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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.

Laboratory tank tests were used to assess the sulfate resistance of a series of portland and blast furnace slag cement concretes. Following different early curing regimes, 100 mm concrete cubes were stored in tanks of sodium and magnesium sulfate solutions for 5 years. The concrete cubes were photographed, and their sulfate attack ratings and compressive strengths measured at 1, 2, and 5 years. The results showed that concretes made with ground granulated or pelletized blast furnace slag and portland cement generally had good sulfate-resisting properties when the slag content was 70 percent and above. The significance of the precuring regime, the tricalcium aluminate (C3A) content of the portland cement, and alumina level of the slag on the sulfate resistance of concrete are discussed. A degree of carbonation of the concrete prior to storage in the sulfate solutions was found extremely beneficial in the prevention of sulfate attack. Sulfate-resisting portland cement (SRPC) of low tricalcium aluminate content and combinations of high tricalcium aluminate ordinary portland cement (OPC) with low alumina slags were shown very resistant after 5 years in high-strength sulfate solutions. The concrete cube results were compared with data previously obtained using the same series of cements in small-scale accelerated methods of test, and a reasonable correspondence was found. Recommendations are made for an acceptance test for determining the sulfate resistance of cements and for maintaining good concrete performance in sulfate conditions. The BRE tank test is a severe test, and its relevance to the ultimate behavior of concretes in the field is discussed.

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.

The exhaust from the auxiliary power unit (APU) of the modern F/A-18 aircraft has caused spalls and erosion on portland cement concrete (PCC) pavements. The exhaust gas has a maximum temperature of 385 F (196 C) and a maximum velocity of 140. At this temperature, PCC seems to lose its integrity when subjected to repeated and prolonged exposure. Spills of hydraulic fluid and jet fuel on the pavement aggravate the spalling process. The main objective of this investigation was to determine effects of cyclic heating on the strength of portland cement concrete subjected to high temperature, and compare the effects of cyclic heating on concrete contaminated with hydraulic fluid and jet fuel with noncontaminated concrete. Five different concrete mixtures were investigated. Twenty-one prisms and 21 cylinders were made from each mixture and tested for compressive strength, flexural strength, pulse velocity, and dry unit weight. Within each group, specimens were tested after each of the following heating/cooling cycles: 0, 15, 30, 60, 120, 240, and 400. A heating and cooling cycle is defined as heating in an oven at 400 F (204.4 C) for 60 min and cooling at room temperature for 30 min. After every 15 heating/cooling cycles, the contaminated specimens were soaked in jet fuel or hydraulic fluid overnight before the next heating/cooling cycles. Test results indicate that jet fuel contamination is more detrimental than hydraulic fluid contamination. Compressive strength, flexural strength, and pulse velocity are adversely affected by the cyclic heating.

A survey was conducted of failures of prestressing steel in bridge members exposed to potentially aggressive environments. It appears that the main cause of corrosion of prestressing tendons is the ingress of moisture laden with corrosion-inducing agents. Moisture can make its way to the prestressing steel by penetrating through leaking joints from a deck slab, or by diffusion from the underside of a bridge. Moisture may penetrate through concrete cover, sheathing and grout (or grease in unbonded tendons), as well as through anchorage systems. The rate of penetration of moisture depends primarily on permeability of concrete, type of sheath employed for protection of a tendon, and condition of grout or grease inside the sheath. Brittle fracture of reinforcing steel can occur due to pitting corrosion and/or stress corrosion cracking (SCC). Two types of SCC have been identified in prestressing steel in bridges: hydrogen embrittlement and fatigue corrosion. The rate of corrosion in prestressed concrete components can be minimized by using proper preventive and remedial measures.