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Concrete slabs containing uncoated reinforcing bars were cast with a concrete cover of 20 mm. The W/C was either .25, .40, and .60. A simulated crack .4-mm wide was formed transverse to the axis of the reinforcing bar. Three types of commercial corrosion inhibitors were added to concrete mixtures for corrosion protection. Slabs were placed in an accelerated exposure cabinet with four cycles of wetting and drying per day in simulated seawater. The corrosion rates were measured using the linear polarization technique. Some of the concrete slabs were broken open at the end of the exposure period and corrosion damage was evaluated. Water-soluble chloride content analysis in the rebar trace was performed at the end of the exposure period for all of the examined specimens. The various types of corrosion inhibitors showed a wide variation in performance and their effectiveness was also found to be particularly sensitive to addition rate. In general all had a greater effectiveness in reducing corrosion rate in a higher water-to-cement ratio concrete than in a lower water-to-cement ratio concrete. Only calcium nitrite at an addition rate of 25 L/m3 provided some level of consistent performance in reducing the corrosion rate in .60 and .40 water-to-cement ratio concrete for uncracked and precracked specimens.

A necessary condition for crack development in concrete due to alkali-aggregate reaction is that the concrete contains: *Reactive rock types or minerals, e.g. porous, opaline chert. *Alkali metal ions, e.g. sodium ions Na+ and potassium ions K+ *Water, e.g. concrete humidity more than 80% RH. Aggregates with alkali minerals may release alkalies in concrete, since the pH values are often 12-13 in most concrete. If alkalies are released from the aggregates it might increase the risk of getting 'deleterious' alkali relations, when alkali reactive aggregates are resent in the concrete in a sufficient intensity. So far, this question has not been given much attention, when specifications for the maximum alkali content in fresh concert has been made. A test series was carried out in order to subject this question to a critical examination. It was decided to perform two main series o mortar bar test with: *Water/cement-ratio=.40 by mass. *Binder/aggregate-ratio=.42 by mass *Flow of mortar+130 mm and variable parameters: *Chert/aggregate-ratio, which varied from 0 to 10 percentage by volume *As inert aggregate either quartz or feldspar were chosen *Concentration of alkali metal ions in the mortar, which was given the values 3.0 and 6.0 kg of equivalent Na 2O per m3 mortar *In order to study the influence of added silica fume systematically, the ratio of silica fume to binder was chosen as 0,4 and 8 percentage by mass. The following conclusions were drawn from the test series performed: * The maximum expansion increases (at pessimum proportion) when feldspar is used as inert aggregate instead of quartz, other parameters being equal *A delay of expansion is observed when silica fume is added to the mortar *The delay increases with the amount of silica fume added.

Forty fly ash samples obtained from twenty four different thermal power stations were used in the pozzolanic reactivity test, and twenty four fly ashes, original ashes, and air stream classified ones from a single boiler were used in the ASR (Alkali-Silica Reaction) controlling tests. The present work evaluates the pozzolanic reactivity of fly ash by estimating consumption ratio of Ca2+ in the cement and fly ash mixed suspension while considering interactions of other alkali ions released from the cement particle. The index derived from the acceleration test was named as Assessed Pozzolanic-reactivity Index (API), estimating the consumed Ca2+ ratio in the suspension. There was a linear correlation between the API and activity indices obtained from mortar tests (JIS A 6201-1999). On the other hand, the API also showed a linear correlation with expansion ratio, the control effect of fly ash on ASR, obtained from mortar tests (ASTM C 441). The API can stand for the ASR-controlling efficiency. The pozzolanic reactivity of fly ash significantly influences the control effect on ASR, the higher the pozzolanic reactivity, the higher the control effect on ASR.

When subjected to wetting-drying cycles, glass fibre-reinforced composites become brittle. This is mainly due to the precipitation of calcium hydroxide crystals at the surface of the fibre, which block the fibres and reduce their deformation. The addition of a polymer to the cementitious matrix will not prevent such phenomenon. Durable composites have been developed using polypropylene fibres and modifying the cementitious matrix by a polymeric addition. The volumic fraction of fibres was 1.6% and the matrix contained either an acrylic polymer or a vinyl acetate-ethylene copolymer (2.5% by mass of the mortar). Ductile composites were obtained for conditions of storage that included: 20 degrees C in sealed plastic bags, immersion in water at 60 degrees C. and wetting-drying cycles.

Reinforced Concrete (RC) beams with two different water-cement (w/c) ratios of .35 and .53, whose dimensions are .2 by .3 by 2 m. were made with the non-reactive river sand and the reactive andesitic crushed stone. After 28 days of the steam during RC beams were exposed outdoors, and then the cathodic protection current of 50mA/m2 was applied to the steel reinforcement in the beams. The expansion and cracking of the beams were monitored for 3 years in order to investigate whether or not the cathodic protection current may actually accelerate the alkali-silica reaction (ASR) around the steel cathode in RC beam. After 3 years of the exposure time in a natural environment, the flexural loading tes was carried out for ASR damaged RC beams with and without the cathodic protection. From the experimental results, it was found that the application of cathodic protection in RC beams increased significantly the risk of damaging expansion and cracking in the concrete containing alkali-reactive aggregates, which resulted in the reduction of load-bearing capacity of RC beam in the bending test. This indicates the importance f the survey relating to the alkali-reactivity of the aggregates used in concrete structures and the alkali content of concrete before the cathodic protection is applied.