This CD consists of 14 papers presented at the ACI Fall Convention, Toronto, Canada, October 2012, and sponsored by ACI Committees 130, Sustainability of Concrete; 213, Lightweight Aggregate and Concrete; and 231, Concrete Properties at Early Ages.These papers cover the following general topics: impact on sustainability, mixture proportioning, internal curing methods and their implementation, hydration impacts, volume change effects, mechanical properties, cracking tendency, durability aspects, life-cycle cost analysis, and case studies that document the use of internal curing in full-scale production applications. 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-290

In this research, ten different high performance concrete (HPC) mixtures internally cured by pre-wetted lightweight fine aggregate (LWFA) and/or shrinkage reducing admixture (SRA) were cast and their drying shrinkage strain was monitored using the ASTM C157 test. The data collected was used to evaluate six shrinkage prediction models, namely, ACI 209 model, CEB90 model, AASHTO model, B3 model, GL2000 model and ALSN model. The study finds that the GL2000 model shows the best overall performance in predicting shrinkage strain for internally cured HPC. However, more accurate long-term shrinkage prediction can be achieved based on the current ACI 209 model with experimental measurements. This proposed procedure is capable to predict long-term drying shrinkage for concrete using local materials mixture by using short-term experimental measurements.

Over the last fifteen years there has been growing interest in using internally cured concrete. While the original intention of using internal curing was to reduce autogenous shrinkage, it has been observed that the internally cured concretes have additional benefits. For example, previous research has shown that internally cured concrete has lower water absorption than comparable conventional (plain) concrete mixtures. This paper presents results of chloride transport experiments performed using a conventional (plain) concrete mixture and an internally cured concrete mixture. Chloride transport performance was evaluated using a series of experimental techniques including: 1) resistivity, 2) rapid chloride penetration (RCP), 3) rapid chloride migration (the Nord Test), 4) migration cell testing (STADIUM cells) and 5) chloride ponding and profiling. The results indicate that internally cured concretes have similar or superior performance to plain concrete. Several testing artifacts are noted associated with the pre-wetted lightweight aggregate that overestimate the transport measures for the internally cured concrete. The experimental results suggest that by reducing the chloride transport rate the use of internally cured concrete can result in structures with improved durability (due to the time it takes chloride ions to cause corrosion at the reinforcing steel).

Internal curing by means of superabsorbent polymers (SAP) is an efficient method for providing additional curing water in high performance concrete with low w/c. In order to fully use the potential of internal curing reservoirs, the water needs to be supplied possibly uniformly in the whole volume of hydrating cement paste and moreover at rates sufficiently high to compensate for the self-desiccation. At the same time, it is of importance to predict how the internal curing process will influence the overall material behavior at the macroscopic level. In this work, the investigation of the aforementioned phenomena is performed at two scales using poromechanical modeling. First, a mechanistic model of cementitious material is applied for the analysis of internal curing at the meso-level to describe water transport from the reservoirs to the surrounding cement paste. The meso-level simulations confirm that curing water can be practically uniformly and instantaneously distributed within the volume of the surrounding paste at the early stages of hydration. Second, based on this information, a source term due to internal curing is introduced at the macro-level, enabling description of the influence of the SAP on such phenomena as self-desiccation and autogenous shrinkage. This approach provides a very good agreement with the experimental data.

This paper reports results from a series of experiments performed in an ongoing FHWA research program that is investigating the potential for using more fly ash in transportation structures. The paper focuses on test results from five mortar mixtures: a water-to-cement ratio (w/c) of 0.30 and water-to-cementitious materials ratio (w/cm) of 0.30 with 40% and 60% fly ash by volume with and without internal curing. A reduction in early age autogenous shrinkage is observed for HVFA mixtures. While initial autogenous shrinkage is reduced in HVFA mixtures, they are more prone to higher rates of shrinkage and cracking at later ages (after seven days). This can be related to pore size distribution as well as continued effects of hydration and the pozzolanic reaction. Chemical shrinkage and isothermal calorimeter results are shown to describe the rate of fly ash reaction at early ages. Internal curing can reduce the propensity for cracking.