Construction and Building Materials 48 (2013) 295–305

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Construction and Building Materials

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Using ceramic sanitary ware waste as concrete aggregate

0950-0618/$ - see front matter � 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.conbuildmat.2013.06.063

⇑ Corresponding author. Tel./fax: +48 81 5384 390.E-mail addresses: a.halicka@pollub.pl (A. Halicka), pawel-ogrodnik@wp.pl

(P. Ogrodnik), bart-z@wp.pl (B. Zegardlo).

Anna Halicka a,⇑, Pawel Ogrodnik b, Bartosz Zegardlo c

a Lublin University of Technology, Department of Civil Engineering and Architecture, ul. Nadbystrzycka 40, 20-618 Lublin, Polandb The Main School of Fire Servce, Faculty of Fire Safety Engineering, ul. Slowackiego 52/54, 01-629 Warsaw, Polandc Collegium Mazovia – Innovative High School in Siedlce, Building Unit, ul. Sokolowska 161, 08-110 Siedlce, Poland

h i g h l i g h t s

� Crushed ceramic sanitary wastes were used as aggregate in concrete.� Procedures of aggregate production and design of concrete mix were described.� Tested concrete displayed high strength and abrasion resistance.� Concrete with sanitary aggregate and alumina cement is temperature resistant.

a r t i c l e i n f o

Article history:Received 4 January 2013Received in revised form 16 May 2013Accepted 17 June 2013Available online 30 July 2013

Keywords:Waste materialsSanitary ceramic waresAggregateConcreteAbrasion resistanceHigh temperature resistance

a b s t r a c t

Sanitary ceramic ware waste is classified as belonging to group of non-biodegradable industrial waste.The paper presents the studies on possible reuse ceramic sanitary wastes as the aggregate (both fineand coarse) in concrete.

The procedure of aggregate production (crushing, dividing particles into two groups – fine and coarseparticles and establishing their proportion) and designing the concrete mix are described. Studies onproperties of this aggregate and properties of concrete containing this aggregate, are presented. Testedconcrete displayed high strength and high abrasion resistance.

This paper presents also results of examination of concrete with alumina cement and ceramic sanitaryware wastes as aggregate in 1000 �C temperature. For comparison purposes, specimens with traditionalnatural aggregate and alumina cement were heated as well. As opposed to specimens of concrete withtraditional aggregate, specimens with ceramic aggregate preserved their shape and cohesion and showedno cracks and defects. Despite some decrease in strength, these specimens after heating continued to dis-play high compressive and tensile strength.

On the basis of described studies, sanitary ceramic aggregate may be recommended for preparing spe-cial types of concrete: abrasion resistant concrete and concrete dedicated for members working in hightemperatures.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

Industrial waste management constitutes one of the major glo-bal problems of our times. Recycling of non-biodegradable waste isparticularly difficult. Ceramic waste has been classified in thisgroup. Due to the fact, that biodegradation period of ceramic isvery long (up to 4 thousand years) and ceramic industry wasteconstitutes significant share in the total production, recycling ofceramic waste is a big problem.

Ceramic ware can be divided into two groups, depending on thematerials used for its production. The first group includes products

of burned red clay (bricks, structural wall and floor tiles, roof tiles).Products made of white clay: technical ceramics (ceramic electricalinsulators), ceramic sanitary ware (washbowls, lavatory pans, bi-dets, bathtubs), medical and laboratory vessels, belong to secondgroup. Ceramic sanitary ware wastes come from defective waresrejected during quality control. Main defects include cracks, nicks,and glaze damage.

One of the natural ways of reusing inorganic industrial wastes,is their use in the production of building materials, especially asraw materials in the concrete manufacture. This manner of recy-cling has positive impact on the environment – it reduces theamount of deposited waste and limits mining of mineral aggregatedeposits. Inorganic ceramic waste has an additional advantage – itneeds no special processing when used as an aggregate. Thetechnology of producing the concrete mix with aggregate using

Fig. 1. Aggregate made of ceramic sanitary ware waste (‘‘coarse’’ particles).

Fig. 2. Dependence of aggregate mixture mass on K1:K2 ratio.

296 A. Halicka et al. / Construction and Building Materials 48 (2013) 295–305

recycled ceramic ware is the same as in the case of production ofconcrete mix with traditional aggregate.

The use of red ceramics as an admixture for concrete dates backto Ancient times. In Ancient Rome, mortar prepared from naturalpozzolana was used in the production of concrete, whereas in re-gions located far away from the volcano, crushed and grinded dis-assembled roof tiles were used as the binder.

Modern experiments on the use of ceramics have been primar-ily focused on its environmental impact. Crushed ceramic waste isused as an admixture to traditional aggregates or as a substitute forsome part of aggregate of a chosen dimension [1–23] and the pow-der obtained from crushed ceramic waste is used as pozzolanicadmixture to Portland cement [24–36]. All studies have confirmedthe possibility to use ceramic waste in concrete, however due todifferent properties of such aggregates, parameters of obtainedconcrete types also differ.

In general, substitution of traditional natural aggregate with redceramics waste adversely affects concrete strength parameters[1–16]. The higher the content of traditional aggregate substitutedby red ceramic waste, the lower the concrete strength.

Descriptions of studies on concrete made with white ceramicware waste may be found in a scarce number of papers [14,17–23,34–36]. Studies on concrete containing sanitary and technicalceramic waste, have confirmed advantages brought about by suchaggregate. Strength parameters of the obtained concrete approxi-mated or even exceeded parameters of concrete with traditionalaggregate [14,17,20,21,35].

Study results [17] have shown, that strength of concrete con-taining from 3% to 9% of coarse aggregate of ceramic sanitary warewaste was higher by 2–8% than that of concrete without thisadmixture. If more ceramic admixture was used the results werebetter i.e. authors [20,21] replaced of 15%, 20% and 25% of aggre-gate by sanitary ceramic waste and concrete strength after 28 daysof curing was higher by 2%, 5%, 11% respectively, and after 90 daysby even 20% when compared with gravel concrete. In the study[20,35] X-ray analysis proved that cement hydration was not dis-turbed by the presence of sanitary ceramics and the interfacialtransition zone between paste and sanitary ceramic aggregatewas compact.

Therefore, study results may be said to have proved possible re-use of ceramic sanitary ware wastes as concrete aggregate. How-ever, in order for the production of sanitary ceramic wareaggregate to be successful, it should not only bring environmentaladvantages, but it should also be economically justified. We as-sumed, that economic advantages will emerge, if produced con-crete has specific properties compensating for high cost ofaggregate production. Specific properties of concrete should resultfrom specific aggregate properties.

Various compositions of ceramic pastes and diversified man-ufacturing processes and their technological parameters (e.g.burning temperature) result in differences in chemical and phys-ical properties of ceramic sanitary ware. According to reference[37] its compressive strength ranges from 60.0 to 600.0 MPa,modulus of elasticity from 22.0 to 80.0 GPa and the coefficientof thermal expansion – from 0.4 to 0.85 � 10�5. In the chemicalcomposition of sanitary ceramics the high silica and aluminadioxide content and insignificant calcium oxide contents is char-acteristic (Ref. [37]). We set ourselves an objective to takeadvantage of the above mentioned features. An assumptionwas put forward that concrete with sanitary ceramic aggregateis resistant to abrasion due to the high strength and high mod-ulus of elasticity of such an aggregate and also resistant to hightemperatures due to chemical composition and low thermalexpansion coefficient of the aggregate. This paper presents studyproving this assumption.

2. Materials and methods

2.1. Studies of sanitary ceramic aggregate

2.1.1. Preparing the aggregateAggregate used in authors’ own research was prepared from ceramic waste

deposited on a dump of a Polish factory producing ceramic sanitary ware. Frag-ments of about 400 � 400 mm, were crushed using jaw crushers. The crushers al-low to separate ‘‘fine’’ particles of 0–4 mm, passing through a 4-mm sieve, and‘‘coarse’’ particles of 4–8 mm remaining on the 4-mm sieve but passing through a8-mm sieve (Fig. 1). Particles larger than 8 mm were re-inserted into the jawcrusher.

The aggregate was composed of ‘‘fine’’ and ‘‘coarse’’ constituents. Percentage ofeach constituent was determined using iterative optimisation method. The mass of‘‘fine’’ particles was referred to as K1, and the mass of ‘‘coarse’’ particles as K2. Theassumed objective was to find percentage of K1 and K2 constituents warrantingmaximum mass of aggregate mixture in a fixed volume. This means minimumamount of free space, maximum bulk density of the aggregate and optimum per-centage share of constituents.

In a laboratory flask with a capacity of 1693 cm3, mixtures of constituents wereprepared. The ratio K1:K2 varied from 1:0.0 to 1:0.45, and changed every 0.05 point.After vibration of each mixture, the flask with the mixture was weighed. A diagrampresenting dependence of the mixture mass on K1:K2 ratio (Fig. 2), was drawn up.The test was interrupted, when the function was reaching the maximum value andchanging from an increasing to a decreasing function. This occurred when K1:K2 ra-tio was 1:0.4. This proportion was regarded as optimum.

2.1.2. Physical and mechanical propertiesSieve analysis of the aggregate composed as set out in item 2.1.1 was per-

formed. The sieve analysis was conducted in accordance with EN 933-1:2012 stan-dard [38]. Results are presented in Fig. 3. Fineness grading modulus FM calculatedin accordance to EN 12620:2002 standard [39] is equal FM = 4,51 and the amount offinest particle (<0,063 mm) was equal 0,37%.

Fig. 3. Gradation of aggregate composed of ceramic sanitary ware waste.

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Particle density and water absorption were tested, in accordance with EN1097-6 standard [40]. It was found, that particle density was 2640.30 kg/m3 (average va-lue of 9 tests). Average water absorption was 1.53%.

Particle density of filler was determined using a method set out in EN1097-7[41]. On the basis of 6 tests, average bulk density was determined as 2362.76 kg/m3.

Fig. 4. Testing aggregate resistance to crushing: aggregate batch ready

Fig. 5. Structure of sanitary ceramic aggregate partic

The resistance to crushing was performed in accordance with the Polish PN-B-06714-40:1978 standard [42]. Aggregate of 4–8 mm was used only. The test wasconducted using a special vessel with a piston crushing the aggregate; the crushingforce was exerted by hydraulic press (Fig. 4).

Aggregate resistance to crushing was evaluated on the basis of the crushing ra-tio. It is the percentage of particles which after crushing failed to pass through a 1-mm sieve mesh. Three tests were performed and average crushing ratio was 8.39%.

2.1.3. Particle structure and chemical compositionStructure of ceramic sanitary ware waste was examined under a scanning elec-

tron microscope SEM (Fig. 5). This structure is porous. The pores are of irregularshapes and different size (up to several micrometers).

Using an EDS detector, elemental analysis was performed. It was found, thattested ceramic sanitary ware mainly contained silica SiO2 (67.63%), aluminiumdioxide Al2O3 (24.05%) as well as potassium oxide K2O (3.0%), nickel oxide NiO(2.78%), sodium oxide Na2O (1.25%), ferric trioxide Fe2O3 (0.55%), molybdenum tri-oxide Mo2O3 (0.37%) and magnesium oxide MgO (0.36%), as is shown in the Fig. 6.Above, the percentage by weight was given.

2.1.4. Bond between cement grout and ceramic sanitary ware aggregateTensile bond between cement grout and sanitary ceramic piece was estimated

on the basis of interface stress in the bonded specimen. Sanitary ceramic warepieces were cut out from a wash basin (Fig. 7), using a diamond disk mounted on

for testing and the aggregate under a piston in the hydraulic press.

le seen under the scanning electron microscope.

Fig. 6. Results of chemical analysis of ceramic aggregate particle.

Fig. 7. Preparation of ceramic sanitary ware pieces for bond testing: wash basin before cutting the pieces, and the cut-out pieces with a layer of glue placed on surface notsubject to testing.

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a hand-operated tool. Four pieces were cut out. Two of them were used for testingthe bond between cement grout and the glaze. Two remaining pieces were used fortesting the bond between cement grout and clear ceramic surface, therefore theglaze was removed by the grinder.

The specimens were moulded as beams of 40 � 40 � 160 mm and subject to thethree-point bending test, as shown in Fig. 8. Flat pieces of ceramic sanitary ware of40 � 40 � 8 mm were placed in the middle of the beams.

The surface of ceramic pieces was exactly 80 mm away from the end of thebeam. In order not to allow debonding on the second surface of the ceramic piece,this surface was roughened and coated by a layer of glue (Fig. 8).

Fig. 8. Bond test scheme.

After such preparation, ceramic ware pieces were placed in the moulds. Next,the moulds were filled with cement grout. For the preparation of the grout,1200 g of Portland cement CEM-II of compressive strength class 42.5R and 360 mlof water were used. It was the proportion ensuring the consistency demanded bystandards for cement grout testing.

The test was performed using a hydraulic testing machine (Fig. 9). The three-point bending test scheme was performed. As expected, the specimens were dam-aged in the centre, by debonding in the interface between cement grout and a pieceof ceramic sanitary ware.

Bond strength was calculated based on the force Fn destroying the specimen:

f ¼ 1:5Fnl

bh2 ; ð1Þ

where l – distance between beam supports (0.10 m), b – the width of the specimen(b = 0.04 m), h – the height of the specimen (h = 0.04 m).

It was found, that tensile bond strength between Portland cement grout andceramic sanitary ware pieces tested under bending amounted to 1.5 MPa, bothfor fragments with and without glaze. It allow to assume that concrete with sani-tary ceramic aggregate would have internal cohesion.

2.2. Studies on concrete with ceramic sanitary ware aggregate

2.2.1. Designing concrete mix and its compositionAssumptions regarding concrete composition were as follows:

1. Use of ceramic sanitary ware aggregate.2. Use of alternative Portland cement and alumina cement, due to expected resis-

tance to high temperatures.

Fig. 9. Bonding test for a bond between cement grout and sanitary cement piece –specimen after destruction (the surface of ceramic fragment is visible).

Fig. 10. Aggregate used in the study: 1 – coarse ceramic sanitary ware aggregate, 2– fine ceramic sanitary ware aggregate, 3 – gravel, 4 – sand, 5 – coarse graniteaggregate, 6 – fine granite aggregate.

A. Halicka et al. / Construction and Building Materials 48 (2013) 295–305 299

3. Lack of additives and admixtures that are not recommended in concrete resis-tant to high temperatures.

4. Higher water content in comparison to concrete based on traditional aggregate,due to higher water absorption of aggregate.

5. The need to optimize cement grout volume, in order to obtain concrete of lowporosity.

Concrete composition was calculated using absolute volume method [43] andwas verified by experiments. Experimental verification consisted in optimisationof cement grout content. Ultimately, the following composition was obtained:

Fig. 11. Testing consistence of concrete mix with ceramic a

– Ceramic aggregate – 1387.9 kg/m3 (the mass ratio of 0–4 mm particles to 4–8 mm particles was 1:0.4).

– Water – 201.4 kg/m3.– Cement – 493.4 kg/m3, alternatively Portland cement CEM II of 42.5R compres-

sive strength class and alumina cement of alumina dioxide content of more than70%.

– Water to cement ratio – 0.40.

The concrete mix made of ingredients specified above, was compactable byvibration, which allowed to obtained compact concrete.

For comparison purposes in some of later experiment, specimens of concretebased on other aggregates (gravel and granite) were prepared as well. In all con-crete mixes, the above mentioned proportion was kept. Fig. 10 presents aggregatesused in the study.

2.2.2. Consistence of the concrete mixConsistence of the concrete mix was examined using the slump cone test, in

accordance with EN-12350-2 standard [44] (Fig. 11). Slump value was 11 mm, fall-ing into the range of S1 slump class.

For comparison purposes, the concrete mix having the same proportions butcontaining gravel aggregate was prepared. In this case, the slump was 48 mm (S2slump class). The gravel absorbed less water than ceramic aggregate.

2.2.3. Compressive strength and tensile strengthMaximum dimension of aggregate grain was 8 mm, and the content of fine

aggregate was above 70%, therefore the strength was tested using beam specimensof 40 � 40 � 160 mm. Tests were performed using a testing machine (Fig. 10). Spec-imens were bent in accordance with EN12390-5 standard [45]. After specimenbreaking, the halves were compressed in accordance with EN 12390-3 standard[46].

2.2.4. Abrasion resistance testsAbrasion resistance of concrete with ceramic sanitary ware aggregate, was

examined in accordance with EN 14157:2005 standard [47], using the Böhme discabrader (Fig. 12).

Prismatic concrete specimens of 90 � 90 � 100 mm were prepared. Proportionsset out in item 2.2.1 were applied, and only Portland cement was used. Two types ofaggregate were used for the preparation of concrete prisms. Three of them weremade of concrete with ceramic sanitary ware aggregate and the other three of grav-el concrete.

Two days after moulding, the prisms were demoulded and cured for 30 days inhumid conditions. Specimens of 72 � 72 � 72 mm were cut out from these prisms,one week before testing. Just before the testing, the specimens were thoroughlymeasured and weighed.

The specimens were grinded using a disc on which corundum powder was dis-tributed. Each specimen was subject to 440 disc rotations. After each 110 rotations,each specimen was turned, direction of rotation was reversed and abrasive materialwas exchanged. After 440 disc rotations, specimens were measured and weighed inthe same manner as before grinding.

Abrasion resistance was determined as the average decrease in specimen heightafter the test. Decrease in height was determined using two methods: by directmeasurement, and calculated on the basis of decrease in weight. The following for-mulas were used:

– abrasion resistance determined on the basis of direct height measurement:

Sh ¼Dh1 þ Dh2 þ Dh3 þ Dh4

4; ð2Þ

where Dhi – difference between height of the specimen before and after grinding,measured along the i side of the specimen.

ggregate: prepared concrete mix and the cone slump.

Fig. 12. Abrasion resistance tests: specimens and the Böhme disc.

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– abrasion resistance calculated on the basis of decrease in weight:

Sm ¼DmA� 1q; ð3Þ

where Dm – decrease in weight of the specimen, A – area subject to grinding,q – bulk density of the specimen.

2.3. Studies on concrete with ceramic sanitary ware aggregate in high temperature

2.3.1. Specimens and stages of experimentExperiments were carried out in two stages (Table 1). In the first stage (denoted

‘‘1’’), specimens of concrete with ceramic aggregate (CA) and alumina cement (HAC)were tested. At this stage, comparative specimens made of concrete with traditionalaggregate of sand and gravel (SGA) and alumina cement (HAC), as well as compar-ative specimens made of concrete with sand and gravel aggregate (SGA) and Port-land cement (PC) were also examined. Dimensions of these prismatic specimenswere 40 � 40 � 160 mm (denoted ‘‘p’’). In the second stage (denoted ‘‘2’’),specimens made of concrete with alumina cement (HAC) were examined only.‘‘2–SGA+HAC’’ concrete was prepared using sand and gravel. ‘‘2–GA+HAC’’ concretewas composed of fine and coarse granite aggregate (GA). ‘‘2–CA+HAC’’ concrete wasbased on ceramic aggregate. Apart from prismatic specimens of 40 � 40 � 160 mm(denoted ‘‘p’’), cylindrical specimens with 100 mm in diameter and 200 mm height(denoted ‘‘c’’) were tested.

2.3.2. Equipment and heating procedureSpecimens were heated in a chamber furnace, type PK1100/1. Casing of the fur-

nace was produced of square tubes and stainless steel sheet. Insulation was made ofceramic fibre blocks and mats. The heating system was made of spiral resistancewire KANTHAL A1. Temperature was recorded and measured using a PC connectedwith a PCL818HG ADVETECH card. The furnace and its equipment is shown in Figs.13 and 14.

Table 1Composition of concrete and the testing program.

Type of specimen Aggregate Cement Time of strength testing

First stage1–CA+HAC Sanitary ceramic Alumina 30 days after heating

1–SGA+HAC Sand and gravel Alumina 30 days after heating

1–SGA+PC Sand and gravel Portland 30 days after heating

Second stageRight after heating

2–CA+HAC Sanitary ceramics Alumina 30 days after heating

Right after heating2–SGA+HAC Sand and gravel Alumina 30 days after heating

Right after heating2–GA+HAC Granite Alumina 30 days after heating

p – prismatic specimens, c – cylindrical specimens.

The heating procedure, i.e. temperature values and temperature growth and fallrates, was prepared individually for each stage of the study, according to the generalrules used while preparing concrete to work in high temperatures given in standard[48]. Three phases of physical and chemical changes should be considered:

– Phase I – free water evaporation whole temperature grows from 20� up to150 �C, the phase should last for 15 h and temperature growing rate shouldbe 10 �C per hour.

– Phase II – separation of chemically bonded water at 550 �C, temperature growsfrom 150 �C to 550 �C at the rate of 15 �C per hour.

– Phase III – agglomeration, i.e. change of hydraulic bonding into ceramic bond-ing, temperature grows above 550 �C at the rate of 20–60 �C per hour.

After achieving limiting temperature values of each phase, concrete elementsshould be kept at this temperature for 24–72 h, depending on their thickness.

2.3.3. First stage of the experimentFirst stage of the study considered prismatic specimens of 40 � 40 � 160 mm.

There were six specimens of each type; half of them were heated and the remainingthree were left unheated for comparison purposes, in accordance with Table 1.

Due to time limitations in using the furnace, heating time during the first stagewas shortened to 8 h. Instead, specimens were dried before heating in a laboratorydrier. Drying temperature was 250 �C – temperature was raised over 4 h and thespecimens were kept in this temperature for the next 4 h. In order to protect thefurnace against consequences of possible spalling effect, i.e. explosive concretedamage as a result of vapour pressure in concrete pores, the specimens were in-serted into special jackets.

The heating procedure was as follows:

1. Raising the temperature to 150 �C over 2 h.2. Maintaining the temperature at 150 �C for 1 h.3. Raising the temperature to 550 �C over 2 h.4. Maintaining the temperature at 550 �C for 1 h.

Heating Type of specimen Number of specimens

Heating in 1000 �C 1–CA+HAC/1000 �C/30-p 3Without heating 1–CA+HAC/30-p 3

Heating in 1000 �C 1–CA+HAC/1000 �C/30-p 3Without heating 1–SGA+HAC/30-p 3

Heating in 1000 �C 1–GA+PC/1000 �C/30-p 3Without heating 1–GA+PC/30-p 3

Heating in 1000 �C 2–CA+HAC/1000 �C/0-c 3Without heating 2–CA+HAC/30-p 3Heating in 1000 �C 2–CA+HAC/1000 �C/30-p 3

Heating in 1000 �C 2–SGA+HAC/1000 �C/0-c 3Without heating 2–SGA+HAC/30-p 3Heating in 1000 �C 2–SGA+HAC/1000 �C/30-p 3

Heating in 1000 �C 2–GA+HAC/1000 �C/0-c 3Without heating 2–GA+HAC/30-p 3Heating in 1000 �C 2–GA+HAC/1000 �C/30-p 3

Fig. 13. Diagram of a PK1100/1 chamb

Fig. 14. The furnace and prepared specimens.

A. Halicka et al. / Construction and Building Materials 48 (2013) 295–305 301

5. Raising the temperature to 1000 �C over one and a half hours.6. Maintaining the temperature at 1000 �C for half an hour.

After heating, the specimens stayed in the closed furnace until it was com-pletely cooled down. After opening the furnace and removing the jackets, they werevisually inspected without touching the specimens.

The compressive and tensile strength of unheated specimens and specimens notdestructed due to heating were examined 30 days after heating.

2.3.4. Second stage of the experimentDue to destruction of specimens with Portland cement in the firs stage of study

all specimens used in the second stage were made of concrete with alumina ce-ment, however they contained different aggregates. Each type of concrete was rep-resented by prismatic and cylindrical specimens. There were three heatedcylindrical specimens each type. There were also six prismatic specimens eachtype; half of them were heated and the remaining three were left unheated for com-parison purposes, in accordance with Table 1.

The heating procedure was carried out in accordance with the Polish standard[48], as follows:

I. Preparation of specimens at 13–20 �C over 7 days.II. Introduction to working in high temperatures.

1. Raising the temperature to 150 �C over 5 h.

2. Drying at the temperature of 150 �C for 32 h.3. Raising the temperature to 550 �C over 2 h.

4. Maintaining the temperature 550 �C for 7 h.5. Raising the temperature to 1000 �C over 10 h.6. Maintaining the temperature of 1000 �C for 4 h.

III. Cooling specimens to room temperature, including the furnace.

er furnace with a cooperating PC.

IV. Proper heating – 5-fold repetition of the following cycle:

1. Raising the temperature to 550 �C over10 h.

2. Maintaining the temperature of 550 �C for 7 h.3. Raising the temperature to 1000 �C over 10 h.4. Maintaining the temperature of 1000 �C for 4 h.5. Cooling specimens to room temperature, including the furnace.

After heating, the specimens stayed in the closed furnace until it was com-pletely cooled down. After opening the furnace and removing the jackets, they werevisually inspected without touching the specimens.

The compressive strength on cylindrical specimens was tested at once afterheating and compressive and tensile strength of prismatic specimens were exam-ined 30 days after heating. Next, the obtained halves were subject to compressiontest.

3. Results

3.1. Characteristic of sanitary ceramic aggregate

Comparison of ceramic aggregate and some traditional naturalaggregates is drawn up in Table 2. While analysing data compiledtherein, it may be noticed that properties of ceramic aggregate donot differ much from properties of aggregates obtained from natu-ral rocks (granite, basalt, quartz sandstone, limestone, dolomite).

It can be noticed that particle density and bulk density of sani-tary ceramic wares are similar to their values characteristic to nat-ural aggregates. It is characteristic, that crushing ratio for ceramicsanitary ware aggregate is low (lower than for granite and lime-stone), which means that resistance to crushing is high. It shouldbe added that sanitary ceramic aggregate particles has an irregularshape and sharp edges.

Another typical feature of tested aggregate is relatively highwater absorption, similar to water absorption of limestone anddolomite (it is higher ten reported by authors [20,21] but in thework [37] even higher values are given).

The chemical composition of tested aggregate presented on theFig. 6 is close to composition obtained by other authors [21,35].The following values are characteristic: above 67% of SiO2, above20% of Al2O3 �24.05%, about 3.0% of K2O, above 1% of Na2O, 0,5–1,4% of Fe2O3 and about 0.3% of MgO. We detect above 2% of NiO

Table 2Comparison of properties of sanitary ceramic aggregate and features of traditional aggregate made of natural rocks [49].

Aggregate obtained from natural rocks Sanitary ceramic aggregate

Property Granite Basalt Quartz sandstone Limestone Dolomite Literature data [37] Results of own tests

Particle density (kg/dm3) 2.3–2.8 2.6–3.2 2.6–2.7 2.6–2.9 2.4–2.8 2.64Bulk density (kg/dm3) 2.1–2.7 2.5–3.1 2.4–2.6 2.5–2.8 2.2–2.6 2.36Compressive strength (MPa) 160–240 250–400 120–200 80–180 60–180 400–600Splitting strength (MPa) 7–14 10–20 7–11 4–10 4–10Modulus of elasticity (GPa) 13–61 56–99 40–43 21–53 18–48 40–70Coefficient of thermal expansion (a�106) 5–9 8–12 12–18 1–8 3–12 6–7Water absorption (%) 0.2–0.5 0.1–0.4 0.2–0.5 0.3–1.5 0.3–2.0 0.75–5.0 1.53Porosity (%) Approx. 1.0 Approx. 3.0 Approx. 5.0 Approx. 3.0 Approx. 4.0

Crushing ratio (%) 18 3.8 15 18–20 20 8.9

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and 0,4% of Mo2O3 – 0.37%. In opposite, authors [21,35] found alsoCaO and TiO5.

3.2. Properties of concrete with sanitary ceramic aggregate

3.2.1. Workability and consistenceIn the stage of concrete mix preparing it was noticed that the

slump of concrete made with sanitary ceramic aggregate is11 mm whereas the concrete mix with the same amount of waterand gravel aggregate displayed 48 mm. This happened due to highwater absorption of sanitary ceramic aggregate.

The authors [35] tested the rheological parameters of concretemix with fine aggregate partially substituted by sanitary ceramicwastes and confirmed that the yield stress of such concrete mixis higher in comparison to concrete mix without recycled aggre-gate. They advice to add superplasticizer to such concrete. Wedid not used superplasticiser because additives and admixturesare not recommended in concrete resistant to high temperatures.

3.2.2. Abrasion resistanceThe average abrasion resistance determined by direct measure-

ment of specimen height was 2.63 mm for the gravel concrete, andonly 2.01 mm for concrete with ceramic aggregate. Average abra-sion resistance determined on the basis of decrease in weightwas 2.59 mm for gravel concrete and 2.10 mm for concrete withceramic aggregate. This means that abrasion resistance of concretewith ceramic sanitary ware aggregate is higher by about 20% thanabrasion resistance of gravel concrete. It is understandable becauseof high strength and hardness of sanitary ceramic wares.

3.3. Resistance to high temperature

3.3.1. 1First stage of experimentIn the first stage of experiment only one cycle of heating was

applied to specimens and the specimen were prepared alterna-

Fig. 15. Specimens during the first stage after heating: 1 – specimens made of concreteceramic aggregate.

tively using Portland and alumina cement. Fig. 15 presents speci-mens inside the furnace after heating. All specimens made ofconcrete with Portland cement were damaged during heating.The damage involved autogenic chipping, visible in upper partsof the specimens (about 20% of specimen height). Immediatelyafter opening the furnace, specimens made of concrete with alu-mina cement were not damaged. No cracking and mass decrementwas observed.

A few days after heating, specimens made of alumina cementand gravel aggregate began to lose their cohesion. After 7 days,upper parts of these specimens began to chip and their autogenicdamage was observed. This process was caused by exposure to amoist environment. The gravel contained considerable amount ofcalcium dioxide and the physical and chemical bounding of watertook place again. This caused an enlargement of gravel grains andconsequently, cracking and chipping of concrete.

The specimens made of alumina cement and sanitary ceramicaggregate remained undamaged for 30 days, until the strength test.

Results of all tests are compiled in Fig. 16. They allow to con-clude that strength of unheated concrete with sanitary ceramicaggregate and alumina cement (CA + HAC) is very high; this refersto both, compressive strength and tensile strength. Compressivestrength of such concrete was higher of 12% and tensile strengthof 30% in comparison to unheated concrete with sand and gravelaggregate and alumina cement (SGA + HAC).

Only specimens made of concrete with alumina cement andceramic aggregate survived heating in high temperatures. Despitedecrease in compressive strength by about 46% and in tensilestrength by 52%, this concrete continued to display high strength.

3.3.2. Second stage of studyIn the second stage of experiment five cycle of heating were ap-

plied to specimens and the specimen were prepared only usingalumina cement and different types of aggregate. The cylindricaland prismatic specimens were heated.

with Portland cement, 2 – specimens made of concrete with alumina cement and

Fig. 16. Compressive strength and tensile strength during the first stage of study, specimen denotations given in Table 1.

A. Halicka et al. / Construction and Building Materials 48 (2013) 295–305 303

Cylindrical specimens (2-SGA+HAC-c, 2–GA+HAC-c, 2–CA+HAC-c) were examined for compressive strength immediately after re-moval from the furnace.

The remaining prismatic specimens were left in the laboratoryfor 30 days. After this period, it was concluded that (see Fig. 17):

– Specimens made of concrete based on gravel aggregate (2–SGA+HAC) lost their cohesion, and when picked up, about 40%of specimen mass was chipped.

– On specimens made of concrete with granite aggregate (2–GA+HAC), cracks and minor mass decrement was observed.

Fig. 17. Specimens of the second stage of the study 30 days after heating: 1 –specimen with gravel aggregate, 2 – specimen with granite aggregate, 3 – specimenwith ceramic aggregate.

Fig. 18. Strength of specimens in the second stage

– Specimens with ceramic aggregate (2–CA+HAC) maintainedtheir cohesion and displayed no decrements.

After visual inspection, strength tests were performed. Un-heated specimens were tested as well. The pattern of damage ofheated specimens with ceramic aggregate (2–CA+HAC/1000 �C/30-p) emerged due to applied forces, did not differ from the rangeof damage of unheated specimens (2–CA+HAC/30-p). Specimenswith granite aggregate (2–GA+HAC/1000 �C/30-p) were subject tostrength test despite cracking and their damage resulted fromextension of existing cracks. Specimens with gravel aggregate (2–SGA+HAC/1000 �C/30-p) were not tested, as the autogenic damageoccurred during heating.

Compilation of all test results from the second stage of thestudy, is presented in Fig. 18. In order to unify the results and drawconclusions, results obtained for cylindrical specimens were con-verted so as to be coherent with results obtained for prismaticspecimens. This was done in the following manner:

1. Based on [43], it may be concluded, that compressive strength ofcylindrical specimens, with diameter of 100 mm fc;/100 and heighttwice their diameter, is 1.04 higher than compressive strength ofspecimens with diameter of 150 mm fc;/150, therefore:

fc;/150 ¼fc;/100

1:04ð4Þ

2. According to [43], in case of concrete with compressive strengthhigher than 15 MPa, dependence between cylindrical compres-sive strength fc;/150 and strength tested on cubical specimenswith diameter of 150 mm is as follows:fc,u150 = 0.78fcube,150therefore:

fc;cube;150 ¼fc;/150

0:78ð5Þ

of the study, denotations according to Table 2.

304 A. Halicka et al. / Construction and Building Materials 48 (2013) 295–305

3. Based on [43], it may be concluded that compressive strength ofcubical specimens with a side of 40 mm fc;cube;40 is 1.2 timeshigher than that of cubical specimens with a side of 150 mmfc;cube;150, therefore:

fc;cube;40 ¼ fc;cube;150 � 1:2 ð6Þ

Finally, the converting expression is:

fc;cube40 ¼ fc;cube150 � 1:2 ¼fc;/150

0:78� 1;2 ¼

fc;/1001:04

0:78� 1:2 ¼ 1:48f c;/100

ð7Þ

On the basis of presented results from the second stage of thestudy, it may be concluded that:

– Compressive strength recorded immediately after heating,decreases when compared to unheated concrete, for all typesof specimens (specimens made of concrete with ceramic aggre-gate displayed decrease by 54%, specimens made of concretewith granite aggregate – 56%, and specimens made of concretewith gravel aggregate – 55%).

– 30 days after heating, compressive strength of specimens withceramic aggregate increased by 45%, in comparison to strengthrecorded immediately after heating, as opposed to compressivestrength of specimens based on granite aggregate thatdecreased by 40% and specimens made of concrete based ongravel which were completely damaged.

– Compressive strength of concrete based on ceramic aggregate,tested 30 days after heating was 65% of compressive strengthof unheated concrete, whereas in case of concrete based ongranite aggregate – 26% and concrete with gravel aggregate –0%.

– Tensile strength of concrete based on sanitary ceramic aggre-gate tested 30 days after heating was 36% of tensile strengthof unheated concrete, whereas in case of concrete based ongranite aggregate – 20% and for concrete with gravel aggregate– 0%.

3.3.3. DiscussionThe results of first and second stage of research (Figs. 16 and 18)

indicate that sanitary wastes may by used as aggregate in concretepredestined for work in high temperatures. Of course the specialhigh temperature resistant cement should be used in suchconcrete.

High alumina cement allowed all tested specimens to pullthrough heating in 1000 �C but the after heating behaviour de-pended on aggregate.

It is known that during cooling of concrete the chemical reac-tions of re-bonding of water from air moisture take place. Thesereactions may occur in cement grout and lead to strength gain.The water may be absorbed and react also inside the aggregate par-ticles and in the interface between aggregate particles and cementgrout. This leads to swelling and disintegration of concrete.

Some days after heating concrete with sand and gravel aggre-gate (2-SGA+HAC) lost their cohesion. In the same time concretewith granite aggregate (2-GA+HAC) cracked and its strength de-creased. These destructions were possibly caused by moistureswelling of aggregate. This effect was smaller in granite in compar-ison to gravel.

Thirty days after heating the concrete with sanitary ceramicaggregate (2-SA+HAC) was coherent and its both compressiveand tensile strength increased. There was no absorption of waterand swelling in the aggregate particles during cooling. It may beexplained by the sintering processes taking place in high tempera-ture inside the big ceramic particles. Also the ceramic powder fill-ing the space in the interface between big aggregate particles and

cement grout might be sintered together. The confirmation of suchprocess will be the subject of the next research planned by authors.

4. Conclusions

The paper presents a method for reusing ceramic sanitary warewaste as the only concrete aggregate. This method includes theprocedure for aggregate production (crushing in the jaw crusher,dividing the grains into two groups – fine aggregate 0–4 mm andcoarse aggregate 4–8 mm, and establishing their proportion) anddesigning the concrete mix.

Detailed conclusions are as follows:

1. Properties of ceramic sanitary ware waste do not depart fromproperties of traditional natural aggregate, and therefore itmay be used as concrete aggregate. Strength is particularly highand the crushing ratio is low. Another characteristic property ishigh water absorption.

2. Ceramic sanitary ware waste aggregate can be used for concreteproduction. Such aggregate allows to compose workable con-crete mixes, which after strengthening turn into concrete dis-playing high strength parameters.

3. By using sanitary ceramic aggregate, high performance concretecan be obtained. High abrasion resistance is also a characteristicproperty of this type of concrete.

4. Presented study results have confirmed the initial assumptionconcerning possible use of sanitary ceramic waste aggregatefor the manufacture the concrete elements intended to workin high temperatures. After heating in 1000 �C, concrete withalumina cement and ceramic sanitary ware aggregate preservedits form and high strength:

– Compressive strength of concrete with ceramic aggregatedecreased immediately after heating by 46%, in comparison tostrength of unheated concrete, whereas tensile strengthdecreased by 54%; strength loss was similar to other types ofconcrete, however high initial strength made the strength ofthis concrete still high after heating.

– 30 days after heating, specimens made of concrete with sanitaryceramics were coherent, as opposed to concrete types contain-ing other aggregates; in comparison to test performed immedi-ately after heating, their strength increased.

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