Dear reader we have published many aspects of ready mixed concrete in this blog. We are providing necessary information regarding ready-mixed concrete which are not frequently available in online.
We have some ideas about measuring admixtures, waters and other constituent materials of ready–mixed concrete. In measuring these constituents, some scales are used to measure these accurately. We are discussing this fact according to ASTM C94/C 94M.
The scales used in these purposes are checked for accuracy before using them for measuring constituents as the accuracy in weighing constituent materials is very important in correct proportioning for a particular design requirement of concrete, supplied by the purchaser for their specific projects.
Now question is when a scale can be said to be accurate. The answer is as follows:
Static load tests conducted for accuracy check within each ¼ th of capacity of scale should be found within ±2 percent of total scale capacity. At least one test should comply with above requirement.
Standard weights to check accuracy of scale should be available. Now requirements comes for cleanliness i.e., the exposed working parts like-
c. Other parts
- Must be kept clean for accurate measurement of constituents.
Beam scales, perhaps we all know about this term, should have sensitive balance indicator to ensure monitoring movements to such readable amount that every weight placement in batch hopper by 0.1 percent of scale capacity (in normal condition) is distinguishable.
Now we are providing pointer traveling requirements. The pointer should travel at a 5 percent of net-rated weigh beam capacity for condition of under weighing. In case of over weighing condition this requirement for pointer travel should be 4 percent for net-rated largest weigh beam capacity. Perhaps you have heard about plant certification for National Ready Mixed Concrete association. This requirements also meet the specification we provided according to ASTMC94/C 94M.