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ACI 318, “Structural Concrete Building Code,” has been completely reorganized for the 2014 edition. While the technical provisions of most of the code have been unchanged, changes have been made in the provisions dealing with responsibility, durability, and construction. The responsibility for use of the code has been assigned to the licensed design professional (LDP.) Minor changes have been made to the durability provisions to clarify the intent of the code and to help the LDP select exposure classes. The most significant changes in ACI 318-2014 are in a new chapter that addresses construction requirements. Previously, construction provisions were located throughout the code. The new code is based upon the premise that the contractor should not have to search the code for construction requirements. Instead, all such requirements must be in the construction documents that are a part of the contract between the owner and the contractor. The new chapter makes the LDP responsible for writing the applicable design information and compliance requirements into the construction documents.

Materials for grouting post-tensioning tendons of a bridge at below freezing temperature (–10oC or 14oF) were studied. The water/cementitious material ratio was a maximum of 0.32 and the grout properties were tested at -10oC (14oF) according to applicable Chinese standards for past-tensioning grouts. After special treatment, the efflux times of the modified grouts were between 14 and 22 seconds after mixing and less than 30 seconds after 60 minutes without agitation. The final strength of the grout reached 50-60 MPa (7975-8700 psi) after 35 days of curing (7 days at below freezing temperature and 28 days at a standard temperature), which was 95%-100% of the reference strength for curing at a standard temperature.

The focus of this paper is a new liquid microspheres-based admixture that has been developed to provide freezing and thawing protection of cementitious-based materials under cyclic, saturated conditions, while addressing and eliminating issues typically associated with the use of surfactant-based admixtures for air entrainment. Consequently, this microspheres-based admixture provides unique opportunities and flexibility in reproportioning or optimizing current air-entrained concrete mixtures with respect to using increased levels of supplementary cementitious materials. It is also shown in the paper that the microspheres-based admixture will facilitate the use of materials that typically hinder air entrainment. A microspheres recovery test method that has been developed to measure the microspheres content of fresh content for quality assurance purposes is also presented and discussed.

For concrete in severe environments, measurement of its resistance to fluid ingress is fundamental to evaluating its potential durability. As a rapid index of concrete’s resistance to fluid penetration there is interest in standardization of a bulk electrical resistivity test. In this study, tests were conducted on a range of concrete mixtures using a bulk resistivity test as well as the ASTM C1202 coulomb test and the Nordtest NT492 rapid migration test. With the objective of development of a performance-based standard for bulk resistivity, rather than specifying the details of the equipment to be used, a verification cell using precision resistors was used to determine the accuracy of results obtained using three different commercially available resistivity test devices. In addition, the influence of conductive coupling gels or water on the resistivity values were evaluated. The results from the verification cell tests demonstrate that all three commercially available test devices are accurate within 4.5% at low resistivity levels (39 ohm-m) and within 1.0% at higher resistivity levels (390 ohm-m). As well, use of water soaked sponges to couple the concrete to the electrodes gave essentially the same results as when a conductive gel was used. For the concretes tested, exponential relationships were obtained between bulk resistivity and either ASTM C1202 coulomb results (r2 = 0.992) or Nordtest NT492 migration results (r2 = 0.86).

The durability and dimensional stability of concrete containing zinc slag as sand is reported in this paper. Concrete mixtures at different water-cement-ratios were prepared by replacing equivalent volume of sand up to 70% by ISF (Imperial Smelting Furnace) slag. The mechanical properties, leaching of toxic metals, durability parameters, and dimensional stability of SRM (Sand Replaced Mixtures) were examined in comparison with CM (Control Mixture). The results showed equivalent to CM strength at all replacement levels; leaching of toxic metals within acceptable limits; abrasion resistance comparable to CM for up to 60% SRM; permeability comparable to CM in most of SRM samples; lower than CM initial shrinkage; carbonation resistance better than CM; chloride diffusion resistivity comparable or better than CM; and, steel corrosion resistance better than CM. Overall, the experimental results ensured the suitability of ISF slag as sand in the production of durable and sustainable concrete with overall very good performance.