The cause and influence of self-cementing properties of fine recycled concrete aggregates on the properties of unbound sub-base

Poon, Chi Sun; Qiao, Xiuchen; Chan, Dwm

doi:10.1016/j.wasman.2005.12.013

Cited by 155 publications

(94 citation statements)

References 9 publications

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“…This may be due to the presence of f-FA, and the pozzolanic reaction between Ca(OH) 2 in the fine recycled aggregate and the fly ash forming additional C-S-H and enhancing strength. This is consistent with the authors' previous findings that fine recycled aggregates possessed certain self-cementing ability [19]. For the RF100 mix, the lower strength recorded was probably due to the excessive amount of water added to compensate for the water absorption of the recycled fine aggregates.…”

Section: Hardened Propertiessupporting

confidence: 92%

Properties of self-compacting concrete prepared with coarse and fine recycled concrete aggregates

Kou

Poon

2009

Cement and Concrete Composites

422

167

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Section: Hardened Propertiessupporting

confidence: 92%

Properties of self-compacting concrete prepared with coarse and fine recycled concrete aggregates

Kou

Poon

2009

Cement and Concrete Composites

422

167

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“…For instance, C 2 S (2CaOSiO 2 ), a primary mineral in portland cement, is very slow to hydrate compared to other cement minerals such as C 3 S (3CaOSiO 2 ) and C 3 A (3CaOAl 2 O 3 ) (Mamlouk and Zaniewski 2011). The C 2 S present in RCA but the amount depends on the age, particle size, and amount of cementitious materials used in the original concrete mix (Poon et al 2006). Although the amount was not measured in this study, the presence of C 2 S in RCA may have caused self-cementation to occur and let to the stabilization of leached metal concentrations from RCA with longer reaction time (i.e., 7 to 28 days).…”

Section: Effects Of Reaction Timementioning

confidence: 83%

“…RCA may also still contain cement minerals such as dicalcium silicate (C 2 S), which is never completely hydrated during service life of the concrete (Poon et al 2006). The rehydration of these cement grains and deteriorated cement paste may influence leaching potential of metals.…”

Section: Changes In Metal Concentrations With Time After Adding Watermentioning

confidence: 99%

Effects of extraction methods and factors on leaching of metals from recycled concrete aggregates

Bestgen

Çetin

Tanyu

2016

Environ Sci Pollut Res

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Leaching of metals (calcium (Ca), chromium (Cr), copper, (Cu), iron (Fe), and zinc (Zn)) of recycled concrete aggregates (RCAs) were investigated with four different leachate extraction methods (batch water leach tests (WLTs), toxicity leaching procedure test (TCLP), synthetic precipitation leaching procedure test (SPLP), and pH-dependent leach tests). WLTs were also used to perform a parametric study to evaluate factors including (i) effects of reaction time, (ii) atmosphere, (iii) liquid-to-solid (L/S) ratio, and (iv) particle size of RCA. The results from WLTs showed that reaction time and exposure to atmosphere had impact on leaching behavior of metals. An increase in L/S ratio decreased the effluent pH and all metal concentrations. Particle size of the RCA had impact on some metals but not all. Comparison of the leached concentrations of metals from select RCA samples with WLT method to leached concentrations from TCLP and SPLP methods revealed significant differences. For the same RCA samples, the highest metal concentrations were obtained with TCLP method, followed by WLT and SPLP methods. However, in all tests, the concentrations of all four (Cr, Cu, Fe, and Zn) metals were below the regulatory limits determined by EPA MCLs in all tests with few exceptions. pH-dependent batch water leach tests revealed that leaching pattern for Ca is more cationic whereas for other metals showed more amphoteric. The results obtained from the pH-dependent tests were evaluated with geochemical modeling (MINTEQA2) to estimate the governing leaching mechanisms for different metals. The results indicated that the releases of the elements were solubility-controlled except Cr.

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“…This improvement may be due to the non-water absorption characteristic of synthetic fibres. In addition, the distribution of fibres can modify the microstructure of hardened cement pastes in the to seal and bridge the capillary pore structure, which results in minimal void interconnection [28]. Figure 6: Water absorption of tested specimens at various curing age …”

Section: Water Absorptionmentioning

confidence: 99%

Properties of Recycled Aggregate Concrete Reinforced with Polypropylene Fibre

Mohammad¹,

Ismail²,

Alwi³

2016

MATEC Web Conf.

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Abstract. This research work is aimed to investigate how the addition of various proportion of polypropylene fibre affects the mechanical strength and permeability characteristics of recycled aggregate concrete (RAC) which has been produced with treated coarse recycled concrete aggregate (RCA). Further research on RAC properties and their applications is of great importance as the scarcity of virgin aggregate sources in close proximity to major urban centers is becoming a worldwide problem. In this study, the hardened RAC properties at the curing age of 7 and 28 days such as compressive strength, flexural strength, ultrasonic pulse velocity (UPV), water absorption and total porosity were evaluated and compare with control specimens. Experimental result indicates that although the inclusion of the treated coarse RCA can enhance the mechanical strength and permeability properties of RAC, Further modification by addition of polypropylene fibre can optimize the results.

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The cause and influence of self-cementing properties of fine recycled concrete aggregates on the properties of unbound sub-base

Cited by 155 publications

References 9 publications

Properties of self-compacting concrete prepared with coarse and fine recycled concrete aggregates

Properties of self-compacting concrete prepared with coarse and fine recycled concrete aggregates

Effects of extraction methods and factors on leaching of metals from recycled concrete aggregates

Properties of Recycled Aggregate Concrete Reinforced with Polypropylene Fibre

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