ABSTRACT
As we know, medium—alkali glass fiber reinforced portland cement is not durable, so, for a long time, the GRC researchers have been thinking that the reason is that there is only an interaction between Ca(OH)2 produced from the hydration of the cement and the silica skeleton of the glass fiber and this interaction may lead to the destruction of the glass fiber.
We have done some studies on the durability of medium—alkali glass fiber reinforced various cement. In doing such tests as X—ray diffraction analysis, SEM analysis, Laser Raman Spectrum analysis and a lot of tests of the macromechanics of the GRC, we have found that Al—O bond of the fiber breaks at first, then comes the destruction of the Si—O bond.According to this, we advance that the destruction of the medium-alkali glass fiber in the cement matrix may be divided into 3 stages: the hydrolysis of the alkali oxides in the fiber network; the breaking of the Al—O bond and the destruction of the Si—O bond. Thus, the tensile strength of the glass fiber decreases considerably.
Based on the above knowledge, we have provided the theoretical basis for using medium—alkali glass fiber as reinforcement of cement matrix. The GRC made with medium—alkali glass fiber and low—alkalinity cement developed by us turns out to be with good durability, which has been proved through ten years’natural weathering test and one and a half years’acceler-ating test.
A series of this kind of GRC products have been developed and have showed their good durability in the application.
