| 1. |
- Pettersson, Dan, et al.
(författare)
-
Influence on crack development in concrete structures from imposed strains and varying boundary conditions
- 2002
-
Ingår i: Construction and Building Materials. - 0950-0618. ; 16:4, s. 207-213
-
Tidskriftsartikel (refereegranskat)abstract
- Crack development due to imposed strains in different types of concrete structures and with varying boundary conditions is studied in order to improve control of cracking. A previously developed two-dimensional FE-method is used, with closing forces in cracks concentrated to spring elements. Temperature changes are used as load, and the calculations are performed stepwise with opening of nodes and implementation of spring elements. The FE-method has also been used to study crack widths and crack spacing for a wall fully restrained at the bottom. It is shown that the type of restraint has significant influence on crack widths. For structures with restraint along the length direction the restraint effectively facilitates distribution of cracking, similar to a wall fully restrained at the bottom. (C) 2002 Elsevier Science Ltd. All rights reserved.
|
|
| 2. |
- Björk, Folke., et al.
(författare)
-
Degradation of components in flooring systems in humid and alkaline environments
- 2003
-
Ingår i: Construction and Building Materials. - 0950-0618 .- 1879-0526. ; 17:3, s. 213-221
-
Tidskriftsartikel (refereegranskat)abstract
- Constituents from products that are used in the flooring on a concrete slab such as carpets of plasticised PVC and water-based adhesives sometimes degrade in an alkaline and humid environment. The concrete itself could be such an environment. In order to examine the effect of different levels of alkalinity and humidity on the mentioned products a specialised procedure was developed. By this procedure it was possible to imitate the effect of an environment of alkalinity and humidity corresponding to a recently produced concrete slab on different substances and also collect volatile degradation products produced. Degradation of some of the constituents was dependent on the levels of alkalinity and humidity, although there were significant differences in the possibility to resist the environmental factors. For some of the components, an increase in alkalinity resulted in a much higher production of degradation products even when the relative humidity was kept on a comparatively low level. The results give basis for a recommendation not to adhere plastic floorings directly to a recently produced slab of high-quality concrete because the alkaline material in the concrete could cause degradation.
|
|
| 3. |
- Björk, Folke., et al.
(författare)
-
Measurement of alkalinity in concrete by a simple procedure, to investigate transport of alkaline material from the concrete slab to a self-levelling screed
- 2002
-
Ingår i: Construction and Building Materials. - 0950-0618 .- 1879-0526. ; 16:8, s. 535-542
-
Tidskriftsartikel (refereegranskat)abstract
- A test procedure for measurement of alkalinity for cementitious materials that is, reliable, simple. and only needs a small amount of sample, was developed and applied to check whether transport of alkaline material from a concrete surface to a covering screed can result in a detectable increase in pH-value. It was found that any transport of alkaline material from a rather humid concrete did not increase the level of alkalinity (or pH-value) of the screed covered with a carpet. It was noted that carbonation Occurred gradually from the surface and inwards when the materials were exposed to ambient air. For the prisms, of 95%, RH pH-value in the concrete surface increased with time. A transport process that allows hydroxide ions solved in the pore water in the concrete to diffuse towards the carbonated surface and thus give an increased pH-value, can explain this.
|
|
| 4. |
- Granne, F., et al.
(författare)
-
Joints between roofing felt and sheet metal flashings - short- and long-term tests
- 2000
-
Ingår i: Construction and Building Materials. - 0950-0618 .- 1879-0526. ; 14:07-jun, s. 375-383
-
Tidskriftsartikel (refereegranskat)abstract
- The adhesion between roofing felt and sheet metal flashings has been measured and analysed and test methods for this have been developed. Both bituminous and polymeric roofing felts have been used. The steel has been PVC-coated galvanised steel sheets and the bituminous roofing felts have been of both SBS and APP modified type. All the joints have been made with heat welding. The tests show that it is possible to obtain joints with sufficient strength using the contractors ordinary welding procedures.
|
|
| 5. |
- Granne, F., et al.
(författare)
-
Wind load resistance tests of heat-welded joints between roofing felt and sheet metal flashings
- 2003
-
Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 17:5, s. 319-324
-
Tidskriftsartikel (refereegranskat)abstract
- The wind load resistance of joints between roofing felt and sheet metal has been measured in a wind uplift chamber. Both bituminous and polymeric roofing felts have been used. The sheet metal has been PVC-coated galvanised steel sheets and the bituminous roofing felts have been of both SBS and APP modified type. All the joints have been made by heat welding. The tests show that peeling is the dominating process in the failure of joints during wind load.
|
|
| 6. |
- Täljsten, Björn
(författare)
-
Strengthening concrete beams for shear with CFRP sheets
- 2003
-
Ingår i: Construction and Building Materials. - 0950-0618 .- 1879-0526. ; 17:1, s. 15-26
-
Tidskriftsartikel (refereegranskat)abstract
- The method of strengthening concrete structures with FRP composites has existed for over a decade; the most common way to strengthen structures is in bending, but also wrapping of columns is quite common. There are also needs for strengthening concrete structures in shear, for example concrete beams, slabs, columns, etc. A typical structure can be a parking garage. However, strengthening concrete structures for shear is not as common as for bending and confinement. This paper presents examples to strengthen concrete beams for shear. First traditional strengthening methods are presented briefly, then the use of CFRP (Carbon Fibre reinforced Polymers) composites for shear strengthening is presented. Tests on beams strengthened in shear with CFRP sheets are presented and a short presentation on how to design for shear strengthening with CFRP is given. Furthermore, a field application of a parking slab strengthened for shear with CFRP unidirectional fabric is presented. The laboratory tests show the importance of considering the principal directions of the shear crack in relation to the unidirectional fibre. The field application shows that it is easy to strengthen existing structures for shear with CFRP fabrics.
|
|
| 7. |
- Adamopoulos, Stergios
(författare)
-
Acoustic emission monitoring of wood materials and timber structures: A critical review
- 2022
-
Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618. ; 350
-
Forskningsöversikt (refereegranskat)abstract
- The growing interest in timber construction and using more wood for civil engineering applications has given highlighted importance of developing non-destructive evaluation (NDE) methods for structural health monitoring and quality control of wooden construction. This study, critically reviews the acoustic emission (AE) method and its applications in the wood and timber industry. Various other NDE methods for wood monitoring such as infrared spectroscopy, stress wave, guided wave propagation, X-ray computed tomography and thermography are also included. The concept and experimentation of AE are explained, and the impact of wood properties on AE signal velocity and energy attenuation is discussed. The state-of-the-art AE monitoring of wood and timber structures is organized into six applications: (1) wood machining monitoring; (2) wood drying; (3) wood fracture; (4) timber structural health monitoring; (5) termite infestation monitoring; and (6) quality control. For each application, the opportunities that the AE method offers for in-situ monitoring or smart assessment of wood-based materials are discussed, and the challenges and direction for future research are critically outlined. Overall, compared with structural health monitoring of other materials, less attention has been paid to data-driven methods and machine learning applied to AE monitoring of wood and timber. In addition, most studies have focused on extracting simple time-domain features, whereas there is a gap in using sophisticated signal processing and feature engineering techniques. Future research should explore the sensor fusion for monitoring full-scale timber buildings and structures and focus on applying AE to large-size structures containing defects. Moreover, the effectiveness of AE methods used for wood composites and mass timber structures should be further studied.
|
|
| 8. |
- Addassi, Mouadh, et al.
(författare)
-
Reactive mass transport in concrete including for gaseous constituents using a two-phase moisture transport approach
- 2020
-
Ingår i: Construction and Building Materials. - : Elsevier. - 0950-0618 .- 1879-0526. ; 232, s. 1-14
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents the further development of a tool for multi-phase reactive mass transport modelingfor durability estimation of cement-based materials, by the addition of the gas phase, adopting a trulyseparate two-phase moisture transport approach. The governing system of equations are based on phys-ically sound hybrid mixture based version of the Poisson-Nernst-Planck system of equations includinggaseous transport in the air-filled space, ionic transport in the liquid phase, electro-migration of ionicspecies, a two-phase moisture transport model, and sorption. The addition of the gas phase and thetwo-phase moisture description enables the user of the model to investigate individual and combinedeffects of different degradation processes in unsaturated systems. The altering of hydrated cement underthree different environments were studied representing an accelerated carbonation environment, a sub-merged marine environment and a cyclic drying-wetting zone in a marine environment, to illustratesome of the model’s capabilities.
|
|
| 9. |
- Al-Ayish, Nadia, et al.
(författare)
-
The influence of supplementary cementitious materials on climate impact of concrete bridges exposed to chlorides
- 2018
-
Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 188, s. 391-398
-
Tidskriftsartikel (refereegranskat)abstract
- In order to reach a specific service life of reinforced concrete structures a certain cover thickness is needed. At present, this is regulated by national standards that also limit the amount and type of supplementary cementitious materials in different exposure environments. The regulations do not, however, consider the actual durability performance of concrete with supplementary cementitious materials. As a consequence, the LCA results might be misleading. This paper shows the environmental impact of concrete with supplementary cementitious materials in chloride environment considering their specific performances. Prescriptive and performance based service life prediction models for chloride ingress are applied and compared.
|
|
| 10. |
- Alhede, Andreas, 1996, et al.
(författare)
-
A two-stage study of steel corrosion and internal cracking revealed by multimodal tomography
- 2023
-
Ingår i: Construction and Building Materials. - 0950-0618. ; 394
-
Tidskriftsartikel (refereegranskat)abstract
- Modeling of corrosion-induced cracking is limited by lacking knowledge on the behavior of corrosion products. In this work, the corrosion and cracking processes were experimentally investigated in 3D at two different stages. The processes were measured at micro-structural scale, applying nondestructive neutron and X-ray computed tomography in two scans at different stages in the corrosion process. A method to evaluate the average volumetric strain of the compressed corrosion layer was proposed and displacements in the concrete matrix were measured. Strain localization revealed cracks not directly visible in the images. Multimodal tomography demonstrated to be an effective method for investigating steel corrosion in reinforced concrete.
|
|
