Haciendo un mejor concreto
Making Better Concrete: Guidelines to Using Fly Ash for Higher Quality, Eco-Friendly Structures
El libro escrito por Bruce King se suma a la biblioteca de quienes
quieran comprender el uso de “fly ash” en concreto. Este
entendimiento resulta importante para las personas que toman decisiones
sobre cuáles productos se utilizan en las construcciones. Las puzolanas
en concreto pueden tener un impacto tremendo en reducir los daños
ambientales del cemento. La producción mundial de cemento Portland
representa el 6-8% del CO2 generado por los seres humanos.
Así, en una sola industria, existe la oportunidad de retardar la
tendencia alarmante del calentamiento global.
Lea el resumen del libro en inglés
Making better concrete: Guidelines to using fly ash for higher quality, eco-friendly structures
It was a pleasure indeed to read the new book, Making Better Concrete, by Bruce King. As a lay person who has been exposed to the theme of alternative concrete for about a decade, I finally have a clearer grasp of what the lofty scientists are talking about.
The starting point for this article will be the last chapter, which presents the big picture. It refers to the effects of fly ash as so many, and so positive, that senior figures in the world of concrete have recently stated that concrete without fly ash belongs in a museum.
Many reasons for using fly ash are global, environmental, or societal in nature. Attention is drawn to the production of Portland cement that puts about a ton of carbon dioxide (CO2, a primary greenhouse gas) in the atmosphere for every ton of cement produced – roughly half a ton from the fuel used to cook the raw limestone, and half a ton from the calcinations of the limestone. Worldwide, the production of Portland cement alone accounts for 6-8% of human-generated CO2 (depending on whom you ask). So here, in a single industry, lies the opportunity to slow the very alarming trend toward global warming.
On the more positive side he refers to one authority who states that for every ton of fly ash used (to replace Portland cement)
- Enough energy is saved to provide electricity to an average American home for 24 days
- The landfill space conserved equals 455 days of solid waste produced by the average American.
- The reduction in CO2 emissions equals 2 months of emissions from an automobile.”
In Making Better Concrete, Guidelines to Using Fly Ash for Higher
Quality, Eco-Friendly Structure, the author has presented a scientific
overview in simple language. Peppered with drawings, provocative
quotations, statistics and graphics, and explanatory appendices, the
book also depicts examples of buildings throughout the world where fly
ash has been used as a replacement for traditional Portland
cement. He clearly states that it is not an academic paper,
rather a guidebook.
The chapters themselves attest to this, beginning with A Short History of Fly Ash and Pozzolans in Concrete, then providing definitions in Chapter 2, What is Fly Ash? What are Pozzolans? Once that is understood he passes on to How do Fly Ash and Pozzolans affect concrete? Here he focusesupon its effects on fresh concrete, on plastic concretes and on hardened concrete.
Chapter 4 on Design Considerations treats the importance of ensuring that “every stakeholder in the construction is educated and aware of the ramifications, potential problems, and benefits of its use.” This involves listening to concerns and suggestions. He confronts specifications by stressing a “Call for the concrete performance you really need”. He draws attention to the importance of design, mix, place and test trial batches ahead of time by referring to the “carpenter´s axiom: measure twice, cut once).
Use of HFAC to counteract common problems such as “heat of hydration in mass concrete, increase resistance to corrosion and degradation caused by high-sulfate soils, reactive aggregates, salt air or water, or caustic chemical (e.g. dairy plants, wineries, and gas station,” opens the door to seeing some of its applications. The importance of expertise is underlined in “Check for availability of fly ash – and expert help”. It goes on to “Pay attention during construction” and “Check for exposure to deicing salts.” It finishes with “Evaluate conditions: a rough guide to how easy or hard it may be to use HFAC in different applications.”
Chapter 5 on Construction Considerations begins with an “Ouch!” where Bruce reveals that “More than a few times in my career as an engineer, I have come to a job site the day after a concrete pour to find the contractor eagerly stripping formwork from walls because the sun can then shine on it and dry it out and make it cure faster.” He uses the word “Ouch” both because the premature exposure to sun has an opposite and terrible effect, because an otherwise competent builder understand so little about a material he works with every day. His final provocation: “In fact, if you don´t plan to control water content and cure the concrete well, throw this book away; it will do you no good.”
This is even more reason to ensure that this book reaches decision-makers and builders.