Research On Measures To Improve The Durability Of Concrete Which Under Sulfate Attack And Dry-wet Cycles Conditions

The main contents of this paper is improvemental measures of resistance to concrete sulfate attack and concrete dry-wet cycles,it made a little progress on the basis of previous research achievements. First, it puted forward some improvemental measures such as multi-elements mineral admixtures mixing, multi-elements mineral admixtures&air entraining agent mixing,and multi-elements mineral admixtures & polypropylene fiber mixing.These measures were puted forward owing to two aspects,one is some materials such as mineral admixture, air entraining agent and polypropylene fiber and their respective characteristics,the other is train of thought about materials compositing. Second, the experimental method was improved. In order to simulate the actual erosion conditions of environmental,an experimental method for sulfate attack in solution which controled PH value,flowing and cycling was applied. This experimental method involves some devices and instruments, they are PH control instrument, one specimens pool and two solution pools which in high and low position separately. In these devices, solution can flow from high position pool to low one is based on fluid mechanics siphon principle,and the PH value of solution in specimens pool was controled by PH control instrument from beginning to end.At the same time,the conventional experimental method for sulfate attack in solution which non-controled PH value and immobile was applied too. The improvement of the measures which were applied to resist concrete sulfate attack and concrete dry-wet cycles has been comparative studied by the above two methods in this paper. Research results show:1. The improvement of the measures which were applied to resist concrete sulfate attack and concrete dry-wet cycles appears to be over strong in experimental method for sulfate attack in solution which non-controled PH value and immobile.But the experimental method for sulfate attack in solution which controled PH value,flowing and cycling is similar to the actual erosion conditions of environmental, so the corrosion resistance of all concrete series appears to be relatively poor in this experimental method,but the improvement of homologous measures appears to be objective and true.2. The measure of multi-elements mineral admixtures mixing is propitious to improving the performance of resistance to concrete sulfate attack and concrete dry-wet cycles. In this measure, component proportion of multi-elements mineral admixtures has certain influence to the performance of resistance to concrete sulfate attack, the performance of resistance to concrete sulfate attack becomes much stronger with increment of slag and silica fume, and with decreasement of fly ash.3. Because the measures of multi-elements mineral admixtures&air entraining agent mixing and multi-elements mineral admixtures & polypropylene fiber mixing have exerted synergy of mineral admixture, air entraining agent and polypropylene fiber's improvement effect in physics and chemistry,so these two measures are superior to the measure of multi-elements mineral admixtures mixing, they have excellent improvements on performance of resistance to concrete sulfate attack and concrete dry-wet cycles.And the performance of resistance to concrete sulfate attack and concrete dry-wet cycles becomes much stronger with increment of air entraining agent and polypropylene fiber while air content of concrete wthin 6% or fiber content wthin 0.2%.4. The permeability of concrete is obviously lowered by the improvemental measures applied. The corrosive coefficient and the anti-salt crystallization erosion coefficient of concrete become lower with it's electric flux increasing, and then the performance of resistance to concrete sulfate attack and concrete dry-wet cycles become much stronger.And it is found that the 6h electric flux is linearly relative to the corrosive coefficient or the anti-salt crystallization erosion coefficien wthin all concrete series.