Physico-Mechanical Performances of Mortars Prepared with Sorted Earthquake Rubble: The Role of CDW Type and Contained Crystalline Phases

Abstract

Construction and demolition waste (CDW) from earthquake rubbles was used here as recycled aggregates (RA) in cementitious binders. The materials were sorted in six groups: concrete (CO), natural stone (NS), tile (TI), brick (BR), perforated brick (PF) and roof tile (RT). The abundance (wt.%) of crystalline phases in each RA type was determined by X-ray Powder Diffraction (XRPD). Each group of RAs was used alone (100 wt.% of RA) and mixed with quartz-rich virgin aggregates (VA) to prepare 13 types of mortars (12 specimens per type): one reference mortar (RM) with only VA, six recycled aggregate mortars (RAM) and six recycled-plus-virgin aggregate mortars (RVAM). The physical and mechanical properties of aggregates and mortars reflect the type and abundance of crystalline phases in each CDW group. Recycled mortars rich in concrete, natural stones and tiles have better mechanical performance than mortars prepared with recycled bricks, perforated bricks and roof tiles. For each RA, RVAMs have superior mechanical characteristics than the corresponding RAM. Since the type and amount of phases contained in recycled aggregates strongly control the mechanical performance of new construction materials, they should be routinely quantified as reported here, in addition to other physical features (water absorption, density, etc.). The separation of heterogeneous CDW into homogeneous RA groups is necessary for the production of new construction materials with stable and predictable performances to ensure CDW recycling, especially in areas hit by major adverse events, where large amounts of still valuable materials could be used for reconstruction processes.

Recovery of Demolished House Rocks from Construction and Demolition Waste with Water Jigs

“…Reis et al [9] reviewed the current applications of the material recovered from CDW, such as sand production, use in pavements and roads, direct reuse in concrete mix as recycled aggregates (RA), fabrication of new concrete blocks, production of cement, and as adsorbents to treat polluted water. Other authors [10,11] also mentioned that the presence of contaminants limits the application of RA in new concrete since they negatively influence the fundamental properties of the aggregates, such as size distribution, shape index, bulk density, and water absorption.…”

“…As a form of initial classification, these plants usually crush the CDW and remove particulates such as plastics, paper, and wood as well as metal parts (ferrous and non-ferrous) by methods such as sieving, use of magnetic mats, or manual removal in the case of materials of larger sizes. The "inert CDW" material contains bricks, tiles, plaster, concrete, mortar, and coarse aggregate [11,16,17]. Figure 2 shows that around 76% of CDWs is composed of solidified and inert materials.…”

Bulk Composition Effects on Vitrification of Mixed Fine Construction–Demolition and Inorganic Solid Waste

“…The main problem in reutilization of CDW materials is related to the heterogeneous composition and the difficulty of selectively extracting some components of potential higher value, or removing some contaminants like asbestos, if present in debris [21][22][23] type is still downgrading applications, as aggregates for road construction or backfilling and, with limitations due to possible diminished mechanical performance, as recycled aggregates in concrete. For instance, CDW previously treated to selectively remove ferrous metals, plastic and wood components, clay, soil, rubber and gypsum is used in the manufacture of structural concrete; in particular, self-compacted (SCC) concrete mixes reached the strength target of the class of concretes C40/50 [24] and references therein.…”