Annual Concrete Labs at Carleton

Confined concrete cylinder after failure
Confined concrete cylinder after failure

Teaching the undergrad students about emerging materials this week. To make our labs more educational this year (with massive amounts of extra safety protocols added), we conducted several concrete compression tests on conventional concrete wrapped in a carbon fiber reinforced polymer (frp). The students are able to compare their normal conventional concrete compression cylinder tests to compression tests of concrete cylinders with frp wrap.

A big thanks to Sika canada for supplying us these frp and adhesive materials, helping with training, and above all making this lab an awesome addition to our undergrad class this year! You can see one of the many tests below;

The above video shows one of the concrete compression tests with frp wrap (the best bit is near the end). A sacrificial camera was used to record failure in a safe way (an old Sony Cybershot from 2006). The cylinder failed with a compressive stress above 65 MPa (around 500 or so KN), whereas the average normal compressive failure strength of this concrete mix (without frp) was about 40 MPa.

The students were asked at the end of the lab to discuss the mechanisms and effects of ‘confinement’ using frp after observing the lab.

New Book on Post-tensioned Concrete in fire

A new book will be published by Springer titled; Structural Fire Performance of Contemporary Post-tensioned Concrete Construction. The book is available now. You can now order or download it here . The book features:

Our book is a concise account of PT concrete behavior in fire.
Our book is a concise account of Post-tensioned concrete behavior in fire. It is an essential first stop for new researchers and firms trying to understand this structural system in real fires.
  • A follow up to my highly cited Fire Safety Journal 2011 literary review paper – doubling the amount of tests analyzed;
  • New insights on bonded post-tensioned concrete construction;
  • Concise account of three large scale multi span post-tensioned concrete floor high temperature tests;
  • Updated five phased deflection theory on post-tensioned concrete continuous members in fire; and
  • New evidence regarding the origins of the standard fire test and discussion regarding that test’s relevancy to unbonded post-tensioned concrete construction.

The book aims to provide raw and valuable test data (restraint, tendon stress, slab temperatures, deflection etc.) from the three large scale tests fire tests on post-tensioned concrete. This information will be useful for structural design firms and researchers interested in understanding concrete structural systems in fire.

A three span continuous post tensioned slab strip before testing under elevated temperature.
A three span continuous post-tensioned concrete slab strip before testing under elevated temperature. An account and raw data of these tests is provided in the book.

Developed based on my internationally recognized doctoral thesis (improving and expanding on portions from: chapter 2 – literary review and chapter 5- large scale testing of concrete slabs), the book represents a balanced and essential overview of the subject. Other chapters and portions of that thesis are being developed for publication elsewhere (future post to come).

The book was copy-edited by a communications intern on my research team and co-authored by the University of Edinburgh’s Luke Bisby. Our goal was to create a highly accessible book for entry undergrad students to senior engineers.

Scanning Electron Microscopy Mysteries

Concrete under SEM
Concrete under SEM

This week, I have been completing some work at the Queen’s University Facility for Isotope Research. There I am using a MLA 650 FEG Environmental Scanning Electron Microscope (ESEM) to investigate micro-cracking of high temperature exposed concrete. This work is part of the Sustainable concrete mixes with recycled concrete aggregates in high temperature project I am working on. I will discuss this project in a future blog entry. To the side is a sample SEM  image (grey-scale) of concrete.

Mystery #1
Mystery #1

But with all my samples completed and half an hour of time left on the 1.2 million dollar SEM machine, what is a researcher to do? Here are images of two different objects. They are not concrete; I challenge readers to solve the mystery of what these objects are. I’ll provide some hints:

The photo on the left is of a stainless steel object. In the past, this object would have been made from iron. The measurements indicate the width of ‘micro scuff marks’.

Mystery #2
Mystery #2

For the photo to the right, a very famous plastic object was used. The raised surface forms part of its branding. Actor Will Farrell recently popularized the object for its ‘sophistication’, but materials experts know it for its precision, which is verified by the measurement shown.

See if you can solve these mysteries! Follow my tweeter feed for the solution.