Voids in the mineral aggregate

Aggregates from a different source were blended using the mathematical technique to obtain five curves as before. The grading curves are shown in Figure 6. Mix 2 is almost coincident with the upper Fuller limit and mix 4 with the lower limit. Strengths, voids in the mineral aggregate (VMA), and densities are given in Table 1. 

For the screening test phase, three replicate specimens of each combination of independent variables were made, and each of the indicator or control tests was run on the specimens of sulfur-asphalt concrete. These indicator tests (dependent variables) included bulk specific gravity, air voids, voids in the mineral aggregate (VMA), resilient modulus, Hveem stability, Marshall stability, and Marshall flow. Table II presents the range of dependent variables determined during the screening test for the AAS system mixtures. 

Mix and Specimen Preparation. Most of the mixes described in this paper were prepared from a fairly one-sized medium-coarse sand with 35% voids in the mineral aggregate and with only 2%% of the material finer than No. 200 mesh. The sand grading is included in Table I. A 150/200 penetration grade asphalt was used. 

It is stated that the specimen s volume required for the determination of other volumetric properties, such as voids in the mineral aggregate (VMA) and voids filled with bitumen (VFB), is determined by the same way as explained above. 

Apart from the general requirements, the target composition should also fulfil some empirical requirements, such as grading, binder content, voids filled with bitumen, voids in the mineral aggregates and void content at 10 gyrations. When the AC is to be applied in airfields, the Marshall values should also be determined. 

The voids in the mineral aggregate (VMA) are defined as the void space between the aggregates in a compacted bituminous mixture that includes the air voids and the effective bitumen content, expressed as a percentage of the total mix volume. 

More details on the determination of the voids in the mineral aggregate can be found in ASTM D 6995 (2005). 

The University of Nottingham has also developed a method for calculating asphalt stiffness (Brown 1980). The data required are the stiffness modulus of the bitumen, in pascals, determined from Van der Poel s nomograph, and the voids in the mineral aggregate (VMA). The equation used to calculate the stiffness is as follows ... 

Another commonly used equation is the Hirsch predictive equation (Christensen et al. 2003). In this case, the dynamic modulus is determined with respect to voids in the mineral aggregate, voids filled with binder and dynamic shear modulus of bitumen. The equation developed is as follows ... 

A more simplified predictive model has been developed by Al-Khateeb et al. (2006), which, for the determination of dynamic modulus, uses only two parameters the voids in the mineral aggregate and the dynamic shear modulus of the binder. As concluded, the model is capable of predicting the dynamic modulus of an asphalt concrete at a broader range of temperatures and loading frequencies than the Hirsch model. It also has the advantage of estimating the dynamic modulus of an asphalt concrete with modified bitumen (Al-Khateeb et al. 2006). The mathematical formulation of the model developed is as follows ... 

The volumetric properties of the asphalt such as air voids, voids in the mineral aggregate and voids filled with bitumen are calculated from the compacted asphalt specimens obtained from the site. The calculations for the determination of the volumetric properties are carried out according to CENEN 12697-8 (2003), ASTM D 3203 (2011) or AASHTO T 269 (2011). 

The minimum percentage of voids in mineral aggregates (VMA) of the compacted specimens is selected from appropriate tables given in CEN EN 13108-1 (2008). 

Voids in mineral aggregates are determined according to the following equation ... 

The volume of the compacted specimen of any bituminous mixture consists of the volume occupied by aggregates, the volume occupied by bitumen and the volume of air voids. The volume, which is occupied by bitumen and air voids, is known as volume in mineral aggregates (VMA). When bituminous binder is added, part of the volume of air voids is filled with bitumen (asphalt). The volume is known as voids filled with asphalt (VFA). The above volumetric characteristic properties are presented in Figure 5.6. 

The SMA design is based on the volumetric properties in terms of air voids (V ), voids in mineral aggregate (VMA) and the presence of stone-on-stone contact. 

First, the air voids serve as a differing refractive environment relative to the surrounding mineral faces within the filler itself. This increases the effective refractive index of the aggregated filler and yields a higher light scattering of the product, as seen in Fig. 6.13 (Gate and Husband, 1986). 

Extension of fibre with filler almost always results in reduced drying demands, as minerals do not absorb water compared to fibre. However, aggregated fillers with very high surface area and internal void volume may result in a wetter web going to the press section. Figure 6.18 shows a comparison between scalenohedral PCC and GCC filler in press solids. Discrete particles, like GCC, typically drain more quickly compared to similarly sized aggregated particles, like scalenohedral PCC. 

Generation of nanoparticles in systems with confined void spaces such as inside the zeolites [82,88], carbonaceous materials [89], metal oxides [90,91], polymers [92,93], minerals [94,95] or metal-organic frameworks [96] is a sound approach of preventing aggregation with the kinetic control of catalytic reactions. 

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