Testing - Concrete Mix Design, Quality Control and Specification - page 133

Analysis for cement content and proportions
In situ tests
Schmidt hammer, pull-out, break-off, cones, etc.
Ultrasonic, ground-penetrating radar (GPR), Impact-Echo,
nuclear, resistivity
Heat generation
Tests on fresh concrete
Workability (slump and over 20 others)
Bleeding
Air content
Setting time
Segregation resistance
Unit weight
Wet analysis
Temperature
Of these many possible tests, in practice well over 90% of all routine
tests on concrete are concentrated on compression tests and slump tests that
should be, but are not always, accompanied by fresh concrete temperature
and hardened density determinations.
Before considering whether this is a desirable state of affairs, it is first
necessary to consider the purpose and significance of the testing. There are
at least three possible purposes:
1. To establish whether the concrete has attained a sufficient maturity
(for stripping, stressing, depropping, opening to traffic, etc.)
2. To establish whether the concrete is basically satisfactory for the pur-
pose intended
3. To detect quality variations in the concrete being supplied to a given
specification
It is very important to be clear about the purpose of the testing because
attempts to fulfill all these purposes simultaneously usually lead to ineffi-
ciency in fulfilling any of them. The true purpose of the majority of tests is
the detection of quality variations.
The selection of compressive strength for the great majority of control
testing relies upon three basic assumptions:
1. That most other properties of concrete are related to compressive
strength
2. That compressive strength is the easiest (most established), most
economical, or most accurately determinable variable amenable
to test
3. That compressive strength testing is the best means available to
determine the variability of concrete.