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

Highway bridges and parking structures, subject to coupled effects of mechanical loads and corrosion, often show early signs of distress such as concrete cracking and rebar corrosion leading to reduced structural performance and shortened service life. One solution to this problem is to use low-shrinkage low-permeability high-performance concrete (HPC) for bridge decks exposed to de-icing salts and severe loading conditions. A new HPC was formulated to achieve low shrinkage and low permeability, high early-strength, and 28-day compressive strength over 60 MPa (8,700 psi). Its mechanical performance and durability were tested both in the lab and field under severe test conditions, including restrained shrinkage, cycling loading, freezing and thawing cycles, and application of de-icing salts. Models were developed and calibrated to predict structural performance and service life of concrete bridge decks under severe exposure conditions. Prediction models indicate that bridge decks designed with low-shrinkage HPC can achieve a service life up to 100 years. Compared to normal concrete decks, short-t t-to-medium span bridge decks using low-shrinkage HPC could be built at a comparable initial construction cost, but at less than 35% of the life-cycle cost.

First noticed by T. C. Powers, et al in 1948, [22] as beneficial for hydration by supplying water internally, specifiers and contractors in 2012 have grasped how the process of internal curing is implemented, how hydration behaves, and how improvements in mechanical properties, durability, and cost may be beneficial. To meet the time-dependent hydration needs of the concrete, having sufficient water internally available, when, as, and where needed, is vital for achieving optimum characteristic qualities. There is lower life cycle cost with internal curing (IC) and frequently lower first cost. In 2012, the number of projects using internal curing is increasing at an escalating rate, because the process is simple and economically implemented. Pavements, bridges, buildings, and pervious parking lots are being started now in this recession, because specifiers and contractors are saving dollars, as they build longer lasting structures while costs and interest rates are low. Developed initially to reduce autogenous shrinkage in low water-cement ratio and high performance concretes, internal curing has been found to reduce drying shrinkage. Other benefits found include reduced permeability, increased compressive and flexural strengths, less warping, stronger interfacial transition zones, greater durability, and lower carbonation.

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.