Proceedings of the Symposium on Concrete Modelling, CONMOD2018

CONMOD2018 is a symposium on Concrete Modelling which is jointly organised by Delft University and Ghent University as part of the RILEM week 2018 in Delft, The Netherlands. The symposium is the 5th in a series dealing with all aspects concerning modelling of concrete at various scales. The symposium consist of 3 key-note papers and 62 regular papers presented over 3 days. Parallel to the CONMOD2018 symposium a conference on Service Life Design (SLD4) and a workshop honouring Professor Klaas van Breugel were organised with topics that are related to concrete modelling. In total more than 350 participants took part in the events organised during the RILEM week 2018

Proceedings of the 4th International Conference on Service Life Design for Infrastructure (SLD4)

SLD4 is a conference on Service Life Design for Infrastructures which is jointly organised by Delft University and Tongji University as part of the RILEM week 2018 in Delft, The Netherlands. The conference builds on the success of the previous three events on this topic held in Shanghai (2006), Delft (2010) and Zhuhai (2014). Service Life Design for Infrastructure is a very broad topic involving aspects starting from the material properties and behaviour, via structural performance, serviceability and durability to integral design and asset management. All related topics from experimental research to modelling and from codes and standards to applications are welcomed to the conference. The conference consist of 3 key-note papers and 132 regular papers presented over 3 days. Parallel to the SLD4 Conference a symposium on Concrete Modelling (CONMOD2018) and a workshop honouring Professor Klaas van Breugel were organised with topics that are related to Service Life Design. In total more than 350 participants took part in the events organised during the RILEM week 2018

Traffic-induced vibrations of frame structures

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

Modelling strategies for the study of crack sefl-sealing in mortar with superabsorbent polymers

In this work, a numerical model is presented to predict the self-sealing effect provided by superabsorbent polymers (SAP) admixtures in mortar. Firstly, the use of a law of absorption kinetics for SAP embedded in a cementitious matrix was validated with experimental results available in literature. Secondly, two extreme strategies are considered for the swelling of SAP in the crack regarding the variation in its deformation capacity under constraint. The results show the appropriateness of the SAP absorption law and explain the mechanisms of water absorption of mortar with such admixtures. Furthermore, the influence of the deformation capacity of SAP on the water penetration in cracks is studied parametrically

Impact of chemically treated waste rubber tire aggregates on mechanical, durability and thermal properties of concrete

CITATION: Khern, Y. C. et al. 2020. Impact of chemically treated waste rubber tire aggregates on mechanical, durability and thermal properties of concrete. Frontiers in Materials, 7:90, doi:10.3389/fmats.2020.00090.The original publication is available at https://www.frontiersin.orgStudies have shown that the incorporation of waste tire rubber aggregates reduces the strength, increases permeability and decrease thermal conductivity of concrete. However, only a few studies have investigated the effect of surface-modified rubber aggregates on the properties of concrete. This study investigates the effect of the surface treatment of waste tire rubber as coarse aggregates with different oxidizing solutions and different treatment durations on the mechanical, durability and thermal properties of concrete. The properties of concrete incorporated with 8% rubber coarse aggregates (by volume of natural aggregates) which were treated with three different solutions: water (H2O), 20% sodium hydroxide (NaOH) and 5% calcium hypochlorite [Ca(ClO)2] (both as% weight of water) for durations of 2, 24, and 72 h, respectively. The effect of these treatments on the compressive strength, splitting tensile strength, water permeability, thermal conductivity and diffusivity of concrete was investigated. Results show that Ca(ClO)2 has a more positive effect on the strength and permeability compared to NaOH solution and water. Experimental results were statistically analyzed using ANOVA and Post Hoc tests. The analyses showed that the improvement of concrete strength is only significant when the treatment with NaOH and Ca(ClO)2 is prolonged to 72 h. Furthermore, the microstructural analysis of concrete showed that the improvement in the strength is due to the improved bonding between cement paste and rubber aggregates as a result of surface treatment. This microstructural improvement also resulted in lower water permeability of concrete. However, the thermal conductivity and diffusivity increased when the surface treatment duration increases as there are less air voids in the samples. This study shows that, with appropriate pretreatment, a certain percentage of natural aggregates can be safely replaced with waste tire rubber aggregates while maintaining sufficient quality of the resulting concrete.Publisher's versio

Impact of surface roughness on the debonding mechanism in concrete repairs

Surface roughness of the existing concrete substrate was considered to have the greatest impact on the bond strength in repair systems. However, the influence of this parameter has been subject for debates in recent years. The effect of concrete surface roughness is not quite clear, nor there exist a clear relation between the surface roughness and the adhesion in multilayer systems. In order to understand and explain this relation, simple numerical experimentation is used. Repair systems with different roughness parameters are simulated in order to get load displacement diagrams and crack debonding propagation. The influence of roughness on the composite response in simulated direct tension, shear and three point bending test using a lattice model, is studied. Results indicate that roughness has different influence on tensile and shear bond strength. In addition, although it seems to have negligible influence on load bearing capacity of the composite system in bending, it enables more monolithic response and slower debonding propagation