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The Concrete Times - November 2015

The CONCRETE Times • November 15 predict concrete performance and improve concrete uniformity? I think that we could if we really wanted to, but we have very limited incentive or ability to do so for the following reasons: • Concrete is comprised of large quantities of mostly natural materials with little processing and every effort to optimize materials combinations results in increased waste. For example, trying to increase the coarseness of naturally fine sand will result in larger reject piles of “dust”, which is difficult to use or dispose of. • People are used to accepting concrete with a strength variability of 3-7%. As long as concrete meets minimum strength requirement, an increase in variability in strength only requires a minimal increase in cementitious materials. If the cost of cement were to increase by a factor of 10 or 100, quality control departments would spend a lot more time minimizing strength variability. • The industry truly doesn’t understand the basic materials we work with. A lot of research was conducted on basic combinations of rock, sand, cement and water during the first half of the 20th century. Researchers learned about the impact of maximum aggregate size or of cement fineness on concrete performance. Tens of thousands of tests were performed on thousands of concrete batches covering years of research. Today a thesis is typically based on one or two dozen trial batches produced during a one to two year postgraduate program. In addition, researchers are naturally drawn to the study of the “darling-du-jour” of the concrete industry, whether it is nano-particles, the latest chemical admixture or the study of a “more sustainable” material. Almost no research is performed today on concrete using just “rock, sand, cement and water” despite the fact that the basic research performed 50 years ago was conducted on materials that don’t even exist today. What should we do to resolve this situation? We need to reexamine much of the older studies that were performed on just rock, sand, cement and water. Do our commonly held beliefs from early studies hold true today or do they need to be tweaked? Today we use more crushed stone and manufactured sand than natural gravel and natural sand. Also, cement physical and chemical characteristics are totally different today than 50 years ago, not to mention the addition of other materials to the cement. How much water does it really take to hydrate cement? What is the best way to proportion aggregates to result in the most efficient concrete? Why has some existing concrete performed well, while other concrete has failed DESIGN IT BATCH IT COLOUR IT MIX IT SHIP IT REINFORCE IT WATERPROOF IT SHAPE IT PRECAST IT PUMP IT FORM IT PLACE IT SCREED IT FINISH IT CURE IT CUT IT POLISH IT JOINT IT TEST IT SEAL IT........... DESIGN IT BATCH IT COLOUR MIX IT SHIP IT REINFORCE IT WATERPROOF IT SHAPE IT PRECAST IT PUMP IT FORM IT PLACE IT SCREED IT FINISH CURE IT CUT IT POLISH IT JOINT IT TEST IT SEAL IT........... After our biggest and best show ever, stands are selling fast at Europe’s Number 1 Concrete Show, the unique concrete industry showcase. Call Paul Shelley on 020 3086 9296 ext 3 or Eddie Milton on ext 2 now to secure your stand - it’s where the concrete industry does business! The UK CONCRETE Show 2016 Sponsorship Opportunities – The UK Concrete Show Raise Your Show Profile – Prices start from just £175.00 – it’s your opportunity to stand out from everyone else! Contact Anthony for details anthony@marwoodevents.com Wednesday 17 & Thursday 18 February, 2016 Hall 5, NEC, Birmingham www.concreteshow.co.uk The whole of the industry on display! 19 our biggest and best show ever, stands are selling fast at Europe’s Number 1 Concrete Show, unique concrete industry showcase. Paul Shelley on 020 3086 9296 ext 3 or Eddie Milton on ext 2 now to secure your stand - it’s where the concrete industry does business! The UK CONCRETE Show 2016 Wednesday 17 & Thursday 18 February, 2016 Hall 5, NEC, Birmingham www.concreteshow.co.uk The whole of the industry on display! prematurely? In addition, we need to develop better ways of sharing planned, current and completed research. Obviously the Internet has greatly facilitated this, but there needs to be greater awareness of both research in progress and research that needs to be conducted. In the U.S. we have a group that has done an exceptional job of this. The National Concrete Consortium, http://www.cptechcenter.org/ ncc/TTCC-NCCMeetings.cfm, is comprised of a group of educational institutions, government agencies, material suppliers and contractors. Twice a year they get together to talk about problems relating to paving and how these problems are being evaluated and resolved. Part of their effort revolves around the Concrete Pavement Roadmap, https://www.fhwa.dot.gov/ pavement/pub_details.cfm?id=338, which details topics that need to be researched to improve our understanding of concrete. The research is then conducted by the educational and governmental groups, often with cooperation from private organizations. In short, we need to reevaluate our basic understanding of concrete and determine if our current knowledge adequately reflects today’s reality, then locate the gaps in our understanding and fill them. If we do this the concrete industry can become more efficient and produce a better product. monthly columnist - jay shilstone continued


The Concrete Times - November 2015
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