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.

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.

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.

The primary purpose of this paper is to introduce and demonstrate the applicability of a statistical concept, the average, for the modeling of the deformations of two-phase composites under load. Concrete is modeled as a well-compacted two-phase composite, the hardened paste as the matrix, and the aggregate as the dispersed phase. Only the paste has creep. The demonstration is done by the development of novel viscoelastic models and their mathematical equivalents for the instantaneous as well as time-dependent deformations of concrete, as a two-phase composite, under load. The underlying principle of the work is based on an extension of earlier publications by the writer in which averages of the averages of the related the phases, the composite averages are offered for the estimation of the modulus of elasticity of composites. Since experimental results supported the composite average method, CAM, quite well for this, it seemed worthwhile to investigate whether the method can be extended for the calculation of time-dependent deformations. The extension consists of the addition of dashboard elements to the existing composite average spring models for the modulus of elasticity of concrete, for the estimation of creep. This is the combinations of two existing spring-dash models for the calculation of the creep: the Poyinting-Thomson model with the Maxwell model the results of which are two CAMs that are determined by the type of combination between these two: one for normal-weight concretes when the two models are connected in a series, and the other, when they are in parallel for lightweight-aggregate concretes. Experimental data on creep with uniaxial loading taken from the literature support these composite models well. Among others, the data and the models show that during the period when the creep development is gradually decelerating: 1. creep values as a function of loading time, give straight lines, let us call them creep lines (compliance functions) in semi-log system as well as in log-log system of coordinates. Consequently, they can be approximated both by logarithmic as well as power functions. Such formulas are suitable for the estimation of creep at a later time from an earlier measurement; and 2. various creep lines of comparable concretes may be parallel, regardless at what age t' the loading started. It is shown that the new models are: well supported by experimental results within reasonable time limits; they are conceptually simple and logical; they are novel; they can consider the composition of the concrete; they represent both E and creep; and they are valid both normal-weight and lightweight-aggregate concretes.

Stresses develop in portland cement concrete pavement at early ages when volume changes associated with hydration reactions, moisture loss, and temperature variations are restrained. Saw-cuts are placed in concrete pavements to provide a weakened plane that enables cracks to form as intended, thereby relieving developed residual stresses. Although the idea of creating a weakened plane by saw-cutting is relatively straight forward, practically determining the timing and depth of saw-cut can be complicated in field construction. This study uses a finite element model (FEMMASSE) to evaluate influence of saw-cut timing on cracking behavior of concrete pavements. The model considers the influence of ambient temperature, cooling effect of wind, and time of casting. It is shown that the saw-cutting time window was reduced as ambient temperature was increased. Higher wind speeds influence the saw-cutting time window to a lesser degree at high ambient temperatures than they do at lower ambient temperatures. It was also shown that the time of casting influences the saw-cutting time window and it needs to be considered in estimating the saw-cutting time window especially at high ambient temperatures.