The composition of clay and sludge resulting from both the BS and PS processes is significantly impacted by the type of raw materials used and the production method. The data provided in Table 2 demonstrates that silicon dioxide (SiO2) and aluminum oxide (Al2O3) make up the largest portions of the clay, with proportions varying between 55.77% and 24.40%. The analysis of the mosaic sludge showed that SiO2 and Al2O3 were the predominant elements, with concentrations between 61.83 and 62.37% and 15.50–20.55%, respectively. The Loss on Ignition (L.O.I) results indicated that both the BS and PS sludge had low organic content, ranging from 7.01 to 7.92%, classifying as inorganic sludges.
Table 3 displays the concentrations of heavy metals in the clay soil and mosaic sludge. The results indicate that both the clay soil and mosaic sludge generated from the BS and PS processes contain measurable quantities of heavy metals. Zr shown the highest concentration among the heavy metals, reaching 2738 ppm in PS sludge and 2507 ppm in BS sludge. Ba followed with levels of 1242 ppm in PS sludge and 1232 ppm in BS sludge. Furthermore, the concentrations of heavy metals such as Fe (ranging from 105 to 136 ppm), Cu (from 234 to 255 ppm), Zn (from 195 to 210 ppm), and Mn (from 89 to 97 ppm) were higher in the PS sludge compared to the BS sludge, except for Cr which showed levels of 915 to 971 ppm. Conversely, the concentrations of Fe and V were notably higher in clay soil compared to both PS and BS sludges.
Compaction test analysis
The compaction analysis was performed at the RECESS Laboratory, UTHM where the water content of each blend was determined. The optimal moisture content (OMC) is a critical parameter in the brick manufacturing process, as it directly affects the compaction and density of the bricks. Higher OMC values facilitate better particle arrangement, leading to improved mechanical strength and reduced porosity. However, excessive moisture can result in shrinkage and cracking during the drying and firing stages. In this study, OMC values ranged from 12 to 24%, with higher sludge percentages requiring higher moisture content due to the finer particle size and increased surface area of the sludge. OMC for both the control brick and mosaic sludge brick. The OMC which greatly influences brick properties, was determined using a combination and test method based on BS1377:1990.
Atterberg limits analysis
Atterberg limit was performed accordance with BS1377-2:1990. The result showed that the type of soil in this research was silty clay or clayey silt with 13.4% within the range of Plastic Index which is between 7 and 17%. The specific gravity (SG) result shows there was no significant different between clay soil and mosaic sludge with 2.6 kg/m³ and 2.4 kg/m³. Thus, the mosaic sludge could be replacing clay soil in terms of percentages by weight.
Firing shrinkage analysis
Shrinkage rate of bricks with 5% BS displayed the smallest shrinkage, measuring at 0.34%. This is succeeded by the bricks with 1%, 10%, 20%, and 30% BS, which showed shrinkage rates of 0.43%, 0.56%, 0.57%, and 0.69% respectively. Particularly, the brick with 30% BS had the highest shrinkage at 0.69%. The shrinkage rate for PS bricks is highest for the 30% PS brick at 0.60%. Subsequently, the shrinkage rates for the 20%, 1%, 10%, and 5% PS bricks are 0.56%, 0.50%, 0.49%, and 0.34%, respectively. Similar findings were documented by30,31, when they combined sludge into fired clay bricks. According to previous studies, in order to yield a good quality brick, the shrinkage value should not be more than 8%32,33.
Density test analysis
The density of BS bricks of 30% displays the least density, at 1665.24 kg/m3. There’s a gradual increase in density for the 20%, 10%, 5%, 1%, and 0% BS bricks, with values being 1677.43 kg/m3, 1679.89 kg/m3, 1683.28 kg/m3, 1688.06 kg/m3, and 1698.24 kg/m3 respectively. PS bricks findings reveal that the brick with 1% PS sludge recorded the maximum density of 1690.03 kg/m3. This is followed closely by the 5% sludge brick with a density of 1689.73 kg/m3. Bricks containing 10% and 20% sludge had a density of 1687.99 kg/m3 and 1678.52 kg/m3. The trend observed in PS brick that of BS brick, where increasing higher proportions of sludge to the fired clay brick leads to a reduction in density. The brick with the low density was the one combined with 30% PS sludge with1661.49 kg/m3. Overall, the density values typically fall within the range of 1500 kg/m3 to 2000 kg/m3. Consequently, the bricks’ densities fall within this range and adhere to the standard weight for common bricks34. Thus, the bricks align with the standard weight of common bricks. As per author35, bricks with a lighter weight are practicable, and such lightweight bricks can lead to reduced manufacturing and transportation expenses.
Compressive strength analysis
The outcomes of the compressive strength testing for BS brick are revealed the highest recorded compressive strength was achieved by the BS brick with 30% sludge content, with 26.58 N/mm2. Following this, the strengths for the 20%, 10%, 5%, and 1% BS bricks were 26.17 N/mm2, 25.81 N/mm2, 24.80 N/mm2, and 17.91 N/mm2, respectively. On the other hand, the PS brick shows the highest compressive strength with 30% of PS brick incorporation with 23.45 N/mm2 and followed by PS brick 20%, 10%, 5% and 1% with 21.91 N/mm2, 19.81 N/mm2 19.50 N/mm2, and 15.43 N/mm2 discretely. The control brick showed the lowest results compared to the other samples, with a measurement of 15.32 N/mm2. This is because BS and PS are categorized as inorganic material compared to organic. clay soil is burned during the firing process, it results in weak inter-particle bonds within the manufacturing brick14,36. Other than that, the BS brick 30% obtained slightly higher compressive strength compared to PS brick 30%. This could happen due to the reaction of silicon dioxide and aluminum oxide that was higher in BS sludge that assisted good bonding37.
Initial rate of suction
Figure 1 illustrates that the initial rate of suction for the BS brick drops as sludge waste increases from 0 to 30%. The peak value is observed in the BS brick (1%) at 12.65 g/mm2, while the lowest average rate is seen in the BS brick (30%) at 3.94 g/mm2. The control brick results revealed an initial rate of suction highest at 12.96 g/mm2. Nevertheless, for PS brick, based on Fig. 1, the PS brick displayed its lowest value at PS brick (30%) averaging 3.75 g/mm2, succeeded by PS brick (20%) with an average of 4.35 g/mm2. The peak value was observed in (1%) PS brick with an average measurement of 11.64 g/mm2. This was categorized according to the initial rate as defined by BS3921:1985. The initial water rate for both the control brick and mosaic sludge (BS and PS) in the range of 1–10% were not satisfied. According to38,39, a lower IRS can build strong bonds in brick because the lower IRS will not allow moisture to infiltrate into a brick. From the results, it was observed that the initial value was high compared to the standard value.
Initial rate of suction proportions of BS and PS brick.
Microstructure analysis
Figure 2a and l present the comparative views of the control brick and the brick with mosaic sludge (BS and PS). These images reveal that the bricks containing mosaic sludge have a more refined surface structure than the control brick. Additionally, the images depict rough surfaces for bricks containing 0%, 1%, 5%, and 10% sludge compared to those with 20% and 30% sludge. The pore sizes of the control brick ranged from 45 μm to 50 μm. Bricks with a sludge content of 1–10% exhibited pore sizes ranging from 18 μm to 44 μm. In contrast, bricks with 20% and 30% sludge had pore sizes between 1.9 μm and 3 μm. Conversely, PS bricks display a similar pattern, with bricks made of 1–10% sludge having bigger pore sizes than those with 20% and 30% sludge content. This occurs because the granularity of mosaic sludge powder is more refined than clay soil, allowing the mosaic sludge to fill the spaces between the clay particles in the mixture. Currently, the mosaic sludge bricks with 20% and 30% content possess a smooth texture, though they display a lighter texture and reduced soil cohesion. The author15 suggests that incorporating sludge can lead to variations in the plasticity and the filler properties of the sludge. Moreover, during the initial tests, BS and PS bricks with up to 40% incorporated showed noticeable affects. This observation aligns with the findings of18, who indicated that bricks with up to 35% sludge content were quite brittle and broke upon removal.
SEM result of (BS and PS) brick materials.
Surface area characterization
The BET experiment results revealed that mosaic sludge bricks had considerably smaller average pore sizes. Specifically, the BS brick 30% had a pore size of 13.40 nm and the PS brick 30% had a size of 15.92 nm, in contrast to the control brick which had a pore size of 123.22 nm. The BS brick 30% and PS brick 30% fall into the mesoporous category with pore sizes ranging from 2 nm to 50 nm, as per40. On the other hand, the control brick is characterized as microporous with pore sizes exceeding 50 nm. Nevertheless, the total pore volume in BS and PS bricks was greater at 0.005 cm3/g, while the control brick had a volume of just 0.002 cm3/g. The formation of mesopores makes the bricks lighter and when combined with 30% BS and PS sludge, they exhibit greater strength compared to the control brick.
Toxicity characteristics leaching Procedure (TCLP)
The concentration of heavy metals present in BS brick were Cd, Mn, Fe, Cr, Cu, Pb, Co, Ba, Ni, Zn, As and Vanadium. All heavy metal levels were below the permissible limits for example Fe for 10% BS brick was 0.65 mg/L, the highest among other heavy metals. Other metals like Mn, Ba, Zn, As and Vanadium also showed visible low concentration within acceptable range limits. The concentration of heavy metals for PS brick has low metal concentration such as Cd, Cr, Cu, Co, Ni, Hg compared to Mn, Fe, Ba, Zn, As and Vanadium. However, TCLP results were compared with the specific limits set by USEPA (e.g., Pb ≤ 5.0 mg/L, Cd ≤ 1.0 mg/L, Cr ≤ 5.0 mg/L) and EPAV guidelines (e.g., Pb ≤ 5.0 mg/L, Cd ≤ 0.5 mg/L, Cr ≤ 1.0 mg/L). Therefore, fired clay brick incorporated with mosaic sludge brick is safe to be discarded to landfill and no special caution is needed.
Synthetic precipitation leaching Procedure (SPLP)
Synthetic Precipitation Leaching Procedure (SPLP) is one of the leachate tests that haves been used to determine the potential for soil contamination leachability into groundwater. SPLP was designed for in-situ (ground surface of the landfill) purposes, which is exposed to rainfall with the assumption that the rainfall is slightly acidic. In the SPLP test, nitric acid and sulfuric acid (40/60) are used to simulate synthetic rain in order to depict the actual situation. The concentration of heavy metals in BS brick detected using SPLP. Lead, Pb element was the highest in BS brick (1%) with 2.307 mg/L, followed by 5% and 10% with 2.173 mg/L and 1.821 mg/L respectively. Other elements like Cd, Mn, Fe, Cr, Co, and Ni showed lower concentration. However, V, Zn, As and Ba showed moderate concentration. The author41 found that bricks made from sludge produced lower amounts of leachate elements. However, the concentration of metals in these bricks comply USEPA guidelines which is 5 mg/L.
Meanwhile, heavy metal leaching from the PS brick. The findings revealed that using SPLP resulted in an extremely low leaching of all heavy metals from the PS brick. Lead, Pb element was the highest in PS brick (1%) with 0.902 mg/L, followed by 5% and 10% with 0.802 mg/L and 0.194 mg/L respectively and it comply USEPA guidelines which is 5 mg/L. Other elements like V, Zn, As and Ba showed values between 0.113 and 0.229 mg/L.
Static leachate test (SLT)
Figure 3 depicts the heavy metal concentration in the control brick between day-4 and day-95. The data indicates that iron (Fe) reached its peak level on day-16 at 2.07 mg/L. This was closely followed by V, which reached 1.790 mg/L on day-28, when compared to the other heavy metals. On day-16, Ba recorded its peak concentration at 1.73 mg/L and then gradually decreases to 0.25 mg/L by day-95. Other metals like Cr, Ni, Cu, Zn, As, Cd, and Pb were present in small quantities and met both USEPA and EPAV guidelines.
Heavy metal concentration for control brick.
Figure 4 presents the heavy metal concentration in a 1% BS brick. The data indicates that vanadium had the higher concentration at 2.14 mg/L on day-32. This was closely followed by Fe with 2.11 mg/L on day-28. Both of these metal concentrations remained unchanged from day-81 through day-95. Zn reached its highest level on day-8 and then rapidly declined until day-95. The concentrations of other heavy metals were consistently below 1 mg/L and far within acceptable boundaries. However, it’s important to note that all heavy metal concentrations within the 1% BS brick within the prescribed standard.
Heavy metal concentration for BS brick (1%).
Figure 5 illustrates the heavy metal concentration in a 5% BS brick. The data reveals that Fe concentration in the 5% BS brick peaked at 2.26 mg/L on day-20, then gradually dropped until day-74, remain constant at 0.52 mg/L by day-88. V concentration was observed at 1.99 mg/L on day-24, which then consistently decreased to 0.10 mg/L by day-95. All other heavy metals were detected at levels below 1 mg/L and were within acceptable standards.
Heavy metal concentration for BS brick (5%).
Figure 6 displays the concentration of heavy metals in a 10% BS brick from day-4 to day-95. The data indicates that iron (Fe) concentration peaked at 2.34 mg/L on day-20, then dropped to 1.81 mg/L by day-24. However, from day 60 to day 95, the concentration remained constant. After Fe, V was observed to be the next most concentrated heavy metal, reaching 2.11 mg/L on day-32. By day-95, its level had reduced to 0.10 mg/L. All other heavy metals had values under 1 mg/L. Therefore, all the heavy metals were within and met the standard guidelines.
Heavy metal concentration for BS brick (10%).
Figure 7 displays the elevated levels of heavy metals in a 20% BS brick. On day-46, there was a significantly increased in V at 3.36 mg/L. But from day-53 to day-95, the concentration of V gradually decreased. On day-28, Fe showed a high level of 2.19 mg/L, but by day-95, its level had substantially decreased to 0.21 mg/L. Conversely, the Zn reading reached its highest point on day-12 at 1.28 mg/L, after which it remained constant from day-46 and above, at a level of 0.04 mg/L. Consequently, all the heavy metal concentrations remained low and within the limits.
Heavy metal concentration for BS brick (20%).
Figure 8 depicts the heavy metal levels in 30% BS bricks. Fe illustrated the highest concentration among all metals on day-8 with 2.79 mg/L and then steadily decreased to 0.23 mg/L by day-95. V reached a higher value of 2.52 mg/L on day-60 and remained stable through day-95. On day-95, Pb had the lower concentration at 0.0008 mg/L, which is below the USEPA level of 5 mg/L. Nonetheless, all the other heavy metals tested met the USEPA standards.
Heavy metal concentration for BS brick (30%).
Figure 9 displays the data for the 1% PS brick. Ba recorded the maximum level at 2.27 mg/L on day-12, but this level decreased, reaching 0.21 mg/L by day-95. Fe had a relatively high level at 2.15 mg/L on day-28 but decreased to 0.50 mg/L by day-95. Meanwhile, V was peaked at 2.06 mg/L on day-60 and then stabilized through day-95. Zn also showed a notable concentration of 1.71 mg/L on day-20. Consequently, all the heavy metal concentrations remained low and within the limits prescribed by the USEPA.
Heavy metal concentration for PS brick (1%).
Figure 10 presents the outcomes of heavy metal concentration in a 5% PS brick. The graph illustrates the variation in brick concentration from day-4 to day-95. The data revealed that V reached its highest concentration at 2.99 mg/L on day-46, while Fe followed at 1.88 mg/L on day-28. On day-20, Zn revealed a peak level of 1.17 mg/L, while Ba reached 0.88 mg/L on day-16. As the study progressed to day-95, all heavy metal levels declined and remained within the acceptable level.
Heavy metal concentration for PS brick (5%).
Figure 11 depicts the concentration of heavy metals in a 10% PS brick, measured in mg/L, from day-4 to day-95. Fe reached a higher value of 3.29 mg/L on day-32. This began to decrease by day-39, and remain stable at 1.51 mg/L until day-95. V the second highest value of heavy metal with 2.13 mg/L on day-32. Ba, on the other hand, reached its highest value of 1.01 mg/L on day-16 and remained stabilized at 0.07 mg/L from day-67 to day-95. The concentrations of Cr and Zn ranged from 0.60 mg/L to 0.85 mg/L throughout the study period. All other heavy metals had values under 0.40 mg/L up to day-95. Therefore, all the heavy metals were within and met the standard guidelines.
Heavy metal concentration for PS brick (10%).
Figure 12 displays the concentration of heavy metals in PS brick (20%). On day-24, Fe had the maximum concentration at 2.36 mg/L, while V was the next highest at 2.18 mg/L on day-67. By day-81, the concentrations of Fe and V remained stabilized at 0.12 mg/L and 2.16 mg/L, respectively. On day-28, Ba reached its highest concentration at 1.10 mg/L, but it decreased to 0.19 mg/L by day-95. Zn and Cr had higher levels on day-16 and day-46, with 0.91 mg/L and 0.89 mg/L, respectively. The remaining heavy metals stayed under 0.35 mg/L until day-95. Consequently, all the heavy metal concentrations remained within the limits prescribed by the USEPA.
Heavy metal concentration for PS brick (20%).
Figure 13 data reveal the concentration of heavy metals in the PS brick (30%) from the day-4 to the day-95. The day-28 recorded the higher concentration of Fe at 3.64 mg/L, other heavy metals. This concentration began to decrease from the day-32 and continued to do so until the day-95. As for Vanadium, it reached a concentration of 1.78 mg/L on the day-53, but this level stabilized and remained constant from the day-88 to day-95. The concentrations of Zn and Ba peaked on the day-24, registering at 0.92 mg/L and 0.88 mg/L, respectively. However, all the concentrations of these heavy metals remained satisfied and followed to the standards limits.
Heavy metal concentration for PS brick (30%).
Apart from that, the most appeared elements that were most frequently observed in both short- and long-term tests were Vanadium, Iron (Fe), Arsenic (As), Barium (Ba), and Zinc (Zn). Hence, by adding mosaic sludge to the fired clay bricks, all heavy metal results satisfied and followed to the standards set by the USEPA and EPAV.
Total volatile organic compound (TVOC)
Figure 14 shows the TVOC values against types of bricks. The findings indicated that the control brick recorded the lowest emissions when arranged in wall and column designs, with values of 0.667 ppm and 0.576 ppm respectively. In the cube design, control bricks emitted the maximum level at 0.917 ppm compared to other bricks. From the graph, the pattern appears to increase from 0 to 30% for wall and column pattern, while the cube form shows a decreasing trend from 0 to 30%.
The values for BS brick 5% and 30% for the wall are 0.715 ppm and 0.912 ppm, higher than the control brick. The values for column patterns were 0.675 ppm for BS (5%) and 0.800 ppm for BS (30%). PS brick also demonstrated an increasing pattern at 0.690 ppm for 5% and 0.819 ppm for 30% in the form of a wall. On the other hand, the cube form of PS brick showed very minimal differences in the comparison between 5% and 30% PS brick which is 0.002 ppm. Compared to the limit for Empty Room (ER), the TVOC level for control brick appeared to be slightly higher in every pattern except for the cube pattern.
In conclusion, the result shows that the amount of TVOC has no significant difference between control, BS and PS brick. This might happen as a result of the organic compounds present in the brick being removed during the firing process. Nevertheless, the increasing value of TVOC is still below the limit which is 3 ppm based on the standard and BS and PS bricks are safe to be used as an indoor brick in terms of the volatile organic compound.
TVOC emissions from control, BS and PS bricks.
Carbon dioxide (CO2)
The emission of carbon dioxide (CO2) for both control bricks and mosaic sludge bricks (BS and PS) for 5% and 30%. The findings shows that control brick (0%) obtained the highest emissions compared to BS brick and PS brick. CO2 was measured in unit ppm by using Yes monitor, based on the standard for CO2 which is 1000 ppm according to the ICOP-IAQ (2010).
The results obtained showed that the control brick had highest emission of CO2 for the wall design at 381 ppm and trailed by column and cube design at 357 ppm and 349 ppm. For BS bricks, the 5% sludge had a higher emission compared to 30% sludge for wall design at 342 ppm and 323 ppm. Cube pattern for BS brick (5%) showed a higher reading at 342 ppm compared to BS brick (30%) at 340 ppm. For the column pattern, both BS bricks show equal readings of 330 ppm. On the other hand, PS brick with 5% sludge incorporation obtained the highest emission of CO2 compared to 30% sludge in the wall pattern (337 ppm and 329 ppm) and column (334 ppm and 329 ppm) pattern. The ER results indicated a lower value compared to the other bricks, confirming that all bricks released CO2 throughout the ER process.
From all the results, it was determined that control bricks emitted the maximum level of CO2 whereas the levels were lower for bricks incorporated with mosaic sludge. Thus, control bricks appeared to emit more CO2 than bricks with mosaic sludge (BS and PS). The BS brick with 30% composition is recommended, as it consistently displayed lower concentration values across all patterns when compared to other brick samples. Nevertheless, it is important to note that all the bricks produced in this study are considered safe for use as building materials within enclosed structures. They meet the requirement of being below the limit of 1000 ppm set by the ICOP-IAQ (2010).
Carbon monoxide (CO)
Overall, the findings indicated that control bricks emitted the most CO when compared to other types (BS and PS) of bricks in the form of wall, column, and cube. These phenomena occur when the control brick carries CO after the firing process. Other than that, the control brick was higher with the organic content compared to BS and PS brick.
Control brick for column shows the higher values 0.200 ppm while both wall and cube with the same result (0.180 ppm). In the meantime, BS brick (5%) showed a higher emission compared to BS brick (30%) for all wall patterns (0.080 ppm and 0.010 ppm), columns (0.010 ppm and 0.050 ppm) and cubes (0.080 ppm and 0.040 ppm). The results obtained for PS brick showed a similar trend with the BS brick. PS brick (5%) obtained higher emissions compared to PS brick (30%) in all forms of wall, column and cube. Empty Room (ER) findings was 0.005 ppm and slightly lower compared to BS brick and PS brick 30%.
Furthermore, the CO values were lower in BS brick and PS brick that have been incorporated with 30% sludge. Thus, the incorporation of mosaic sludge has the potential to reduce the CO content in fired clay bricks. Nonetheless, all the bricks followed to the CO standard, ensuring levels remained below the 10 ppm.
Ozone (O3)
The values of O3 were obtained from control bricks and mosaic sludge (BS and PS) bricks in wall, column and cube patterns. The result shows that control bricks have the lowest emission among the others with 0.009 ppm for wall, 0.011 ppm for column and 0.013 ppm for cube. Meanwhile, for BS bricks, the result for wall pattern showed that 30% of sludge had the highest emission at 0.012 ppm compared to 5% sludge at 0.011 ppm. The same trend was obtained for the column and cube which were 0.013 ppm and 0.023 ppm for BS brick (30%) compared to BS brick (5%) which are 0.012 ppm and 0.013 ppm respectively. The result measurements for PS brick also showed the same trend with PS brick (30%) having higher O3 emissions compared to PS brick (5%). On the other hand, PS brick (30%) showed that the cube pattern was the highest with 0.026 ppm, trailed by column and wall designs with 0.023 ppm and 0.019 ppm. In the experimental phase, the concentration of O3 value for ER appeared lower possibly because of the empty state of room conditions. Nonetheless, when the brick was placed inside the chamber, both types of fired clay bricks indicated a rise in the O3 concentration within the room.
The data revealed that incorporating sludge into fired clay bricks increases the release of ozone emissions. Among all brick samples tested, the BS brick with a 5% composition revealed the most favourable result, emitting the least amount of gases. However, all the bricks followed to the ICOP-IAQ (2010) standards, ensuring emissions stayed below the 0.050 ppm. Thus, mosaic sludge bricks are safe to be used.
Formaldehyde (HCHO)
Generally, there is no significant difference in the HCHO emission between control bricks and mosaic sludge bricks. The ER value was determined lower with 0.001 ppm as expected.
The control bricks show the lowest emission values compared to other bricks i.e., wall, column and cube (0.018, 0.013 and 0.015 ppm). BS brick showed that 5% sludge bricks showed lower HCHO emissions compared to 30% sludge bricks in all forms. The results showed that the HCHO emissions for BS brick (5%) for wall was 0.019 ppm for cube and column form at 0.016 ppm and 0.014 ppm. BS brick (30%) also showed similar results whereby the highest was obtained for wall (0.021 ppm), followed by cube (0.018 ppm) and column (0.017 ppm). On the other hands, PS brick (5%) has a lower value at 0.023 ppm (wall) compared to PS brick (30%) at 0.025 ppm, followed by cube at 0.016 ppm for PS brick (5%) and 0.017 ppm for PS brick (30%). Furthermore, PS brick for column pattern had a similar trend with PS brick (5%) which is 0.012 ppm compared to PS brick (30%) at 0.015 ppm.
However, the wall pattern utilizing BS brick (5%) emitted lower HCHO emissions in contrast to the other patterns. Nevertheless, all bricks adhered to the standards and can be considered suitable for use as indoor building materials. Other than that, the finding indicates that HCHO emission for all bricks did not exceed 0.100 ppm based on the ICOP-IAQ (2010) standards required.
Particulate matter (PM10)
PM10 levels of various types of fired clay bricks. While the ER result was at a lower level of 0.015 mg/m3, the measurements for the bricks (control, BS and PS) revealed slightly higher PM10 levels, but they still remained within the accepted standards. The results obtained showed that the wall, column and cube pattern values for BS brick increased with the increasing sludge percentages with 0.115 mg/m3 (0% sludge), 0.127 mg/m3 (5% sludge) and 0.133 mg/m3 (30% sludge) for wall, 0.111 mg/m3 (0% sludge), 0.124 mg/m3 (5% sludge) and 0.136 mg/m3 (30% sludge) respectively for column. As for cube it showed 0.1403 mg/m3 (0% sludge), 0.147 mg/m3 (5% sludge) and 0.149 mg/m3 (30% sludge) respectively. Meanwhile, for PS brick there was an increase for the wall pattern at 0.115 mg/m3 (0% sludge), 0.120 mg/m3 (5% sludge) and 0.127 mg/m3 (30% sludge) each.
However, for the column and cube pattern, the lowest PM10 value was shown by 5% sludge brick with column (0.104 mg/m3) and cube (0.129 mg/m3). Overall, this finding shows that PS (5%) emitted the lowest PM10 value for all patterns compared to other bricks. Nevertheless, all bricks satisfied the standard ICOP-IAQ (2010) limit which is below 0.150 mg/m3.
In terms of emission due to IAQ, the BS brick containing 5% sludge was considered safer and more suitable than other variants. Consequently, it is recommended to employ the BS brick (5%) as a building material since it released lower gases emission into the environment and adhered to the ICOP-IAQ standard. It also has lower emissions than the control brick. However, for full utilization of mosaic sludge as raw material it could use up to 30% mosaic sludge. As all parameters in each pattern closely aligned with the standards set by ICOP-IAQ, every pattern is considered suitable from a design perspective. However, based on the overall findings suggest that the wall pattern is the most advisable choice for construction purposes.
Nevertheless, the overall results obtained show that the wall pattern is most recommended to be used in construction work.