Study case about the production of masonry concrete blocks with CDW and kaolin mining waste

AIMS Materials Science, Volume (Issue): Page. 1 DOI: 2 Received date, 3 Accepted date, 4 Published date 5 http://www.aimspress.com/journal/Materials 6 7 Research article 8 Study case about the production of masonry concrete blocks with CDW 9 and kaolin mining waste 10 Felipe Bastos1,2,*, Adeildo Cabral2, Perboyre Alcântara2, Lino Maia1,3,* 11 1 CONSTRUCT-LABEST, Faculty of Engineering (FEUP), University of Porto, Rua Dr. Roberto 12 Frias, 4200-465 Porto, Portugal 13 2 Federal institute of education, science and technology of Ceará - IFCE, Avenue 13 de Maio, Ceará, 14 Brazil 15 3 Faculty of Exact Sciences and Engineering, University of Madeira, Campus da Penteada, 9020-105 16 Funchal, Portugal 17 * Correspondence: Email: [email protected], [email protected]. 18 Abstract: The worldwide generation of construction and demolition waste is about 30% to 35% of the 19 total solid waste produced annually. In addition, the extraction of minerals leaves a high-grade 20 environmental liability with tailings, such as kaolin clay, Brazil being one of the countries with the 21 largest deposits and production of this mineral in the world. The kaolin clay extraction serves several 22 industries such as ceramics, crockery, and paper, among others. The objective of this work is to insert 23 these two wastes as raw material of construction elements, specifically masonry concrete blocks, thus 24 giving an end to the residues, demonstrating their reutilization potential. Here, blocks were 25 manufactured with replacement of natural aggregates, stone powder, and sand, by construction and 26 demolition waste and of kaolin clay waste. The replacement percentages were up to 34% and 16%, 27 respectively. The blocks made with pneumatic vibration compacting procedure presented strength 28 beyond than what is established by norm, thus giving a favorable perspective of use for these residues 29 as building elements. 30 Keywords: CDW, Concrete block, Construction, Kaolin Clay, Residue. 31 32 1. Introduction 33 From the first decades of the last century, many urban centers grew inordinately, due to the 34 2 AIMS Materials Science Volume x, Issue x, 1-X Page. promise of jobs, improvements in living conditions and migration of the population from other areas 35 in search of opportunities. And mainly peripheral areas and sparsely populated areas became very 36 dense and, consequently, with inadequate infrastructures [1]. 37 The need to meet the demands arising from the disorderly growth of urban centers made civil 38 construction one of the activities in high demand of materials. Making this sector one of the industries 39 that causes the greatest impact on the environment. Constructions without proper planning and 40 supervision cause considerable environmental impacts to the environment due to excessive solid waste 41 generation. 42 Brazil is an essentially urban country, with more than 80% of the population and most economic 43 activities installed in urban areas. Cities concentrate a large part of the problematic of government 44 management issues. Public authorities at all levels of government have not been able to intervene 45 efficiently in the urban issue. Despite these difficulties, the implementation of instruments, such as the 46 statute of cities, tries to alleviate the difficulties faced by large metropolises. Despite these instruments 47 and guidelines being approved by law, the problem of waste management is still far from over. 48 According to ABRELPE [2], in 2019 the Brazilian percapta production of construction and demolition 49 waste (CDW) was 0.650 kg/inhabitant per day. 50 Civil construction ends up following the pace of economic growth and development of cities and, 51 consequently, generates high levels of waste. In addition to meeting the housing deficit, there was a 52 need to create urban facilities such as day care centers, schools, hospitals, squares, as well as 53 commercial areas such as shopping centers, to meet the population's increasingly demanding needs. 54 In another scenario, not very different, the extraction of minerals and ores for the manufacture of 55 industrialized products used as raw material has a great impact on the environment. Extraction 56 techniques end up leaving residues that part of the times they are not reused in the process that 57 generated them or in any other industry. Like the residue from the extraction of kaolin, one of the main 58 ores extracted in the world according to DNPM [3], Brazil is one of the largest producers of this mineral 59 with the main deposits being located in the states of Paraíba, Rio Grande do Norte and northern Minas 60 Gerais. 61 Kaolin is a mineral associated with pegmatite, which is a variety of granitic rock in which there 62 is similarity with the mineralogical composition, but differing in the sizes of the constituent minerals, 63 which in pegmatite is abnormally large [4]. Kaolin is a clayey material with low iron content, white or 64 almost white color and fine grain size. It is called feldspar the minerals consisting of aluminosilicates 65 of potassium, sodium and calcium, and quartz can be of primary origin (quartzites) or secondary (sands 66 and sandstones) used in ceramics. Clays, due to their plasticity, influence the mechanical strength of 67 samples when they change from green to dry. In the white ceramic and coating industry, various 68 formulations containing raw materials are used to obtain products such as porcelain, bathroom fixtures, 69 tiles, tiles, tiles and ceramic floors. 70 Kaolin is a product that results from the process of deep transformation of aluminum silicates, 71 which may be feldspars, plagioclases and feldspatoids, which are contained in rocks. For this 72 transformation to occur, hydrolysis of the silicates takes place with solubilization of alkaline and 73 alkaline-earth ions in the form of carbonates, with the hydrated aluminum silicates remaining insoluble, 74 which crystallize due to high temperature and pressure [5]. The mineral kaolinite, whose formula is 75 Al2O3.2SiO2.2H2O, is the main component of kaolin. It presents in a compact, earthy, microcrystalline 76 mass, 1.0 Mohr hardness, specific weight 2.6 g/cm3 and low gloss. 77 According to the mineral summary [3], kaolin mining is processed manually without any covered 78 3 AIMS Materials Science Volume x, Issue x, 1-X Page. protection, that is, without a covered deposit. Processing goes through the following phases: first 79 sieving, then it undergoes a decanting and drying process, and then it is heated in a wood oven. 80 Firewood is taken from native trees in the municipality, which are large and small. When already 81 processed, it is transferred to the qualification sector, which is considered good, with a low Fe2O3 82 content, and these are destined for the ceramic industries. When it does not contain the mineral 83 halloysite in its composition, these are destined for the paper industries [3]. 84 As exploration methods are still inefficient, kaolin is extracted together with undesirable materials 85 such as quartz, feldspar and muscovite mica. The separation of kaolin from these materials ends up 86 leaving a high rate of residues that are often deposited near the mining plant itself. 87 The waste generated and discarded by the kaolin processing industries located in the producing 88 municipalities between the states of Rio Grande do Norte and Paraíba (Brazil) affect the entire 89 surrounding community. Usually, this waste is removed and clandestinely placed in vacant lots, on the 90 banks of rivers and on the streets of the neighborhoods on the outskirts of cities. 91 CDW and kaolin extraction waste in Brazil are important environmental liabilities because they 92 are deposited in large volumes and are often subject to inadequate disposal. The impacts caused by 93 inadequate waste management affect the environment and people's health, compromising the well- 94 being and, in the long term, even the survival of the human species [6]. 95 In the search for a product that would meet the simple and common need for civil construction, 96 we incorporated kaolin and CDW waste in the masonry blocks, as this is a constructive element widely 97 used in the construction of buildings. 98 The various studies on the use of waste in the construction sector have been growing visibly in 99 recent decades, seeking to improve cheap and simple construction techniques, always having a 100 sustainable vision for replacing materials conventional [7]. With this expressive expectation, these 101 proposed materials have a high potential for use for this purpose. 102 Kaolin residues have been used in other research [8] to replace aggregate in the production of 103 ceramic bricks and roofing. As kaolin residue has kaolinite (a pozzolanic material) in its composition, 104 as a result, specimens were burned at different temperatures. The results showed that a residue 105 composed of quartz, kaolinite and mica allows formulations with incorporations of the residue up to 106 50% to produce ceramic bricks and tiles. Another research [9] showed that in the case of using the 107 waste to replace fine aggregates for concrete, satisfactory results were obtained in the proportion of 108 30%. 109 The use of kaolin waste is also seen as a substitute for cement, because there are percentages of 110 kaolinite in the extraction, which has pozzolanic properties when kaolinization is done above 600 ºC. 111 This factor is found both in the extraction of mining waste and in the excavation of marine 112 infrastructure in which the waste can be a substitute for cement [10]. 113 Recycled aggregates from construction debris and kaolin waste have different physical 114 characteristics, such as grain size and grain shape. Therefore, the introduction of these two residues to 115 replace conventional aggregate can contribute to obtaining more adequate mixtures to produce 116 concrete blocks in pneumatic machines. 117 Thus, the approach of this work seeks an alternative for the technically and environmentally 118 adequate disposal of these two wastes and, thus, collaborate to reduce these negative impacts. The act 119 of recycling waste can represent economic, social and environmental advantages, such as savings in 120 the acquisition of raw materials, reduction of pollution generated by waste and preservation of natural 121 raw material reserves. The objective of this work is to produce masonry concrete blocks with recycled 122 4 AIMS Materials Science Volume x, Issue x, 1-X Page. aggregates from civil CDW and kaolin mining waste to be applied in non-structural elements. Here, 123 we analyze comparatively the physical and mechanical aspects of the blocks obtained with and without 124 the additions of recycled aggregates, observe their characteristics of water absorption, compressive 125 strength, dimensional and mass variation. 126 2. Materials and Methods 127 2.1. Experimental program 128 The methodology used was based on the comparative experimental research format, in order to 129 replace the natural aggregates with kaolin residue in the fine part and at the same time replace the 130 natural gravel with the CDW, in general compositions of percentages of 15%, 15% and 35% thus 131 making a comparative analysis of the physical indices and compressive strength of the blocks. 132 The experiment was carried out at the Civil Construction Materials Laboratory (LMCC) of the 133 Federal Institute of Ceará, Fortaleza campus, the production of the blocks was done at the company 134 EcomatBrasil, which has 6 bar pneumatic pressing machines and a 320 L vertical concrete mixer. 135 The cement used was the Brazilian commercial type CPV-ARI with high initial strength, as it has 136 a high reactivity and strength at low ages depending on the degree of grinding to which it is submitted, 137 providing greater yield to the concrete, according to the Brazilian standard NBR 16697:2018 [11]. The 138 water used was potable supplied by the Water Supply and Sewage Company (CAGACE). 139 The plasticizing additive used was Muraplast FK 320-MC. It should be noted that only in the 140 preparation concrete was used an additive in the proportion of 0.25% in relation to the cement mass, 141 as recommended by the manufacturer for use in concrete and precast. 142 The physical and mechanical tests of both the materials and the blocks were performed at the 143 Civil Construction Materials Laboratory (LMCC) of the IFCE - Campus Fortaleza, Brazil. 144 In the tests, the Technical Standards were followed as described in Table 1. The process of 145 sampling and reducing field samples for tests, the recommendations of ABNT NM 26: 2009 [12] and 146 ABNT NBR NM 27: 2001 [13] standards were followed. 147 Table 1. Laboratory tests and the corresponding standards. 148 Property Technical norm Tested in: Unit Mass NBR NM 45/2006 Aggregates Specific mass NBR MN 52/2009 Aggregates water absorption NBR NM 30/2000 Aggregates Powder Material NBR NM 46/2003 Aggregates Granulometry NBR 7211/2009 Aggregates Dimensional stability NBR 6136/2014 blocks Variation Compression NBR 6136/2014 blocks 149 The equipment used for the production of the blocks basically consisted of a 320 L inclined 150 concrete mixer, with a concrete shaft, a vibropressing machine Model Atlantimaq E321 ACP 151 Pneumatic up to 6 bar pressure, this machine having a 2 hp motor for form vibration (Figure 1). 152 The manufacturing procedure of the blocks was to put the concrete in the machine with each mix 153 determined, with the aid of a trowel and shovel to fill the form, a waiting for the vibration for 154 5 AIMS Materials Science Volume x, Issue x, 1-X Page. compaction of 30 seconds per cycle, to apply the pneumatic pressing, producing 3 blocks per cycle. 155 This time is enough to give a good compaction to the blocks produced, being the standard used by the 156 factories as determined by Fernandes in the Ref. [14]. 157 158 Figure 1. Pneumatic machine used in the manufacture of concrete blocks. 159 2.2. Formulation of the mixes used 160 The designed mix compositions were planned in order to reach the parameters established by 161 Brazilian STANDARD 6136/2014 [15], in particular, the minimum value of the characteristic 162 compressive strength for the Class C blocks for selling, which is 3 MPa. There is no common pattern 163 of mix composition in the literature but the type of compaction machine to be used directly influences 164 cement consumption [14]. A correlation between the moisture content of dry concrete and the use of 165 machines with high compaction power (hydraulic) with the same moisture content it is possible to have 166 a greater resistance than in manual and pneumatic equipment, as there is a reduction in voids. Thus, it 167 was necessary to observe aspects related to the composition of the aggregate mixture, moisture content 168 and the manufacturing and curing process. Table 2 summarizes that information about the replacement 169 percentage of the materials in mixes. 170 Table 2. Percentage of aggregate replacement. 171 Composition Fine aggregate replacement by kaolin waste Coarse aggregate replacement by CDW Mix 0 0% 0% Mix 1 5% 10% Mix 2 8% 17% Mix 3 12% 23% 172 6 AIMS Materials Science Volume x, Issue x, 1-X Page. The normal setting multifunctional plasticizer additive (Muraplast FK 320) from the manufacturer 173 MC-Bauchemie Brazil was used, in the proportion of 0.25%, respecting the adequate water/cement 174 ratio for the molding of the blocks. The cement/aggregate ratio (1:6) by volume, with the ratio being 175 1:4:2 (1 cement; 4 stone dust; 2 crushed gravel) was the same as in the first stage, except for sand 176 replacement. Table 3 shows the mix proportions used with the pneumatic vibration machine. 177 Table 3. Description of the mix proportions by volume used in the manufacturing of blocks. 178 Mix 0 Mix 1 Mix 2 Mix 3 Cement 1 1 1 1 Stone dust 4 3.80 3.68 3.52 Kaolin waste - 0.20 0.32 0.48 Crushed gravel 2 1.80 1.66 1.54 Waste const. - 0.20 0.34 0.46 Water w/c ratio 0.55 0.55 0.55 0.55 Plasticizing additive 50 ml 50 ml 50 ml 50 ml During the concrete cure, the evaporation of the water used in the concrete mixing was prevented 179 and, thus, guaranteed the hydration of the cement components. These precautions are even more 180 important for the manufacture of precast materials, such as concrete blocks, whose concretes have a 181 lower w/c ratio than conventional concretes. To optimize the curing process of the blocks at this stage, 182 the black plastic sheet for rain was also used to prevent premature evaporation of water, with the blocks 183 being wet and covered for 7 days after the date of manufacture. 184 During the concrete cure, the evaporation of the water used in the concrete mixing was prevented 185 and, thus, guaranteed the hydration of the cement components. These precautions are even more 186 important for the manufacture of precast materials, such as concrete blocks, whose concretes have a 187 lower w/c ratio than conventional concretes. To optimize the curing process of the blocks at this stage, 188 the black plastic sheet for rain was also used to prevent premature evaporation of water, with the blocks 189 being wet and covered for 7 days after the date of manufacture. 190 3. Results 191 3.1. Construction and demolition waste 192 When determining the composition of the waste, it was assumed that it could not present 193 impurities that could affect the performance of concrete blocks, such as paper, cardboard, wood, metal, 194 glass and plaster. This sorting is done inside the plant when the truck arrives with waste and prepared 195 for crushing. Therefore, these materials were discarded in the process of separation and 196 characterization of the sample. 197 The composition of the visual characterization was made by the quartering method, following the 198 procedure by ABNT NM 26:2001 [12] and procedure by NBR 27:2001 [13] for laboratory tests. 199 However, for the visual characterization, 1 kg of CDW was considered and sieved in a 4.8 mm sieve, 200 with the passing material being discarded. The material characterized was only the material retained 201 in this granulometry, because by NBR NM248: 2001 [14]: Aggregate whose grains pass through a 202 7 AIMS Materials Science Volume x, Issue x, 1-X Page. sieve with a 75 mm mesh opening and remain retained in the sieve with a mesh opening of 4.8 mm, 203 they are characterized as coarse. In this work, this grain size was used to replace graded aggregates by 204 CDW aggregates. As shown in Figure 2, the materials with the highest percentage in the recycled 205 aggregate are concrete and mortar. 206 207 Figure 2. Composition of the CDW by visual characterization. 208 3.2. Kaolin residue composition 209 The manufacture of the blocks, only kaolin residues from the first stage were used, the so-called 210 tantrum material with a particle size of material retained from the sieve 4.8 mm, to be adjusted for the 211 manufacture of the blocks. This material consists mainly of kaolinite, muscovite and feldspar 212 according to the chemical analysis already done by Menezes in Ref. [1] for this material taken from 213 Mineradora Brazil Mineiro. 214 The composition of minerals in the kaolin waste, according to the extraction company, around 215 70% of the extracted ore is waste that is separated into two processes during the kaolin extraction. For 216 the visual characterization, the same procedure as the CDW was performed, referring to the quaking 217 and separation of 1 kg of the material. Figure 3 presents the mineral composition of the kaolin residue 218 used. 219 220 Figure 3. Visual composition of the waste kaolin by visual characterization. 221 8 AIMS Materials Science Volume x, Issue x, 1-X Page. It shall be noted that, although the kaolin waste has kaolinite in its composition, in the present 222 study the calcination of the waste to benefit the pozzolanic properties of kaolinite was not carried out. 223 The authors decided to do not carry out the calcination process because this (no calcination) was just 224 the purpose of this exploratory research wherein the addition of this residue was incorporated with a 225 maximum of 23%. For future research work and for a full-scale production of blocks with high 226 percentages of kaolin waste, the calcination process shall be deeply evaluated especially for the 227 economic and sustainability analyses. 228 3.3. Physical characterization of aggregates 229 The materials were tested according to NBR 45/2006 [18] which has the purpose of using the 230 transformation from mass to volume with voids between the aggregate grains. The unit mass also 231 serves as a parameter for classifying the aggregate in terms of density [17]. 232 The specific mass of the aggregates used in the manufacture of the blocks was performed as 233 determined by NBR NM 52 [20], which defines the specific mass as the ratio between the dry aggregate 234 mass and its volume, excluding permeable pores. 235 Water absorption was done following NM 30 [21] for fine aggregates - Determination of water 236 absorption for fine aggregates. According to the determination of NBR NM 46 [22] and the 237 determination of the quantity of powdery material by NBR 7211 [23] for powdery materials, these are 238 defined as mineral particles with a dimension less than 0.075 mm, including water-soluble materials, 239 present in the aggregates. Table 4 describes the percentage of powdery materials used and presents the 240 determination of water absorption of the materials used. 241 Table 4. Physical characterization unit mass, specific mass and aggregate absorption and percentage 242 of fines of the materials used in manufacturing of the concrete blocks. 243 Aggregate Bulk specific Mass [g/cm³] Specific mass [g/cm³] Water absorption [%] Percentage of fines [%] Stone dust 1.43 2.62 0.97 10.5% Gravel 1.40 2.66 0.85 0.98% Kaolin Waste 1.35 2.63 0.26 4.06% CDW 1.41 2.37 4.68 7.05% 3.3.1. Granulometric correction 244 Particle size corrections can be made for different purposes, in order to obtain a final product 245 more suitable for different applications. In the case under study, it was made with the aim of correcting 246 the granulometry to fit within the limits of the curves suggested for concrete blocks, proposed by 247 Fernandes in Ref. [14]. In this way, the lines used in the experiment were adjusted according to the 248 granulometric ranges in Figure 4. The red curve is the representation of strokes made from 1:2:4 for 249 all strokes with percent replacement. It is noticed that all the curves with the percentages overlap with 250 small variations between the replacement percentages. Thus, it is possible to verify that the mixture of 251 aggregates, for all waste additions, is within the limits suggested by Fernandes in Ref. [14], for the 252 manufacture of concrete blocks. 253 9 AIMS Materials Science Volume x, Issue x, 1-X Page. 254 Figure 4. Particle size distribution of the CDW aggregate. 255 3.2. Determination of water absorption of blocks 256 To determine if there was a variation in the water absorption of the blocks as determined by NBR 257 12118/2013 for individual blocks in accordance with NBR 6136/2014 [15], there was a separation of 258 samples for the absorption test, as determined by the procedures of NBR 61636/2014 [15], with the 259 following absorption results being obtained in Table 5. 260 Table 5. Water absorption of blocks. 261 Block Type Dry block weight (kg) Block moist Moisture (%) Mix 0 8.07 8.69 7.07 Mix 1 8.5 9.09 6.50 Mix 2 8.2 8.84 7.14 Mix 3 8.01 8.64 7.34 3.4. Dimensional analysis and appearance of blocks 262 The measurements, texture and appearance of the blocks were measured both nominal and real 263 and verified within the standardization determined by NBR 6136/2014 [15], which establishes the 264 standard measurements and classification for masonry blocks of sealing type 10x40. In Figure 5 it is 265 possible to verify the texture and color of the blocks with the residues. 266 267 Figure 5. Appearance of concrete blocks. 268