Exploration of Waterproofness of Concrete and Alkali-Aggregate Using Hydrophobic Impregnation and Coating

Part of the tunnel spoil can not be used for concrete due to alkali-aggregate reaction (AAR). Water is an indispensable condition for AAR, so separating the alkali-aggregate from water is of great benefit to controlling the AAR. This paper investigates the modification of concrete and aggregate by hydrophobic impregnation and organic coating and then evaluates their waterproof and mechanical properties by dynamic contact angle (DCA), ultrasonic wave velocity, scanning electron microscope (SEM), nuclear magnetic resonance (NMR), and so on. For waterproofness, hydrophobic impregnation and organic coating can both improve the waterproofness of concrete and aggregate. The organic coating is suitable for aggregate because it wrap aggregate well. And aggregate coated by PVA can improve the interfacial transition zone (ITZ). For mechanical properties, both materials will weaken the strength of the interface. Furthermore, concrete made by aggregate with organic coating shows plastic deformation and has a good correlation with the film thickness, a plastic estimation model based on film thickness is proposed. This paper evaluates the waterproof of concrete and aggregate and finds plastic concrete with good aggregate waterproofness which provides a new idea for the application of alkali-aggregate in seepage control facilities of water conservancy projects.