| Abstract | Generally, concrete becomes deteriorated under acidic attack. In this research, to
investigate this response of concrete to weak acids, an accelerated Laboratory Test
Program was conducted considering the different influencing factors such as different
levels of pH (2, 3, 4 & 5) water/cement ratios (60% & 80%), temperatures of acid
solution (25°C & 50°C), types of cement etc. Test specimens consisted of standard
concrete cylinders having a diameter of 10 cm and a height of 20 cm. The total number of
the specimens (with and without reinforcement) were one hundred and fifty two, made by
using Ordinary Portland cement and 30% Fly ash cement, crushed limestone as coarse
aggregate and river sand. All these specimens were immersed in acidic solutions, having
different pH levels respectively, for three months. To accelerate the effect, two days
drying (humidity=60%) and three days immersion (humidity=95%) was conducted
cyclically during whole exposure periods. During and after continuous accelerated
exposure test, all specimens were tested to investigate their change in color, size, weight
and compressive strength. The reinforced specimens were examined to check the effect
of acidic solutions on corrosion of reinforcing bars.
Test results showed that fly ash cement Concrete (herein after called "FACC") specimen
had better resistance to corrosion of steel bars compared to the ordinary Portland cement
concrete (herein after called "OPCC") specimen. In strong acid, OPCC specimens lost
less weight than FACC whereas in weak acids FACC specimens found better to use due
to less reduction in surface materials. Both types concrete specimens got change in their
color during exposure test in pH=2 and 3 of the acid solutions. In other weak acid having
pH=4, more color change occurred in case of FACC compared to OPCC. During 91-days
exposure period, FACC specimens showed the increasing rate of compressive strength
from 28-days one to higher in both strong and weak acids whereas this strength of OPCC
specimens in the solutions having pH=2 & 3, fall down in exposure periods than 28-days
compressive strength. The overall test results indicated that FACC specimen is less
effective to deterioration of concrete under weak acidic environment compared to OPCC. |