Investigating the Effect of High Temperature Ranging from 100°c to 300°c on the Compressive Strength of Grade 40concrete

Concrete is a low conductor which exhibits high resistance to temperature
transients, but however because concrete is important in construction work, its ability to
resist high temperature when exposed is important. The investigation study carried out
shows results of the effects of temperature variation on the compressive strength of Grade
40 concrete. Research have been done before on Grade 30 concrete and other grade by
different individual, like Hanson and Ericsson (1966) studied the effects of temperature
change between room temperature and 100°c on the normal concrete under load and
cement mortar. The researcher that rapid rates of heating permanently reduce the modulus
of elasticity in cement mortar; an indication of internal destruction of the concrete
structure and they concluded that thermal cycling leads to elastic deflection and
occasionally to failure. And also Salau (1990) presentareport ofcomparative study of heatresistant characteristics of theconcrete and concrete containing basalts as aggregates.
The study that the water absorption and porosity of basalt concrete falls within
acceptable range for normal refractory material and that while the concrete specimens
display some coherence and stability in the water absorption and porosity of basalt
concrete falls within an acceptable range for normal refractory material and that while
basalts concrete specimens display some coherence and stability in volume expansion, the
normal concrete starts chipping and cracking at temperature above 450°c, furthermore, at
the end of the first heating-cooling cycle, the subsequent cycles have no significant effect
of the weight loss of both types of concrete and at the end of the third heating cooling
cycle, the normal concrete has lost its entire strength while the basalt concrete still shows
more than 17% residual compressive strength which it retains even after the sixth cycle.
This work or research which is the study on Grade 40 concrete had mix ratio 1:2:4
(cement: sand: granite) with water cement ratio of 0.44 was designed and cured for 7days
and 28days before it was subjected to uniaxial compressive loading tests a room and
elevated temperature of 100°c, 150°c, 200°c, 250°c, 300°c at one hour duration
respectively.
The result indicated 14.49%, 25.51%, 35.51% and 43.88% decrease in
compressive strength at 100°c, 150°c, 200°c and 250°c respectively. As temperature
increase to 300°c it showed a 53.47% peak decrease in compressive strength.