Alkali-silica reactions in Scania, Sweden : a moisture problem causing pop-outs in concrete floors

Problemen med alkali-kiselsyrareaktioner i Sverige ('AKRIS') är nya och började uppträda då ett cement med högre alkalihalt ersatte det tidigare lågalkalicementet som använts i södra Skåne, där betonggrus normalt innehåller alkalireaktiva korn av opalflinta och opalsandsten.Bara på 'fuktiga inomhuskonsruktioner', som har haft en speciell fukthistoria, har pop-outs uppkommit

A new model for CO₂-absorption of concrete structures. CO₂-cycle in cement and concrete Part 7: Models for CO₂-absorption.

After further laboratory and field studies we have now used the previous and new findings to create a model for CO₂-absorption of concrete structures. Some knowledge is still missing and some results are still not fully understood. In those cases we have done our best to base the model on reasonable assumptions, from what could be expected from some new literature that has been studied

Moisture transport under a temperature gradient – some old and new studies

Moisture transport in concrete under a temperature gradient is a topic that has challenged researchers for at least some 60 years. No conclusions are still drawn on how to describe it theoretically and how to quantify it experimentally. In this paper some of the theoretical and experimental work done is summarized. A description of the flux of moisture by the relative humidity and the water vapour content as the two transport potentials is proposed. A comparison with laboratory and field data is given and the consequences in some applications are discussed

A comparison between different methods to determine moisture transport properties of cementitious materials

A number of methods for measuring moisture transport properties of cementitious materials were compared in a series of experiments. Two OPC mortars with two water-binder-ratios were wet cured for six months and used to produce specimens as discs with different thicknesses and diameters. The cup methods were easy to use, reliable and fairly rapid but need a stable, surrounding, CO2-free climate, however. Evaluating the fundamental potential PSI eliminates the derivation that adds to the uncertainty. Steady-state moisture distribution measurements are very time-consuming and the RH-profiling is a delicate matter. Moisture contents are scattering. Sorption experiments are very easy to perform but difficult to evaluate, because of the peculiar moisture-dependency of the diffusivity Dw and the difficulties to estimate the equilibrium conditions. Initial uniform conditions are difficult to obtain for low w/c-materials, except to initial self-desiccation. Sorption experiments in small steps are uncertain; the initial and final conditions are difficult to define properly

Värme i betonggolv. Pilotförsök

På uppdrag av Wirsbo Bruks har Avd Byggnadsmaterialära gjort en mindre laboratorieundersökning för att framför a1lt studera fuktförhöjning då kvarvarande byggfukt omfördelas i betongen vid användning av golvvärme. Uttorkningen av byggfukt måste drivas något 1ängre, dvs större mängd måste uttorkas