Compressive Strength of Concrete with Cubic Aggregate of Cement Mortar

Abstract

The purpose of this experimental study is to investigate the strength of concrete having the cubic aggregates of cement mortar under uniaxial compression. The cement mortar aggregate with and without thin coating of paraffin were provided respectively, to examine the effect of bond between aggregate and mortar matrix on the compressive strength of concrete. The cylindrical concrete specimens of φ10×20cm were made by mixing the above mentioned aggregate and the cement mortar, and were tested at the age of 28 days of concrete.The test results are summarised as follows;(1) The bond strength between the aggregate without paraffin coating and the mortar matrix was about 13-14kg/cm2.(2) The bond strength between the paraffin coated aggregate and the mortar matrix was almost zero.(3) The compressive strength of concrete decreased with increase of the volume fraction of aggregate in concrete, regardless of the surface condition of aggregate.(4) The compressive strength of concretes hardly increased in spite of increase of the compressive strength of aggregate, expect the concrete having lower volume fraction of aggregate than 0.2.(5) The compressive strength of concrete having the aggregate with paraffin coating was only about 20-25 percent of the strength of concrete having the uncoated aggregate, under higher volume fraction of aggregate in concrete than 0.45.