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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 11 Abstracts search results
October 1, 2009
J.M. Ruiz, S.I. Garber, Q. Xu, J.C. Dick,
G.K. Chang, and R.O. Rasmussen
This paper describes the enhancements made to the FHWA’s HIPERPAV software program for simulating early-age concrete pavement behavior. It gives a brief background describing the software, discusses the modeling improvements that have been made, and suggests future work for additional improvements. An enhanced moisture transport model has been developed and incorporated into the HIPERPAV software, and results show that the moisture distribution and associated stress/strength developments are significantly affected by the model parameters, environmental, and construction conditions. New inputs were included in the software to define the experimentally determined hydration curve parameters to improve predictions of degree of hydration and portland cement concrete (PCC) temperature development. A batch mode was added for analysis of multiple strategies at once, and a comparison module was created that allow users to compare simulation results from multiple strategies and run sensitivity analysis for multiple variables.
D.P. Bentz, E.J. Garboczi, N.S. Martys, K.A. Snyder, W.S. Guthrie, K. Kyritsis, and N. Neithalath
The transport properties of concrete are critical to its field performance. Commonly encountered degradation mechanisms are dependent on ionic diffusivity, sorptivity, and permeability. In this paper, virtual testing of two of these concrete transport properties, diffusivity and permeability, will be reviewed. Virtual evaluations of ionic diffusion (and equivalently conductivity) will be presented as one example that spans the full range of applications, from computations on cement paste with micrometer resolution to a virtual rapid chloride permeability test (RCPT) that simulates the standard ASTM test method for conductivity of concrete cylinders. At the concrete scale, a hard core/soft shell (HCSS) microstructural model may be employed to estimate diffusion coefficients, while finite difference solutions of Fick’s laws that incorporate sorption/reaction may be employed to evaluate remediation strategies for real world bridge decks. Virtual evaluations of permeability are dependent on a sufficient resolution of the pore sizes that are critical for flow under pressure. Two recent successful evaluations will be presented in this paper: the permeability of cement pastes (hydroceramics) cured at elevated temperatures, where transport is controlled by micrometer-sized pores, and the permeability of pervious concrete that is dominated by its coarse porosity (scale of mm). Many of the presented computational (virtual) tools are freely available over the Internet, either for direct access (remote computation) or for downloading.
K. Sobolev and A. Amirjanov
A simulation algorithm was developed for modeling the dense packing of large assemblies of particulate materials (in the order of millions). These assemblies represent the real aggregate systems of portland cement concrete. Two variations of the algorithm are proposed: Sequential Packing Model and Particles Suspension Model. A developed multi-cell packing procedure as well as fine adjustment of the algorithm’s parameters were useful to optimize the computational resources (i.e., to realize the trade-off between the memory and packing time). Some options to speed up the algorithm and to pack very large volumes of spherical entities (up to 10 millions) are discussed. The described procedure resulted in a quick method for packing of large assemblies of particulate materials.
The influence of model variables on the degree of packing and the corresponding distribution of particles was analyzed. Based on the simulation results, different particle size distributions of particulate materials are correlated to their packing degree. The developed algorithm generates and visualizes dense packings corresponding to concrete aggregates. These packings show a good agreement with the standard requirements and available research data. The results of the research can be applied to the optimal proportioning of concrete mixtures.
M. Pour-Ghaz, F. Rajabipour, J. Couch, and J. Weiss
The long-term durability of concrete is related to its ability to impede or reduce fluid transport. The long-term durability performance of concrete pavement can be dramatically influenced by the ingress of water or other fluids at saw-cut joints. Research is needed to better understand the role of complex geometries, like saw-cuts, on fluid transport. This paper uses x-ray attenuation to study the unsaturated fluid transport in systems containing a saw-cut (notch). The rate of water transport is greater in the direction perpendicular (i.e., horizontal) to the wall of the saw-cut when compared to the penetration below the tip of the saw-cut. This can be explained by the geometry of the source. To study the influence of fluid properties on transport, two fluids were tested with dramatically different viscosities and surface tensions. The results indicate that for the solution with higher viscosity and lower surface tension the absorption rate is reduced significantly. A finite element based code (Hydrus) is used to simulate the unsaturated flow based on solution of Richard’s equation. Results of simulations show good agreement with experimental results and confirm the effects of the geometry of the saw-cut on fluid transport.
E. Grimal, A. Sellier, S. Multon, E. Bourdarot
The alkali aggregate reaction (AAR) is affecting numerous civil engineering structures and is responsible for unrecoverable expansion and cracking which can affect their functional capacity. In order to control the safety level and the maintenance cost of its hydraulic dams, Electricité de France (EDF) has to get a better understanding and a better prediction of the expansion phenomena. In this context, EDF is developing a numerical modelling based on the finite element method in order to assess the mechanical behavior of degraded structures. Obtaining a good prediction of expansive phenomena requires the identification and realistic modelling of the underlying physical, chemical and mechanical phenomena. The model takes into account the mechanical damage, the creep of concrete and the stress induced by the formation of AAR gel. Coupling between the different phenomena (creep, AAR and anisotropic damage) are taken into account through a rheological modelling. First , experimental results obtained on concrete cylinders and beams affected by AAR are simulated to verify whether the model can describe the behavior of degraded structures.
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