From Utah to Panama Following a Humanitarian Call

Author: Lorella Angelini, Angelini Consulting Services, LLC

Do engineers have a warm heart? Yes and a generous one!
Behind their notoriously serious face, engineers have a generous attitude, which responds to their social call. At the core of their work there is a dedication to servicing the communities by designing sound structures that are safe and last long, even in difficult environmental conditions.

A story that underlines engineers’ generous attitude is being written by Joshua Sletten, bridge management engineer with Utah DOT. Leaving temporarily aside his responsibility of managing bridges across the state, Joshua has taken the commitment of building a 150-foot suspension bridge in Luna, Panama, thus replacing the rickety, life-threatening bridge that is currently used by the local population.

Joshua will lead a 10-person volunteer team with “Bridges to Prosperity”. This non-profit organization based in Colorado has an inspiring mission, which entails providing isolated communities with access to essential health care, education and economic opportunities by building footbridges over impassable rivers.

LINKAGE
Information and a video about Joshua Sletten project in Panama can be seen here:
http://www.ksl.com/?sid=38846775&nid=148
Information about Bridges to Prosperity non-profit organization can be found here:
http://bridgestoprosperity.org/
https://www.facebook.com/BridgestoProsperity
https://en.wikipedia.org/wiki/Bridges_to_Prosperity

Current and Futuristic Methods to Seal Concrete Cracks

Lorella Angelini
Author: Lorella Angelini, Angelini Consulting Services, LLC

There are many ways to design concrete mixes. Different types of ingredients and dosages can be used in various combinations so as to respond to construction and specification requirements. However all concrete mixes share one basic, common denominator: they should not develop cracks, even under stress conditions.

Not only are cracks aesthetically unpleasant, they are also very detrimental since they provide a way of entry for contaminants, such as chlorides and sulphates, into concrete. Once it penetrates into the cracks, water alone can cause concrete spalling by freeze-thaw cycles.

Between the technologies for permanently sealing cracks in concrete, epoxy resins are widely used, especially for structural cracks. Epoxies have great adhesion to concrete, high compressive and tensile strength, volume stability, and are available in a variety of formulations for different types of applications. For example, wall cracks can be sealed by injecting epoxies at low or high pressure, preferably moving from the bottom to the top of the wall. Other types of epoxies with low or ultra-low viscosity can be used to seal cracks in concrete decks or pavements. In this case the material is fed into the cracks by gravity. This application method is also used with HMWM (High Molecular Weight Methacrylate) or MMA (Methyl Methacrylate) resins that have a level of viscosity so low that can be compared to water.

In the future these proven technologies may have to confront with a new, experimental method to seal concrete cracks that is based on the use of natural bacteria. By introducing bacteria into concrete cracks, simply using a garden sprayer, long, thin cracks can be sealed in a relatively short time with the limestone compound produced by the bacteria, when these organisms come in contact with water. More information about the sealing mechanism is reported in the links. The Netherlands and the UK appear to be on the leading edge of this exciting development program.

Epoxy injection:

http://www.concretenetwork.com/concrete/crack_injection/basicsteps.html

http://www.concreteconstruction.net/repair/epoxy-injection-for-cracked-concrete_o.aspx

https://www.concrete.org/store/productdetail.aspx?ItemID=503707&Format=DOWNLOAD

Gravity fed epoxies:

http://docslide.us/documents/crack-repair-by-gravity-feed-with-resin.html

Gravity-fed MMA:

http://trrjournalonline.trb.org/doi/10.3141/2202-10

Bacteria-healed cracks:

http://digg.com/video/concrete-bacteria-heals-cracks

http://www.nbcnews.com/id/40201539/ns/technology_and_science-green_innovation/t/designer-bacteria-can-heal-cracks-concrete-buildings/#.VujQVeYk3HA

The Effects of De-Icing Salts on Concrete Pavements

Lorella Angelini
Author: Lorella Angelini, Angelini Consulting Services, LLC

“…If you can meet with Triumph and Disaster
And treat those two impostors just the same…”

                                   From “If” by Rudyard Kipling

Can de-icing salts be regarded as “impostors”? On one end they keep bridge and road traffic surfaces clean from ice during the winter, while on the other they generally create serious deterioration of steel reinforced concrete.

Not all the de-icing salts perform the same. Between Sodium Chloride (NaCl), Calcium Chloride (CaCl2) and Magnesium Chloride (MgCl2), the last two are much more effective against ice than NaCl, but at the same time significantly more aggressive against concrete.

CaCl2 can decompose the Portland cement binder due to its reaction with calcium hydroxide (Ca(OH)2), which is generated by the reaction between water and cement.

MgCl2 can decompose the Portland cement binder at an even deeper level than CaCl2 because of its reactions with calcium silicate hydrates (C-S-H), which are the backbone of concrete giving it its structural framework.

Deicers containing ammonium nitrate and ammonium sulfate can also rapidly attack and disintegrate concrete.

Here are a few studies on the effect of different de-icing salts on concrete.

http://www2.udot.utah.gov/main/uconowner.gf?n=8081525197623431

http://www.ctre.iastate.edu/pubs/midcon/lee.pdf

http://www2.ku.edu/~iri/publications/SLR073.pdf

Modern Trends for Concrete Repair – My Top Three

International Concrete Repair Institute Convention

Author: Lorella Angelini, Angelini Consulting Services, LLC

The upcoming International Concrete Repair Institute (ICRI) Convention in Fort Worth, TX, from October 14 to 16, is titled “Modern Trends in the Repair Industry”. The Convention will gather consulting engineers, contractors, owners and manufacturers, who are experts in the field of concrete repair and restoration. Here is the link to the program of the Convention.

http://www.icri.org/Events/2015_Fall/conv_home.asp

According to ICRI, the way we do business in the repair industry is changing from strategies to materials and from techniques to technology. Based on my education as a civil engineer specialized in construction materials, my top three trends for the repair industry are as follows.

  1. Use of materials that fully integrate with the structure to be restored, providing strength and durability but also the capacity to respond to stress and deformation consistently with the original structure.
  2. Give preference to materials that can be applied easily and successfully, even by unspecialized crews.
  3. Choice of materials that are safe for applicators, users and the environment.

Do you agree with my opinion?

 

Let’s Start Our Conversation…

ed lorellaThe purpose of this blog, “A Conversation about Bridge Preservation”, is to speak about bridge preservation in an open and informal way, thus reaching the general public in addition to the specialists. TSP2 believes in the value of exchanging opinions, ideas and experiences between people who have a stake in bridge preservation or simply are passionate about it.

The writers, Ed Welch and Lorella Angelini, are two civil engineers who share a strong commitment to increasing awareness of bridge preservation within and beyond the construction industry.

Ed is from the Northeast and after a long career as the New Hampshire DOT Bridge Maintenance Engineer, is now the Bridge Preservation Engineer for the AASHTO-TSP2 Program facilitated @ MSU. Lorella is an independent consultant who lives in Minneapolis. She has decades of experience with manufacturers of specialty products in the area of concrete repair and protection..

During the next months, we will be covering two topics; the value of NTPEP (National Transportation Product Evaluation Program) for bridge preservation and the importance of Communicating the Value of Bridge Preservation.  Feel free to suggest any other topics you would like to explore!

Stay tuned for an interview with Drew Storey and Jeremy Hunter of Indiana DOT.