Calcareous aggregates on BSE mode

Studying the composition of concrete samples can be performed easily under the ESEM. Sometimes, the origin of the aggregates and their main composition must be determined. In this case is the presence of calcareous (CaCO3) aggregates in the concrete mix. In some countries, Aggregates are obtained from crushed rocks. Calcium carbonates have a similiar intensity under the BSE mode when compared to CSH. This quite be uncommon in places where aggregates are commonly from siliceous origin.

 Sample w/b ratio 0.45

 

Sample w/b ratio 0.65

A quick look on the previous images confirms the presence of calcium carbonate as the main aggregates in concrete samples. In the coming future, more explanations regarding the EDS analysis on this type of samples will be shown.

Until next time,

Bending cracks in reinforced concrete cubes

During the course of the M3C4 research, a Modified Wedge Splitting Test (MWST) was employed as the main source of getting controlled cracks in reinforced concrete specimens. For this purpose, we used concrete cubes that contained a recess, where the action of the wedges is applied; and two reinforcing bars embedded in concrete.

After cracking, one can only measure the COD (Crack Opening Displacement) at the concrete surface by means of LVDTs. After some other procedures, we're now able to visualise the shape of the crack inside the concrete cubes.

More results are about to come.
Until next,

Corrosion induced cracking

When steel corrodes, a rust layer is created around it which exerts pressure on the concrete cover. Although much is known about this process, it would be nice to be able to study it non-destructively. How? Well, we might have a trick up our sleeve! Keep checking the blog for news!

And here is an update:

Big city, big Conference

The view of Chicago's skyline from Jon Hancocks's Observatory.

 The 35th International Conference on Cement Microscopy was held from April 29th to May 1st in Chicago, Ill. The M3C4 had the opportunity to attend and show some of the research lines we've been currently looking into. The conferece had a lot of interesting presentations and extensive discussions regarding cement microscopy.

We also had the opportunity of visiting the headquarters of PCA (Portland Cement Association) based in Skokie, Ill. The facilities were excellent for research on cementitious materials.

From the M3C4 here's a big shout-out to the organizing team of ICMA and hopefully, we'll see you again next year in Italy.

Headquarters of PCA, Skokie, Ill.

Cracking of the concrete cover due to reinforcement corrosion

 Our paper titled "Cracking of the concrete cover due to reinforcement corrosion: A two-dimensional lattice model study"
 has just been published in Construction and Building Materials. It deals with numerical modelling of cracking of the concrete cover as a consequence of reinforcement corrosion, based on the Delft lattice model framework. Registered subscribers can download the article at: http://www.sciencedirect.com/science/article/pii/S0950061813002730
I hope you find it interesting and useful.
Cheers! 

Concrete butchers

Chlorides in concrete can be washed away when concrete is sawn by employing water as lubricant. For this reason, we took some samples and sawn them in dry conditions. The experiment had an overall success, but the environmental conditions were the problem. It was really cold outside!

Branko as a concrete butcher

Chloride penetration fronts and profiles are about to be assessed from the sawn slices of concrete containing chlorides. Results will come soon.

Until next time.

FraMCoS-8

FraMCoS-8 came and went... One of the best conferences with regards to fracture mechanics of concrete was a great opportunity to get a sneak peak at the newest and most innovative research in the field. We had a great time, filled with nice presentations and fruitful discussions. The official website of the organization is now www.framcos.org (under development). The next one is in three years, somewhere in the US... We will try to perform even better in the next one! Till then!

Traffic-induced vibrations of frame structures

A paper titled "Traffic induced vibrations of frame structures" (Marija Nefovska-Danilovic, Mira Petronijevic, Branko Šavija) , related to Branko Šavija's diploma thesis work, has been published in Canadian Journal of Civil Engineering.
Abstract:
"Using the spectral element method (SEM), a 2-D numerical model of multi-storey frame structures has been developed. The model has been used to predict traffic-induced vibrations of two, six, and twelve-story concrete buildings measured along the route of a future metro line in Belgrade, the capital of Serbia. Vibration simulations of the six-storey frame match satisfactorily the measured dynamic response. However, there is a difference between numerical simulation and the actual measurements for the two-storey and twelve-story buildings. The results indicate a great potential of the proposed SEM to simulate ground-induced vibrations of frame buildings. However, more complex structural models should be developed to better replicate actual situations."
Subscribers can download the full paper at  http://www.nrcresearchpress.com/doi/abs/10.1139/cjce-2011-0247#.UUbKWGf4LTp

FraMCoS - 8 begins today!

The 8th International Conference on Fracture Mechanics of Concrete and Concrete Structures begins today in Toledo, Spain. Two members of the M3C4 team: Branko Šavija and Erik Schlangen will contribute with presentations. 

The major topics for FraMCoS-8 are as follows:

• Recent advances in fracture mechanics of concrete

• Fracture and cracking behavior of reinforced and prestressed concrete structures

• High-performance, high strength concretes and FRC

• Advances in structural design codes

• Structural monitoring and assessment

• Repair and retrofitting, practical application

• Durability and corrosion-induced cracking

• Interface fracture and debonding phenomena

• Constitutive relations, time-dependent effects, cyclic and fatigue behaviour

• Brick masonry, concrete-like and quasi-brittle materials

• Computational aspects in fracture mechanics of concrete

You can see the conference program here.

When the levee (or concrete) breaks

This week finished with a set of concrete specimens being cracked for chloride penetration and reinforcement corrosion tests. Overall, it was a successful experiment.
Cheers