A new semi-empirical concrete shrinkage and creep model, called the CPRH Model, is proposed and calibrated. The new model proposes a coupling between autogenous and drying shrinkage using a volume-average pore relative humidity and treats drying creep as an additional stress-dependent shrinkage, linking together all these phenomena. The proposed expressions are designed to facilitate traditional integral-type analysis, but also uniquely support rate-type calculations that can be leveraged by analysis software. Model calibration uses the Northwestern University (NU) database of creep and shrinkage tests to determine new model parameters. The proposed model uses minimal inputs that are often known or may be assumed by the design engineer. Comparison of the proposed model to historical time-dependent models indicates that the new model provides a superior fit over a wider range of inputs.

Most concrete service life models are designed for uncracked conditions and the effect of microcracks on such models has not been as well researched. A service life model for concrete structures that takes into account microcracking is presented A unique feature of this model is that its input parameters can be determined using only non-destructive methods, thus allowing it to be used when samples for lab tests cannot be extracted, e.g. in-service or critical infrastructure. The model was developed for low-water to cement concrete mixtures and validated on full-scale prestressed concrete girders. The results showed that the presence of a large number of microcracks could cause a loss in the remaining service life of concrete structures, even if individual microcracks did not cause a significant impact.

In this paper, the applicability of the modified A&A particle packing model for designing pumpable flowing concretes, according to ACI 211.9R-18, is analyzed. An experimental investigation is undertaken to evaluate consistency, compressive strength, and shrinkage of flowing concretes designed with this model. The results show that the modified A&A model optimizes the particle size distribution of concrete ingredients and produces pumpable concretes according to ACI 211.9R-18. The distribution modulus of the model controls the combined grading, the ratio of coarse-to-fine aggregate, and the percentage of fine aggregate passing 300 µm and 150 µm. At a distribution modulus of 0.35, the model serves as the ACI’s recommended boundary limit for ideal-for-pumping combined grading. A high distribution modulus results in a high coarse-to-fine aggregate ratio and lowers the drying shrinkage of concrete. This insight enables a straightforward mix design methodology that results in concrete that meets ACI 211.9R-18 recommendations.

Concrete mixture design is the foundation of cement and concrete research. Innovations in concrete materials could, should, and would inevitably be incorporated into new mixture designs. Thus, a rigorous method for concrete mixture design can better bridge the research community and the construction industry with high reliability and high fidelity. However, current methods for concrete mixture design vary a lot in the literature, thus compromising the accuracy and consistency in interpreting the properties of concrete subject to changes in its raw ingredients. Moreover, the extraneous variables in controlled experiments are not always controlled well. To solve this old but critical problem, this paper summarizes the prevalent concrete mixture design methods in the literature and in practice. By contrast, the volume-based mixture design method is superior to the mass ratio-based mixture design method in terms of simplicity, accuracy, and consistency. Further discussion on packing density measurement and water or slurry film thickness (SFT) as a basis of volume-based mixture design is elaborated. Mathematically, the hardened properties were linked to the particle packing behavior and fresh properties of concrete. This research contributes to a unified volume-based design method to bridge the research community and the construction industry. In the end, it is conducive to upgrading from concrete technology to science.

The use of performance-based specifications (PBS) may increase quality and sustainability while lowering project costs through innovations in concrete materials selection and proportioning. A preliminary survey was conducted showing that barriers to implementation for PBS still exist, the main barrier being the enforcement of the specification, followed by cost and time. This study aims to develop guidelines to overcome the identified barriers by presenting a laboratory-scale case study of six concrete mixtures that both conform (one) and do not conform (five) to Georgia Department of Transportation specifications. This case study includes experimental results of mechanical (flexural and compressive strength) and resistivity performance properties, as well as three additional parameters: time, cost, and carbon dioxide (CO2) emissions associated with each mixture design. This study showed that innovation in material use and mixture design can increase durability and performance while reducing the overall project cost and environmental impact.