14th ICAAR - Austin, Texas

ICAAR conference series continued in Austin, Texas. Thanks to University of Texas, it has been a remarkable organization from 21st to 25th May. It has been a warm but a knowledgeable week for PAT-ASR team. We had the opportunity to experience interesting researches from around the world. We have share knowledge and connected with researches from our field. Our team also presented 2 papers during the conference and collected useful feedback. one of the highlights of the conference was the visit to Texas University ASR Exposure site (see images). They showing a considerable effort and dedication to run this site.

Over all, it has been a informative week for everyone.

Gel Expansion and Loading differences in model

Crack formation changes according to localization of the gel. this correlation brings a challenge in modelling. Which loading point will successfully represent Gel expansion?
Recently explored various loading options on a hypothetical section with a low aggregate-paste ratio. Different images represent various loading points, On; aggregate, ITZ, aggregate+ITZ, respectively.

Also comparative stress distribution after certain amount of crack growth

Just a reminder!

First 2D simulations

Using digital imaging from reacted structure samples, we managed to run a 2D simulation for ASR expansion (size of 9.6 cm x 9.6 cm) .

Using thresholding and edge detection images are convereted to binary images. Three Phases (aggregate - mortar - ITZ) identified and superimposed with a lattice mesh including (79600 beam elements). Based on earlier studies (Schlangen and Copuroglu, 2010) material properties are assigned and expansion is defined on all interfacial transition zone (ITZ) elements.

Cracked beam elements after 3000-8000-20000 steps.

First attempts assumed local lodings on the ITZ elements only and swelling to start simultaneously. Currently we are working on identification reactive components in a 2D medium and implementing non-simultaneous expansion patterns in the section. After execution of small scale testing device we will have more insights about pressure progress and gel propeties (those details for another post). Alternate reactive regions and shifted timing regimes to be defined later on.

Deformed version of sample after 20000 steps

Still a lot to do, in modeling but first results seems promising for improvement.



Schlangen, E. and C. Copuroglu (2010). Modeling of expansion and cracking due to ASR with 3D lattice model. Framcos7, Jeju, Korea.

Performance Testing for AAR (Nautesund)

(A delayed post)

After busy preparation period in November, it's been a productive December for experiments. Reassuring way to end year 2011. Experimental part of our project is divided into several workpackages consisting of RILEM AAR-3 (38°C) and AAR-4 (60°C) performance tests.

 

One of which is backward compatibility tests. By the courtesy of Norwegian Public Roads Department, we have accessed materials from Nautesund bridge.


As mentioned earlier, we have received several cores from Norway.
After analysis on the samples, original mix has been identified. In December we cast 4 mixes (3 of which with original mix design -with varied w/c ratios, and 1 standard RILEM recommended mix). Currently running performance tests on these specimens.

Preliminary results show that specimens reached RILEM limits within 5 weeks in to the experiment (espacially for 60°C test)

AAR-4 (60°C Expansion values as of 01/03/2012)

To understand the progress of gel and crack propagation within sample we have adopted extra specimens sizes of 10x10x10 cm.These samples will be used for thin and polished section analyses. Data collection schedule for a standard concrete performance testing is as follows:

Data collection scheme for RILEM recommended testing

Specimen quantities and dimensions

For performance and parameter testing more castings are schedules for March 2012.
... more results and detailed analysis to follow, soon.