No abstract

No abstract

No abstract

Corrosion of re-bar within reinforced concrete is a major problem in countries where salt is applied to roads for de-icing. Concrete structures are periodically inspected in order to monitor possible damage caused by chloride induced corrosion of the reinforcement. However, bridge decks covered with asphalt pavements are not accessible for visual inspection and probing is limited. As a result, the planning of rehabilitation of bridge decks is usually based on a small number of probes. Consequently, the condition of bridge decks can only be assessed with low certainty. Therefore, a method enabling to study the conditions of concrete bridge decks covered by asphalt pavements is desirable. This paper describes a laboratory experiment aiming at the investigation of the effects of moisture and chloride content on the amplitudes of radar signals. It can be shown that both, moisture and chloride content have a measurable influence on signal amplitudes. This may enable the J. Hugenschmidt (1:

Self-compacting concrete (SCC) used in Switzerland contains about 80 l/m 3 more volume of paste than conventionally vibrated concrete (CVC). Consequently, there are some systematic differences in the properties of the hardened concrete. Normally, shrinkage of SCC is higher than shrinkage of CVC. Therefore, risk of cracking in case of restrained deformations can be increased for SCC. In this study shrinkage of thirteen different SCC mixtures using volume of paste, water content, type of binder, grain size distribution or content of shrinkage reducing admixture (SRA) as variables was compared with shrinkage of three different CVC mixtures with constant volume of paste but variable w/b. Furthermore, the risk of cracking of the different SCC-and CVC-mixtures in restrained conditions was studied under constant and varying curing conditions. The results show that shrinkage is mainly depending on volume of paste. Due to the higher volume of paste, SCC displayed higher shrinkage than CVC. Adding an SRA was the only measure to reduce shrinkage of SCC to values of CVC. Restrained shrinkage cracking is depending on shrinkage rate, mechanical properties and drying velocity. For slow shrinkage stress development, cracking risk of SCC can be lower compared to CVC despite the higher shrinkage rate.

No abstract

No abstract

Although the use of self-compacting concrete (SCC) is widespread nowadays, relatively few data about its stress-strain-behaviour are available. In this project, the influence of paste volume and cement type (CEM I 42.5 N, CEM II/B-M (V-LL) 32.5 R and CEM III/B 42.5 L-LH HS) on shrinkage, creep and stress development under restrained conditions is investigated using three SCC mixtures and three mixtures of conventionally vibrated concrete (CVC) with identical water-tocement ratio. Furthermore, E-modulus and strength are measured. SCC reaches lower values for E-modulus, compressive and tensile strength. While shrinkage is dominated by the volume of paste, with SCC showing higher values than CVC, the influence of cement type plays a more important role regarding creep. Mixtures with higher free shrinkage develop higher stresses and cracked under restrained conditions. Composite models are able to confirm that the differences in E-modulus and shrinkage between CVC and SCC are caused by the differences in paste volume.