Test method for de-icing salt-frost scaling in high-performance concrete.

This paper describes a de-icing salt-frost scaling test method for analysis of the salt-frost scaling behaviour in high-performance concrete with various binders. The method was therefore designed to result in considerable scaling damage for the concrete considered to be salt-frost resistant. In addition, the experimental set-up was designed to avoid leakage, and to allow testing of a large number of samples. The method was validated by testing concrete with three different binders with a water-binder ratio of 0.40 with 5% air content. Various preconditioning procedures and freeze-thaw cycles were evaluated. The results show that the freeze-thaw cycle chosen results in a large mass of scaling and the salt-frost scaling behaviour agreed with the findings of previous studies. Thus, the method was considered suitable to study the salt-frost scaling behaviour in high-performance concrete. Three distinguishing features of the method are the following: •The freeze-thaw cycle result in a large mass of salt-frost scaling to enable study of high-performance concrete.•The concrete sample is above the salt solution to prevent leakage. The test surface is submerged 2 mm into the salt solution inside a cup.•Freezers with air as the thermal medium are used to allow a large number of samples.

Calculating CO2 uptake for existing concrete structures during and after service life.

This paper presents a model that can calculate the uptake of CO2 in all existing concrete structures, including its uptake after service life. This is important for the calculation of the total CO2 uptake in the society and its time dependence. The model uses the well-documented cement use and knowledge of how the investments are distributed throughout the building sector to estimate the stock of concrete applications in a country. The depth of carbonation of these applications is estimated using two models, one theoretical and one based on field measurements. The maximum theoretical uptake potential is defined as the amount of CO2 that is emitted during calcination at the production of Portland cement, but the model can also, with some adjustments, be used for the other cement types. The model has been applied on data from Sweden and the results show a CO2 uptake in 2011 in all existing structures of about 300,000 tonnes, which corresponds to about 17% of the total emissions (calcination and fuel) from the production of new cement for use in Sweden in the same year. The study also shows that in the years 2030 and 2050, an increase in the uptake in crushed concrete, from 12,000 tonnes today to 200,000 and 500,000 tonnes of CO2, respectively, could be possible if the waste handling is redesigned.