Significant basis of this experimental study was the fact that all
samples should be carried out under comparable conditions. In order
to obtain reproducible results to compare drilling process with
or without Dust Bubble, only a study in a test room was taken into
consideration. With measurements taken at a real-life workplace,
environmental impacts like air change rates, teat area sizes or
changes in material mixtures can seldom be eliminated sufficiently.
However, conditions of the experimental study should be
set up as close as possible to those in practice. Therefore, all the
materials used were kept the same as the practice.
It was estimated that it would take around 1 min for 1 hole
when Dust Bubble was used. In order to make comparison, samenumber of holes should be drilled during the two drilling processes
(with or without Dust Bubble). Therefore, a total of 180 holes were
drilled for each 3-h sample. A 13 mm (in diameter) masonry drill
was used for drilling. Each hole was around 3 cm deep into the
block. The model of the hand drill was Bosch GBH 2-20 D Professional
(as shown in Fig. 3). A support as shown in Fig. 4 has been
prepared to hold the testing material. The construction material
(concrete block, C30) for treatment was placed vertically. The size
of concrete block was 1 m 1m 12 cm. The edge distance and
interval distance between holes was 20 cm and 5 cm respectively
so that 196 holes could be drilled on one side. Therefore, a total
392 holes could be achieved on both sides, which was enough for
two samples. A number of 10 blocks were produced to achieve
20 samples.
The assumption of this experimental study was that all the
paired samples should be carried out under comparable conditions.
In order to obtain reproducible results to compare drilling process
with or without DustBubble, two samples were collected at the
same time in the test area to eliminate the environmental impacts
(e.g. wind, temperature, and material mixtures), as shown in Fig. 5.
For each set of paired samples, the work load and duration were
the same. The workers could take a 5-min break for every
20 min. Photos and