Abstract: An improved turbidimeter apparatus (10) is provided for accurate, rapid, field testing of fresh concrete mixes in order to determine the water-cement ratios thereof. The apparatus (10) includes an upright sieve chamber (12) adapted to receive a concrete sample (56), together with a turbidimeter (14); a recirculation system (16) is interposed between the chamber (12) and turbidimeter (14), and permits separation of the aggregate from the concrete sample (56) and formation of a dilute dispersion suitable for turbidimetric determinations. In use, dilute water-cement dispersions are created using the apparatus (10) and turbidimeter determinations are made via turbidimeter (14); these readings can then be used with standard, previously developed water-cement ratio versus turbidimeter reading curves to accurately measure the initial water-cement ratios of concrete mixes.