500 g). These bricks are labeled as sample 1.
Procedure 2 (Dried Clay)
Clay material and rice-husk sample were dried until a constant weight was obtained (2-3 days). Then
dried clay and a known amount of water were mixed to produce bricks to be used as the control
(sample 2) to compare the effect of rice husk. The same amount of clay and water were mixed with
either five percent of rice-husk (sample 3) or rice-husk ash (sample 4). In each case, five bricks were
made. All the brick samples were dried under sunlight for four days. Firing process of the bricks was
done using a common rice-husk burning kiln or using an electrical furnace at 1000 C during this
research.
All bricks were tested for compressive strength, weight, volume, density, water absorption, and color
changes. Bricks made with rice husk (sample 3 and 4) were compared against premix samples
(sample 1) and bricks made without rice husk (sample 2).
Results and Discussion
Density of the prototype bricks
The dimensions and weight of the bricks were recorded for all samples before and after firing. These
data were used to calculate the volume and density of bricks. According to the results, volumes of
unfired bricks samples are almost equal, but after firing the bricks have different values for volume
due to evaporation of water and burning of organic matter during firing process. The lowest density
was recoded for sample with rice husk (3) compared to the control sample (2). Also addition of rice
husk in sample 3 resulted in lower density compared to the sample with rice husk ash (4). This
observation is in agreement with the expected trend in density where rice husk burning will result
higher loss in weight compared to rice husk ash.
Description
Keywords
Science and Technology, Technology, Materials Sciences, Mineral Sciences, Soil Science