Empirical requirements

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 grading envelope of the target composition mixture should be within maximum and minimum values for the percentages passing through the following sieves 1.4D, D, a characteristic coarse sieve, 2 mm, a characteristic fine sieve and 0.063 mm. The grading envelope should be within the overall limits specified (see Table 5.2 for the basic sieve set plus set 2 or CEN EN 13108 for the basic sieve set plus set 1). 

In addition, the grading envelope may include the percentage passing through one optional sieve between D and 2 mm and one optional fine sieve between 2 and 0.063 mm. The optional fine sieve can be one of the following sieves 1, 0.5, 0.25 or 0.125 mm. 

The ranges between the maximum and minimum values for the grading envelope should be selected as a single value within the given limits provided in Table 12 of CEN EN 13108-1 (2008). 

The minimum binder content of the target composition should range from 3.0% to 8.0%, by mass of total mixture, assigned to 26 categories from B 3 o to o (see CEN EN 13108-1 2008). 

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Holland Ah = (1.5V,d -H 0.04QJ/U where Ah — plume rise (m), Vj = stack exit velocity (m/s), d = stack diameter (m), = heat emission rate (kcal/s), U = stack top wind speed (m/s) Highly empirical. Requires stack testing confirmation on case-bycase basis... 

The two most common coal analyses are the proximate analysis and the ultimate analysis. In addition, there are a number of miscellaneous analyses. Many of these tests are empirical, requiring strict adherence to specified conditions. In the United States, the American Society for Testing and Materials (ASTM) standardizes these methods. International standards are developed by the International Organization for Standardization. 

The mixture at target composition, when empirical requirements are used, should fulfil general requirements plus empirical requirements selected from Sections 5.4.1.3 and 5.4.1.4. 

BBTM in Europe is designed in accordance to CEN EN 13108-2 (2008). The standard, apart from specifying requirements for constituent materials, also specifies empirical requirements for the particular bituminous mixtures. 

The HRA in Europe is designed in accordance to the CEN EN 13108-4 (2008) specification. There is no sufficient experience available with regard to fundamental testing of HRA. As a consequence, this European standard, for the moment, specifies empirical requirements combined with a stiffness requirement. However, the ultimate aim of the specification is to specify the required fundamental properties of the HRA. 

The composition of HRA, as mentioned, is based on empirical requirements (properties)... 

SMA in the EU is designed in accordance to CEN EN 13108-5 (2008). Although the aim of the standard is to specify the required fundamental properties of the SMA, at the moment, it specifies empirical requirements only. Needless to say, the standard sets requirements for the constituent materials. 

SA is designed in accordance with CEN EN 13108-3 (2008), which employs empirical requirements. 

The variety of sites encountered by Roman engineers across the empire required the exploitation of all types of indigenous materials, and construction techniques were adjusted to meet as-found characteristics, exploiting strengths and suppressing weaknesses. Rapid weathering revealed defects more quickly and encouraged innovation and evolutionary development. 

In Table 3.2, typical examples of high temperature-type proton-conducting oxides and their distinct features are listed classifying them as their crystal structure. It is still unclear what is essential for good protonic conduction in this class of oxides. However, empirical requirements for good protonic conductors of this type seem to be (1) high basicity of the constituent cation... 

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