Studies of slag activation by alkalies have been carried out since 1973 at the Institute of Building and Refractory Materials, Academy of Mining and Metallurgy, in Cracow, Poland. Laboratory tests were followed by production of the activated slag on a large scale. It appeared that the new cementing material composed of the granulated blast furnace slag mixed with an alkaline activator showed high strength and corrosion resistance. The present work deals with the problem of reinforcing steel corrosion in the alkali-activated slag mortar exposed to the attack of concentrated chloride solution. The observations of reinforcement in ordinary portland cement (OPC) mortars, OPC plus silica fume (SF) mortar, or OPC plus limestone flour mortar were carried out simultaneously. The resistance of alkali-activated slag mortar to the attack of a solution of high Cl- concentration was proved previously. The effective, protective action of the alkali-activated slag mortar was confirmed by electrochemical measurements and weight loss determination after 365 days' exposure to a chloride solution. A similar effect was found in the case of silica fume or limestone flour addition to the OPC mortar, but the corrosion of the reinforcement was clearly visible, as shown by corrosion pits in the reference standard OPC mortar samples.

Ten different polymers, six latices, and four epoxy systems were added to two base mortars of water-cement ratio (w/c) = 0.55 and 0.40. The latices were PMMA, PMMA/PBA (two compositions), PVAc/PE/PVC, PVAc/Veo Va and SBR. Two of the epoxies were based on Bisphenol A resin (epoxy F1 and L), while the other two also contained a reactive thinner based on hexyleneglycol diglycidylether (epoxy F0 and V). The hardeners were both polyamine (epoxy L) and a water-soluble hardener based on polyamide. The cement paste in the base mortars was partly substituted with 5, 10, 15, and 20 volume percent polymer (10 and 20 volume percent for the epoxies). The binder volume was kept constant in all mortars, and the w/c was constant within each series. The carbonation rate of the PCCs with w/c = 0.40 is equal to or higher than the unmodified mortar. The only exceptions are the 15 and 20 percent PVAc/PE/Pvc-modified mortars, which withstand carbonation significantly better than the control. The epoxies L and V, together with the SBR PCCs, performed particularly poorly. Among the PCC with w/c = 0.55, PVAc/PE/PVC/PCCs, together with the 10 percent PMMA/PBA I PCC, performed better than the control. All the other PCCs resisted carbonation equal to or less than the control. In the latter case, however, it is difficult to state the contribution from the air content which may imply that the performance of the polymer actually is even better. The results are assessed with respect to the degree of hydration of the PCCs, their air content, the replacement of cement binder with polymer, and the neutralization effect following a possible hydrolysis of the polymer.

The Canadian association of large public real estate companies has initiated a 5-year research project aimed at determining the most cost-effective way to rehabilitate deteriorated parking structures. A sample of 49 garages includes office, retail, and residential buildings. The repair history of each building has been documented and, in some cases, a formal condition survey of the garages is undertaken yearly. The collected data serve as a basis for the evaluation of the effectiveness of the various repair techniques and strategies. The project is now in its third year. The investigation was carried out concerning the excessive cracking noted in some garages constructed with epoxy-coated reinforcing steel. The benefits of intensive maintenance and good housekeeping have been shown by the analysis of the case history of a garage. Various types of concrete sealers have been evaluated by testing in the laboratory 57 products applied to 8 types of concrete substrate. Preliminary results indicate waterproofing membranes are an effective means to reduce the moisture content in the slab.

The durability of concrete is generally regarded as its ability to resist the effects and influences of the environment while performing its desired function. In an offshore or marine environment, the concrete can be subjected to the influences of wetting and drying, freezing and thawing, abrasion by ice and other debris, chemical attack or mineral depletion by water it is in, salt accumulations, and attack by marine organisms. The paper reviews these dteriorating mechanisms and also reviews the recent trends in strength development for concretes made with modern materials. Chloride ion penetration into concrete information from 33-year old Gulf of Mexico offshore concrete platforms is presented. The advantages of supplementary cementing materials in offshore and marine concretes are discussed along with recommendations for producing durable marine concretes.

The sulfate resistance of concretes with compressive strengths between 60 and 110 MPa was evaluated. The test comprises several soaking/drying cycles of samples in a Na2SO4ù10H20 solution, followed by measurement of mass variation and residual compressive strength. Visual inspection and sulfate recovery by distilled water immersion increased the accuracy of test results. Results reveal significant differences compared to those tests normally used, involving prolonged immersion. The resistance to sulfate attack depends on concrete porosity and capillary absorption and not on permeability, because pozzolanic reactions seem to interrupt pore continuity. The reduced water-cement ratio obtained with the aid of the superplasticizer was much more effective than the chemical characteristics related to the presence of mineral admixtures in concrete regarding its resistance to sulfates.