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Abstract

The objective of this research was to examine the deterioration and explosive spading of high strength concrete at elevated temperatures. The following three types of concrete beam specimens were considered; using three different types of aggregates. These concrete specimens were:

a) . Plain concrete beams
b) . Reinforced concrete beams and
c) . Fibre concrete beams. The three aggregate types used were:

a) . Limestone
b) . Lightweight aggregate (LWA) and
c) . Limestone partly replaced by LWA (modified normal concrete).

A fractional factorial method of experimentation was adopted to investigate six factors at three levels each. The factors were curing before heating, rate of heating, loading level, water cement ratio, type of aggregate and polypropylene fibre content. Three main series of tests were carried out on 27 plain concrete beams, 27 reinforced concrete beams and 27 fibre reinforced concrete beams.

The high temperature work was carried out in a purpose built rig capable of applying loads to beams in flexure within the furnace and at the same time measuring the loads, deflections and expansions of the specimens.

All the beams tested deteriorated after heating to 700 °C. None of the plain concrete beams and reinforced concrete beams were immune from explosive spalling given certain combination of factors. The beams that deteriorated early during heating were unlikely to spall explosively. Although the fibre concrete beams deteriorated at high temperatures, none of them failed violently.

A change in the factor level sometimes influenced the deterioration, linearly in the plain concrete specimens and non-linearly for the reinforced concrete specimens. In some cases a change in the level of a factor influenced the behaviour of the reinforced concrete specimens but not the plain concrete specimens. At times a change of factor created a maximum deterioration in the reinforced concrete specimens but had minimal effect on the plain concrete specimens.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology > Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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