Aggregates for concrete - Concrete Mix Design, Quality Control and Specification - page 46

using data from Kerrigan (1972), which shows plots of flow time and voids
for sands having artificially adjusted gradings. The grading variations
were applied to two basic sands to give two series: one having good particle
shape and smooth surface texture (Series 1) and the other poorer particle
shape and rough surface texture (Series 2). It can be seen that with deterio-
ration of shape and surface texture, and the same specific surface (SS), the
plot moves toward higher voids and longer flow time.
Norwood Harrison conducts training courses for Humes concrete tech-
nology (Harrison, 1988). As part of setting up the mortar demonstration,
he obtained a quantity of a coarse but long-graded sand, and sieved it out
into a series of particle sizes corresponding to each interval in the sieve mesh
sizes. These were then recombined to give three standardised sand gradings:
RES30 (30% passing 600 microns), RES50 (50% passing 600 microns), and
RES80 (80% passing 600 microns). Sand flow results for the three sands
are shown in Figure 3.5. The plot is very close to a straight line, and RES50
shows the test parameters are proportional to the change in specific surface.
Malhotra (1964) used a form of the flow test to evaluate shape and sur-
face texture of a range of sands and the effect on workability of mortars

Sand Flow Results
Donmix

33

32

31

30

29

RES30

28

27

RES50

26

25 RES80

Grading
Designation

Speci�c
Surface

24

23

RES30 40

RES50 51

22

RES80 66

21

20 40

41 42 43 44 45

% Voids

46 47 48 49

Figure 3.5 Comparison of flow time and void content for sand of varying specific surface.
(From N. Harrision, personal communication, January 2013.)