QUALITY ASSURANCE SERVICES
Quality assurance services are used to ensure that an ordered service or product has been provided according to the contract. Quality assurance is carried out both visually and by measuring.
Road Consulting Oy offers quality assurance for new or repaired road structures and structural layers and for private construction and monitoring of structural improvement. Measurable variables include e.g. the thickness, qualities and carrying capacity of the material.
Measuring methods used in quality assurance include
Surface and structure radar
Falling weight deflectometer
Ridge and smoothness survey
With surface radar, the quality of the road surface is determined using void. The measuring is carried out as continuous surveying and without disturbing other traffic by driving at a speed of 40 km per hour. The measurement is done from the outer ridge of each lane, nowadays also at the middle seam. In addition to the measurements, a reference sample is taken of the surface, i.e. a so-called core sample from which the void and density of the surface is determined by a lab study. From the measurement results, the diaelectricity value is determined for each material, and the void of the surface is determined based on the lab study results as a continuous graph. The report includes the mean, standard deviation, minimum and maximum value and percentage deviations (exceeding and falling below) of the void and, when necessary, the amount of a possible fine. The survey is usually tied to pile-driving work on the site, and with the air void graph it is easy to find interesting spots on the site for visual or closer examination.
With the surface radar, the thickness of the carrying and distributing layers, the location of steel nets and the depth location are determined.
The thicknesses of the structural layers or the whole structure are measured with a structure radar. The measurement is carried out as continuous surveying by driving at a speed of 20 km per hour. The measuring is usually done from the outer groove by recording the radar signal at least every 10 cm. In addition to thickness data, the survey gives information on e.g. depths of mass displacements, tilts of displaced structures, the position of drums, location of steel nets and the switching points of the improvement method.
The carrying capacity of the constructed layer or the whole structure is shown with the falling weight deflectometer at certain points of the road or structure. The surveys are point-based.
In spring 2010, Road Consulting Oy purchased a French Vectra Ecodyn retroreflection radar. The device is used to measure the retroreflection value of road markings. The retroreflection value of a road marking describes the visibility of a line/lines e.g. in the dark in rain; in other words, the retroreflection value describes the quality of the marking. The device is used to demonstrate the quality of new road markings and for quality control and guidance for marking work, i.e. targeting worn-down sites and analysing the condition of old markings. Main clients are companies that make road markings and owners of street and road networks.
With point-based structural sampling, it is possible to ensure the thickness and quality of the constructed layers and the materials used, and a sample is also taken for lab studies. Sampling is done with a window sampler, making only a c. 100 mm diameter hole into the structure, which will be patched and carefully sealed after sampling. The thicknesses of materials are measured directly from the sampler.
For profile surveys of paved roads (groove, smoothness and side slopes) we use equipment developed and built by VTT (Technical Research Center of Finland).
A longitudinal profile, i.e. smoothness, affects vibration of the vehicle, and therefore it directly affects driving and travelling comfort.
Vertical unsmoothness, i.e. grooves, cause the danger of hydroplaning. Over time, water sitting in grooves also causes damage to the surface and the road structure. Data on grooves and smoothness are one of the most important starting points for road re-paving and programming of improvement procedures for structures.