Has there been any practical test method developed for rapid determination at me jobsite of the cement content of fresh concrete?
The method that has long been in use is the Willis-Hime method (described in CONCRETE CONSTRUCTION, October 1957, page 8). A new British method has recently been reported in the Cement and Concrete Association publication Precast Concrete for April 1973, page 201. It requires equipment that is expected to sell commercially for about œ 600, or about $1,500. It is designed to produce an answer in about five minutes, the maximum time that it is considered economically practical to delay the discharge from a ready mixed concrete truck. The process of analysis is one that elutriates the concrete, washes small particles over a weir, from which a small sample is automatically taken. The particles are then flocculated and measured. If the known silt content of the total aggregate in the concrete is in error by one percent it can lead to an error of around five percent in the cement content reported. The apparatus is said to be sturdy, as well as easy to prepare for use, operate and clean.