Secondary aggregates and seawater employment for sustainable concrete dyke blocks production: Case study

Abstract

11The main objective of this research work was to validate the on site real scale production of 12 dyke blocks employing coarse mixed recycled aggregates, steel slag aggregates and seawater. 13A laboratory experimental phase (Phase 1) was carried out prior to real scale concrete block 14 production within Barcelona's port (Phase 2). According to the results, the concretes 15 produced with a combined mixture of 50% coarse mixed aggregates and 50% of coarse steel 16 aggregates achieved the most adequate properties for use in dyke block manufacturing. The 17 concrete produced employing high percentages of coarse mixed recycled aggregates (without 18 steel slag aggregates) could achieve adequate properties in its saturated state. The use of 19 seawater instead of freshwater reduced the concrete's setting time as well as the porosity of 20 the concretes produced, resulting in both the reduction of water penetration and the capillary 21 water absorption capacity of the concretes. The use of seawater increased concrete's 22 compressive strength at early age. It was also concluded that the results obtained in the 23 laboratory studies and the technical know-how achieved can be transferred to large scale 24 projects. 26 27Keynotes: sustainable concrete; recycled aggregates; steel slags; sea 28 water; concrete block; case study; cores; properties 29 30 31 INTRODUCTION 32The use of recycled aggregates (obtained from the treatment of construction and demolition 33 waste) and steel slag industrial by-products as coarse aggregate in normal concrete mixes is 34 primordial in reducing the environmental problems created by the dumping of these materials, 35 thus helping to maintain sustainability of the environment by reducing the opening of new 36 quarry developments for concrete production. 37 *Manuscript Click here to download Manuscript: manuscript_reviewed_FINAL.docx Click here to view linked References Due to its diverse content, i.e. large amounts of ceramic material and other impurities besides 38 concrete and raw aggregates, the resulting recycled aggregate sourced from the C&DW 39 treatment plants is commonly designated as mixed recycled aggregate (MRA) [1-3]. 40Concretes produced with high percentages of MRA suffer a decrease of density, and 41 mechanical and durability properties with respect to those of conventional concrete [2,[4][5][6][7]. 42However it is well-known that concrete produced with steel slag aggregates achieve a higher 43 density as well as higher mechanical properties than those of conventional concrete [8][9][10]. 44This is due to both their high density and rough surface which results in an effective ITZ [11,45 12]. 46The use of steel slag aggregates together with recycled aggregates can produce better 47 structural concrete [13]. The percentage reduction in compressive strength is greater than that 48 of the flexural strength when recycled concrete aggregates are incorporated. However, the 49 strength reduction in mixes containing slag aggregates is much less resulting in the production 50 of...

The effects of seawater and nanosilica on the performance of blended cements and composites

“…The production of Ordinary Portland Cement (OPC) is energy-intensive and contributes to about 5-7% of total anthropogenic CO 2 emissions (Shaikh and Dobson 2019). Moreover, due to the over-exploitation of available deposits, sand and freshwater are now the two most valuable commodities of the twenty-first century (Etxeberria et al 2016a;Dhondy et al 2019). According to the United Nations (2019), over 40% of the world's population faces a scarcity of freshwater.…”

“…It is widely agreed that seawater has an accelerating effect of cement hydration processes (Govindarajan and Gopalakrishnan 2011;Li et al 2018a;Younis et al 2018;Montanari et al 2019;Sikora et al 2019b) and contributes to a decrease in the setting time and workability of concrete (Etxeberria et al 2016b;Younis et al 2018;Li et al 2019;Teng et al 2019). Early strength improvement, as an effect of accelerated cement hydration, has been widely reported (Demir et al 2010;Wegian 2010;Otsuki et al 2012;Abdel-Magid et al 2016;Etxeberria et al 2016a;Li et al 2018a). After 28 days of curing, the effects of seawater in OPC-based concrete are considered to be minor and strength improvements (if at all observable) are generally limited to 5-10%, with long-term mechanical performance being reported as slightly lower than that of OPC-based concrete produced with freshwater (Mbadike and Elinwa 2011;Etxeberria and Gonzalez-Corominas 2018;Guo et al 2018;Bertola et al 2019).…”

Feasibility of utilizing 2304 duplex stainless steel rebar in seawater concrete: Passivation and corrosion behavior of steel rebar in simulated concrete environments

“…Therefore, it is necessary to use seawater to mix or cure concrete at times during infrastructure construction on islands . Previous studies have shown no significant difference in the mechanical properties of concrete when mixed and cured with seawater or freshwater . It seems feasible to apply seawater in plain concrete or concrete filled with glass fiber reinforced polymers .…”

Properties of Plain Concrete Produced Employing Recycled Aggregates and Sea Water

“…In series 3 concrete a maximum of 50% of RMA (RC50-3) could be allowed for dyke block production. The use of 50% of RMA employing Portland cement for concrete production is possible when 50% of the aggregates are mixed together with 50% steel slag aggregates [21] [31].…”

“…In series 3 concrete a maximum of 50% of RMA (RC50-3) could be allowed for dyke block production. The use of 50% of RMA employing Portland cement for concrete production is possible when 50% of the aggregates are mixed together with 50% steel slag aggregates [21]. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 7 Water absorption and permeable porosity followed similar tendencies to those of the density property, the increase in RMA replacement produced an increase in water absorption and porosity.…”