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International Concrete Abstracts Portal

Showing 1-5 of 11 Abstracts search results

Document: 

SP266-01

Date: 

October 1, 2009

Author(s):

J.M. Ruiz, S.I. Garber, Q. Xu, J.C. Dick, G.K. Chang, and R.O. Rasmussen

Publication:

Symposium Papers

Volume:

266

Abstract:

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.

DOI:

10.14359/51663268


Document: 

SP266-10

Date: 

October 1, 2009

Author(s):

K. Sobolev and A. Amirjanov

Publication:

Symposium Papers

Volume:

266

Abstract:

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.

DOI:

10.14359/51663277


Document: 

SP266-03

Date: 

October 1, 2009

Author(s):

J.W. Bullard, P.E. Stutzman, L.M. Ordoñez Belloc, E.J. Garboczi, and D.P. Bentz

Publication:

Symposium Papers

Volume:

266

Abstract:

The NIST-Industry Virtual Cement and Concrete Testing Laboratory (VCCTL) Consortium has developed an integrated software package for performing simulations of a number of engineering test measurements, including isothermal calorimetry, adiabatic temperature change, chemical shrinkage, elastic moduli, and compressive strength. In the last two years, the software interface has been redesigned to be easier to navigate, with online tutorials and documentation for easy reference. As a result, VCCTL is now ready to be integrated in industrial settings as a supplemental tool to accelerate research on mix designs and to streamline routine quality testing procedures. This paper will demonstrate the software interface, and two applications will be described to illustrate the utility of the software to help solve practical problems. In the first application, we address sustainability issues by investigating the replacement of coarse clinker particles with limestone and its effect on elastic moduli and compressive strength. In the second application, we illustrate VCCTL’s potential for screening the quality of incoming cement clinkers by providing rapid estimates of compressive strength development in mortar specimens.

DOI:

10.14359/51663270


Document: 

SP266

Date: 

October 1, 2009

Author(s):

Editor: Jussara Tanesi / Sponsored by: ACI Committee 118 and ACI Committee 236

Publication:

Symposium Papers

Volume:

266

Abstract:

This CD-ROM consists of ten papers that were presented by ACI Committees 236 and 188, at the ACI Fall 2009 Convention in New Orleans, LA, in November 2009. The papers cover durability models, early age models, virtual testing and mechanical behavior models. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-266

DOI:

10.14359/51663325


Document: 

SP266-02

Date: 

October 1, 2009

Author(s):

D.P. Bentz, E.J. Garboczi, N.S. Martys, K.A. Snyder, W.S. Guthrie, K. Kyritsis, and N. Neithalath

Publication:

Symposium Papers

Volume:

266

Abstract:

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.

DOI:

10.14359/51663269


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