Toner and Brick aggregates used in the Development of Foamed Concrete

Paybar Shawnim

P. Shawnim is with the School of Architecture, Design and the Built Environment, Nottingham Trent University, Burton Street, Nottingham, NG1 4BU, UK. Phone: (+44 7438199426), e-mail: (paybar.shawnim2014@my.ntu.ac.uk )

Abstract

This paper investigates compressive strength and permeability of a new foamed concrete. The aim is to test for viability of other materials, such as toner and brick aggregates in the development of FC to produce a hydrophobic lightweight foamed concrete with enhanced properties. Foamed concrete generally is made of ordinary Portland cement (OPC), sand, foaming agent, and water with a well spread pore structure. Compressive strength and permeability (capillary and total water absorption) testing were carried out on 100 mm cubes to test the behaviour of those materials in the development of foamed concrete (FC). Results show toner inclusion of all the mixes, showed high improvement for compressive strength and water penetration particularly, inclusion at 5% of the cement by weight is an excellent viable material for improving all the properties of the FC examined so far within this research when added in the right quantities. While the use of brick aggregates (Bp) (of (0-5) mm as a filler and 10 mm as fibre reinforcement) showed improvement in compressive strength but adverse effect on permeability. Also, improvement in compressive strength and water penetration decrease with a reduction in density.

Keywords—Brick aggregates, Compressive strength, Foamed concrete, Permeability and Toner.

1. INTRODUCTION

Foamed concrete (FC) is a lightweight material made up of Ordinary Portland cement paste (OPC and a filler, usually sand) and water with a well spread air voids or pore structure created by the introduction of air by mechanical means of foaming. The foam can be originated from an agent made of natural surfactants or synthetic materials, and can be added to the concrete mix either as pre foamed (where the foam is prepared in advance by the foaming machine and added later) or as mixed foaming (the foam is added to the mix at the same time as it is prepared) [1]. Foamed concrete is a lightweight material with low densities of between (400 to 1800) kg/m3 incorporating a high volume of air, highly workable, self-flowing, self-compacting and self-levelling with fire resisting, thermal insulating and sound proofing properties. The typical strength value for foamed concrete of densities between (800 – 1600) kg/m3 is between (1–10) N/mm2, see table (1) [2,3]. Foamed concrete produced in this range can only be used for general purposes, such as gap fillings. But at a minimum strength of 25 N/mm2, foamed concrete has the potential to be used as a structural material [4]. While,

table (2) shows the maximum compressive strength of 28.5 N/mm2 reached [5]. It is to be developed further to accommodate a wider range of construction applications.

This paper determines the strength and permeability of a new foamed concrete

It examines strength and permeability of toner (newly introduced material with the details given bellow) and brick aggregates. These two materials are chosen because they are widely available as waste disposable at a cheap cost to help a cleaner green environment thorough their wise reuse instead of disposing them of at landfills. Also, their influence and effect have never been examined before in FC. The well graded brick aggregates of (0 -5) mm size is used in place of sand with a 10 mm size for strength as coarse aggregates.

in the development of FC to produce a hydrophobic lightweight foamed concrete with enhanced properties.

Foamed concrete is highly permeable, recently its potential as a semi-structural material came to light. It is generally used in building construction as low strength concrete for foundations, thermal and sound insulations, and in areas where resistance to frost is a requirement [6]. Classification of aerated concrete (AC) based on the method of pore-formation can be summarized as air-entraining method (gas concrete), foaming method (foamed concrete, FC) and combined method [6]. Autoclave is a form of curing, using heat treatment for early gain of concrete strength. The second type of aerated concrete is foamed concrete (FC), for which no chemical reactions are involved.

Table (1) Summary of properties of hardened foamed concrete [2].

Density (kg/m3) Compressive strength (N/mm2)

400 0.5 – 1.0 600 1.0 – 1.5 800 1.5 – 2.0 1000 2.5 – 3.0 1200 4.5 – 5.5 1400 6.0 – 8.0 1600 7.5 – 10.0

Table (2) Splitting tensile strength of foamed concrete compared with normal weight and

lightweight concrete [5].

Fine aggregate

Type

Plastic density kg/m3

28-day compressive

strength N/mm2

Splitting Tensile Strength (N/mm2)

Foamed concrete

Normal weight

Lightweight aggregate

1400 13.5 0.8 1.2 1.3Sand 1600 19.5 1.8 1.6 1.7 1800 28.5 2.1 2.1 2.2

The cement content of the foamed concrete for all research studies was kept constant at (500 – 600) kg/m3, which is comparable to other studies [8, 9, 10]. Addition of toner at 1% or 5% by weight of the cement, had no effect on water demands for the mixes involved.

1.1 Clay brick aggregates (coarse and fine) as a filler in concrete

It has been estimated that brick remain a dominant material in residential construction [11] and can account for a large proportion of construction and demolition waste on new residential construction sites in the world [12, 13]. Brick is the second most consumed building material after concrete, which has a share of around 25% of the total building material requirements [11]. The left over and those failed the (QA) at the manufacturers can be collected at a cheap cost.

Bricks in general are treated as waste when broken or damaged from the brick production line or from construction and demolition sites [12, 13, 14, 15]. Studies have shown that brick and concrete waste can constitute up to 75% of construction and demolition waste from a construction site and that a big proportion of this waste is due to poor internal handling and excessive cutting [12, 13]. As an example to this effect, for a job requiring 1,100 bricks, 1,500 bricks must be ordered resulting in 27% waste. Through the above reports review, while brick waste can be obtained at a very cheap cost and to contribute to a cleaner environment, it was chosen to be tested for viability usage in FC. Ground clay brick of up to 5 mm as brick powder (Bp), and 10 mm as coarse brick aggregates are the types used for this research. There are a number of researchers using ground clay brick powder (Bp) as partial replacement of cement in concrete, and classified Bp as pozzolanic materials [16, 17]. For chemical composition of the cementitious materials of clay brick powder (GBP), table (3).

Table (3). Chemical composition of the cementitious materials of clay brick [18].

Aliabdo et al. [19] noticed improvement on compressive strength at 25% and 50% replacement of the cement, for which continues by increasing ground clay brick aggregate content, while foamed concrete compressive strength gradually decreases at the same replacement levels [20]. They also found that it was possible to achieve concrete of high strength using clay brick as coarse aggregates as a filler replacement. Debieb and Kenai [21] used both coarse and finely ground clay bricks, found strength decreased in the range of 20% to 30% depending on the degree of substitution. Also, using only ground bricks as fine aggregates, Khatib, and Poon and Chan [22, 23] found a decrease in strength, while Khaloo and Hansen [24, 25] noticed that there was an increase in tensile strength when ground clay

Composition (%) Ground clay brick powder (GBP)CaO 0.81SiO2 69.90Al2O3 15.38Fe2O3 6.78MgO 1.58SO3 0.04K2O 2.78Na2O 1.02Loss on ignition 0.16

brick aggregates were used. This may be attributed to the fact that ground clay brick is very weak in compression and strong in tension for the bonds it makes with the cement.

1.2 Toner

This is a newly introduced material particular to this research, therefore, there is no published information or data available at all for its usage in this field. This material comes in the form of a powder, and it is going to be used as an additive to the mix, at 1% and 5% of the binding cementitious material (cement). A brief description on toner reuse or recycling, 70 million laser cartridges are sold in the U.S. annually, and less than 30 percent are currently being recycled. 70% of the non-recycled used toner cartridges exist in the U.S for which they go directly into trash cans and end up in landfills, 12% per year is the annual growth rate of non-recycled print cartridges. Despite the environmental and bottom-line benefits of recycling print cartridges, every year over 300 million cartridges with a combined weight of 150 million pounds are buried in the landfills.

As for its environmental impact, the Green House Gases emissions from manufacturing a single mono toner cartridge have been calculated to be approximately 4.8 kg CO2; per cartridge, and the life cycle assessment of toner reveals that the GHG emissions are approximately 16 metric tons per 1 metric ton toner produced. On average a cartridge with a yield of 5000 pages contains 200 grams toner. This equals 3.2 kg CO2 emission per cartridge. This material was chosen for this research because it is widely available for recycling or reuse as the above literature review shows and to help in cleaning the environment by reducing buried waste and CO2 emission around the world. One way is the recycling or re use of the old printer cartridges to use for this purpose, second, may be collection of the expired and waste toner materials, these may come at no cost. Table (4) shows chemical composition for toner. Also, toner includes the following additives for flow and lubrication purposes: Fumed silica, metal stearates e.g. zinc stearate, fluoropolymers powders, magnetite, and carbon black.

Table (4). Chemical composition of toner [26].

Toner Type CompositionPlastic (Styrene acrylate copolymer, polyester resin)

65-85% or 55-65%.

iron oxide 6-12% or 30-40%.Wax, ground sand 1-5%Amorphous silica 1-3 %Carbon black 1-10%.

2. EXPERIMENTAL WORK

The experiments were carried out in the laboratory in accordance to the relevant British Standards (BS) for each part of the process. Sets of 100 x100 x 100 mm plastic cube moulds were used to cast the normal weight concrete samples. Whereas, disposable polystyrene cube moulds were used to cast all concrete samples containing foam to avoid the use of release agent and enabling the sealed curing process of the desired period of 28 days, figures (1and 2). Sand and Brick aggregates (Bp) ((fine aggregates of (0-5) mm and coarse aggregates of (10 mm)) used as fillers, and toner as an additive to the binding OPC.

2.1 Compressive strength was measured at 28 days, in accordance with BS EN 12390-3:2009 [27].

The test was carried out with a digital log keeping and digitally controlled automatic loading machine, figure (3). The oven dried cubes were placed centrally under the loading plates and positioned to have even surfaces in contact with the loading plates, figures (4). Results quoted in each case are the average of six specimens.

Figure (1) Disposable polystyrene cube moulds of the size (100 x 100 x 100) mm are used for casting, also, temperature reading can be seen.

Figure (2) Different methods of Curing, Left; (NC) in water. Right; (FC) sealed in cling film.

Figure (3) Crushing machine with digital computing screen.

A B CFigure (4), A; Cubes oven dried, B; Cube between plates under compression, C; Cube after crushing

2.2 Permeability

Permeability is measured through capillary water absorption and total water absorption. These two tests were carried out to determine moisture movements and their related functions, this is one way of examining the development of the foamed concrete properties.

2.2.1 Capillary water absorption test was carried out under 5 bar pressure in accordance with BS EN 12390-8:2009 [28].

Three oven dried specimens put under the 5 bar permeability test apparatus for 72 hours, after which they are taken out and split open to mark and measure water penetration from bottom up, results expressed in millimetres (mm), figures (5 and 6).

Figure (5) Left; Permeability apparatus, Right; Cube specimen under 5 bar pressure.

Figure (6) Specimens split open and marked. Figure (7) Specimens immersed in water.

2.2.2 Total water absorption was carried out in accordance with BS 1881-122:2011 [29].

Three oven dried specimens were totally immersed in water for at least 72 hours, after which they were taken out to measure weight of absorbed water. The absorbed water was determined from the difference in weight between fully water saturated and dried state of a specimens. Results expressed in (kg/m3) or in (%) of the dried weight, figure (7).

3. RESULTS AND DISCUSSIONS

3.1 Compressive strength

Setting out the density as the bases for this experimental analysis, and only mentioning those mixes which meet the 28.5 N/mm2 set as a standard, or the minimum compressive strength requirements of 25 N/mm2, then we can see the following analysis from figure (8) and table (5): At 1800 kg/m3 density, specimens with brick aggregates, S7, showed 52 N/mm2, which is higher than 49.7 N/mm2 for S2 specimens made with sand, while S13 with toner inclusion specimens having 49.3 N/mm2 an almost equal compressive strength for these three types of mixes recorded (82%, 74% and 73%) over the maximum recorded compressive strength of 28.5 N/mm2 respectively. At 1700 kg/m3 density, specimens with brick powder (Bp), S8 showed 59 N/mm2, and S14, 55.1 N/mm2, an increase of (107%, 54% and 93%) were noted. At 1600 kg/m3 density, S16, 50.5 N/mm2, S15, 40.6 N/mm2, and S3, 30 N/mm2, they were increased by (77%, 42% and 5%). At 1300 kg/m3 density, S4, 26.1 N/mm2, thus, an increase of 4% over the 25 N/mm2. At 1100 kg/m3 density, S18, 38.2 N/mm2 and S10, 35.6 N/mm2, again, they were increased by 34% and 25%. At 1000 kg/m3 density, S11, 30.8 N/mm2, it was only increased by 8%.Through the above numerical results, it is evident that: The use of toner upgrades the strength to a much higher level, taking S14 of 55.1 N/mm 2

as an example, the strength has increased for close to two folds i.e. 93% over the 28.5 N/mm2 set as a standard.

Brick aggregates (Bp) added to any of the mixes, upgraded the strength, see S7 with 52 N/mm2 as an example.

Even at the rest of the densities of (1000 and 1100) kg/m3, namely, S11 of 30.8 N/mm2, S18 of 38.2 N/mm2, and S10 of 35.6 N/mm2, a noticeable increase is recorded.

Looking at the very low densities of the 500 kg/m3, S19 of 5.1 N/mm2 and 600 kg/m3, S6 of 3 N/mm2, again, they have shown improvement by about 40 % compared to those

figures published within the literature review of (0.5 – 2.0) N/mm2 for those matching densities.

Most of the above discussed results obtained for foamed concrete of the different mixes, closely match that of the sand mix normal concrete of 2000 kg/m3, namely, S1 of 53.3 N/mm2, taken as a controlled concrete mix for comparison, in turn it means, the FC has been upgraded to the form which can be used as structural elements in terms of strength.

Table (5) Labelling for fillers of different concrete mixes and their densities. Dry density

(Kg/m3)

S1 Sand 2000S2 Sand 1800S3 S and 1600S4 Sand 1300S5 Sand 1000S6 Sand 600S7 Sand and Brick powder 1800S8 Brick powder 1700S9 Brick powder 1300

S10 Brick powder 1100S11 Sand and Brick powder 1000S12 Brick powder 800S13 Sand and Toner 1800S14 Sand and Toner (5%) 1700S15 Brick p and Toner (1%) 1600S16 Brick p and Toner (5%) 1600S17 Sand and Toner (1%) 1100S18 Brick p and Toner (5%) 1100S19 Sand and Toner (1%) 500

Type of concrete castLabeling

Figure (8) Compressive strength versus density for different mixes contain sand, brick, and toner.

3.2 Permeability3.2.1 Capillary eater absorption under 5 bar pressure

All specimens made with sand, brick or sand and brick composition with toner inclusion, showed superior qualities over those made with the same mixture but without the inclusion of toner, S13 of 1800 kg/m3, 2 mm, S14 of 1700 kg/m3, 1 mm, S15 of 1600 kg/m3, 5 mm, S16 of 1600 kg/m3, 3 mm, S17 of 1100 kg/m3, 60 mm, and S18 of 1100 kg/m3, 16 mm, figure (9) and table (5). Amongst the fore mentioned specimens, S18 of 1100 kg/m3 showed 16 mm

water penetration, which is less than 26 mm for the normal concrete of S1 specimens made with sand of 2000 kg/m3 density. Looking at S18 and S16 of (1100 and 1600) kg/m3, (16 and 3) mm respectively, and S14 of 1700 kg/m3, 1 mm. This indicates that specimens with the inclusion of 5% toner in their mixes, improving the capillary water penetration better than the 1% inclusion. Furthermore, specimens made with the inclusion of toner in their mixes in addition to the mixing materials, showed a significant high resistance to the 5 bar capillary water absorption of an average of 5 mm or less, and a water absorption of 5% or less across all the foamed specimens tested so far. Using brick as filler is just as bad as sand for capillary water absorption, as can be seen from S12 of 800 kg/m3, 100 mm and S5 of 1000 kg/m3, 100 mm.

Figure (9) Capillary water absorption (mm) versus density for different mixes contain sand, brick and toner.

3.2.2 Total water absorption

Looking through figures (10 and 11), all specimens with the inclusion of toner recorded permeability of the range between (10.1 % to 12.5 %) or (111.5 to 138.5) kg/m3 of their dry weight. This shows high improvement, while all the rest of the specimens of sand made or brick made show higher permeability of the range between (9.3% to 30 %) of their dry weight, or (187.7 to 394) kg/m3 water absorption. At low density of 1100 kg/m3, water absorption is 111.5 kg for S18, a less water absorption of 76.2 kg compared to normal concrete of S1 of 2000 kg/m3, which is 187.7 kg. This means high improvement in this respect, figure (11) and table (5).

Figure (10) Total water absorption (%) of dry weight versus density for different mixes contain sand, brick and toner.

Figure (11) Total water absorption (kg/m3) of dry weight versus density for different mixes contain sand, brick and toner.

4. CONCLUSIONS

The following conclusions can be drawn from the present study:Toner at 5% dose, proved to be an excellent viable material for inclusion in foamed concrete (FC), improving compressive strength by close to two folds compared to those demonstrated through figures published by BCA [2].

Permeability test through capillary water absorption was improved to reach a minimum of a few millimetre water penetrations, i.e. close to zero, which is not easily obtained even with normal concrete of high densities. Also, Permeability test through total water absorption was also improved to values that only the normal concrete of high densities of 2000 kg/m3 and beyond can reach, i.e. permeability reached the minimum comparative values. This is because toner has the ability to embed the pores with a hydrophobic membrane which gives it the tendency to prevent water absorption, as it has been demonstrated above for permeability within some of this research specimens with almost zero water penetration.

Brick aggregates as a filler also shown a noticeable improvement in FC. Mixes contained this material have led to a significant improvement in compressive strength for the foamed concrete, in comparison with controlled samples made with normal concrete within this research, and with the results published by BCA [2] in this relation. Contrary to the ordinary practice of excluding coarse aggregates in the FC mixes, the 10 mm brick coarse aggregates proved further strengthening without causing any segregation.

Compressive strength is directly related to concrete density; concrete of high density exhibits high compressive strengths. Compressive strength for all those made of brick powder (Bp) only as a filler, S7 to S12, equals or exceeds the compressive strength of those made with sand only as a filler of their corresponding densities S1 to S6, this is mainly due to the fact that brick powder has the power to react with the binding cement making stronger

intercellular bonds. Also, Brick aggregates have the ability to absorb and hold more water in advance within their particles to enhance the curing regime later by keeping the matrix hydrated for a longer time than for the other sand made specimens. While compressive strength of those made of brick powder and toner contained at 1% and 5%, S15, S16 and S18, equals or exceeds the compressive strength of those made with either sand only or Bp only. As demonstrated through the results and discussions, toner will enhance the compressive strength and permeability when added to the mix at 5%, compared to the 1%.

Toner mainly contain carbon, iron oxide , silica, styrene powder and waxes, it is partly reactive with the cement inducing a vacuum shaped matrix of well spread micro pores, acts as an air tight space against external pressure which is held by a strong intercellular connecting bonds, this gives the strength of the FC. While partly has the ability to embed the pores within a hydrophobic membrane which gives it the tendency to prevent water absorption, as is explained above.

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