Utilization of recycle paper mill residue and rice husk ash in production of light weight bricks

Utilization of recycle paper mill residue and rice husk ash in production of light weight bricks

archives of civil and mechanical engineering 13 (2013) 269–275 Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/a...

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archives of civil and mechanical engineering 13 (2013) 269–275

Available online at www.sciencedirect.com

journal homepage: www.elsevier.com/locate/acme

Original Research Article

Utilization of recycle paper mill residue and rice husk ash in production of light weight bricks S. Rauta,b, R. Ralegaonkara,, S. Mandavganec a

Department of Civil Engineering, VNIT, Nagpur-10, Maharashtra, India Department of Civil Engineering, YCCE, Nagpur-10, Maharashtra, India c Department of Chemical Engineering, VNIT, Nagpur-10, Maharashtra, India b

art i cle i nfo

ab st rac t

Article history:

Resource recovery and utilization of industrial by-product materials for making construc-

Received 2 May 2012

tion material has gained significant attention across the world. In this research study,

Accepted 24 December 2012

recycle paper mill residue (RPMR) and rice husk ash (RHA) are utilized to improve the

Available online 5 January 2013

properties of bricks. This research study evaluated the feasibility of utilizing RPMR and


RHA for making construction bricks. A homogeneous mixture of RPMR–RHA–cement was

Recycle paper mill residue

prepared with varying amount of RHA (10–20% by weight) and RPMR (70–80% by weight)

Rice husk ash

and tested in accordance with the IS codes. Characterization of RPMR and RHA was


performed using XRF, TG-DTA, XRD and SEM techniques. The SEM monographs show that

Light weight

RPMR has a porous and fibrous structure. The TG-DTA characterization demonstrated that

Compressive strength

RPMR can withstand temperatures up to 280 1C. The results indicate that RPMR-bricks prepared from RPMR–RHA–cement combination are light weight and meet compressive strength requirements of IS 1077-1992. This novel construction material serves objectives of resource recovery through prudent solid waste management. & 2013 Politechnika Wrocławska. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.



Brick is one of the widely used construction materials in India. In the past, rudimentary brick making techniques used locally available natural materials such as clay. With industrial revolution, economic growth and overall increase in population, tremendous demand is exerted on natural resources for creating new infrastructure. The increasing demand for the construction materials especially bricks are exploiting natural resource to the large extent. With dwindling resources and emphasis on sustainability and resource recovery, novel approaches to utilize the waste material as a

construction material has gained widespread attention of the scientific community, since the 1980s (http://www4.uwm. edu/cbu). Growing environmental awareness in the building industry has brought about the need to investigate ways to incorporate residuals and by-products materials in place of traditional construction material and preserve the environment while maintaining the material requirements stipulated in the standards [1]. Brick is one of the most accommodating masonry units as a building material in India due to its physical, chemical and mechanical properties. Utilization of residuals and by-products materials as a construction material could address two issues;

Corresponding author.

E-mail address: [email protected] (R. Ralegaonkar). 1644-9665/$ - see front matter & 2013 Politechnika Wrocławska. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved. http://dx.doi.org/10.1016/j.acme.2012.12.006


archives of civil and mechanical engineering 13 (2013) 269–275

it will not only lead to conservation of natural resources, but will herald better ways of managing residuals and by-product materials. As per the recent report of Indian Paper Manufacturers Association (IPMA), recycle paper mills (RPM) contributes nearly 30% of the total pulp and paper mill segment. With 85% average efficiency of RPM, around 5% (by weight) of total pulp and paper mill production is generated as RPMR annually. As a by-product, often times RPMR are landfilled without any resource recovery. Use of such recyclable materials as a raw material in the production of bricks has been an evolving process [2]. They have been successful in creating a brick-making material by mixing recycle paper mill waste

and cement with varying proportions (up to 20% by weight) of cement. Their research shows that the bricks made by using recycle paper mill waste are light weight and increased acceptable compressive strength. Continuous efforts are made to incorporate industrial by-products as a raw material in the production of bricks. For example, Mucahit and Sedat [3] developed porous and light-weight bricks by using paper processing residues as an additive to a clay brick. They have been successful in creating a brick-making material by mixing brick-making raw materials with varying proportions (up to 30% by weight) of paper residues. Their research shows that the bricks made by using paper processing residues had

Fig. 1 – (a) Dry RPMR, (b) OPC and (c) RHA.

Table 1 – Details of compositions. Sr no.

Sample name

Wt of wet RPMR (g)

Wt of dry RPMR (g)

Wt of cement (g)

Wt of RHA (g)

% Consistency of RPMR Dry RPMR/(waterþdry RPMR)

1 2 3


3200 3200 3200

716.8 672.0 627.2

89.6 89.6 89.6

89.6 134.4 179.2

0.23 0.22 0.21

Table 2 – Material balance. Sample: no of samples




Weight (wt) of wet RPMR, g Wt of dry RPMR, g Wt of cement, g Wt of RHA, g Water, g Wt of wet brick after P1, g Amount of water removed during P1, g Amount of water removed by partial solar drying, g Wt of wet brick before P2, g Wt of wet brick after P2, g Amount of water removed during P2, g Wt of dry brick, g Amount of water removed by partial solar drying, g Wt of dry material, g Wt of water in brick, g Wt of water removed by pressing, g Wt of water removed by evaporation, g

3200 716.8 89.6 89.6 2304 2630 570 325 2305 2089 216 973 1179 896 77 786 1504

3200 672 89.6 134.4 2304 2725 475 376 2349 2142 207 1006 1136 896 110 682 1512

3200 627.2 89.6 179.2 2304 2794 406 394 2400 2179 221 989 1221 896 93 627 1615

% Average

2474n 1573n

1072n 4275n 872n 3575n 5775n

0.1 0.1

Sr %



Mn % 0.41

0.03 0.6 0.05 0.22 0.13 0.92 1.69 0.16 2.44 0.15 0.32 1.07 0.67 3.59 0.37 2.06 3.31 60.57 34.46 14.94 1.44 15.83 46.36

Si %

Al %

Mg %


Ti %


Fe %

Na %

Cu %


Cl %



Recycle paper mill residue (RPMR) and the RHA were obtained from the industries in the vicinity of study location (Nagpur, India). Ordinary Portland cement (OPC) (43-grade) conforming to IS 8112-1989 was purchased from a local vendor. Fig. 1 shows the photographs of the raw materials procured. The RPMR was added to varying proportions of RHA (weight basis) and cement (Table 1). The characterization of RPMR and RHA has been carried out. Various batches of mix of RPMR, cement

Ca %

Materials and methods



Table 3 – Elemental analysis of RPMR.

reduced thermal conductivity and increased acceptable compressive strength. Demir et al. [4] investigated the utilization potential of Kraft pulp production residues in clay bricks. Due to the organic nature of pulp residue, the authors investigated the pore-forming ability in the clay bricks by increasing the amount of residue from 0% to 10% by weight and mixing it with the clay mixture for making bricks. Furthermore, the authors also investigated the effect of increasing the pulp residue on shaping, plasticity, density and mechanical properties. They demonstrated that 2.5–5% residue additions were effective for the pore forming in the clay bricks with acceptable mechanical properties in accordance with the requirements of Turkish Standards. In 2007, the worldwide production of rice husk was estimated to be 130 million tons with China and India alone accounting for more than half of the entire production [5]. This enormous amount of rice husk is difficult to manage in an effective way primarily because it has very low nutritional value and cannot be used as animal feed, it takes a long time to degrade and is not suitable to use as compost [6]. Often times the rice husk is landfilled or used as a supplementary fuel in a kiln which in turn generates rice husk ash (RHA). Depending on the incineration temperature the RHA could have as much as 80–95% reactive silica [7]. When RHA is mixed with cement and water, it forms calcium silicate hydrate gel by consuming calcium hydroxide during the hydration of cement. Saraswathy and Song [8] reported that incorporating 25% RHA in concrete results in better corrosion control with reduced chloride penetration, decreased permeability and increased strength. Off-white RHA (OWRHA) which is considered an improvement over traditional RHA because it has no crystalline SiO2 or toxic metal can improve concrete compressive strength, splitting tensile strength and overall performance just at 15% replacement level [9]. These studies have demonstrated the effectiveness of RHA in producing high strength concrete. The present research work focuses on development of bricks using RPMR–RHA–cement combinations, which would be useful for the sustainable development of the brick-construction industry. In order to manufacture the bricks under laboratory conditions, a low-cost, hand operated mixing and molding machine was specially designed and fabricated. Optimal composition of the bricks with respect to RPMR–RHA–cement compositions was determined using various proportions by evaluating the physical, chemical and mechanical properties. Most of the performance tests recommended by the Indian Standards were performed to make sure that the bricks conform to the standards stipulated for conventional burned clay bricks.

Zr %

archives of civil and mechanical engineering 13 (2013) 269–275



archives of civil and mechanical engineering 13 (2013) 269–275

with varying amount of RHA were prepared. Sixty (60) samples, each comprising of varying percentage of RPMR, RHA and cement were prepared (Table 2). Sample set A has, 80% RPMR, 10% RHA and 10% of cement by weight, sample set B has 75% RPMR, 15% RHA and 10% cement by weight whereas sample set C has 70% RPMR, 20% RHA and 10% of cement by weight. All sample compositions were prepared with uniform consistency (2271%). The RPMR weight percentage in the final composition of the mix was observed to be in the range of 70–80%.


Test methods

The compressive strength of bricks was determined using Compression Testing Machine (CTM). Three samples of each composition were subjected to a compressive strength test, and the average strengths were recorded. Compressive strength test, water absorption test and efflorescence were performed according to IS 3495 (Part 1–3): 1992. Physical properties such as specific weight, voidage and equilibrium moisture content and dimension change on drying were determined following the IS 1077:1992 guidelines. Block density and moisture movement for the hollow and solid blocks were measured according to the IS: 2185(Part 1): 1979.


Results and discussion


Characterization of RPMR and RHA

Elemental analysis (Table 3) shows that pozzolanic silica content in RPMR and RHA were 60.57% and 34.46% respectively. Pozzolanic silica participates in pozzolanic reaction to form cementitious material. Heavy metals copper (Cu), strontium (Sr), zirconium (Zr) and manganese (Mn) were present in traces (less than 0.1%). Therefore, the possibility of leaching heavy metals is insignificant. From proximate analysis (Table 4) it is observed that RPMR mainly contains ash (40.6%) and volatile materials (44.7%). Silica present in RPMR appears as ash, whereas, short length carbonaceous material like paper fibers contributes to high volatile content. The presence of carbonaceous material (22.7%) is confirmed by ultimate analysis (Table 5). 23.6% oxygen content is due to presence of oxides of various components. Thermogravimetric Analysis (TGA) of RPMR was carried out to measure the amount and rate of change in the weight of a material as a function of temperature or time in a controlled atmosphere. Measurements were used primarily to predict thermal stability at temperatures up to 1000 1C. The results from thermogravimetric analyses are usually reported in the form of curves relating the mass loss from the sample against temperature. In this form the temperature at which certain

processes begin and are completed are graphically demonstrated. TGA curve obtained from heating a sample of RPMR from 30 1C to 1000 1C is shown in Fig. 1. The curve shows the loss in weight that occurred at different temperatures. According to the TG curves shown in Fig. 2, RPMR samples showed the mass loss of 45% between 29 1C and 300 1C. It should be noted that this mass loss was observed on the samples which were not thermally pre-treated. This curve reveals the appearance of three distinct mass loss regions. The first loss (7.5%) occurred between 30 1C and 280 1C which is premature loss and could be attributed to the removal of superficial water molecules that may be present in the solid pores. The second mass loss occurs beyond 280 1C where the material gets thermally degraded and gets sintered. Based on the TG curves, it can be concluded that the bricks made from RPMR can withstand at the minimum of 300 1C. The third mass loss beyond 300 1C is due to combustion of solid organic matter present in RPMR. Differential scanning calorimetry (DSC) (Fig. 2) measures Specific Heat Capacity, Heat of Transition, Temperature of Phase Changes and Melting Points. In the present case DSC thermal analysis was carried out to determine the phase change. DSC measures the rate of heat flow. DSC compares differences between the heat flow rate of the test sample and known reference materials. Vertical axis denotes rate of heat liberated per unit mass of RPMR (mW/mg). From TGA and DSC second mass loss coincides with maximum heat liberated. It confirms that phase change of RPM takes place at 280 1C and it gets thermally degraded. The diffraction patterns shown in Fig. 3 were obtained by continuously scanning from 201 to 801 as 2y angle. The diffractograms of virgin (0%) and varying composition of cement mixed RPMR material shows that the samples exhibited amorphous patterns based on small reflection angles and 2y peaks between 251 and 301 which is a typical characteristic of commercial cement (43 grade). The nature of materials did not show any significant change even after different amounts of cement were added to RPMR (5–20 %wt). X-ray diffraction analyses were also performed to identify amorphous or crystalline silica of RHA. A qualitative assessment of the crystallinity of the samples can be ascertained from the intensity of the narrow reflections as compared to the broad band around 221 (2y) as shown in Fig. 4. The intense broad peak observed for the RHA samples indicates the amorphous nature of silica. SEM monograph (Fig. 5) for RPMR clearly indicate the presence of irregular pores and fibrous nature of RPMR. The Table 5 – Ultimate analysis of RPMR. Sr. no.

Wt. (g)













Table 4 – Proximate analysis of RPMR. Sr. no.

Wt. (g)

Moist %

Ash %

Volatile materials %

Free carbon %

GCV kJ/kg








archives of civil and mechanical engineering 13 (2013) 269–275


Fig. 2 – TG-DTA of RPMR.

Intensity (A.U)

0% 5% 10% 15% 20%

(35–50 mm) appearing in parallel rows. It is evidenced from SEM monograph that RHA has porous and amorphous structure with a good amount of active silica.







2 theta

Fig. 3 – XRD pattern of RPMR–cement (0–20%wt). Counts




0 20











2 Theta

Fig. 4 – Broad peak at 2h¼ 22 1C shows amorphous, active silica, RHA (450 1C, 12 h). RPMR holds the moisture in the pores and the fibrous structure of RPMR encapsulates the moisture thereby creating a barrier for moisture to move towards the surface. Fibers of RPMR are intern woven and spread uniformly in the RPMR– RHA–cement mix that gives better deformability and hence energy absorption. Presence of pozzolonic silica in RHA and RPMR gives higher binding property and hence compressive strength. SEM monographs of RHA sample (Fig. 6) indicate more porous structure of active silica. SEM monograph also shows the regular spherical structure of almost equal size

Brick analysis

Three brick samples each from A, B and C compositions were used for conducting the compressive strength tests. Additional three samples were also used for conducting the specific weight, voidage, and water absorption tests. The test results shown in Table 6 indicate that the bricks conform to the minimum compressive strength requirements stipulated in IS 1077 (Part 1):1992. Initial moisture content of RPMR is approximately 75%. The final moisture content of the brick is approximately 10%. On drying, the space occupied by moisture is occupied by air. Voidage fraction is the ratio of volume occupied by the dry solid (dry RPMRþRHAþcement) to the total volume of the dry brick (length  breadth  height). From the results it is observed that with increase in RHA proportion the voidage fraction decreases. It was also observed that voidage of the brick sample increased with an increase in RPMR content. Voidage fraction impacts water absorption property of brick. For water absorption test, brick is sample is soaked in water for 24 h. Water molecules enter into the bulk of the brick and occupy the void. It is observed that with decrease in voidage fraction from 0.2 to 0.1, the water absorption decreases from 100% to 61%. Thus with increase in proportion of RHA, voidage fraction and % water absorption decreases. Swelling of bricks i.e. dimension change on water absorption is less in RHA–RPMR–cement brick than in RHA– cement. RHA acts as filler. It is also observed that with increase in RHA, volume change on drying decreases. The reason for decrease in dimensions on drying is removal of almost 60% moisture on drying (initial moisture content 77% and final moisture content is 10%). Hence when moisture is removed by drying the brick shrinks and volume of the brick decreases.


archives of civil and mechanical engineering 13 (2013) 269–275

Fig. 5 – SEM monograph of virgin RPMR sample.

Fig. 6 – SEM monograph of RHA sample.

The probable reason for decrease of voidage fraction, decrease of % water absorption and decrease in volume change with increase in % RHA is that, RHA acts as a filler material. Moisture content of dry brick samples of A, B, and C was observed in the range of 6–12%. The plus/minus bracket in Table 6 stands for the maximum/minimum from the results on three samples per test per used material. Moisture content of sample A in Table 6 is reported as 872%, it means that moisture contents of three samples of A varies between 6% and 10%. The higher water absorption for bricks with higher RPMR content is due to the voids. Specific weight of RPMR–cement is 0.65 g/cc. RHA is lighter than RPMR hence with increase in proportion of RHA, specific weight of RPMR–RHA–cement brick decreases. Thus with increase in proportion of RHA, bricks become lighter. Specific weight of burnt clay brick is 1.7 g/cc. Pozzolanic activity of RHA is also explored in the present work. Compressive strength of RPMR–cement brick is 9.9 MPa. Keeping cement proportion constant at 10% when RHA was added to RPMR, the overall compressive strength of RPMR–RHA–cement brick was increased and found to be more than 11 MPa in all the three samples. All brick samples had excellent compressive strength (11–15 MPa) which is nearly five times higher than the compressive strength of the conventional burnt clay brick (370.5 MPa). The bricks under compressive strength test shrunk but did

not break indicating greater tolerance for failure due to rupture. Though the overall compressive strength of RPMR–RHA– cement is higher than RPMR–cement brick, it is observed that with increase in proportion of RHA in RPMR–RHA–cement brick, the compressive strength decreases. The probable reason is the different nature of RPMR and RHA. RPMR is fibrous in nature whereas RHA is porous powder. Higher proportion of RHA impacts the rheology of RHA–RPMR and yields non-homogeneous mixture. As gm RHA/gm dry RPMR increases the degree of homogeneity decrease which adversely affects compressive strength. Another factor influencing compressive strength is amount of fibrous material in raw material. From sample A to C amount of fibrous material decreases from 80% to 70%. RHA and cement are non fibrous materials. Therefore, compressive strength of A (80% fiber: 20% non-fiber) was observed to be 15 MPa whereas that of C (70% fiber: 30% non-fiber) is 11.9 MPa. Thus compressive strength is directly proportional to fibrous material present. Results of the water absorption test indicated water absorption was directly proportional to the RPMR content. This could be attributed to the high voidage and cellulosic nature of the RPMR. Water absorption increased by almost 100% (by mass) as the RPMR content increased from 70% to 80%. The high water absorption of RPMR can be reduced by applying water proof coating over the brick surface without compromising other physical and mechanical properties of the brick material. RHA acts as filler and pozzolanic material. At higher proportion of RHA predominantly acts as filler materials and at lower proportion predominantly as pozzolanic material.



The physical and mechanical properties of brick samples prepared from paper pulp, rice husk ash and cement were investigated under laboratory condition. It is concluded from the results that the RPMR–RHA–cement combination can be potentially used in the production of new brick material. The new brick material resulting from the varying composition of RPMR–RHA was observed to be lighter and weighing nearly 50% less compared to the conventional bricks. The brick composition with RPMR (70–80%), RHA (10–20%) and cement


archives of civil and mechanical engineering 13 (2013) 269–275

Table 6 – Brick testing results. Sample




Volume of RPMR, cm3 Volume of cement, cm3 Volume of RHA, cm3 Volume of solid, cm3 Voidage, % Specific wt., g/cm3 Dimension change on drying, % g cement/g dry RPMR g RHA/g dry RPMR Moisture content of the bricks, % Compressive strength, MPa Water absorption, % Dimension change on water absorption, % Density of brick, g/cm3 Efflorescence

1076.2 28.44 298.66 1403.3 0.20270.01 0.5570.02 671 0.125 0.125 7.9272 15.0070.5 100.5275 771 0.58870.01 NIL

1009 28.44 448 1485.44 0.15670.01 0.6470.02 571 0.133 0.20 10.9372 14.8470.5 85.475 671 0.5670.01 NIL

942 28.44 597.33 1567.77 0.10970.01 0.5670.02 4.571 0.143 0.28 9.4072 11.9070.5 61.275 671 0.5470.01 NIL

(10%) demonstrated high compressive strength of 11–15 MPa, which is five times greater than the compressive strength of the conventional burnt clay bricks (3 MPa) (IS 1077:1992) and as such the newly brick meets and surpasses the requirements of IS 3495 (Part 1): 1992 for building materials generally used in the indoor structural applications. With further increase in the amount of RHA beyond 10% did not yield any appreciable improvement in the physical and mechanical properties of the bricks. Instead, increase of RHA amount beyond 20% resulted in significant deterioration of the quality of the brick. The bricks were observed to be highly fragile with very low binding strength. In summary, after testing 60 samples each of three different compositions, results suggests that the optimum mix, both in terms of the strength parameters and overall physico-chemical characteristics will be 80% RPMR, 10% RHA and 10% cement.

Acknowledgment The authors are thankful to the funding agency, Department of Science and Technology, Government of India for the ongoing project. Authors would also like to acknowledge Dr. B.D. Kulkarni (Distinguished Scientist, CSIR, India) and Dr. S.S. Bhagade, (Retd. Prof. LIT, Nagpur, India) for constructive technical inputs and Prof. H.T. Thorat and Mr. Mayur Birla (Department of Mechanical Engineering, VNIT, Nagpur, India) for designing the brick moulding and mixing machine.

r e f e r e nc e s

[1] S.P. Raut, R.V. Ralegaonkar, S.A. Mandavgane, Development of sustainable construction material using industrial and agricultural solid waste: a review of waste-create brick, International Journal of Construction & Building Materials 25 (2011) 4037–4042. [2] S.P. Raut, R. Sedmake, S. Dhunde, R.V. Ralegaonkar, S.A. Mandavgane, Reuse of recycle paper mill waste in energy absorbing light weight bricks, International Journal of Construction & Building Materials 27 (2012) 247–251. [3] S. Mucahit, A. Sedat, The use of recycled paper processing residue in making porous brick with reduced thermal conductivity, Ceramics International 35 (2009) 2625–2631. [4] I. Demir, M. Serhat, O. Mehmet, Utilization of kraft pulp production residues in clay brick production, Building and Environment 40 (2005) 1533–1537. [5] K.V. Harish, Fundamental investigations into performance of carbon-neutral rice husk ash as supplementary cementitious material, J. Trans. Res. (2010) (Board No. 2164; Washington DC: 35-26). [6] E. Beagle, Rice Husk Conversion to Energy: Agricultural Service Bulletin 1978; 31, Food and Agricultural Organization, Rome. [7] R. Kishore, V. Bhikshma, P.J. Prakash, Study on strength characteristics of high strength rice husk ash concrete, Procedia Engineering 14 (2011) 2666–2672. [8] V. Saraswathy, H.W. Song, Corrosion performance of rice husk ash blended concrete, Construction and Building Materials 21 (2007) 1779–1784. [9] R.M. Ferraro, A. Nanni, R.K. Vempati, F. Matta, Carbon neutral off-white rice husk ash as a partial white cement replacement, Journal of Materials in Civil Engineering 22 (2010) 1078–1083.