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

High performance concrete (HPC) mixtures may be prone to early-age cracking. While uncracked HPC can protect steel reinforcement from corrosion reasonably well, cracking can dramatically accelerate the corrosion of reinforcement and reduce the service-life of structures. Several approaches have been developed to reduce the risk of cracking. One of these approaches is internal curing (IC) which uses prewetted lightweight aggregate. This paper describes a series of experiments performed using full-scale restrained concrete elements in an effort to quantify the performance of internally cured concrete on reducing the early-age shrinkage cracking thereby increasing the resistance to corrosion. The results show that concrete made using internal curing experienced a slight swelling at early-ages and experienced very little shrinkage. As a result the IC concrete did not crack while the conventional concrete cracked. Upon exposure to a chloride solution, extensive and nearly immediate corrosion activity was detected in the plain specimen while the internally-cured concrete did not exhibit any cracking or signs of corrosion during the time of this study (approximately 1 year). The benefits of internal curing are reduced cracking as well as reduced transport properties.

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.

Constructing large capacity, monolithically placed water storage tank slabs is a complex proposition. Previously, specifying low-shrinkage concrete mixes and monolithic placement of the slab within a specified time period was the prescribed method, yet shrinkage cracking still occurred. We felt more could be done to improve concrete placing and finishing, reducing shrinkage cracking and enhance durability. An investigation on the use of an Internally Cured Concrete mix on the floor and roof slabs of the Denver Water 10-Million Gallon [MG] (38-Million Liter [ML]) Lone Tree Tank No. 2 that Bates Engineering Inc. was designing was pursued. The tank floor and roof slab are each about 61,000 ft2 (5,700 m2) and would be monolithically placed. Laboratory trial batches performed determined plastic and hardened characteristics of the ICC as compared to traditionally proportioned mix designs. Tests performed in the laboratory included: compressive strength and drying shrinkage (ASTM C 157(1), modified 7-day saturation). An ICC mix was selected based on durability expectations. Results of the floor slab placement were successful and only two shrinkage cracks were observed, 7-day and 28-day compressive strength tests, workability and consistency surpassed expectations. As a result, it was decided to use ICC concrete on the remaining structural components.

In an effort to improve the durability and the life cycle of infrastructure concrete, new advances have been made. These improvements have included the development of High Performance Concrete (HPC). HPC has utilized lower water cementitious ratios and supplementary cementitious materials (SCMs) in an effort to improve the durability of these structures. Unfortunately the use of SCMs and low water cementitious ratios have led to others problems including shrinkage cracking and cement that is not fully hydrated. To help improve these characteristics a supply of additional curing water is needed throughout the cement matrix. Water supplied from saturated pores of expanded shale, clay, and slate lightweight aggregates has shown promise in several research projects. New York State has developed a program to examine the benefits of internal curing and has utilized the technology on several bridges throughout the state. This paper will discuss the performance and construction of several of these bridges.