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The application of magnesium oxychloride cement (MOC) is promising, but its poor water resistance seriously hinders its development and application. In this paper, we describe a new type of MOC with excellent water resistance, prepared using fly ash and hexadecyltrimethoxysilane (HDTMS). SEM, XRD, FTIR, TG/DSC, and other microscopic-scale studies were conducted to investigate the mechanism underlying the water-resistance enhancement of the new MOC. It was found that adding 20% fly ash and 3% HDTMS can strengthen the water resistance of MOC while retaining high mechanical properties. In particular, the residual coefficient remained at 0.91 after 7 days of immersion. This is because these two additives, when used together, can increase the content of the gelling 5-phase of MOC, as well as optimize the pore structure of MOC.

Reflective cracking is a common distress in hot-mix asphalt (HMA) overlay. A test method that can provide comprehensive information about reflective cracking is thus needed. In this study, an apparatus named Joint Motion Simulation System (JMSS) was developed, which consists of two hydraulic servo-systems and a temperature chamber. A newly developed reflective cracking test method (NRCTM) based on JMSS was proposed, which is applicable for airport pavement. This method considers the influences of both traffic and thermal loads under controlled temperature conditions. Laboratory tests were conducted to verify both repeatability and sensitivity of the NRCTM. The tests results revealed a coefficient of variation that was lower than 13%, indicating that the NRCTM exhibited satisfactory repeatability. In addition, the method was sensitive to four factors: test temperature, combination of loads, compaction of specimen, and type of mixture. Moreover, three types of interlayer structures were evaluated with the NRCTM: geotextile, stress-absorbing layers, and atactic polypropylene modified linoleum. The geotextile performed better than the other two interlayer systems. Thus, the NRCTM can be used for measuring the reflective cracking in HMA overlay with acceptable repeatability and sensitivity.

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