White cement concrete

White Cement Concrete Mary Gillette 30 March 2004 Questions one might ask: • What makes white cement white? • Where is white cement being produced and how is it being used? • Does it perform differently from gray Portland cement? Questions one might ask: • How does this cement choice affect mix design, aggregate choice, and admixture usage? • How is construction influenced? • Are there different mechanical properties with white cement concrete? What makes white cement white? • Coloring Oxides make normal Portland cement gray or slightly brown • White cement has raw materials that reduce these Table Coloring Oxides Compound Recommended limit Color influence on clinker Fe2O3 < 0.4 % gray Mn2O3 < 0.02% grayish-violet, reddish-violet Cr2O3 < 0.01 % greenish MgO < 3% greenish-brown What makes white cement white? • Such raw materials could be white chalk or limestone and china clay (kaolinite) – Remove fine particles, because they contain more coloring oxides • Manufacturing process also controlled so that coloring oxides don’t enter clinker – Grinding media, mill lining materials, fuels used in burning What makes white cement white? • Regulations specifically for whiteness not exist in USA • They follow same regulations as normal Portland cement, ASTM C150 • White Portland cements are made in Types I, II, III, and V, where I and III are most common What makes white cement white? • The resulting white cement has the following chemical composition: Table YYY: Cement compositions Composition Percent by weight, for various cements Gray (type I) White (textbook) Aalborg White (types I, II, III, V) Middle East White C 3S 45 – 55 59.4 62 48.5 C 2S 20 – 30 23.5 25 30.5 C 3A – 12 12.9 13.4 C4AF – 10 0.6 0.8 Ỉ How white is white enough? • Whiteness is measured by comparing reflectance with a reference standard Table Whiteness Levels Whiteness Less than 80 % Classification Not white enough 80 – 84% Ordinary commercial grades 84 – 88% World market quality More than 88% Obtained only with special raw materials Where is white P.C produced? • White Portland cement is produced all around the world: • North America • Europe • Middle East • Aalborg White (Denmark) is the largest world-wide producer • 1.5 million metric tons / year How is it being used? • It’s still a novelty or luxury product – Can make any shape – Imitates more expensive, flawed stone How is it being used? • Can be practical, too – Draws attention, which is good for safety reasons – Reflects area lighting which can save on energy costs over time Does it perform differently? • Mostly, the mechanical properties are assumed to be the same for white and gray Portland cement • However, there are differences in strength gain Does it perform differently? Figure 1: Strength gain of white and gray cement concretes Does it perform differently? • Reasons for this: – High C3A and C3S – More silicates Ỉ more C-S-H, less CH – Ground finer Æ This isn’t a significant difference in strength, though How does it affect mix design? • The mix design: – Is richer in cement • This makes it appear whiter – Has more fine sand • Finer looks lighter – May have a higher water cement ratio • Higher w/c looks lighter – Has very careful aggregate choice • Sands act like pigments • Chosen for color and possible staining of paste How does it affect mix design? • Admixtures Usage – Use ones as close to white as possible – For very white concrete, use: • Silica fume • Metakaolin • Slag – Superplasticizers more effective • More even adsorption of superplasticizer because less C3A + C4AF • This makes cement more fluid at same dosage How is construction influenced? • “VIGILANCE, constant vigilance” with uniformity • Use clean, non-staining equipment • Keep batches uniform – Different w/c will show! How is construction influenced? • Set time is usually faster: 129 or 100 versus 166 • Use formwork that doesn’t stain and that doesn’t leak – No untreated wood – avoid ones with coloring oxides • Use experienced finishers – Avoid metal trowels and over-trowelling Case Study: Jubilee Cathedral • Near Rome in Tor Tre Triste • Many cathedrals nearby for comparison—this one is very different! It “upholds … the city’s rich architectural tradition…(but) was always intended to be a work of contemporary architecture, meaningful for our time and one that is marked with openness Transparency and light cascade down from the skylit roof, literally invading the interior of the church…People in the atrium are enveloped with mystical light.” Richard Meier, architect Case Study: Jubilee Cathedral • Concrete was precast, post-tensioned by Italcementi Gruppo • Designed for “aesthetic durability” in what they call “Bianco TX Millenium” – Added titanium dioxide that “oxidizes the organic and inorganic air pollutants in the presence of air and light” References [1] James A Farny White Cement Concrete, EB217 Portland Cement Association, Skokie, Illinois, U.S.A, 2001 [2] Enterprise Solutions Group website, http://www.esg-inc.com/cu-5.htm Access on 18 March 2004 [3] D Kupper and K.-H Wiemer “Modern technology of white cement manufacture,” ZKG International, No 10 (1986) p 531 – 541, translated to English for issue No 12 (1986) p 355 – 360 [4] D Kupper and W Schmid-Miel “Process engineering and raw material factors affecting the lightness and hue of ‘white’ clinker and cement,” ZKG International, No 12 (1987) p 589 – 597, translated to English for issue No (1988) p 30 – 32 [5] G C Bye Portland cement: Composition, production and properties Thomas Telford Publishing, London, 1999, p 5, 164-165 [6] “Decorative Concrete: Mixing and Handling White Cement Concrete,” Portland Cement Association, Skokie, Illinois Accessed via internet (www.portcement.org) on 17 March 2004, 9:30pm [7] Annual Book of ASTM Standards, vol 04.02 ASTM, West Conshohocken, Pennsylvania, p150 – 153 [8] “White Concrete Technology – a world of possibilities” Aalborg White product information (downloaded from www.aalborgwhite.com on 16 March 2004, 8:48pm) [9] S Chandra and J Bjornstrom “Influence of cement and superplasticizers type and dosage on the fluidity of cement mortars—Part I”, Cement and Concrete Research 32 (2002) p1605 – 1611 available online at www.sciencedirect.com [10] Bilal S Hamad “Investigations of Chemical and Physical Properties of White Cement Concrete,” Advanced Cement Based Materials, issue (1995) p 161 – 167 available online at www.sciencedirect.com [11] ArchNewsNow, photos by Andrea Jemolo “Iconic Arcs: Jubilee Church by Richard Meier & Partners.” Access via internet (http://www.archnewsnow.com/features/Feature123.htm) on March 2004 [12] Italcementi Press Releases, dated 24 October 2003 accessed via the internet (http://www.italcementigroup.com/newsite/Chiesa_2000.htm) on March 2004  ... different mechanical properties with white cement concrete? What makes white cement white? • Coloring Oxides make normal Portland cement gray or slightly brown • White cement has raw materials that... makes white cement white? • The resulting white cement has the following chemical composition: Table YYY: Cement compositions Composition Percent by weight, for various cements Gray (type I) White. .. burning What makes white cement white? • Regulations specifically for whiteness not exist in USA • They follow same regulations as normal Portland cement, ASTM C150 • White Portland cements are made