Development of Colored Concrete in Jordan

Size: px

Start display at page:

Download "Development of Colored Concrete in Jordan"

Ferdinand West
6 years ago
Views:

1 ICCBT2008 Development of Colored Concrete in Jordan M. Resheidat *, Jordan University of Science & Technology, JORDAN B. Al-Kharabsheh Graduate of Faculty of Graduate Studies, Jordan University of Science and Technology, Irbid, JORDAN ABSTRACT This research study has focused on the possibility of producing colored concrete that can be used for floor tiles, bricks, precast concrete products as well as a colored structural concrete. Realizing the objectives of this research and with the scope of this study, the use of processed natural and locally available raw materials were used. The physical and mechanical properties of such materials have been recorded and documented. The experimental investigation has dealt with the fresh properties of the concrete mixes as well as the mechanical properties of the hardened concrete by testing specimens in compression, direct tension, splitting and flexure. The obtained results have been compared with the well know empirical code formulas. The color of the produced concrete can only be judged by inspection. An added value to this study is an attempt to outline the cost analysis by using the coloring pigments in lieu of using the similar imported ones. In addition to that The microstructure of the produced concrete was studied by using XRD and SEM analyses to investigate the bond between aggregates and the colored paste. The beam analysis used to determine the elements in the resulted matrix. It should be noted that no additives, admixtures or any other workability agents such accelerators or retarders were used. Of prime concern was to produce colored concrete and achieve a realistic concrete strength. Conclusions derived and drawn from this study as well as recommendations for further research were also outlined. Keywords: Colored Concrete, Pigments, White Cement, Zeolitic Tuff, Zircon Sand *Correspondence Author: Professor Musa Resheidat,Jordan University of Science & Technology, Irbid, Jordan. Tel: , musar@just.edu.jo musaresheidat@yahoo.com

2 Development of Colored Concrete in Jordan 1. INTRODUCTION In developed countries, colored concrete can be considered one of the most successful ways to improve the outward show of a project. Landscape architects, property owners, and landscape designers are constantly watchful for new and inventive methods to improve the appearance of properties and developments at a reasonable cost. These objectives can be met with decorative colored concrete. Concrete colors can be obtained by using color additives. Any thing that can be made with concrete can be colored. There are a variety of ways to enhance concrete projects with beautiful colors. Color schemes are often chosen to blend with each other and blend with nature. Concrete can be scored with tooling joints or saw cutting patterns and stained with Alkali Reactive Chemical Stains. It can also be improved with Dry Shake Color Hardener, Integral Colors, or Stamp able Overlays along with a variety of stamping patterns such as textures to simulate brick, flagstone, pavers, or tile. Many of the above listed techniques can be used in combination. On large areas of concrete, different sections of the concrete can be stamped or scored and stained to visually break up the areas. Lastly, multiple colors side by side can be used to create outstanding effects. It is often necessary to have the permanency and the durability of concrete. Where plain concretes gray color draws attention to areas such as pool decks, patios, entrances, driveways and porches; colored concrete can be used to avoid notice and help its features blend with the other natural landscape elements. Concrete color and texture come from the constituents used to make the concrete. These constituents include course and fine aggregates, cement, water, admixtures and pigments. When concrete color comes from the constituents, it is developed from the paste (hydrated cement), matrix (sand and paste). All the constituents can affect the color, but depending on finish and exposure, some constituents will dominate. Paste is the primary contributor to color when smooth and light exposure finishes are used. The color of paste comes from the cement, water and pigments when used. Since the hydration of cement, which creates paste, is a chemical process, the color generated is sensitive to many things. Some of the critical ones include water-cement (w/c) ratio, curing procedures, cement type, temperature and form materials. It is crucial to minimize fluctuations in these variables from batch to batch to minimize color variations. It is likewise important to use the same type of cement throughout a project; this will help to minimize color variations. Cement typically is available in gray and white. Gray cement receives most of its color from tetra calcium aluminoferrite, which is a component in cement that helps reduce the temperature of clinker during manufacturing. Gray cement can have color variations from one lot to the next since color control is not a monitored parameter when producing gray cement. Most of the gray cement produced ends up in structures, bridges, etc. When using gray cement, it is a good idea to maintain a dry powder sample from each lot or shipment, which can be compared visually for color differences. While purchasing enough cement for a project is the best approach, noticeable variations may require adjustments in mix design or pigment dosage. This has been done successfully to maintain color consistency of the final product but requires prior experimentation. White cement, on the other hand, has very little ferric (iron) components and is monitored for color variations during production. White cement is manufactured for use in colored concrete. It is available in several types and is fairly consistent from one lot to the next. Therefore, precast products made with white cement have less color variation. Also, white cement has been used to create more brilliant colors than gray cement and usually requires less pigment. Sometimes white and gray cement are blended in order to improve uniformity of the final product. 154

3 M. Resheidat and B. Al-Kharabsheh 1.1 Pigments A pigment can be defined as a material that can changes the color of light it reflects according to selective color absorption. Pigments have been used to color concrete for about a century. Pigments actually tint the color of the paste portion of concrete. The most common pigments are made from iron oxides. Iron oxides consist of 325 mesh particle sizes that provide stable colors that do not fade or leach out of concrete. The primary iron oxide colors come in yellow, red and black, with the reds having either a blue or orange tint to them. Combinations of these basic colors are used to create a multitude of other colors or shades of color. Other colors such as greens are commonly created from chromium oxides and blues from cobalt. These pigments work well but are used more sparingly, since they are more expensive. In general, pigments are inert and do not react with cement, therefore they are not considered as part of the cementitous material content. Instead, pigments bond with the cement via the hydration process, masking the color of cement grains. Raw pigmentary materials should meet ASTM C 979, Standard Specification for Pigments for Integrally Colored Concrete. Pigments are typically dosed by weight of cement, usually in the 1 percent to 7 percent range, and should never exceed 10 percent by weight of cement. Higher doses of pigments usually do not improve color but may reduce strengths. Pigments come in powdered, granular and liquid forms. All three forms work fine but require different handling, dosing and mixing procedures. The oldest form powders have been described as somewhat messy and labor intensive when weighing, since this is often done by hand. Some pigments are available in pre-weighed, dissolving bags that can be tossed into a mixer, which helps reduce handling problems. Granular forms were developed as an improvement for handling and dosing pigments. Some systems automate the dosing of granulated pigments, which allows for easier storage and varied batch sizes without having to use a partial bag. Again, these types of pigments must be protected from moisture until use. More recently, liquid dispersions have been developed that work quite well. Pigment particles are suspended in a liquid, usually water, and can be disbursed like any other liquid admixture. This allows for easy handling, accurate dosing (usually done automatically) and complete distribution of the color throughout the concrete with minimal mixing time. Pigment dispersions should be agitated often to maintain a uniform concentration of the pigment. While liquid dispersion coloring admixtures are typically batched with the mix water, always follow the manufacturer s instructions in regards to use, dosage, storage, etc., of any pigment. The major apparent use of colored concrete is very well developed for interlocking blocks, paving tiles, hollow paving blocks, curb stones and many other products to serve decorative purposes [1]. The main advantage of such products is the flexibility in forming creative patterns and the ease in repair and/or replacement. In addition to that, these products are their resistance to chemical and harmful attacks. 1.2 Significance of Research In developing countries such as Jordan, the technology of using colored concrete is not focused on whether in the concrete industry or in research institutions such as universities and research centers. Very little information is available in the literature due to the nature of this technology which is developed by mainly the concrete industry in developed countries. Recently, one of the pioneering plants has started the production of such products based on using imported pigments. The prices of the products which are mainly paving tiles are 155

4 Development of Colored Concrete in Jordan expensive due to the high prices of imported pigments that is reflected of the overall cost. Luckily, there are good studies about surveys about the natural resources in Jordan that could be used in producing, processing such pigments in this study [2, 3, 4]. Apart from the cited references, information is mainly dependent on direct contacts with engineers and technicians in the Natural Resources Authority, Amman, Jordan. This pilot study is directed to use pigments that could be processed from the available local raw materials in Jordan. The prime objective is to produce pigments for colored concrete products as well as the possibility of producing colored structural concrete. The study examines the material properties such as the concrete strength in compression, direct tension as well direct shear. The produced color depends on the mix proportions and the type of cement [5, 6]. Preliminary findings of this study have been published [7]. 2. EXPERIMENTAL PROGRAM Having gathered the necessary data about the materials used for producing colored concrete, several trial mixes have been carried out in the form of small cubes (50x50x50 mm) aiming at estimating the consistency, workability, mix proportions and the target strength of colored concrete. The raw pigments were processed by grinding the aggregates to grain size 45 micron in general and in some cases to a grain size 500 micron. The pigment basic size was taken 45 micron. Seven mixes were taken to use seven available pigments. The focus was directed to use the grain size 45 for the majority of the produced colored concrete specimens in the form of cylinders, cubes and prisms. The basic concrete mix proportions are given in Table 1. Table 1. Basic Mix Proportions Constituents Weight, kg/m 3 Course Aggregates 1100 Fine Aggregates 809 Cement 550 Water 308 Pigment 74 Table 2 presents the type and weight of pigment used in the mix. The available local crushed stone aggregates and sand were also used. Depending on the predicted color, either white cement or Portland Jordanian cements were used in the concrete mixes. The experimental regime for the selection of pigments and the relevant colored concrete specimens is shown in Figure 1. The testing setups for compression, splitting, direct tension as well as direct shear in addition to SEM pictures are shown in Figure2. 156

5 M. Resheidat and B. Al-Kharabsheh 3. EXPERIMENTAL RESULTS Concrete mixes were made according to the design mix proportions and the main parameter is the type of pigment or coloring constituent. For each mix, a number of specimens in the forms of cubes, cylinders and prisms were cast and properly cured. Due to size limitation of the paper, the detailed test results presented herein is only for one mix as shown in Table 3. It is necessary to document the mechanical properties of the produced colored concrete aiming at laying out the basis for future development in terms of workability by using superplasticizers, strength and may be self compacting colored concrete. As structural colored concrete, this experimental investigation was focused on twofold objectives; namely: the color of concrete and the strength of concrete that aimed to be used as a structural concrete. Accordingly, the properties of the produced colored concrete were described through the classical testing procedures for compression, flexure, direct tension, splitting and direct shear. Each of the tests and the results will be presented in the following sections. Table 2 Type, Size and Weight of Pigment in the Concrete Mix Mix No. Pigment Pigment Size micron Weight (kg/m 3 ) 1 Red Zeolitic Tuf Red Zeolitic Tuf Zercon Sand Red & Black Zeolitic Tuf Black Zeolitic Tuff Lime, by product Bentonite Table 3. Test Results of Colored Concrete Mix No. 1 [Red Zeolitic Tuff] Flexural Tensile Specimen Compressive Splitting Strength, MPa Strength, MPa No. Strength, MPa Cube a Cylinder b Cylinder b Prisms c Mean S.D a Cubes 100 x100x100 mm b Cylinders of 3 x6 c Prisms of 40 x40x 160 mm 157

Development of Colored Concrete in Jordan 1 2 3 4 5 6 The number in the circle refers to the Mix number: 1-Mix 1 2-Mix 2

6 Development of Colored Concrete in Jordan The number in the circle refers to the Mix number: 1-Mix 1 2-Mix 2 3-Mix 3 4-Mix 4 5-Mix 5 6-Mix 6 7-Mix 7 7 Figure 1. Material Selection of Pigments and Preparation of Concrete Specimens 158

7 M. Resheidat and B. Al-Kharabsheh Figure 2. Testing Setups and Microscopy Photographs of Concrete Specimens 3.1 Compressive Strength Test The compressive strength is regarded as one of the most important properties of hardened concrete, and it s the main property that the concrete mix based on. It used also for the classification of concrete in national and international codes. It should be noted that the compressive strength of concrete was highly influenced by the type of the pigment used and the w/c ratio of the mix as its clear from the lime and Bentonite mixes these two mixes have higher w/c ratios because the lime and Bentonite water absorbent. Since it is the most 159

Development of Colored Concrete in Jordan common performance measure of concrete used by engineers and is measured by testing standards cubes and/or standard cylinders.

Compression test was done using a universal testing machine. The results of compressive strength are then calculated at failure load divided by cross sectional area of the specimen.

It may also be used for quality control and acceptance criteria at the job site.

8 Development of Colored Concrete in Jordan common performance measure of concrete used by engineers and is measured by testing standards cubes and/or standard cylinders. However, this pilot study employed smaller size of specimens by scaling down the size by 50%. Accordingly, the cubes were of size 100 x100x100 mm and the cylinders were 3"x6" concrete specimens. Compression test was done using a universal testing machine. The results of compressive strength are then calculated at failure load divided by cross sectional area of the specimen. Compressive strength test results are primarily used to determine that concrete mixtures as delivered meet the requirements of the specified strength f c in the job specification. It may also be used for quality control and acceptance criteria at the job site. Testing of compressive strength colored concrete cylinders has been carried out following the same procedures as those described in ASTM C39, using universal testing machine at age of 28 days from the date of casting. Testing of cubes and cylinders are shown in Figures 3 and 4. The compressive strengths of colored concrete mixes are comparable to those of conventional concrete made with similar mix proportions. Prime results for the modulus of rapture for the seven mixes are also given in Table 4. It could easily be observed that an acceptable compressive strength of this colored concrete was achieved. Although a target nominal strength of about 20 MPa was realized for all tested specimens with the exception of specimens Nos. 6 and 8. Other results for cubes in compression, splitting and flexure were very consistent with the norms. Table 4. Cube and Cylindrical Compressive Strength Mix No. Cube Strength, MPa Cylinder Strength, MPa f CYLINDER /f CUBE (a) Cube specimen under compression (b) Cube specimen at failure. Figure 3. Cube test in compression Figure 4. Cylinder Tested by Universal Testing Machine 160

9 M. Resheidat and B. Al-Kharabsheh The recorded deformations versus applied load on the cylindrical concrete specimen were documented to estimate the compressive stresses and the corresponding vertical strains in order to obtain the stress strain relationship for this colored concrete. It should be however guided by the well known relationship as shown in Figure Splitting Tensile Test Splitting tensile strength is a measure of a material's ability to resist a diametric compressive force placed on a cylindrical specimen with its axis placed horizontally between the platens of a test machine as shown in Figure 6. The results were calculated by the formula f sp = 2P/ (π L D) where, f sp = the splitting strength (MPa); P = Maximum applied load (kn); D = the diameter of cylinder (mm) and L =is the length of cylinder (mm). The test results of the cylindrical specimens (3 x 6 ) under line load are given in Table 5. It can be seen from the results of the seven mixes that all parameters which influence the characteristics of the microstructure of the cement matrix and of the interfacial transition zone are of decisive importance in respect of the tensile load bearing behavior. The test results are in harmony and agreement with the approximate estimate in terms of the ultimate compressive strength of concrete, f c. Table 5. Splitting Tensile Strength MIX ID f p MPa f sp 010f c, MPa Modulus of Rupture It is a measure of tensile strength of plain concrete beam to resist failure under bending. It was measured by 40 x 40 x 160 mm prism. The flexural strength is expressed as Modulus of Rapture (f r ) and it is determined by center point loading as shown in Figure 6. f r is about % of the compressive strength depending on type, f r was calculated from the ultimate load using flexural formula f r = 3PL/2bd 2 where, b = 40 mm; d = 40 mm; L= 160 mm The results are given in Table 6 It is should be noted that the test results are almost twice as much as of the ACI Code estimates. The main reason is that the depth to span ratio of the tested specimens classify the beam as a deep beam. There will be aching effects that highly influence the results. It will be recommended that the span should be taken longer so that the beam shall fall under the category of normal beams. Furthermore, a 2-point loading is preferred to be considered to provide vicinity for pure flexure. 161

Splitting Tensile Strength Test for Cylinders Table 5 Test Results for the

10 Development of Colored Concrete in Jordan Figure 5 Stress-strain curves of all mixes. Figure 6. Splitting Tensile Strength Test for Cylinders Table 5 Test Results for the Modulus of Rapture Mix No f r, MPa f =.62 f ` r 0 c 162

11 M. Resheidat and B. Al-Kharabsheh 3.4 Modulus of Elasticity of Colored Concrete The Modulus of Elasticity of Colored Concrete is estimated in accordance with the ACI Code formulas. The calculated values are given in Table 6. It is concluded that ACI Code equations can easily be applied to this type of concrete. Table 6. Modulus of Elasticity of Colored Concrete Mix ID f c, MPa Concrete Density, w, kn/m E = w c f c ` E c = 4700 f c ` It should be noted that during the submission of this paper, the results as well as the analysis and interpretations of the images taken by the X-ray diffract meter(xrd) and scanning electro microscope(sem) were not fully completed. The reader is invited to obtain this information as well the full documentation and all details that are presented in Reference CONCLUSIONS AND RECOMMENDATIONS The following conclusions may be drawn from this study: 1. Colored concrete for producing concrete products was achieved. 2. The use of local pigments in colored concrete will replace the imported ones. 3. The colored structural concrete could also be produced. This study should be further extended to consider the following points: 1. Other pigments should be studied to produce other colors. 2. As a structural concrete, the interaction with the reinforcing bars and chemical effects of using there oxides should be studied. REFERENCES [1]. Various Cement Based Products, Technical Note, Cement and Concrete World, Journal of Turkish Cement Manufacturers Association, pp , January February issue, [2]. Nawasreh M. and YASIN, S., "Minerals Status and Future Opportunity-Zeolitic Tuff" Geological Survey Administration, Amman, Jordan [3]. Nawasreh M., "Minerals Status and Future Opportunity-Bentonite" Geological Survey Administration, Amman, Jordan, [4]. Nawasreh M., Madanat, M., Mehyar, N. and Mahmood S., "Minerals Status and Future Opportunity-Heavy Minerals " Geological Survey Administration, Amman, Jordan,

12 Development of Colored Concrete in Jordan [5]. Hyun-Soo Lee, Jae-Yong Lee, and Myoung-Youl Yu, Influence of Iron Oxide Pigments on the Properties of Concrete Interlocking Blocks, Cement and Concrete Research Journal, Elsevier Ltd., Vol.. 33, pp , [6]. Chiochon, S.Garcia, et al, Cement Paste Coloring in Concretes, Cement and Concrete Research Journal, Elsevier Ltd., Vol.. 34, [7]. Resheidat, M. and Al-Kharabsheh, B. Experimental Study on Colored Concrete using Pigments from Raw Local Materials. Proceedings of TCMB 3 rd International Symposium, May 21-23, 2007, Istanbul, Turkey, Volume 2, pp [8]. Al-Kharabsheh, Buthanyna., " An Experimental Study on Colored Concrete using Pigments from Raw Local Materials", M. Sc. Thesis, Department of Civil Engineering, Jordan University of Science and Technology, May [9]. Abdel-Halim, M. Basoul, M., and Abdel-Karim, R., Structural evaluation of concrete-backed stone masonry, ACI Struct. J., V. 86, pp ,

CHAPTER 5 FRESH AND HARDENED PROPERTIES OF CONCRETE WITH MANUFACTURED SAND

61 CHAPTER 5 FRESH AND HARDENED PROPERTIES OF CONCRETE WITH MANUFACTURED SAND 5.1 GENERAL The material properties, mix design of M 20, M 30 and M 40 grades of concrete were discussed in the previous chapter.