ABSTRACT
Density was selected as the key Quality control (QC) parameter as its high precision was recognized in the early days. Precision in QC was chosen in favour of more relevant but difficult to measure parameters at the time. Precision is not the same as accuracy. As dry density ratio (DDR) index is now fully embedded in QC, one may mistakenly think that the factors measured are the key factors. DDR was intended to be just part of the decision-making process of quality and verification of the design requirements. On projects which use end product specifications, a DDR value then becomes THE de facto decision on pass/fail. This simplifies the site decision in having assessment metronomically stated. Because traditionally industry did not or cannot measure something should not diminish its importance. Several in-situ devices have been available for the past two decades and various research has shown the benefits. Data was acquired as part of field trials over multiple “live” projects. Conventional QC testing was supplemented with other field strength and modulus tests. Correlating to established DDR tests is blind to the influences of other factors influencing strength and modulus. Such tests measure a combination of underlying material, material quality, moisture content and density. A 95% DDR does not have a singular strength or modulus value as measured with one-to-one correlated testing as this is governed by material type.
