Optimization of the Compressive Strength Characteristics of Four-Component Concrete Mixes Made with Unwashed Local Gravel using Second-Degree Polynomial

Being able to predict the strength
characteristics of concrete can be of great advantage in
the design and construction of structural members. This
research work set out to develop a model for the
compressive strength characteristics of concrete made
with unwashed local grave based on Prof. Osadebe’s
optimization theory or second-degree polynomial. The
unwashed aggregate was from Abagana and the river
sand from Amansea, both in Anambra State. These
aggregates were tested for their physical and mechanical
properties based on BS 812: Part 2:1975 and BS 812:
Part 3: 1975. Sixty concrete cubes of dimensions 150 mm
X 150mm X 150mm —three cubes for each experimental
point were made, cured and tested according to BS
1881:1983. The model equation developed was Ŷ= -
2006.1Z1+ 1401.02Z2 -90.3Z3 -105.47Z4 +91.79Z1Z2 --
9086Z1Z3 + 3268.26Z1Z4 +7888.31Z2Z3 -1636.57Z2Z4
+427.5Z3Z4. The student’s t-test and the Fisher’s test
were used to prove the adequacy of the model. The
strengths predicted by the model were in complete
agreement with the experimentally obtained values and
the null hypothesis was satisfied.