Construction and Building Materials 199 (2019) 115–123
Contents lists available at ScienceDirect
Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Flexural fatigue strength of demolition aggregates stabilized with alkali-activated calcium carbide residue Alireza Mohammadinia a,⇑, Arul Arulrajah a, Itthikorn Phummiphan b, Suksun Horpibulsuk c,⇑, Mehdi Mirzababaei d a
Department of Civil and Construction Engineering, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia Singburi Rural Road Office, Department of Rural Roads, Thailand and Graduate Program in Construction and Infrastructure Development, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand c School of Civil Engineering, and Center of Excellence in Innovation for Sustainable Infrastructure Development, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand d School of Engineering and Technology, Central Queensland University, 120 Spencer Street, Melbourne, Victoria 3000, Australia b
h i g h l i g h t s Alkali-activation of demolition materials can provide a sustainable alternative to conventional construction aggregates. Aluminosilicate gel can improve the serviceability of the stabilized recycled aggregates under repeated loadings. Combination of fly ash and slag or calcium carbide residue can improve the durability of the stabilized product.
a r t i c l e
i n f o
Article history: Received 2 October 2018 Received in revised form 22 November 2018 Accepted 5 December 2018
Keywords: Calcium carbide residue Fly ash Slag Alkali-activation Pavement Railway tracks
a b s t r a c t Replacing the base and subbase layers in flexible pavements and sub-ballast layer in railway tracks with recycled materials has attracted significant attention from industry and researchers alike. The semi-rigid stabilized layers in the flexible pavement structure and railway tracks sustain high flexural and tension stresses which reduces the serviceability life of the superstructure. The flexural and compressional modulus of the stabilized materials under repeated loads and at at-rest k0 condition is highly dependent on the specifications of the binder. Industrial by-products including calcium carbide residue (CCR), Fly Ash (FA) and Slag (S) were utilized to improve the compressional resilient modulus, flexural strength, durability and fatigue life of recycled aggregates. The variation of ductility in the blend with different precursors indicated that the service life of the stabilized layers not only depended on the strength but was also controlled by the deterioration rate of the flexural modulus and stiffness of the sample. The ductility of binder with aluminosilicate gels fabric can potentially absorb the stresses of the cyclic loading and postpones development of tension cracks. Ó 2018 Elsevier Ltd. All rights reserved.
1. Introduction The sustainable use of recycled materials in civil engineering applications has been extensively practiced in recent years [1,2]. To minimize the concerns related to the life cycle durability of recycled aggregates which has endured crushing loads and potentially contain micro cracks, chemical stabilization has been used ⇑ Corresponding authors at: Swinburne University of Technology, PO Box 218, Hawthorn, Victoria 3122, Australia (A. Mohammadinia). E-mail addresses:
[email protected] (A. Mohammadinia),
[email protected] (A. Arulrajah),
[email protected] (S. Horpibulsuk),
[email protected] (M. Mirzababaei). https://doi.org/10.1016/j.conbuildmat.2018.12.031 0950-0618/Ó 2018 Elsevier Ltd. All rights reserved.
extensively by the industry sector. Chemical stabilization has been found to improve the quality of alternative pavement and rail track structure materials, such as recycled construction and demolition (C&D) aggregates for higher-end applications [3,4]. However, the use of traditional carbon-intensive binders such as Portland cement and lime diminishes the sustainability and economic justification for using recycled products [5]. A widespread attention to recycling both granular waste and fine sludge and by-products from industrial activities back to construction of transportation structures [6,7] and ground improvement [8] and injection grouting have been previously attempted with recycled products [9,10]. Alternatively, industrial by-products such as calcium carbide residue (CCR), fly ash (FA) and slag (S) which are rich in calcium,
116
A. Mohammadinia et al. / Construction and Building Materials 199 (2019) 115–123
Table 1 Geotechnical properties of C&D aggregates.
à y
Geotechnical properties
Test standards
CB
RCA
RAP
Fine Content (%) Sand Content (%) Gravel content (%) Coefficient of uniformity (Cu) Coefficient of curvature (Cc) Particle density – coarse (Mg/m3) Particle density – fine (Mg/m3) USCSà Water absorption – coarse (%) Water absorption – fine (%) Water absorption - average Organic content (%) pH Flakiness index Los Angeles abrasion loss Unbound UCS strength (MPa)
ASTM [29] ASTM [29] ASTM [29] ASTM [29] ASTM [29] AS 1141.6.1 [30] AS 1141.5.1 [31] ASTM D2487 [32] AS 1141.6.1 [30] AS 1141.5.1 [31] AS 1141.5.1 [31] ASTM D 2974-87 AS 1289.4.3.1 [33] BS 812–105.1 [34] ASTM C131 [35] ASTM [22]
7.7 33.8 33.8 37.9 1.6 2.66 2.62 GWy 7.02 10.60 9.0 1.72 10.92 23.3 34.9 0.34
6.0 31.5 62.5 38.8 1.3 2.69 2.64 GW 6.05 13.60 9.7 3.07 11.85 15.3 31.1 0.55
4.4 29.1 66.5 12.9 1.9 2.63 2.65 GW 3.47 5.22 4.3 4.05 10.79 10.1 20.7 0.73
Unified Soil Classification System. GW: Well Graded Gravel.
alumina and silica can be used as effective stabilizing materials without increasing the carbon footprints. In recent years, several researchers have demonstrated that to accelerate the gel production rate at moderate temperatures using precursors with high content of amorphous and crystal silica and alumina, alkaline solutions can potentially produce a matrix with suitable stiffness and ductility, which can perform equally or better than cement stabilized blends [11,12]. Similar to cement stabilization, there are a number of factors which can impact the strength and stiffness of the stabilized sample which include curing environment, mixing methods, alkaline content and the type of produced gel. The majority of research on chemical stabilization focuses on optimizing the blends based on compressive strength. While the compressive strength is generally accepted to monitor strength development, it will not measure the durability of the specimen, particularly under tension or flexural stresses. Alkali-activated slag-based gel products are predominantly aluminium-substituted C-A-S-H gel that is produced by the dissolution of glassy particles in the precursor, which generates the initial solid phase followed by a dynamic chemical diffusion [13,14]. However, precursors with low-calcium content, produce disordered, cross-linked aluminosilicate binder gels with a tetrahedral matrix [15,16]. The alkali-activated blended systems benefit
0.001 100
0.01
0.1
1
10
from stable C-S-H gel products of hydration (from clinker, slag or calcium source) along with aluminosilicates gel from silica-rich and alumina-rich sources activated with alkaline solutions [17,18]. Class C FA is widely used as partial cement replacement in construction activities, while Class F FA has limited applications due to low calcium content. The fine sphere shaped FA particles are collected downstream of coal-fired electricity power stations that are rich in a combination of amorphous and crystalized silica. Slag and CCR also used as rich sources of calcium to compliment the reaction products with C-S-H gels. Granulated blast furnace slag contains impurities from furnace and iron ore along with high CaO content. CCR is collected after drying the disposal slurry after acetylene gas production [19]. A combination of sodium silicate (Na2SiO3) and sodium hydroxide beads (NaOH) diluted to an 8
Table 2 Physical specification of binders.
100 100
Capping Upper Limit
Specification
CCR
Slag
FA
Diameter at 10% – D10 (mm) Diameter at 50% – D50 (mm) Diameter at 90% – D90 (mm) Mean Diameter (mm) Specific Gravity*, Gs Bulk density (Mg/m3) Solubility in water (g/L) pH (25 °C) y
9.16 40.2 72.5 41.3 2.92 2.10 N/A8 12.5
6.4 20.5 54.6 20.7 3.15 0.88
