Ann: EdenCrete - Continued Growth of CDOT Market, page-37

is this a 1970’s civil engineering exam?

2013. University of Texas.

The entire point of the question is that stronger is not necessarily better. it also mentions that cost control is critical even though the price differences may seem very small.


"From the data shown in Table 3 it is clear that none of the measured slumps met the target. Failure to meet the target slump may indicate a poor concrete mixture and might affect the installation process on a construction site. For example, a mixture with too high of a slump could result in excess segregation, while a mixture with too low of a slump could result in inadequate compaction. In order to reduce the possible negative effects of concrete with poor slump, modifications to the concrete mixture can be made. Simply adding water would increase a slump that is too low, but would weaken the concrete, potentially resulting in a failure to meet the target compressive strength. A better approach would be to reduce the content of fine aggregate and correspondingly increase the content of coarse aggregate, which would reduce the surface area of aggregate needed to be coated by paste, resulting in a better ability of the paste to lubricate the mixture and a higher slump. To reduce a slump that is too high, one could reduce water, which would also increase strength by lowering the w/c. However, as shown in Table 2, this would come with a correspondingly higher cost for the mixture. All of these factors must be weighed when deciding to make an adjustment to the designed mixture. "

The devil is always in the detail. What may seem like huge advantages to a layman may be worthless (or negative) to an expert.

A few years ago an ASX company was touting a very cheap and tiny device for chemical analysis. The problem was that the a) device was far too sensitive and would constantly give false alarms and b) the method (near IR spectroscopy) has very limited applications. To a non-expert it seemed brilliant. To the intended users - chemists - it was essentially worthless.