# Complex Method of Airfield Pavement Condition Evaluation Based on APCI Index
## 5 Results
### Input Data for APCI Method
The evaluation of anti-skid properties is carried out by measuring the coefficient of friction on the airfield pavement based the Polish military standard NO-17-A501: 2015 Airfield pavements--Friction tests [38] and measurement of the surface texture, according to the requirements of standard EN 13036-1: 2010 Road and airfield surface characteristics--Test methods--Part 1: Measurement of pavement surface macrotexture depth using a volumetric patch technique [39] and applicable documents of international air organizations such as: European Union Aviation Safety Agency, International Civil Aviation Organization or Federal Aviation Administration. Both methods were described in [40]. Studies are performed by a device for continuous measurement of the friction coefficient mentioned in the above documents. During the test, the friction coefficient between breaking wheel and the pavement surface is measured. The test is carried out at a speed of 65 km/h or 95 km/h, ensuring the thickness of the water film in front of the measuring wheel with a value of 1 mm. The obtained results refer to tables with requirements contained in the above documents. Requirements relate to a specific measuring device and specific measurement conditions. The test result is a dimensionless number from 0 to 1, where 0 means lack of friction, and 1 means friction force with a value equal to load force. The assessment of the airfield pavement textures is carried out by a volume method by measuring the Mean Texture Depth or the profile method by measuring the Mean Profile Depth. However, these are point methods of the surface texture. Bearing in mind the geometrical dimensions of the airfield functional element, including the most important of them, which is the runway, as well as short time of access to it for operational reasons at every airport, the Airfield Division of the Air Force Institute of Technology designed the innovative measuring system used for measuring anti-skid properties of airfield pavements in a continuous way. It enables a dynamic, simultaneous measurement of the friction coefficient and depth texture of airfield pavement in the trace of measuring tire of the friction tester, in accordance with the applicable regulations. In the APCI model, the result of testing the anti-skid properties is taken into account by an anti-skid indicator derived from the Equation (11), wherein the anti-skid properties indicator is less than 0.4, and its value should be adopted as 100. \[Wpp=(4.6-6.6\cdot W_{ST})\cdot 100, \tag{11}\]  
where: \(W_{pp}\) is an anti-skid indicator, and \(W_{ST}\) is an anti-skid properties indicator [-]. Evenness of airfield pavement is assessed on the basis of measurements of inequality, in accordance with the requirements of the Polish military standard NO-17-A502:2015 Airfield pavements--Evenness testing [41], which were described in [42]. The measurement is performed using the planograph, which measures and records clearance values between the theoretical reference line connecting the bottom of the device wheels and the surface at the center point. The measurement is carried out with a frequency every 10 cm with an accuracy of 0.3 mm. The measuring route is divided into sections of 5 m and such samples are subjected to evaluation. The measure of inequality is the imperfection, presented in percents, which means the percentage of samples exceeding the requirements. In the APCI model, the evenness indicator is equal to the imperfection and determines it from the following, Equation (12). \[R=max(R_{T};R_{L}), \tag{12}\]  
where: \(R_{T}\) is longitudinal evenness [%], and \(R_{L}\) is transversal evenness [%]. The bond strength of the surface layer of airfield pavement is tested according to standard EN 1542:2000 Products and systems for the protection and repair of concrete structures--Test methods--Measurement of bond strength by pull-off.