SURFACE BLAST-CLEANING WASTE AS A REPLACEMENT OF FINE AGGREGATE IN CONCRETE

S t r e s z c z e n i e W artykule zaprezentowano badania na temat możliwości zastąpienia całości lub części drobnego kruszywa w betonie żużlem pomiedziowym – odpadem z piaskowania. Badano beton z w/c = 0.6 i zawartością cementów CEM I 32.5 R i CEM II/B-V 32.5N 300 kg/m3. Stosunkowo wysoka wartość współczynnika w/c pozwoliła na dobre zagęszczenia mieszanek bez użycia plastyfikatora. Stopień zastąpienia drobnego kruszywa (0–2 mm), żużlem pomiedziowym wyniósł odpowiednio 33%, 66% i 100%. Beton o tym samym składzie ze 100% piasku rzecznego jako kruszywa drobnego służył jako referencyjny. Przeprowadzone badania koncentrowały się na: wytrzymałości na ściskanie i rozciąganie (po 28 dniach), sorpcyjności, nasiąkliwości i odporności na ścieranie. Uzyskane wyniki wykazały, że wytrzymałość i niektóre inne badane właściwości betonów z odpadem jako zamiennikiem piasku były podobne lub nawet lepsze niż właściwości betonu referencyjnego. K e y w o r d s : Sustainable development, Waste utilization, Fine aggregate, Copper slag, Concrete, Recycled materials. 3/2017 A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T 89 A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T The Si les ian Univers i ty of Technology No. 3/2017 W . K u b i s s a , R . J a s k u l s k i , T . S i m o n The usage of copper slag in concrete production provides potential benefits both environmentally and economically for all related industries, particularly in such areas where considerable amount of copper slag is produced. Using copper slag with gravel improves the consistency of the mixture [7, 11]. It has been found that the usage of copper slag instead of sand, without changing the amount of tap water, significantly improves consistency and compressive strength [9]. However it is possible to reduce the amount of water by 22% and obtain the same consistency. In this case the compressive strength increases up to 20%. No negative impact of copper slag on concrete contraction was found [6]. Copper slag is also used as an abrasive in blast-cleaning processes during corrosion protection. The copper slag particle size after this process is smoother. The content of 0–0.125 mm and 0.125–0.25 mm fractions is significantly increased. The waste also contains a small amount of corrosion products and corrosion protection coatings [12]. The use of blast-cleaning waste as a substitute for sand was tested and described in the article. Since the tested concrete can be used in the production of prefabricated elements, part of the research and evaluation of the results were carried out according to the PN-EN 1340:2004 “Concrete kerb units – Requirements and test methods” standard. 2. MATERIALS AND METHODS Portland cement CEM I 32.5R and Portland-composite cement CEM II/B-V 32.5N from Ożarów Cement Plant as per PN-EN 197 were used. All concrete mixes contained 300 kg/m3 of cement by 0.6 w/c ratio. Fractions of River sand 0–2 mm and natural gravel of 0.5–16 mm were used. Aggregates were at laboratory air-dry condition. Copper slag waste from blast cleaning was used as a partial replacement of sand. The ratio of substitution was 33%, 66% and 100% of sand amount by volume. Regular tap water was used as mixing water. Grading curves of the used aggregates and the waste is shown in Figure 1. Boundary grading curves were adopted according to PN-B-06250:1988. Grading of all mixes of the aggregates were similar. They differed mainly in the amount of finest fractions 0–0.125 mm. If only sand and natural gravel were used, the portion of this fraction was about 0.5% while after replacing 100% of the sand with CS it increased to about 5.0%. Eight concrete mixtures were prepared. Mix IDs and proportions are presented in Table 1. The consistency of fresh concrete was measured by slump test, in accordance with PN-EN 12350-2. In the case of mixes CI100 and CII100 also test mixes were prepared with using superplasticizer for concrete with an extended workability Ha-Be PANTARHIT® RC540 (FM) according to PN-EN 934-2. For these mixtures only the consistency of the mixture was determined to find the right amount of the necessary amount of plasticizer to provide such a consistency as that of the reference concrete. Eight concrete mixtures were prepared. Mix IDs and proportions are presented in Table 1. The consistency of fresh concrete was measured by slump test, in accordance with PN-EN 12350-2. In the case of mixes CI100 and CII100 also test mixes were prepared with using superplasticizer for concrete with an extended workability Ha-Be PANTARHIT® RC540 (FM) 90 A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T 3/2017 Figure 1. Grading curves of aggregate fractions and mixtures SUR FA C E B L A S TC L E AN I N G WAS T E A S A R E P L A C EMEN T O F F I N E A GGR E G AT E I N CONCR E T E according to PN-EN 934-2. For these mixtures only the consistency of the mixture was determined to find the right amount of the necessary amount of plasticizer to provide such a consistency as that of the reference concrete. Specimens were prepared and cured as per PN-EN 12390-2. They were cast in plastic moulds and compacted by double vibration (half and full) on a vibrating table. After 2 days they were stripped and then water cured in the laboratory for 28 days. 2.1. Compressive and tensile strength test The compressive strength test was conducted on 100 mm cube specimens on the 28 day of hardening. The test were carried out in accordance with PN-EN 12390-3. The splitting tensile strength test was conducted on the same type of specimens in accordance with PN-EN 12390-6. The strength tests were performed by using a Matest instrument, having 3000 kN compression force capacity. The rate of loading was maintained at 0.5 MPa/s for compressive strength test and 0.05 MPa/s for splitting tensile strength test. 2.2. Free water absorption and sorptivity test The free water absorption test was conducted on the halves of cubic specimens of 100 mm edge by means of mass method. Specimens after splitting were stored 12 hours in water. Then the surface-dry mass of the specimens ms were determined. Prior to the sorptivity test, the specimens had been oven-dried to the stable mass at a temperature of 105°C. The measurements were conducted at the temperature of approximately 20°C. The specimens were weighed (to determine mass md for calculation of free water absorption) and then arranged in a water containing vessel. The specimens were immersed up to the height of 3 mm. In the specific time intervals from the beginning of the test the specimens were weighed again to define their weight gain resulting from water sorption. Subsequent weight measurements were conducted for 6 hours. Sorptivity S in g/(cm2 h0.5) was defined as a slope of the linear function expressing the dependence of the mass of the water absorbed Δm by the area F on the time root t0.5 [13]: Free water absorption has been calculated using formula 2: