Characteristics of Paper-cement Composite

This study “discusses the benefit of “addition waste paper as a “new cellulose material “in mortar mixes. A partial addition of waste paper by cement weight was achieved to produce cement composite mortar. Pulp and paper is the third major industrial dumper of air, soil and water. In recent year, paper and paperboard constitute a greater portion of many countries’ urban solid discarded generation. Beside, it increases characteristic “strength due to existence “of hydrogen links “in the microstructure of “paper. Furthermore, it consume “better thermal protection. The addition percentages “of waste paper used “in this work were (5%, 10%, 15% and 20%) by “mass of cement to measure and evaluate some “properties of the mortar produced (compressive“, direct “tensile, and flexural) strength, thermal “properties such as (thermal conductivity), and “microstructure investigation “like (scanning electron microscope “(SEM)). The results indicated that the fresh mortar “properties affected expressively with higher wastepaper percent. The mechanical properties (compression, direct tensile and flexural strength) were “reduced by increasing the content of waste paper, it reduces to (74%, 50%, and 86%) respectively, with (20%) addition of waste paper than the reference mix. Moreover, using waste “paper with different percentages “led to noticeable “decrease in thermal “conductivity, especially with increasing addition percentages.


INTRODUCTION
During the last recent " years, many enhancements in our "countr y have happened "in all parts of life "such as social, " industrial, economical, etc. "Utilization of the widely spread "industrial wastes in the "civil construction "practice may cause a real "possibilit y of significant "decrease in the "environment pollution "and perceptibly economize the "price of civil "construction, Mymrin, et al., 2009.Papercrete can be "used as a very "good supplement of "wood as it has strength "comparable to wood.Papercrete is an experimental "material which replaces an amount of "cem ent with paper in "the normal "concret e mix, Bukhari, et al., 2016.The use of waste "pap er; has a role in "gettin g rid of their huge "quantities, which, constitute a "fundamental, environmental problem "because of the difficulty "of its degradation.Various "attempts have been therefore "made, in the building "material manufactures "to use waste material "products."Ppaper recycling ,,has "been ,performed "about 60% ~ "80% in many , "countries, In this study, the paper pulp "was used in mortar and concrete "to study the mechanical "properties of the produced "mix some mechanical "properties.It was possible to "produce low cost "concrete with better "properties, incorporating paper "pulps with "cement.
1.1 Origination "of Waste "Paper "and Papercrete Papercrete is "a composite primarily "dev eloped 80 years ago " but it "is only lately re-discovered.Moreover, it is a fibrous "cementitious composition embraced "Portland "cement and paper "pulp.These components "are mixed with water to "inspire a paper-cement "pulp, which can then be "cast into a mold, permitted "to dry and be profited as a "durable construction "material, Subramani, and Angappan, 2015.Paper is "basicall y "timber fiber, cellulose is nearly "the second "abundant substantial on "earth "after "rock.
Cellulose is a " "normal polymer, long " "chain of "linked "sugar "particles "m ade by "the networking of " "smaller "molecules.The links in "the "cellulose chain "are a form "of "sugar: ß" -D-" " glucose.The cellulose "chain "hackles "with "polar-OH "assemblies.These "assemblies "form many "h ydrogen bonds "with OH assemblies "on adjacent "fetters, pushing "the chains "to gether, Plate 1.This hydrogen "connection forms the "sou rce of papercrete strength, Khandelwal, et al., 2015.The dry" , paper pulp "mainl y consists of "calciu m oxide and silica, followed by "magn esium oxide and "alumina.Vegas, et al., 2009 showed that, adding 10% and 20% "paper pulp by cement weight "displays significant decrease in compressive strength than the reference mortar mix,

Applications "of "Papercrete
There are different "applications that can "be produced by using "papercrete mortar or "concrete Khandelwal, et al., 2015: 1.It can be "used as a sound-" proofing "material.2. Sufficient "for roof floor loads "in low-height "buildings.

LITERATURE "REVIEW
Higher "than 4" 50 million tons of "paper is generated worldwide per "annum and the expected demand for paper, will reach "500 million tons per "annum by the "end of ,20"20, Ali, et al., 2013.In spite of "having more "information about how to "use papercrete as a "building material, some research, works , " have been done to "determine their structural, "suitabilit y, Fuller, et al., 2006.Akinwumi, et al., 2014, investigated using "wast e paper to obtain "their expediency for "use as a construction building "material.The percentages of "cement: sand: wastepaper "used were, (1" :1: "0.2, 1:1:0."4, 1: "1:0.6 and 1:1:0."8), the bulk "densit y results indicate that "papercrete is a light-weight concrete."Papercrete has a high fire "resistance, it should, not "be used for external "walls and "near ground walls "becaus e of its higher ability to absorb "water.While, Asha, et al., 2017, used recycled paper in "construction field, a total of "ten concrete mixes were "creat ed.Fine "aggregat e was replaced by "waste paper accordingly "in the range of 10% to "20%.As a result, it was "found that the "workabilit y for both M" 20 "and M" 25 grade of concrete "decreases with the increase "in percent replacement "of paper pulp.The lower bulk "density of papercrete "refers that they are "light-wei ght and can be used to produce of either hollow or "solid blocks for buildings papercrete wall with good fire resistance.Many studies have shown "natural or lingo-cellulosic fibers, can be, "considered as one of the "most important candidates "for asbestos fiber in fiber-cement "board because of the "individual properties, availability and economic aspects, Agopyan, et al., 2005.Fiber reinforced cement board, products are "compatible for most "an y light, load bearing "or non-load bearing "structures.Furthermore, they are suitable "for a situation where "ch aracteristics of other materials "are exceeded, such as "resistance to lightness, durability, acoustics, and fire, Olorunnisola, 2009.Tonoli, et al., 2009, studied the lingo-cellulosic fibers "su ggest that these fibers "have the possibility for use "as a reinforcing factor in cement "composites.The first advantage "of using lingo-cellulosic "fibers as additives in cement "are the low cost, low density, "non-ab rasive "nature, high potential filling levels ", lower consumption energy, and wide "variet y of fibers "available throughout the "world.
It is better alternative "waste material to "substitute wood because "it is abundant, "widespread, and easily "availabl e.In addition to "plentiful and "renewabilit y, employment of "recycled paper has "advantages for the economy "and environment Ren, et al., 2009.Salem, and Al-Salami, 2016, the addition of waste "paper cellulose to mortar at "certain percentage improves its "thermal insulation properties "and affect its density to "produce light-weight "and insulating building "materials.However a much "l ower thermal "conductivi ty than concrete "was reported by, Fuller, et al., 2006, showing that its insulation value is "much higher.This is because the R-value of papercrete is in between (0.078 -0.12 per mm) with a thickness in walls (304.8 -406.4mm) in one or two "stor y house.Similarly, Titzman, 2010, reported the thermal "conductivit y of papercrete "to be "0.10W/m.K. Seyyedalipour, et al., 2014, produced, papercrete "b y replacing some amount of "waste, paper by weight of Portland " cement, type I and mix with aggregate and water.The workability and mechanical properties were studied and compared reference normal weight "concrete.The slump results showed a decrease "with increasing the percent of waste paper (having, higher "abso rption ratio).The replacement of 5% waste paper by weight of "cement shows a slight "increase (about 5%) in slump value, while adding "paper pulp above 5% the slump "was decreased.The results indicated "that the mechanical "strengths (compressive, splitting "tensile and flexural strength) were "increased up to 10%, addition of waste, "paper pulp and any increase, "in waste paper pulp cause the strengths to decrease.The most appropriate replacement of "pap er pulp was, between 5 to 10% by "wei ght of "cement.The new production "technolog y comprises the application "by injection of cellulose fibers, reused "newspaper as a raw "material, treated "with special additives for "fire "proofin g.It can be applied for thermal insulation of walls, floors, as well as ceilings and roofs enclose at the same time good sound, insulation, Aciu, et al., 2014.Higher "than 50" 0,million;tons of waste paper are created global per " year, Ali, et al., 2013.Experimental works "of this paper deals "with the mechanical "properties of mortar "mix ed with variable "percent of, waste "paper pulp as (5%, 1" 0%, 1" 5% and 2" 0%).The objectives are:  Study the fresh and hardened properties of "papercrete produced using locally materials. Limiting the optimum papercrete "mix . Determining the possibility of producing non-structural elements from the optimum papercrete "mix .

Cement
The commercially cement called "as (Krasta) was used in this work, the physical and chemical "properties are listed in Table 2 and 3

Fine Aggregate
Natural sand of maximum size 4.76 mm was used in this investigation.It was brought from Al-Ukhaider region and its gradation lies in zone (2).The grading test results conform to Iraqi specification IQS., No.45-1984.Table 4 and Fig. 1 show the properties of fine aggregate.

Water
Tape water "was used for both "casting and curing of "specimens.

High-Range "Water
Reducing "Admixture (Superplasticizer) A High "Performan ce Superplasticizer concrete admixture "commerciall y called as Visco" -Crete 5930 and "manufactured by "S IKA Construction Chemicals was depended on "modified,Pol ycarboxylate which was "used in this study.The "dosage suggested," by the producer is "from (0.2-0. "8) liters "for each (100) kilograms of cement.This admixture type "confi rms to, ASTM, C494, 2015, type G "an d type F. The technical description of superplasticizer is shown in Table 5.

Waste "Papers
Waste papers were "collected from many sources offices, schools, newspapers.Table 6 and Table 7 present their physical " properties.The preparation process of the waste paper include many stages; first cutting to small pieces and soaking in water for three days then, "put on non-absorbent "filter for squeezing out "supplemental water content as indicated in Plates 2 and 3. Lastly a kitchen blender was used to crush the waste till the "required size of paper "sludge.Plate 4 shows the "papers after "crushing in the wet "grinder.

Mechanical "Investigation 4.2.1 Flow, "test
A flow test "acco rding to, ASTM, C1437, 2013 for determining the workability of all mortar "mix es was done.

Dry density
Density (ρ) is the mass of a unit volume of hardened mortar expressed in kilograms per cubic meter.The cube specimens with (100mm) were tested according to ASTM C567-2005a and the average result of three samples at 28 days were calculated.

Total absorption
The total absorption test was concluded on (100) mm cubes according to ASTM C642-2013.The absorption at 28 days for all mortar mixes were prepared and the average of three cubes were determined.

Compressive "strength
The compression strength for all mortar mixes was achieved using cubes with (50×50×50mm) which conform to ASTM, C109/C109M, 2013.The average of "three cube strength at ages of (7, 28 and "60) days were gain.

Direct tensile strength
The test was "done; according to BS, No.6319-Part:7, 1985, the direct tensile "strength of three "briquette samples were gain at ages 7, "28, and "60 days.

Modulus of "rupture
The flexural strength (modulus of rupture) was achieved using (40×40×160) mm prism, that conform "with, ASTM, C348, 2014.Central point load system of three prisms "were calculated at (7, 28 and 60) days age for "each mix.The flexural test was "tested by EL" E Digital "Electric testing machine "with 10 KN "cap acity.

Thermal "Conductivity Test
Thermal conductivity (K) for all mortar mixes was determined by using Hot Disk "method.Moulds with "diameter of (50) mm and (10) mm thickness were prepared; two specimens for "each mix were tested at (28 days).Awareness of "locally thermal, conductivity is essential "in the evaluation of "heat transfer rates.

Microstructure "Investigation
This test requires to prepare a sample of "test according to, ASTM, C856, 2014 with the "suitable dimensions (1*1*1) cm.All "specimens were dried in an oven prior to testing at 60 o "C for 7 days, to avoid "disturbance.The next step involves "immersion of the sample in a "low-viscosit y epoxy "resin.
The epoxy was, "cured at 40 o C for at "least 24 hrs.The final stage involves, "painting with thin layer of liquid gold to avoid the collection "of electric charge when the electron ray looks at the sample by using scanning "electron microscope (SEM).

Fresh "Mortar Properties Table 8 presents the flow table test "values.
A "redu ction in flow values with increasing the content of "waste paper pulp, this is due to greater water absorption of the "paper.It requires more water to "get the same flow, thus the "flow of mortar containing "paper pulp was enhanced "by , the addition "of the super-plasticizer."Th e percent of super" -plasticizer was higher with increasing "in waste paper percent as "indicated in Table 8.The requirement of flow table must be in the range of (100 ± 10)%.

Hardened "Mortar Properties
The average dry density and water "abso rption results of all mortar mixes, are "listed in Table 9 and Fig. 2. A decrease in dry density "results was indicated, while water absorption "was increased with the "increasin g of waste, paper addition "in, the mixes, the higher amount "of, water absorption is due to the "presence of cellulose resources that easily "absorbs water, and keeps it for a period.Results "of mechanical properties (compressive strength, direct tensile strength and flexural, strength) at 7, "28 and 56 day's age for all mortar mixes are listed "in Table 9.It indicated "that there is an increase in all strengths with the progress of "curing age due to continuing hydration, "process .All mortar mixes with waste paper show lower strength than reference mixes for all, test ages except that mix with (5%).Mixture with (5%) shows slightly higher than the reference, this is due to considerable amount of alumina-siliceous material (presented in waste paper) which is combined with calcium and led to this slight increase in strength.Compressive strength results for all mixes are indicated in Fig. 3, for all ages (7, 28, and 56 days).Direct tensile strength was indicated in Fig. 4, which has same trend as in compressive strength.The reduction is due to the vanishing in cohesion "with the binding of calcium-hydrate -" silicate (C-S-H), gel on the cellulosic material is "particularl y weak.The modulus of rupture (flexural strength) results are drawn in Fig. 5, indicate that "mortar mixes with 5% paper "pulp gave similar strength as "reference mortar mix and the "strength decreases as the content of paper pulp "increas es.Thermal "Conductivit y test; is most important "characteristics of the insulating "mortar.Results of thermal conductivity at 28 days for all mortar mixes are listed in Table 9. Thermal conductivity results for mortar with (10%, 15%, and 20%) waste paper are "less than refernce mortar."Due to the cellular nature of papercrete mortar which will produce a resistance to heat movement through papercrete and effect on the conductivity.Therefore, "the paper pulp is the important "factor to minimize the "thermal conductivity.Fig. 6 demonstrates the relationship between dry density and thermal conductivity at 28 days age.The figure denotes that the dry density is the main factor, "disturbing the (K) value, improvement in density will cause an increase in "thermal conductivity (K), due to "minimizing of density, the gaps, and pores between the particles which block the passage,of the heat through it.Because of increasing the "number and size of pores "and voids which cause to "decreas e in thermal,conductivity ,as "compared,,with mix without "paper, the statement of lower "densit y resulting in lower thermal conductivity "was proven true and it is "also supported by other "research er like, Rehman, 2017.The scanning electron microscope "observations of the transition zone; contrast the "good, bonding of cement paste with particles" , that demonstrates in Plate 5. Also in Plate 6, the paper "pulp surface is covered with the hydration "products.So, it results in a decrease "in porosity and small voids in the "matrix .The compact matrix, "with pulp enhanced the mechanical "strengths of composites.On the other "hand Plate 7, Plate 8, and Plate 9 illustrated a debonding between paper "pulp and cement paste with a small content of "CaCO3 compared "wi th, reference symbols due to the transmigration of the "carbonate composites.The results "showed some micrograph of micro" -cracks generated from bond "zone between paper "pulp and cement paste, " because of weak bonding "charact eristic around "cement paste and paper pulp.In addition to that, it was observed that increasing "the content of paper pulp will produce closed pores in the specimens, the results also "were reported by Sangrutsamee, et al., 2012.

CONCLUSIONS
The following "con clusions can be "drawn from the experimental works: 1. Producing light-weight insulating papercrete mortar can be achieved by adding waste paper with low bulk density.The waste paper could be important material as alternative sustainable resources.2. It was established that adding waste paper has a distinct opposed effect on the flow test.For which request "higher water or higher chemical "admixture dosages to keep the "flow values approximately the "same for all mortar "mixes.With increasing the addition of waste paper percentages causes more reduction in flow table test than the reference mixture.3. Decrease in dry density was mentioned with increasing the content of waste paper added to the mortar mix.This is attributed to the absorbability of paper pulp causes a noticeable reduction in the unit weight of the mortar mixes as a result of the creation of voids and the porous structure of the paper, thus leading to an essential increase in the absorption in comparison with reference mix.The results of dry density demonstrate that light-weight "mortar could be created by adding waste paper.4. Increasing waste "paper led to an "increase in the water "absorption by about (14.5%, 32.9%, and 44.8%) for (M10, M15, and M20) respectively as compared with the reference mix.While the reduction "in dry density was (6.7%, 22.8%, and 44.7%) for (M10, M15, and M20) respectively as compared with the reference mix. 5. Compressive strength, direct tensile strength and flexural strength for mixes with (10%, 15% and 20%) waste paper pulp content declined with the increase of the content of waste paper than reference mix except the mortar with (5%) which indicates nearly equal strength to that of reference mix.

.
The results conform to ordinary Portland cement (type I) of the Iraqi "Specifications, IQS., No.5, 1984.

Figure 4 .
Figure 4. Results of direct tensile strength of papercrete mortar.

Figure 6 .
Figure 6.Variation in dry density with thermal conductivity.

Table 1 .
Recycling ratio of paper in, some countries, Mymrin

Table 3 .
Chemical Composition and Main Compounds of Cement.

Table 4 .
Properties of Fine Aggregate.
Figure 1.Grading curve for used fine aggregate.

Table 5 .
The technical descriptions of superplasticizer.

Table 6 .
Physical properties of waste paper.

Table 7 .
Grading of Paper Pulp.
Plate 2. Sample of paper shredder.Plate 3. Paper pieces soaked in water.Plate 4. Paper mass after soaked and grinding.

Table 8 .
Results of flow table and percentages of super-plasticizer addition.