**4. Granulation by cold-bonding technique**

Dowling (1993) and Skalny & Mindess (1989) indicated that the higher packing density of component materials of cement-based composite, the higher properties of cement-based composite will be. In order to ensure that characteristics of cold-bonding recycling coarse aggregates are able to satisfy with the related criteria, a higher stress was adopted to the cement-based composites as recycling coarse aggregates. The various methods, molds, and conditions of granulation are discussed in this section.

#### **4.1 Method of granulation**

Three various methods were conducted to granulate the cement-based composites as coldbonding recycling coarse aggregates. They are: 1) spirally push method; 2) immediately squeeze out method; 3) press ingot method. The granulation energy of spirally push method

SP(%) = 4.59 × 10-5 × X2 – 1.81 × 10-2 × X + 1.98

120 140 160 180 200 Total water (kg/m3)

Fig. 5. The SP dosage for cold-bonding recycling coarse aggregates (Chang et al., 2009).

According to the procedure of DMDA described in Section 3.3, the mixture proportions of cement-based composite with various recycling resources for producing the cold-bonding recycling coarse aggregates are shown in Table 7. For instance, B2-3-200 represents a cement-based composite contains the construction residual soil of B2-3 category and a cement amount of 200 kg/m3; B-100 represents a cement-based composite with B granite sludge and a cement amount of 100 kg/m3; L-50 represents a cement-based composite with

Dowling (1993) and Skalny & Mindess (1989) indicated that the higher packing density of component materials of cement-based composite, the higher properties of cement-based composite will be. In order to ensure that characteristics of cold-bonding recycling coarse aggregates are able to satisfy with the related criteria, a higher stress was adopted to the cement-based composites as recycling coarse aggregates. The various methods, molds, and

Three various methods were conducted to granulate the cement-based composites as coldbonding recycling coarse aggregates. They are: 1) spirally push method; 2) immediately squeeze out method; 3) press ingot method. The granulation energy of spirally push method

where *X* is total amount of water (kg/m3).

0

**3.4 Mixture of cold-bonding recycling aggregate** 

lime sludge and a cement amount of 50 kg/m3.

**4. Granulation by cold-bonding technique** 

conditions of granulation are discussed in this section.

**4.1 Method of granulation** 

0.1

0.2

SP percentage (%)

0.3

0.4

is too small to adequately form the recycling aggregates (see Fig. 6) due to the intended cement-based composite contains lower moisture to minimize the shrinkage rate or the expansion rate and ensure the durability of cold-bonding recycling coarse aggregate. On the contrary, while the cement-based composite with higher moisture could be successfully granulated by using spirally push method, but the produced recycling aggregates will not have nice properties.


Table 7. Mixture proportions of cold-bonding recycling aggregates.

Regardless of the cement-based composite contains how much moisture, the immediately squeeze out method will not successfully achieve the granulation of cold-bonding recycling coarse aggregate. This is due to the water within cement-based composite was drained out as shown in Fig. 7, like consolidation in geotechnical engineering (Holitz & Kovacs, 1981), during the process of granulating recycling coarse aggregates. Therefore the immediately squeeze out method also cannot be employed to form the cold-bonding recycling coarse aggregates.

Cold-Bonding Technique – A New Approach to Recycle

(a) Step 1: To fill the mixed cement-based composite into the mold

> (c) Step 3: To press and form the recycling aggregates

Fig. 8. The procedure of press ingot method.

Young, 1981).

Innocuous Construction Residual Soil, Sludge, and Sediment as Coarse Aggregates 109

adequately granulated; 2) with higher moisture: the cold-bonding recycling coarse aggregates don't have only sufficient durability (Mehta, 1986; Mindess & Young, 1981; Neville, 2000) but the redundant water also will be drained out during forming recycling aggregates (like consolidation in geotechnical engineering). The drained water will result in the excessively high water-to-cement ratio (w/c) or water-to-cementitious materials (w/cm) around the surface of the recycling aggregate. And the excessively high w/c or w/cm will immensely affect the strength, hardness, abrasion resistance, soundness, permeability of the cold-bonding recycling coarse aggregate (Mehta, 1986; Mindess &

> (b) Step 2: To set up the pestle into the mold

(d) Step 4: To take off the recycling aggregates from the mold

Fig. 6. Spirally push method.

(a) A commercial spirally-push machine (b) Photo of improper recycling aggregates

(a) The water within cement-based composite was drained out

(b) Photo of broken recycling aggregates

Fig. 7. Immediately squeeze out method.

Finally the press ingot method (see Fig. 8) was developed and successfully granulated the cold-bonding recycling coarse aggregates. Fig. 8 also shows the procedure of press ingot method and the procedure is described as follows:

Step 1: To fill the mixed cement-based composite into the mold.

Step 2: To set up the pestle into the mold.

Step 3: To press and form the recycling aggregates.

Step 4: To take off the recycling aggregates from the mold.
