Color stability in mortars and concretes. Part 2: Study on architectural concretes

Construction and Building Materials 123 (2016) 248–253

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Color stability in mortars and concretes. Part 2: Study on architectural concretes Anahí López a,b,c,⇑, Gastón Alejandro Guzmán d, Alejandro Ramón Di Sarli d a

LEMIT: Laboratorio de Entrenamiento Multidisciplinario para la Investigación Tecnológica, CICPBA, Calle: 52 e/ 121 y 122, B1900AYB La Plata, Buenos Aires, Argentina CONICET: Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina c UTN-FRLP: Universidad Tecnológica Nacional-Facultad Regional La Plata, Av.60 esq. 124 s/n, B1900AYB La Plata, Buenos Aires, Argentina d CIDEPINT: Centro de Investigación y Desarrollo en Tecnología de Pinturas, CICPBA: y CONICET, Calle: 52 e/ 121 y 122, B1900AYB La Plata, Buenos Aires, Argentina b

h i g h l i g h t s
The color stability in architectural concretes was studied.
Color was characterized using the CIELAB color space.
Results from CIEDE1976 and CIEDE2000 color-difference formulas were compared.
The weathering effect on the concretes color was analyzed.
Concretes with iron oxides lost the color but retained the hue.

a r t i c l e

i n f o

Article history: Received 1 February 2016 Received in revised form 16 June 2016 Accepted 29 June 2016 Available online 11 July 2016 Keywords: Color stability Architectural concrete CIELAB color space CIEDE1976 CIEDE2000

a b s t r a c t The aim of the present study was determining the color stability levels in architectural concretes. The color was defined using the CIELAB space proposed by the Commission Internationale de l’Eclairage (CIE), while the color stability was evaluated comparing the results coming from the CIEDE1976 and CIEDE2000 color-difference formulas. The color of samples exposed to different environments as well as the color-difference among the different instances of measurement are reported. The studied material was white and grey cement colored with iron oxides or phthalocyanines pigments. Results revealed loss of color in natural environment, important changes when phthalocyanines were used, and better color stability in the Colored Self-Compacting Concrete with iron oxides pigments. Ó 2016 Elsevier Ltd. All rights reserved.

1. Introduction The architectural concrete is considered a special concrete [1], which stresses the color and texture of the finished surface [2–4]. The great number of surface finish possibilities makes it an attractive material to be incorporated in the modern architecture [5]. Among the most used materials to decorate the appearance of concrete, the white cement and the pigments guarantee the added surface value. The white cement modifies the lightness, and the addition of small amounts of pigment provides the saturation and hue properties. This type of concrete must fulfill not only the

⇑ Corresponding author at: LEMIT: Laboratorio de Entrenamiento Multidisciplinario para la Investigación Tecnológica, CICPBA, Calle: 52 e/ 121 y 122, B1900AYB La Plata, Buenos Aires, Argentina. E-mail addresses: [email protected] (A. López), [email protected]. ar (A.R. Di Sarli). http://dx.doi.org/10.1016/j.conbuildmat.2016.06.147 0950-0618/Ó 2016 Elsevier Ltd. All rights reserved.

physical, mechanical and durability properties with which it was designed, but also some characteristics related to the visual impact expected by the different users; among such visual demands, homogeneity and color stability are some of the aesthetic qualities affecting the surface quality [6]. The limitless finish possibilities of architectural concrete need further studies that guarantee their attainment in all kind of surfaces. For example, if conditions imply a specular surface, the material for the mold should be preferably polished and not absorbent. In order to achieve this aim as quickly and economically as possible, an useful alternative is using mortars (i.e. cement, pigment, mineral addition, sand, and water combinations) and thus to minimize the volume of tests performed with concrete (i.e. cement, pigment, mineral addition, sand, water, and stone combinations) [6,7]. Different proportions of materials allow developing cementitious mixtures with a wide range of properties either in the hardened or in the fresh states. Among them, flowability is one of

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the properties that in the fresh state facilitates its displacement in the molds and the color uniformity [6]. The color homogeneity or uniformity is connected to the complete material mixture as well as on the concrete flowability and placement. Color variations on the concrete surface may be caused by changing the materials, their incomplete mixture and/or segregation during the placement, and/or the variations among batches [6–8]. Due to the above-mentioned facts, it is strongly recommended to apply control measures for reducing the effects of possible potential risks. One of the main uncertainties arising from the need of coloring concrete is associated to the color stability. This depends on both the pigment quality and the concrete durability on the surface [9]. The possibility that the concrete keeps up its original surface color depends on internal and external causes capable of changing completely the color of the surface. Internal causes include typical characteristics of the structure of the materials affecting the different mechanisms of fluids transport. External causes include the interactions between the concrete and the environmental conditions to which it is exposed. When the concrete quality is involved, once the materials deterioration and subsequent loss of its structural function begin, deep and regular inspections become very important. Particularly in the case of architectural concrete, damages such as stains, leaching or specifically color variations, which do not affect the structural properties, become an issue of great interest [10]. In the process of concrete deterioration, the development of calcium carbonate (CaCO3) deposits or efflorescence is one of the factors affecting the concrete coloration. When this process occurs in a colored concrete, the contrast is sometimes more marked. In order to reduce the efflorescence it is recommended to use low soluble salt level materials in the right proportions to minimize porosity [9,10]. The color analysis as a function of time involves relating the L* (lightness) and the coordinates a* and b* values. Therefore, using a parameter such as the total color-difference (DE), where those variables interfere may be simpler than making evaluations of each of them. Color measurements in concrete exposed to different environments or curing conditions show changes in the color parameters with a lightness increase associated to the humidity loss and a saturation decrease attributed to the efflorescence occurrence. The concretes were prepared by adding yellow, red, or black iron oxides to white or grey cement. The observed changes in concretes with white cement were greater, while the highest stability was achieved with concretes without pigments. The surface cleanness was not enough to reach the original color parameters in samples subjected to different environments and the hue changes were remarkable. In particular, when the samples were exposed to humidity the changes were less important compared to the effect of the humidity/drying cycle or the ultraviolet radiation. Finally, important lightness increases and saturation decreases were more significant when using red pigment in samples exposed to outdoor conditions [11]. On the contrary, other

accelerated aging experiments conducted in concretes with yellow, red, or black iron oxide pigments showed low saturation increases, which were attributed to efflorescence incidence, and also great changes in saturation after the white particles were removed [12]. Recently, another study conducted to develop a cover to protect building materials improved the resistance to weather highlighting the good color stability [13], though the exposure period was very short (4 months). This paper gives a description of the methodology used to evaluate the color evolution on concretes exposed to different environments. To avoid ‘‘color” subjectivities, color values defined according to the CIELAB color space. The CIEDE1976 and CIEDE2000 color-differences formulas were used to evaluate the color stability. In particular, it is shown an application of the method by comparing the color stability between the Colored Self-Compacting Concrete (C-SCC) and the Colored mechanically compacted Concrete (CC). 2. Materials and methods 2.1. Materials proportions The mixtures were developed using local materials (La Plata, Province of Buenos Aires, Argentina) with the characteristics recommended in the bibliography to be used in Self-Compacting Concretes [14]. According to the IRAM 50000 standard [15], two batches of grey Portland cement with calcareous filler (identified in this paper as G1 and G2), and one of ordinary white Portland cement (as W: IRAM 50001 standard) [16] were used. As well, two batches of different calcareous filler (FC1 and FC2) were employed in order to increase the viscosity and reduce the cement amount. The G1 and G2 are equivalent to CEM II/AL 42.5 N cement, while the W is equivalent to CEM I 42.5 N cement of European standard. Chemical compositions, physical and mechanical features of cements and fillers are detailed in Table 1. Table 2 shows the main characteristics of the yellow (Y, y), red (R, r) and black (b) iron oxides, and those of the green (v) and blue (z) copper phthalocyanine pigments here studied, provided by Alquimia S.A.Ò and Meranol S.A.C.I.Ò. In this Table, the capital and lower case letters identified the Alquimia S.A. and Meranol S.A.C.I. suppliers, respectively. Table 1 Cement and filler. Chemical composition (%)

CaO SiO2 Al2O3 Fe2O3 SO3 MgO K2O Na2O LOI f0 c

1d 28 d

Densitiy

Physical (MPa) (MPa) (g/cm3)

Cement

Admixture

G1

G2

W

FC1

FC2

62.0 19.9 3.2 3.4 2.4 0.7 0.9 0.1 5.2

61.9 20.1 3.3 3.2 2.4 0.6 0.9 0.0 7.0

65.1 21.8 4.41 0.24 3.63 0.95 0.16 0.14 2.81

50.9 4.9 1.3 0.8 0.4 3.5 0.4 0.1 31.8

50.2 9.2 1.1 0.7 0.1 0.3 0.4 0.1 37.8

– – 2.8

– – 2.8

and mechanical features 17.9 13.8 27.2 45.7 52.2 66.3 3.11 3.11 3.09

LOI: loss on ignition.

Table 2 Pigments. Color Iron oxide

Red Yellow

Carbon black Copper phthalocianyne *

Agglomerated particles.

Black Black Green Blue

Identification

Density (g/cm3)

Minimum size (lm)

Maximum size (lm)

R r Y y b Cb v z

4.75 4.85 3.70 3.80 4.75 1.90 2.00 2.00

0.1–0.5 – 1.0

1.0 – 8.0

0.5–1 0.001-0.01 5–25* <20*

4.0 <0.1 50* 40*

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Table 3 Proportions of the materials in C-SCC. Group

Concrete

Water

Cement

Filler

Pigment

Sup.

Sand

Stone

18.0 10.0 10.0 17.0 – 18.0 17.0 8.5 8.5 9.0 15.0 9.0 16.0

3.7 4.2 6.1 3.3 7.5 8.0 9.0 8.5 6.7 2.5 5.5 4.0 5.4

775 770 775 780 828 840 835 793 780 855 702 887 754

830 850 695 815 797 810 805 768 730 934 741 990 795

3

(kg/m ) A1

A2

B3

R5a Y3a Cb3b b5b w r5b y5b z2b v2b r-CCb r-SCCb y-CCb y-SCCb

164 166 166 166 170 172 171 152 166 165 152 167 163

331 328 331 333 339 344 342 325 309 330 303 334 325

265 266 258 256 238 231 227 216 205 – 234 – 248

w: Concretes whitout pigment. 1 G1 cement, FC1 filler and S1 superplasticizer. 2 W cement, FC1 filler and S2 superplasticizer. 3 G2 cement, FC2 filler and S2 superplasticizer. a Alquimia S.A.Ò. b Meranol S.A.C.I.Ò.

Additives identified as S1 (GLENIUM C 315, solid content about 35%) and S2 (GLENIUM B 255, solid content about 18%) from BASF Argentina S.A.Ò were used as superplasticizer to increase the mixtures flowability and reduce water contents to avoid the lost of the mechanical resistance afforded by the cement mixture, both additives are based on a policarboxylated ether. The mixtures were prepared using tap water, a silica natural sand (fineness modulus: 2.39, density 2.63 g/cm3 and absorption rate 0.5%) and a granite crushed stone (maximum size of 12 mm) as aggregates. Finally, an oleo-based release agent recommended for steel surfaces was used. Three groups of Colored Self-Compacting Concretes were evaluated. Table 3 details the concrete proportions of each group made with: A1) grey cement (G1), filler (FC1), and superplasticizer (S1), which include the R5, Y3, Cb3, b5 concretes; A2) white cement (W), filler (FC1) and superplasticizer (S2), which include the w, r5, y5, z2, v2 concretes; and B3) grey cement (G2), filler (FC2), superplasticizer (S2), which include the as r-CC, r-SCC y-CC and y-SCC concretes. To evaluate the color stability in concretes with different flowability, four colored mixtures: two with red pigment (r) and two with yellow (y) pigment, were prepared (see Table 3, B3 group). With regard to the cement and filler, the pigment content was constant. The additive content corresponds to the amount of liquid expressed in weight. It should be noted that the fine and course aggregates content correspond to saturated surface-dry condition and that the water/cement relationship = 0.50 was the same in all the mixtures.

To assess the color stability, the total color-difference parameter (DE) was calculated using successive measurements performed at different times. This work compares the results from the CIEDE1976 (DE⁄76) [20,22] and CIEDE2000 (DE00) formulas [20,23–25]. In both equations, the L*, a*, and b* values calculated as average of five readings made on each face exposed to the environment. They are

Table 4 Color stability in C-SCC (A1 group and someone concrete of A2 group). LP environment. Conc

i

Li

ai

bi

DE76

DE00

Y3

1 2 2 3 3 4 1 2 2 3 3 4 1 2 2 3 3 4 1 2 2 3 3 4 1 2 2 3 3 4 1 2 2 3 3 4

65.2 64.2 64.2 59.2 59.2 56.5 48.9 54.1 54.1 47.0 47.0 45.2 31.3 47.5 47.5 49.6 49.6 53.0 44.7 58.9 58.9 59.3 59.3 52.7 61.5 76.9 76.9 74.7 74.7 72.5 62.5 74.0 74.0 76.2 76.2 73.9

4.7 3.7 3.7 5.1 5.1 5.4 23.0 16.0 16.0 17.6 17.6 17.6 0.6 0.5 0.5 0.3 0.3 1.6 0.1 0.1 0.1 0.5 0.5 0.7 9.1 0.6 0.6 0.3 0.3 0.9 8.6 1.2 1.2 1.2 1.2 1.4

21.7 20.3 20.3 23.5 23.5 23.4 10.6 9.1 9.1 10.9 10.9 11.6 1.1 2.8 2.8 4.2 4.2 6.2 0.1 0.7 0.7 0.4 0.4 2.1 5.3 2.7 2.7 4.2 4.2 6.7 9.4 6.2 6.2 6.1 6.1 7.5

2.0

1.39

6.1

4.73

2.7

2.47

8.8

6.62

7.5

7.22

1.9

1.76

16.7

14.64

2.6

2.48

4.1

4.06

14.2

14.09

0.7

0.76

6.9

6.45

19.3

16.73

2.8

2.42

3.4

2.73

15.4

14.96

2.2

1.57

2.7

1.98

R5

2.2. Environments Cb3 The color of concrete samples exposed to different environments was periodically measured. The chosen environments were: 1) a chamber (C1) operating under controlled humidity (RH = 55 ± 5%) and temperature (T = 21 ± 2 °C) conditions; and 2) two natural environments in Argentina: La Plata station (urban-industrial area) (LP), annual average values of the climatic variables: RH = 70%, T = 16 ± 2 °C, a rain (D = 1300 mm); and Mar del Plata (marine area) (MP), average climatic parameters: RH = 80%, T = 16 ± 2 °C, D = 813 mm. Before their initial measurement and transfer to different exposure conditions, only the A group samples were kept in the C2 chamber at 21 ± 2 °C and 95 ± 5% for 28 days as suggested by the IRAM 1534 standard [17]. 2.3. Samples preparation Pieces of different shapes and sizes were obtained from the concrete mixtures. Therefore, different areas were considered to determine the color. These pieces were obtained by using steel molds, where a release agent (Rheofinish 255) recommended for this type of material was added. With the aim of preparing all the samples following the same procedure and start each color measurement test, the samples were kept in the C1 environment for 24 h. The surface dust was removed in order to minimize possible interferences in the color measurements. 2.4. Color measurements and color stability The color of the samples was determined using the CIELAB color space [18–21], from the initial and final L*, a*, and b* values obtained using a BYK Gardner spectrophotometer [20–23].

b5

z2

v2

Visual assessment of DE76: 0.5–1.5: slight; 1.5–3.0: obvious; 3–6: very obvious. 6– 12: large. Conc: Concrete

A. López et al. / Construction and Building Materials 123 (2016) 248–253

Fig. 1. DLi, Dai and Dbi in C-SCC concrete (A1

identified in the Tables as Li, ai and bi, where i = 1, 2, 3 or 4 represents the exposure time alt which the color was measured. These numbers also indicate which moments were compared, i.e. number 1 is the averaged values before the exposure, and 2, 3 and 4 are the averaged values in the corresponding month of exposure, respectively. In the A1 group, Y3, R5, Cb3, b5, z2 and v2 samples of C-SCC were exposed to LP environment for 42 months were analyzed. As well, replicates of the w, r5, y5, z2 and v2 concretes were exposed to the C1, LP, or MP environments for 18 months (See concretes in Table 3). The effect of the concrete type (Self-Compacting Concrete and mechanically compacted concrete) was studied on B3 group samples obtained from concretes with different flowability and pigments (yellow or red). All these samples, defined as Concrete r-CC, r-SCC, y-CC or y-SCC, were exposed to the MP environment for 18 months. The r-SCC showed a Df = 700 mm and T50 = 2.0 s [26], while Dȷ = 650 mm [27] and the Tm = 4.4 s [14]. On the other hand, the y-SCC reached similar Df and Dȷ values and had a slightly more viscose behavior since the T50 and TV increased to 2.3 s and 5.8 s, respectively. In the r-CC and y-CC concretes, consistency was measured with the Abrams cone equal to 150 mm (IRAM 1536 standard) [28].

3. Results and discussion 3.1. Color stability in concretes with grey and white cements To evaluate the influence of the pigment type on the color stability, Y3, R5, b5, Cb3, z2 and v2 Concretes were exposed to the LP environment. It should be pointed out that the carbon black and phthalocyanines are recommended for indoors use, i.e. under exposure conditions similar to that offered by the C1 environment. Table 4 shows the Li, ai, and bi average values initially measured (sub-index 1  age 1) after 18 months (sub-index 2  age 2), 30 months (sub-index 3  age 3) and 42 months (sub-index 4 

and 2

251

groups).

age 4) of exposure to the LP environment. It also includes DE76 and DE00 values calculated among the average data obtained at 1, 2, 3, or 4 time. The color of the concretes changed significantly over 42 months due to pigment discoloration. The major changes in Y3 concrete were attributed to the decrease in Li and to a lesser extent, at the ai and bi variations; however, in R5 concrete, ai changed 6 units and to a lesser extent Li and bi. The evaluation of these two pigmented concretes indicated that although the hue remained the original color did not. This did not happen in v2 and z2 concretes since the hue values moved towards the first quadrant of the chromatic plane and simultaneously a significant increase of Li took place, i.e. they adopted values similar to the of grey color [28]. The behavior of concretes pigmented with black iron oxide or carbon black was similar regarding the significant loss of initial lightness or, in other words, Cb3 and b5 concretes changed to greater clarity surface. Even-though the initial lightness obtained with the carbon black was much lower than that obtained with black iron oxide, a double loss of lightness was observed. Fig. 1 displays the DLi, Dai, Dbi differences in the A group and their random tendency overtime (remember that 1 and 2 indicate the exposure time). The DE00 values were less than those of DE76 and in the concretes with phthalocyanines (Concretes z2 and v2), two of them kept the same level of DE variation, suggesting color stability. On the contrary, the level of DE variations were very significant among the sequential measurements of the other concretes. The w, r5 and y5 Concretes were analyzed to determine the effect, if any, of the exposure to different environments on the samples color stability. Table 5 shows the Li, ai, bi; DE76 and DE00

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Fig. 2. DLi, Dai and Dbi in C-SCC and CC concretes (B3 group).

Table 5 Color stability in white C-SCC. (someone concrete of A2 group). LP, MP and C1 environments. Env.

Conc.

i

Li

ai

bi

DE76

DE00

LP

w

1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2

76.9 75.4 53.9 50.8 74.4 75.2 56.1 53.9 69.3 66.3 76.1 76.0 54.9 54.2 68.9 69.7

1.1 1.1 21.2 22.7 1.3 1.4 15.1 19.9 6.4 8.4 1.2 1.1 18.6 18.4 7.6 7.3

4.2 4.5 11.6 13.5 6.9 6.3 11.1 12.0 26.6 27.4 5.9 6.2 11.3 11.4 26.8 25.8

1.6

1.13

3.9

3.31

1.0

0.75

5.4

3.77

3.8

2.94

0.4

0.31

0.7

0.66

1.3

0.77

r5 MP

b r5 y5

C1

w r5 y5

Visual assessment of DE76: 0.5–1.5: slight; 1.5–3.0: obvious; 3–6: very obvious. 6– 12: large. Env: Environment. Conc: Concrete.

average values obtained at the beginning of measurement (age 1) and after 18 months (age 2) of exposure to the C1, LP, or MP environments. As expected, after 18 months testing, the samples exposed to the MP highly aggressive marine environment presented greater color variations than those exposed to LP. The r5 and y5 concretes exposed to MP environment showed that Li decreased but the values ai and bi values increased, revealing that these environments caused strong color changes. Again, samples tested in the C1 environment showed minimal color changes as indicated by lower levels of DE calculated according to the CIEDE1976 and the CIEDE2000 color-difference formulas. Finally, to evaluate if there were differences between the CC and C-SCC concretes, samples of the same color with red or yellow pigments were assayed. Table 6 shows the Li, ai, bi; DE76 and DE00 average values of data obtained at beginning of measurement (age 1), after 12 months (age 2), and 18 months (age 3) of exposure to the MP environment. Important color changes were observed after 12 months. In the r-CC, the ai and bi values decreased with significant increase in the Li. This tendency repeated to a lesser

Table 6 Color stability in C-SCC and CC (B3 group). MP environment. Concrete

i

Li

ai

bi

DE76

DE00

r-CC

1 2 2 3

46.8 55.1 55.1 58.3

27.5 18.2 18.2 18.0

19.6 12.6 12.6 10.0

14.3

9.84

4.1

3.41

1 2 2 3

51.8 55.2 55.2 54.7

27.5 19.9 19.9 20.7

19.3 14.9 14.9 15.9

9.4

5.15

1.4

0.81

1 2 2 3

65.7 67.7 67.7 66.5

6.7 5.4 5.4 6.0

34.2 26.0 26.0 27.9

8.5

3.84

2.3

1.29

1 2 2 3

70.2 68.5 68.5 60.5

6.0 5.8 5.8 4.6

32.6 26.5 26.5 21.2

6.3

2.99

9.8

7.19

r-SCC

y-CC

y-SCC

Visual assessment of DE76: 0.5–1.5: slight; 1.5–3.0: obvious; 3–6: very obvious. 6– 12: large.

extent for the r-SCC suggests a greater resistance to color changes in this aggressive environment during the first year of service life. Meanwhile, the red hue was kept in both concretes. In the y-CC, the main variation was due to the great decrease in the bi coordinate. Similar evolution was observed in the y-SCC, being in both cases indicative of a greater resistance of the concretes to change its color. Fig. 2 illustrates the DLi, Dai and Dbi differences along 12 months of exposure. It is very probable that less porosity and the best surface termination of the SCC favored the necessary conditions to diminish the aggressive agents deposit and, as a consequence, to reduce the original color loss. Like occurred in the other analyzed concretes, differences between DE76 and DE00 values became more significant due to the higher accuracy and precision with which changes of the DE00 values could be calculated.

4. Conclusions This work analyzes the color evolution in concretes exposed to two aggressive environments and to another one presenting stable

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humidity and temperature conditions. In such circumstances, the color was specified according to the CIELAB color space and its evolution characterized through the CIEDE1976 and CIEDE2000 colordifference formulas. The concrete pigmented with any of the tested iron oxides showed good color stability under controlled exposure conditions; nevertheless, replicates of the same samples exposed to an industrial or marine environment showed significant color variations. This fact indicates that the color stability is strongly dependent on the exposure conditions. During the first months of exposure greater color changes took place on Colored Self-compacting Concretes where phthalocyanines were used as pigments; even though it should be remarked that the use of these products is recommended only indoors ambient. On the other hand, and independently of the exposure conditions, when the original color of concretes pigmented with iron oxides changed over time, its hue did not do it. The total color-differences in the C-SCC were less than those in the CC, perhaps due its lower porosity. The CIELAB color space allowed an accurate definition as well as evolution monitoring of the concrete color. In this sense, the measurement and/or calculus of each parameter included in the colordifference formulas gave an objective evidence if there was or not color changes. Besides, the analysis of each Li, ai, and bi value permitted detecting which of these parameters contributed to eventual changes of the total color-difference values. Acknowledgements The authors thank the Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CICPBA), the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), and the Universidad Tecnológica Nacional-Facultad Regional Córdoba (UTN-FRC) of Argentina for their monetary support to this work. References [1] A. Benítez, H. Bálsamo, Hormigones arquitectónicos: blancos y coloreados, in: E.F. Irassar (Ed.), Hormigones Especiales, AATH, La Plata, Argentina, 2004, pp. 75–90. [2] J. Fernández Gómez, Estructuras de concreto aparente, in: Simposio Internacional sobre Concretos Especiais, IEMAC-UVA, Sobral-CE, Brasil, 2000, pp. 1–22. [3] H. Benini, Concreto Arquitetônico e Decorativo en Concreto, in: G.C. Isaia (Ed.), Ensino, Pesquisa E Reliazações, IBRACON, São Paulo-SP, Brasil, 2007, pp. 1413– 1551.

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[4] H.A. Esqueda Huidobro, Concreto Arquitectónico, IMCYC, México, 1996. [5] H. Müller, U. Nolting, M. Halst, Vorwort im Sichtbeton-Planen, Herstellen, Beurteilen, in: 2. Symposium Baustoffe und Bauverkserhaltung Universität Karlsruhe, 2005. [6] A. López, Diseño y Caracterización del Hormigón Autocompactante Coloreado, in: Tesis doctoral, Facultad de Ingeniería Universidad Nacional de La Plata, 2012. [7] S. Mindess, F.J. Young, D. Darwin, Concrete⁄⁄⁄, EE.UU Pearson Education, 2003. [8] A. Skarendahl, P. Billberg (Eds.), RILEM TC 188-CSC: Casting of Self Compacting Concrete, 2006. [9] V.S. Ramachandran, Concrete admixtures handbook, Properties, Science, and Technology, Noyes Publications, New Jersey, USA, 1995. [10] E. Püttbach, Pigments for the Colouring of Concrete-Questions of Quality, Betonwerk+Fertigteil-Technik/Concrete Precasting Plant and Technology, 1992, vol. 10. Disponible en . [11] F. Coelho, Variación Del Color Y Textura Superficial De Hormigones Vistos, Con Adición De Pigmentos Inorgánicos, Sometidos a Distintos Estados De Exposición Ambiental Tesis doctoral, Universidad Politécnica de Madrid, 2000. [12] M.J. Positieri, Propiedades Físico-Mecánicas Y Durabilidad Del Hormigón Coloreado Tesis doctoral, Universidad Tecnológica Nacional Fac. Reg. Cba, 2005. [13] G.M. Revel, M. Martarelli, M.Á. Bengochea, A. Gozalbo, M.J. Orts, A. Gaki, M. Gregou, M. Taxiarchou, A. Bianchin, M. Emiliani, Nanobased coatings with improved NIR reflecting properties for building envelope materials: development and natural aging effect measurement, Cement Concr. Compos. 36 (2013) 128–135. [14] EFNARC Specification and Guidelines for Self-Compacting Concrete, EFNARC (European Federation of Producers and Applicators of Specialist Products for Structures), 2002. Disponible en . [15] IRAM 50000, Cement, Common cement. Composition, specifications, conformity evaluation and reception conditions, 2014. [16] IRAM 5001-2000, Cement, Cements with special properties. [17] IRAM 1534, Concrete, Making and curing test specimens for compressive and diametrical tensile compressive in the laboratory, 2004. [18] R.D. Lozano, El Color Y Su Medición, Américalee S.R.L, Buenos Aires, 1978. [19] R.D. Lozano, A new approach to appearance characterization, Color Res. Appl. 31 (2006) 164–167. [20] CIE 15.3 Technical Report draft, Colorimetry, third ed., 2004. [21] A. López, G.A. Guzmán, A.R. Di Sarli, Color stability in mortars and concretes. Part 1: study on architectural mortars, Constr. Build. Mater. 120 (2016) 617622. [22] BYK Gardner GmbH, Manual of instruments for color measurement. Spectroguide 45/0 gloss-Spectro-guide gloss, 2009. [23] EN 12878. Pigments for colouring of building materials based on cement and/ or lime – Specification and methods of test, 2005. [24] M. Melgosa, R. Huertas, Relative significance of the terms in the CIEDE2000 and CIE94 color-difference formulas, Opt. Soc. Am. 21 (2004) 1–7. [25] G. Sharma, W. Wu, E.N. Dalal, Color-difference formula: implementation notes, supplementary test data, and mathematical observations CIE 2000, Color Res. Appl. 30 (2005) 21–30. [26] ASTM C1611/C1611M-2014. Standards test method for slump flow of self-consolidating concrete. [27] ASTM C1621/C1621M-2014. Standards test method for passing ability of self-consolidating concrete by J-Ring. [28] IRAM 1536, Hormigón fresco de cemento pórtland. Método de ensayo de la consistencia utilizando el tronco de cono, 1978.