FUNDAMENTAL STUDY ON THE INFLUENCE OF DIFFERENT KINDS OF BINDER AND FINE AGGREGATE ON THE COLOR OF COLORED MORTAR

Abstract

　Colored concrete is concrete that is colored by the addition of pigment to the concrete mix. Previous studies have shown that the color of colored concrete is influenced by the color of the mortar. To confirm the color values of mortar colored with pigment, the authors have so far reported the change over time of the color values of mortar with different water-binder ratios when using a white base mortar. However, during actual construction, measures to make the color of the base concrete close to white are rarely taken. Thus, in practice, the concrete or mortar that is used as the base of colored concrete is affected by the color of the cement and aggregate commonly used by ready-mixed concrete plants.

　The object of this study is to investigate the effect of the color of binder and fine aggregate on the color values of colored mortar with two different water-binder ratios. The findings were as follows

 

1)　The material which had an influence on the color of the mortar most was cement. And, the influence of fine aggregate to the color of the mortar was small compared with influence of cement. In the measurement results of white specimen, L* value of mortar decreased about 10 regardless of water-binder ratio when limestone crashed sand was changed to andesite crashed sand. And, L* value of mortar decreased about 30 to 40 when white portland cement was changed to ordinarily portland cement.

2)　It was confirmed that hardened cement using ordinarily portland cement can't be colored effectively compared with hardened cement using white portland cement. The effect of coloring to mortar using ordinarily portland cement was different depending on the color of the pigment. When using blue pigment for mortar using ordinarily portland cement, the mortar which can be manufactured will be the color near the gray. As this reason, ordinarily portland cement may include complementary color element against blue pigment.

3)　The brightness of mortar with water binder ratio 0.2 fell about 10 % compare with mortar with water binder ratio 0.5.