A study on Different Bricks & Identification of Quality of Bricks Based on Existing Data

: The purpose of this study is to investigate the different types of bricks as a construction material. In this study, monitoring different technical specification or characteristics of the bricks. At the end of study, Brick Quality Index (BQI) evaluated. According to BQI, bricks were classified poor to excellent quality.


Introduction:
Bricks is one of the most important construction materials. Bricks may be manufactured from clay, shale or combination of these materials [1]. Other materials such as Silica, Alumina, Lime, Iron oxide, Magnesia may be used for manufacturing good quality brick [2]. Depending on manufacturing process, uses, shape bricks can be classified as different types [4]. In this study some general types of bricks will be investigated with their technical specification including dimension, visual appearance, compressive strength, average water absorption (%), efflorescence characteristics and unit weight. On the basis of manufacturing & preparation burnt clay bricks can be classified as 1 st class, 2 nd class, 3 rd class bricks. Based on constituent materials bricks can be classified as Common Burnt Clay Bricks, Sand Lime Bricks (Calcium Silicate Bricks), Engineering Bricks, Concrete Bricks, Fly ash Clay Bricks etc. [2].
To know the quality of bricks different tests are performed such as Compressive strength test, Water Absorption test, Efflorescence test, Visual appearance test etc. [2,5,9]. Water absorption results represents in percentages and for good quality value is less than 20% [4,11]. Larger compressive strength indicates higher stability, efflorescence test finds out the presence of alkalis which is very essential for building structures [2].
In this study all of these test results for several bricks collected and analyzed for final outcomes.
Hope this study will be helpful for knowing some general types of bricks with their technical specification and create a new dimension for further brick quality investigation.

Materials and methods:
This study includes data collection, data rearrangement, analysis and final outcomes. The data were collected from several existing study [1,[3][4][5][6][7][8][9][10][11][12][13][14]. After collection, data were analyzed by MS Excel 2016 software. First general technical specification was identified, after that some plots were generated for comparative study among different bricks type. At the end of the study Bricks Quality Index (BQI) was evaluated to know the quality of several types of bricks.
For brick quality evaluation the steps were followed as bellow: 1. Rating the specification/ characteristics of bricks from 1 to 5. Where 1 for poor quality, 2 for slightly poor, 3 for moderate, 4 for good and 5 stands for excellent quality of bricks.
2. The rating is provided based on some general class. For example, first considering the value of compressive strength (kg/cm 2 ). According to this, bricks are classified as poor (which has 0-30 kg/cm 2 compressive strength), slightly poor (which has 31-75 kg/cm 2 compressive strength), moderate (which has 76-100 kg/cm 2 compressive strength), good (which has 101-140 kg/cm 2 compressive strength), excellent (which has >141 kg/cm 2 compressive strength). When bricks are classified as poor then rated it 1, rated 2 for slightly poor, rated 3 for moderate, 4 for good and 5 for excellent class of bricks.

General characteristics:
The general characteristics of several types of bricks displayed in Table-2. The table includes the visual appearance of bricks, dimension of bricks (Length, weight and height), water absorption rate (%), compressive strength (kg/cm 2 ), Efflorescence and unit weight (kg/m 3 ).

Average compressive strength of bricks type
Figure-1 represents the average compressive strength of several bricks. The outcomes clarify that engineering bricks have larger compressive strength than others. Clinker bricks have also larger compressive strength. In case of different blocks such as porothem blocks, AAC or CLC blocks compressive strength is lesser. The lower value indicates lower crushing strength that means lower pressure required to break the bricks. It also indicates lower stability of bricks.

Average water absorption rate of different bricks type
The water absorption test performed by weighting the bricks at dry condition and weighting these after 24 hours immerged in fresh water. The lower value of water absorption represents good quality. In reverse the higher value of water absorption represents poor quality. It can be noticed that the water absorption rate for 1 st class bricks, engineering bricks and 1 st class machine made bricks are low which clarify these are good quality bricks. In case of AAC blocks,2 nd class or 3 rd class bricks the water absorption rate is comparatively high which indicates the lesser quality.

Average unit weight of different bricks:
Unit weight represents the weight of any materials per unit volume. This weight help to evaluate the structure's weight, to specify the load which the structure of such materials can carry, to quantify amount of material required for specific space, to determine whether the materials will sink or float on water [10].

Bricks Quality Index Evaluation
The quality of different types of bricks displayed in Table-

Conclusions:
• For compressive strength, it can be seen that engineering bricks and clinker bricks have high compressive strength. On the other hand, different types of blocks such as porothem blocks, AAC, CLC, and 3 rd class bricks also have lower compressive strength.
• The good quality bricks have lower water absorption rate but poor-quality bricks have higher water absorption rate.
• For excellent or good quality bricks efflorescence is nil, compressive strength high, water absorption low and unit weight is also high.
• According to BQI 1 st class machine made bricks & engineering bricks classified as excellent quality bricks, Picked Jama bricks, clinker bricks, common burnt 1 st class bricks classified as better quality, concrete bricks, calcium silicate/ sand lime bricks classified as good quality bricks, 2 nd class blocks, porothem blocks etc. classified as slightly poor and common clay burnt 3 rd class bricks classified as poor-quality bricks.