sustainability Article The Utilization of Waste Marble Dust as a Cement Replacement in Air-Cured Mortar Nadhir Toubal Seghir 1 , Mekki Mellas 1, Łukasz Sadowski 2,* , Aleksandra Krolicka 3 , Andrzej Zak˙ 3 and Krzysztof Ostrowski 4 1 Civil Engineering Research Laboratory, Biskra University, Biskra 07000, Algeria; [email protected] (N.T.S.); [email protected] (M.M.) 2 Faculty of Civil Engineering, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland 3 Faculty of Mechanical Engineering, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland; [email protected] (A.K.); [email protected] (A.Z.)˙ 4 Institute of Building Materials and Structures, Cracow University of Technology, 24, Warszawska Str., 31-155 Cracow, Poland; [email protected] * Correspondence: [email protected]; Tel.: +48-71-320-37-42 Received: 5 March 2019; Accepted: 9 April 2019; Published: 12 April 2019 Abstract: The aim of this study is to assess the possibility of utilizing waste marble dust (WMD) as a partial cement substitution in air-cured mortar (ACM). Three different levels of cement replacement were analyzed: 5%, 10% and 15% by cement weight. The specimens were manufactured in a local laboratory at an air temperature of 22 2 C and a humidity equal to 20 1%. The chemical and ± ◦ ± physical properties of ordinary Portland cement and WMD has been found to be the most crucial parameters. A variety of macroscopic tests, such as apparent density, porosity and compressive strength, were proposed in order to explain the effect of utilizing the WMD on the ACM. To confirm the results of the macroscopic properties, thorough microstructural analysis using scanning electron microscopy (SEM) was performed. The obtained results of this study indicate that replacing cement with WMD affects the physical and mechanical properties of air-cured mortar. The apparent density and compressive strength decrease while the porosity increases. Keywords: air-cured mortar; waste marble dust; compressive strength; porosity 1. Introduction The leading factor influencing the quality of cement-based composites and their appropriate adherence is ordinary Portland cement. The manufacturing of ordinary Portland cement requires a meaningful consumption of energy [1,2] and the production of enormous greenhouse gas emissions, including carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx), black carbon (BC), and sulfur dioxide (SO2)[3], therefore contributing to environmental pollution [4,5]. Global cement production (4.18 billion tones in 2014) is the third biggest source of carbon dioxide emissions [6]. The average value of CO2 intensity emissions from all worldwide cement production is 222 kg of CO2/t of cement [7]. From an economic point of view, it can be seen to be reasonable to replace a part of ordinary Portland cement with waste mineral dust. In addition, this treatment is an environmentally friendly solution [8–10]. Due to an excessive amount of very fine particles in dust, the voids in cement-based materials could be thoroughly filled. The particle size and chemical composition of this by-product allow this material to be treated as an attractive additive in cement-based material technology [11]. Marble has been widely used as a building material in the civil engineering industry [12]. During the mining process and in the polishing of marble stone, marble dust is perceived as a waste material [13]. Sustainability 2019, 11, 2215; doi:10.3390/su11082215 www.mdpi.com/journal/sustainability Sustainability 2019, 11, x FOR PEER REVIEW 2 of 14 Sustainability[13]. These2019 by-products, 11, 2215 are present in the environment and contribute to pollution [14,15].2 ofThe 14 utilization of marble dust reduces the cost of cement-based material production and also decreases Thesethe costs by-products of removing are it present from the in theenvironment environment [16]. and contribute to pollution [14,15]. The utilization of marbleThe possibility dust reduces of theusing cost waste of cement-based materials such material as marble production dust as and a partial also decreases substitution the costs in the of removingproduction it fromof mortar the environment and concrete [16]. has often been investigated by researchers [5,17–29]. Its mechanicalThe possibility properties of are using the wastemain aspect materials of the such analysis. as marble Consequent dust asly, a it partial has been substitution proved that in the productionutilization of mortarwaste marble and concrete dust (WMD) has often in been cement investigated mortar improves by researchers its mechanical [5,17–29]. Itsand mechanical physical properties arewhen the subjected main aspect to the of the water-curing analysis. Consequently, condition [10]. it hasThe been author’s proved previous that the study utilization showed of wastethat the marble water-curing dust (WMD) condition, in cement when mortar compared improves to the its air-curing mechanical condition, and physical was profitable properties for when the subjectedacceleration to theof the water-curing hydration conditionrate of cement-based [10]. The author’s materials previous blended study with showed WMD that dust the [30]. water-curing However, condition,on real construction when compared sites, cement-based to the air-curing materials condition, are mainly was prepared profitable and for stored the acceleration in air conditions of the hydration(in nature) rate [10]. of cement-based materials blended with WMD dust [30]. However, on real construction sites,Based cement-based on the performed materials literature are mainly review, prepared there and is storedno study in related air conditions to the properties (in nature) of [10 air-cured]. mortarBased containing on the performed WMD. To literaturefill this knowledge review, there gap, is nothis study research related studies to the the properties effect of of the air-cured partial mortarreplacement containing of ordinary WMD. Portland To fill this cement knowledge with WM gap,D on this the research macro and studies micro the properties effect of theof mortars partial replacementstored at an air of ordinarytemperature Portland equal cementto 22 ± 2°C with and WMD a relative on the humidity macro and of micro20 ± 1% properties by determining of mortars the storedcompressive at an air strength temperature and equalapparent to 22 density.2 C and In aaddition, relative humidityscanning of elec 20 tron1% microscopy by determining (SEM) the ± ◦ ± compressiveanalysis was strengthalso performed and apparent to determine density. the In porosity addition, and scanning Si/Ca ratios electron of ACM microscopy after 28 (SEM) days of analysis being wascured. also performed to determine the porosity and Si/Ca ratios of ACM after 28 days of being cured. 2. Materials and Methods 2.1. Materials The following materialsmaterials werewere usedused toto manufacturemanufacture the the mortars: mortars: ordinary ordinary Portland Portland cement cement CEM CEM I 42.5I 42.5 R, R, produced produced by Biskriaby Biskria ciment, ciment, containing containing 95% clinker 95% clinker with 5% with gypsum 5% forgypsum the setting for the regulation. setting Asregulation. the partial As ordinary the partial Portland ordinary cement Portland replacement, cement replacement, waste marble waste from themarble aggregate from productionthe aggregate of marbleproduction stone of in marble the CHATT stone/ FilFilain the quarryCHATT/FilFila of the Skikda quarry region of the was Skikda used. region Before was use, used. it was Before ground use, to theit was proper ground size to in the order proper to obtain size in a order WMD to fineness obtain a inWMD the ordinary fineness Portlandin the ordinary cement Portland fineness cement range (betweenfineness range 3000 to(between 4000 cm 30002/g) [to30 4000cm]. 2/g) [30]. Sand from the Biskra region (Oued-Djedi River) with a particle size between 0 and 5 mm was used as finefine aggregate.aggregate. It It was first first cleaned and fr fractionatedactionated with the use of a sieving machine to receive aa 00/2/2 particleparticle size size (Figure (Figure1) 1) according according to to the the standard standard EN EN 196-1 196-1 [ 31 [31].]. Tap Tap water water was was used used in the in manufacturingthe manufacturing of the of mortars.the mortars. Max, 1.6-2mm with proportion of 7% Min, < 0.08mm with proportion of 1% Figure 1. Particle size distribution curve (PSD) of reconstituted river cleaner sand (0/2 mm). Figure 1. Particle size distribution curve (PSD) of reconstituted river cleaner sand (0/2mm). Sustainability 2019, 11, 2215 3 of 14 Table1 presents the mineralogical and chemical composition, as well as the physical properties of the ordinary Portland cement, WMD and sand used in the study. Figure2 presents the X-ray di ffraction (XRD) spectrum of these materials. Table 1. Properties of the ordinary Portland cement, WMD and sand [10]. Oxide Content (%) Ordinary Portland Cement WMD Sand SiO2 20.83 0.05 58.15 Al2O3 4.13 0.05 0.34 Fe2O3 5.58 0.02 0.65 CaO 62.91 56.94 22.08 MgO 1.42 0.92 0.28 SO3 2.30 0.32 0.018 K2O 0.38 0.009 0.00 Cl 0.028 0.001 0.018 Loss on ignition (L.O.I) 2.04 41.63 18.23 Insoluble Residue (I.R) 0.382 0.06 0.234 Mineralogical composition C3S 62.03 - C2S 13 - C3A 1.5 - C4AF 16.98 - Sustainability 2019Physical, 11, x FOR properties PEER REVIEW 3 of 14 Solid density (kg/m3) 3150 2740 2656.5 Table 1 Bulkpresents density the (kg mineralogical/m3) and chemical980 composition, as 980 well as the 1631.23 physical properties of the ordinaryBlaine Portland fineness (cmcement,2/g) WMD and sand3571.78 used in the study. 3869.46 Figure 2 presents - the X-ray diffraction (XRD) spectrum of these materials. FigureFigure 2. X-ray 2. X-ray diffraction diffraction (XRD) spectrum(XRD) spectrum of: (a) ordinary of: (a) Portlandordinary cement; Portland (b) cement; waste marble (b) waste dust (WMD); (c) sand.