Experimental Study on the Preparation of Recycled Admixtures by Using Construction and Demolition Waste

Abstract

The use of construction and demolition waste (CDW) to prepare recycled admixtures is of great significance for the complete resource reutilization of CDW. In this paper, different kinds of CDW were prepared into recycled powder (RP) with a specific particle size (0–45 µm or 0–75 µm). The fineness, water requirement ratio (WRR), fluidity, loss on ignition (LOI), strength activity index (SAI) and compatibility of cement and superplasticizer (CCS) were examined. The above test results were analyzed by advanced analysis tools, such as laser particle size analysis, XRD, XRF, DSC-TGA, SEM, and BET. The properties of different types of RPs varied greatly, which was closely related to the microstructure, particle morphology and chemical composition of the RP. The experimental results showed that all kinds of RPs after grinding had a high fineness and good particle size distribution, and the mineral composition was dominated by SiO2 with the content exceeding 50%. The WRR of various RPs was between 105% and 112%, and the SAI was between 68% and 78%, but the LOI varied greatly. Different types of RPs had a negative impact on the CCS, but the compatibility of cement and naphthalene-based superplasticizer was less affected. The content of recycled brick powder (RBP) in a hybrid recycled powder (HRP) was an important factor. When the content of RBP in HRP exceeded 50%, the HRP could meet the basic performance requirements of fly ash.

Thermal Performance of Concrete with Recycled Concrete Powder as Partial Cement Replacement and Recycled CDW Aggregate

“…Further to the X-ray fluorescence (XRF)-determined chemical composition of the GRC and OPC shown in Figure 1a, the major oxides were SiO 2 (46.10 wt%) and CaO (40.0 wt%). The figure also presents graphically the minimum and maximum ground concrete replacement ratios used in earlier studies [20][21][22][23][24][25][26] on pastes, mortars and concrete.…”

Using Eco-Friendly Recycled Powder from CDW to Prepare Strain Hardening Cementitious Composites (SHCC) and Properties Determination

“…Figure 2b shows the XRD results, whereby the SiO 2 content in RBP is much higher than that in cement and FA, and there are no hydrated compounds (such as CaO, Ca(OH) 2 ) in RBP. Attributed the SiO 2 being the main component that takes part in the pozzolanic reaction of cementitious materials, the high fineness RBP can be used as the SCM in the cementitious materials [40]. Figure 2b further shows the SEM images of RBP, and an irregular micro-structure can be observed.…”

Accelerating the Reaction Kinetics of Na2CO3-Activated Slag Mortars by Calcined Recycled Concrete Fines

“…Previous studies demonstrated that the RCF exhibited potential reactivity, which can be used for new concrete production [ 21 ]. However, the workability, strength, and durability of concrete containing RCF would significantly decrease due to the high porosity and low reactivity of RCF [ 22 , 23 , 24 ]. Therefore, only a minimal amount of RCF can be utilized, and the rest is disposed of by landfilling and dumping, failing to take full advantage of waste resources and causing environmental and groundwater pollution [ 2 , 19 ].…”