Evaluation of Recementation Reactivity of Recycled Concrete Aggregate Fines

Abstract

The use of recycled concrete aggregate (RCA) as a drainage material in exfiltration trenches and base and subbase layers is becoming increasingly common. During crushing, stockpiling, transporting, and placing, however, RCA may produce fines that could recement and clog the pavement drainage system. Many previous studies indicated that not only the structural capacity but also drainage of pavement subsurface layers can be greatly affected by the properties and gradation of the aggregate used. This study evaluated the recementation reactivity of RCA fines that could eventually impair drainage performance. RCA fines passing the No. 200 sieve (less than 75 μm) were produced through the simulation of an in-place aggregate abrasion process, and cement paste cylinders were cast with complete replacement of cement with RCA fines. The hydration properties of the paste samples with RCA fines were evaluated by means of heat of hydration, pH variation, and Vicat needle penetration in their early age. Compressive strength tests and petrographic examinations such as scanning electron microscopy, energy dispersive X-ray, and X-ray diffraction were also performed to mechanically and chemically verify the recementation reactivity of the hardened paste with RCA fines. Test results demonstrated that recementation of RCA fines was modest, and therefore the compressive strength of the paste specimens with RCA fines was minimal compared with that of ordinary cement paste specimens. The microstructural and chemical composition analyses also indicated that the recementation reactivity of RCA fines was negligible.

The Properties of Composites with Recycled Cement Mortar Used as a Supplementary Cementitious Material

“…Tests carried out by some researchers [22,23] have proved that recycled mortar contains non-hydrated cement, calcium hydroxide (CH) and dicalcium silicate (C 2 S), which are capable of hydration and creation of rehydration products. Some research has shown, however, that the mortar remaining on the surface of the recycled aggregates stored outside for a longer time does not show any rehydration reactivity [24]. Nevertheless, a study carried out by Vegas et al [25] of the mix proportions and characteristics of mortars made with recycled concrete aggregate showed that up to 25% recycled aggregate can be used in cement-based masonry mortars with no significant decline in performance and no new admixtures or higher cement content required.…”

Recycled concrete aggregate coated with quaternary ammonium compounds for water disinfection

“…This is probably due to hardened cement paste that adheres to the surface of aggregates. The XRD analysis found that calcite (CaCO 3 ), quartz (SiO 2 ), jennite (Ca 9 H 2 Si 6 O 18 (OH) 8 Á6H 2 O), and larnite (Ca 2 SiO 4 ) are the main mineral components of RCA, confirming that RCA mainly consists of hydrated cement, sand, and limestone (Nam et al 2014(Nam et al , 2015Kim et al 2014).…”

“…A series of laboratory tests were performed to evaluate the basic physical properties of RCA such as specific gravity, unit weight (kg/m 3 ), and void content (%) (Table 1). X-ray diffractometer (XRD, Rigaku D/MAX XRD II) with CuKa radiation, 2 theta scanning from 5°to 80°with step size of 0.02°, was used for mineralogical investigation (Wagih et al 2013;Nam et al 2014Nam et al , 2015Kim et al 2014).…”

“…Recycled Concrete Aggregate (RCA) is one of the major construction and demolition (C&D) wastes, and its reuse has drawn considerable attention due to its environmental impacts and economic advantages. RCA can minimize both the need of landfills and the emission of carbon dioxide from resource extraction (Wagih et al 2013;Nam et al 2014;Kim et al 2014;Ding et al 2016) and reduce cost of waste disposal and use of natural resources (Donalson et al 2011;Wagih et al 2013;Nam et al 2015a, b;Puthussery et al 2016). Recently, recycled RCA has been utilized in large scale as stabilized base, subbase, and drainable base materials in the transportation construction sector (Cawley et al 2004;Rana et al 2016).…”

Investigation on the Effect of Recycled Asphalt Shingle (RAS) in Portland Cement Mortar

“…According to the USEPA, total shingle waste generated in the U.S. is approximately 11 million tons per year [2]. Beneficial utilization of byproduct and waste materials in road construction have been made and it contributes to the success of sustainability [3][4][5][6][7][8][9][10][11][12][13][14]. It consists of roughly 90% representing post-consumer scrap (or tear-off shingles) and 10% comprising post-manufacture scrap [15].…”