Study On Effect Of Slate Powder On Alkali Activity Of Slate Aggregate

According to alkali-aggregate reaction inhibition test subject research of GUI GUANG railway, subproject of major technological project of Guizhou province (20106005), the effect of slate powder is studied systematically. The alkali active of slate aggregate is tested. Effect of slate powder on alkali activity of slate aggregate is studied. And the text also studied the interaction between slate powder and admixtures in order to analyze the feasibility of using slate powder as mineral admixtures. The mechanism of slate powder suppressing alkali-silica reaction has been studied in this thesis. The main contents and results are as follows:(1) In order to study the effect of manufactured-sand’s feature on the alkali activity of slate aggregate, refer to the accelerated mortar bar test in the "Standard for Constructional Quality Acceptance of Railway Concrete Engineering" TB10424-2010, the text has studied the expansion of the specimens that are made from slate aggregate with different powder contents or different particle size distribution. The result shows that:When the content of powder in slate aggregate is less than10%, the powder dose not have adverse effect on the expansion of specimens, but when powder content is between15%and20%, the expansion has downward trend. Slate powder is an active powder. It can reduce the expansion of specimens. Particle size has influence on the expansion of specimens. The most unfavorable particle size of slate aggregate for the alkali activity is0.16-0.315(mm). And the reason for the existence of the most unfavorable particle size is analyzed.(2) In order to research the interaction between slate powder and mineral admixtures, the text has studied the expansion of specimens that are made from slate aggregate with different contents of the powder using the accelerated mortar bar test. The results show that:The alkali-silica reaction of high-activity slate aggregate can be suppressed while using30%fly ash and5%silica fume as mineral admixtures; and the interaction of15%powder in the aggregate is the best while using30%fly ash and5%silica fume as mineral admixtures; When the content of powder in slate aggregate is less than20%, the powder dose not have adverse effects on mineral admixtures in suppressing alkali-silica reaction of slate aggregate. In addition, the expansion of the specimens with different powder content and different mineral admixtures content is studied; the result shows that the powder can effectively improve the long-term expansion properties of specimens.(3) In order to study the feasibility that using slate powder as mineral admixtures and its inhibition mechanism, the expansion of the specimens with different content of powder and fly ash using the accelerated mortar bar test and an improved steam curing method. Microscopic analysis is done at the same time via polarized electron microscope. The results show that:The alkali-silica reaction of high-activity slate aggregate can not be suppressed effectively while using slate powder separately as mineral admixtures. While using fly ash as the mineral admixtures, the relationship between the amount of fly ash and the expansion rate of the specimens is the bilinear relationship, the cut-off point is around20%, so the thesis recommends that the amount of fly ash should be greater than20%. Microscopic analysis shows that the main mechanism that the slate powder can suppress alkali-silica reaction of slate aggregate is that the alkali in concrete can be consumed and physically diluted by slate powder.