In mountainous areas where the falling rocky blocks constitute a major hazard, the protection systems of roads are usually rock sheds composed of over dime nsioned reinforced concrete elements. This is mainly due to the lack of knowledge of the dynamic effects caused by these falling rocks. A thick backfilling layer that prevents the direct impact of falling rocks by constituting a damping medium commonly covers the roof slab of protection structures. This allows the design of the slab with static dead loads. Recent experiments were performed on a new type of protection system characterized by a roof slab without damping medium and simply supported by a set of "fuse" steel supports. The roof slab resists directly the falling rocks impacts, which cause limited local damage to the impact zone or the yielding of steel supports. The main advantage of this protection system is to allow continuous uses of the structure trough the repair of the damaged zones in the roof slab or the replacement of the "fuse" support after each impact. The aim of the present study is to predict the structural response of the proposed system by a rigorous three-dimensional modeling of the roof slab and its supporting elements. The analysis introduces the impact load in a way similar to that of the performed experiment, and a realistic representation of the concrete behavior under dynamic loads and its corresponding damages. The comparison of the experimental measurements with those obtained from the present analysis proves the accuracy of the built model in predicting the real behavior of the protection structure.

A low-cost method for galvanic cathodic protection of reinforcing steel in concrete was examined. In this method, arc-sprayed zinc is deposited on the external concrete surface of steel-reinforced marine substructure bridge components, which are normally subject to corrosion of the reinforcement as a result of chloride ion contamination of the concrete. The concrete cover of corrosion-damaged substructure components is removed, exposing the reinforcing steel. After sandblasting, the zinc is arc-sprayed over the exposed steel and surrounding concrete, creating a 1/2 mm thick galvanic anode which is in electronic contact with the steel and in electrolytic contact with the water in the concrete pores. In this investigation, the ability of the system to deliver protective current was examined by experiments in the laboratory and at field installations at bridges in the Florida Keys. The field tests showed that the anodes retained physical integrity over at least 4 1/2 years in a subtropical environment. Typical current densities were 0.5 mA/ft 2 (0.54 9A/cm 2) on structures containing corroding epoxy-coated reinforcing steel, and 1 mA/ft 2 (1.1 _A/cm 2) on a plain rebar structure. Steel polarization decay tests with field rebar probes showed that 100 mV polarization decay was routinely achieved. The laboratory tests revealed that in the marine substructure conditions of interest, concrete resistivity does not represent a main limiting factor in the performance of the galvanic anodes. However, absence of direct wetting of the anode surface can result in long-term loss of adequate current delivery, even when the concrete is in contact with air of 85% relative humidity. The results indicate that periodic water contact (as encountered in the splash-evaporation zone of marine bridge substructures) is necessary for long-term anode performance. The method can be viewed as a competitive alternative to impressed-current cathodic protection systems, and also as a considerable improvement over simple gunite repair of corrosion-damaged substructure concrete.

This report describes part of the work associated with Texas Department of Transportation Project 0-4069 (?Mitigation Techniques for In-Service Structures with Premature Concrete Deterioration?). The Texas Department of Transportation is interested in developing techniques for mitigating or remediating premature concrete deterioration due to alkali silica reaction (ASR), delayed ettringite formation (DEF), or both, in order to extend the life of potentially affected structures. The parts of Project 0-4069 reported here consist of: a literature search for mitigation or remediation techniques; fabrication of concrete specimens intentionally susceptible to premature deterioration; and the application and monitoring of the mitigation techniques using laboratory testing and acoustic emission (AE) procedures. Specimens were exposed to three series of environmental conditions: an indoor series; an outdoor series; and a wet/dry series. Expansion and internal relative humidity were measured to determine the efficacy of the mitigation techniques at reducing expansion from premature concrete deterioration. Based on the test results, recommendations are made for choosing mitigation treatments now, and for additional research.

Many steel-reinforced concrete bridges in the United States are subject to corrosion from chloride ions. This corrosion is a more significant problem in chloride-rich coastal areas and in northern states with heavier snowfall, where roads are kept free of snow and ice with the use of chloride salts. Many concrete bridges in these areas become contaminated with chlorides, which in turn begin to corrode the reinforcing steel. The corrosion affects bridge components, including the deck, abutments, beams, cross-beams, diaphragms, piers, and piles. Applying a sealer to the concrete can be an effective and initially inexpensive method of tackling this corrosion problem, thus increasing the service life of a reinforced concrete structure. However, not all sealers have an equal service life; some will require more maintenance costs and more frequent reapplications. To determine how long various sealers extend the service life of bridges affected by chloride corrosion, Jerzy emajtis and Richard E. Weyers examined generic sealer types typically applied to steel reinforced concrete bridges in the U.S. They concluded the service life of a sealer is affected by various factors, including environmental conditions, traffic wear, penetration depth, ultraviolet (sun) light, and exposure type (horizontal or vertical). Results of their investigation were reported in "Concrete Bridge Service Life Extension Using Sealers in Chloride-Laden Environments" (Transportation Research Record 1561).

Report on the use of Linseed Oil in the protection of Concrete Surfaces and instructions for doing so.

This study examined and developed feasible chemical methods for the corrosion protection of reinforcing steel in concrete bridges. A broad spectrum of chemicals were evaluated: corrosion inhibitors, chloride scavengers, and polyaphrons. Inhibitors were evaluated and recommendations were made. Reinforced concrete specimens were cast and subjected to repeated exposure to sodium chloride solution and evaluated to investigate the inhibitors effectiveness after removing contaminated concrete. Corrosion progress was monitored. Polyaphrons were investigated as a possible corrosion preventor/reducer inhibitor. Based on results, polyaphrons are not recommended as a practical concrete bridge treatment.

The purpose of this article is to describe concrete problems and show that advanced high molecular weight (hmw) meth-acrylate can provide a viable solution for protecting and repairing concrete. Some publicly available information and private research is cited, including several research reports, trade journal articles by experts and reference standard documents. General industry and specific case histories are cited.