Proceedings of 2nd International Symposium for Color Science and Art 2020

A Fundamental Study on the Effect of Pigment Use Amounton the Color of Colored Mortar
Hiroshi JinnaiTokyo Polytechnic Univ., 1583 Iiyama, Atsugi, Kanagawa 243-0297, JapanABSTRACT
Focusing on the mortar portion, which is considered todetermine the color of concrete, experimental verification
was conducted on the effect of the amount of pigmentused on the color of colored mortar. In the preliminary
experiment, the color of the mixed powder of cement andpigment constituting the cement paste appearing on thesurface layer of the mortar was measured. As a result, it
was found that the region in which the color of the mixed
powder effectively changes as the pigment substitution
rate increases or decreases is in the range where thepigment substitution rate relative to the cement mass islower than 5% to 10%. Further, in the range where thepigment substitution rate relative to the cement mass islower than 5%, a clear change appears in the L*a*b*values of the mortar as the pigment use amount isincreased or decreased. As the pigment substitution rateincreased, the L* value decreased and the a*b* value
approached the pigment color. However, since mortar withthe low pigment substitution rate of 1.25% can be clearly
confirmed visually to be blue, green, or yellow, relatively
inexpensive colored mortar is considered to be usable,
taking into account the optimum use method, including thefactor of cost.

Photo 1 Experiment on the effect of pigment
substitution rate on cement color

100Blue

L*80

GreenYellow

60
40
2000

2 0

4 0

6 0

8 0

1 00

2 0

4 00

2 0

4 0

6 0

8 0

1 00

2 0

4 0

6 08 01 00-20

1. INTRODUCTION
Colored concrete colored with pigments is used forbuilding exterior walls and floor slabs. The amount ofpigment added to such concrete is often based on thestandard addition amount specified by the pigment
manufacturer. However, a wide variety of materials andblends are used for concrete, and the dosage of pigment isadjusted as required. When determining the dosage ofpigment, factors such as the water-cement ratio ofconcrete and color change over time must be taken intoaccount, but there are very few research reports on suchsystematic experiments. In the present study, focusing on
the mortar portion, which is considered to determine thecolor of concrete, experimental verification was conductedon the effect of the amount of pigment used on the color ofcolored mortar.

a*-40-60-80

-100
20

Blue
02 04 0

6 0

8 0

Green
6 0Blue0

Yellow

1 0
8 0

1 00

2 0

4 0

6 0

8 04060

1 0Green

b*-20-40-60

Yellow-80
020406080

100 0204060

80

100 02080

100

Additive rate of pigment (%)

Fig. 1 Relationship between pigment substitution
rate and L*a*b* values of mixed powder

2. Preliminary experiment with mixed powder
Prior to the main experiment, a preliminary verificationexperiment was conducted regarding the color of themixed powder of cement and pigment constituting thecement paste that appears on the surface layer of themortar. Photo 1 shows a picture of the experiment. In theP hoto 2 Color Measurement of Co lored mortar

17

Proceedings of 2nd International Symposium for Color Science and Art 2020change appeared in the L*a*b* values of the mortar as thepigment dosage was increased or decreased. As thepigment substitution rate increased, the L value decreased
and the a*b* value approached the pigment color.
Moreover, although color change over time occurred in themortars with the water-cement ratio of 50%, thedifferences in Lab values due to the different substitution
rates were not narrowed.

experiment, powders in which blue, green, or yellow
pigment was mixed with white portland cement at a
substitution rate of 0% to 100% were manufactured, andthe L*a*b* values of the mixed powders were measured.
The experiment's results are shown in Fig. 1. Similarly, topast findings in other fields, the influence of the pigment
substitution rate on the color of the basic powder (cement)
becomes milder as the pigment substitution rate increases.
Looking solely at the L*a*b* values of the mixed powders,
the region in which the color of the mixed powder
effectively changes as the pigment substitution rateincreases or decreases was considered to be in the range
where the pigment substitution rate relative to the cement
mass is lower than 5% to 10%.

4. CONCLUSIONS
1) The region in which the color of the mixed powdereffectively changes as the pigment substitution rateincreases or decreases was considered to be in therange where the pigment substitution rate relative tothe cement mass is lower than 5% to 10%.
2) In the range where the pigment substitution rate relative
to the cement mass is not over than 5%, a clear change
appeared in the L*a*b* values of the mortar as thepigment dosage was increased or decreased.

Ｌ*100
90
80
7060
50
4030
20
100

B50-1
B50-1/2
B50-1/4
1000 1

B50-1
B50-1/2
B50-1/4

10100
Age (Days)

1000 110100
Age (Days)

G50-1
G50-1/2
G50-1/4

50
4030
20100-10-20-30-40-50

10100
Age (Days)

1000 110100
Age (Days)

1000 110100
Age (Days)

ｂ*

B50-1
B50-1/2
B50-1/4

G50-1
G50-1/2
G50-1/4
10-1-2-3-4-5-6-7-8-9-10

10100
Age (Days)

1000 1

Weight change ratio (%)

B50-1
B50-1/2
B50-1/4

110100
Age (Days)

10100
Age (Days)

1000 1

G50-1
G50-1/2
G50-1/4

1000 110100
Age (Days)

1000 1

Y50-1
Y50-1/2
Y50-1/4
10100
Age (Days)

Y50-1/4

1000

10100
Age (Days)

1000 1

B20-1
B20-1/2
B20-1/4

10100
Age (Days)

1000 1

Y20-1
Y20-1/2
Y20-1/4
10100
Age (Days)

1000

G20-1
G20-1/2
G20-1/4

Y20-1
Y20-1/2
Y20-1/4
1

50
40
30
20
100-10-20-30-40-50

1000

Y50-1
Y50-1/2

10100
Age (Days)

50
40
30
20
100-10-20-30-40-50

1000

G20-1
G20-1/2
G20-1/4

B20-1
B20-1/2
B20-1/4
1

1000

Y50-1
Y50-1/2
Y50-1/41ｂ*

10100
Age (Days)

Y50-1
Y50-1/2
Y50-1/4

ａ*ａ*150403020
100-10-20-30-40-50

G50-1
G50-1/2
G50-1/4

1009080706050
4030
20
100

Weight change ratio (%)

Ｌ*3. Mortar experiment
The color measurement results are shown in Fig. 2.
Further, in the range where the pigment substitution rate
relative to the cement mass is not over than 5%, a clear

10100
Age (Days)

1000 1

B20-1
B20-1/2
B20-1/4

10100
Age (Days)

1000 110100
Age (Days)

1000

G20-1
G20-1/2
G20-1/4

Y20-1
Y20-1/2
Y20-1/4
10-1-2-3-4-5-6-7-8-9-101

10100
Age (Days)

1000 110100
Age (Days)

1000 110100
Age (Days)

1000

B20-1

G20-1

Y20-1

B20-1/2

G20-1/2

Y20-1/2

B20-1/4

G20-1/4

10100
Age (Days)

1000 110100
Age (Days)

1000 1

Y20-1/4
10100
Age (Days)

1000(Blue specimen) (Green specimen) (Yellow specimen)(Blue specimen) (Green specimen) (Yellow specimen)
W/B=0.5
W/B=0.2
Fig.2 Measurement results of L*a*b* value and weight change ratio18