Over the vast Northwest China, arid desert contains high concentrations of sulfate, chloride, and other chemicals in the ground water, which poses serious challenges to infrastructure construction that routinely utilizes portland cement concrete. Rapid industrialization in the region has been generating huge amounts of mineral admixtures, such as fly ash and slags from energy and metallurgical industries. These industrial by-products would turn into waste materials if not utilized in time. The present study evaluated the suitability of utilizing local mineral admixtures in significant quantities for producing quality concrete mixtures that can withstand the harsh chemical environment without compromising the essential mechanical properties. Comprehensive chemical, mechanical, and durability tests were conducted in the laboratory to characterize the properties of the local cementitious mineral admixtures, cement mortar and portland cement concrete mixtures containing these admixtures. The results from this study indicated that the sulfate resistance of concrete was effectively improved by adding local class F fly ash and slag, or by applying sulfate resistance cement to the mixtures. It is noteworthy that concrete containing local mineral admixtures exhibited much lower permeability (in terms of chloride ion penetration) than ordinary portland cement concrete while retaining the same mechanical properties; whereas concrete mixtures made with sulfate resistance cement had significantly reduced strength and much increased chloride penetration comparing to the other mixtures. Hence, the use of local mineral admixtures in Northwest China in concrete mixtures would be beneficial to the performance of concrete, as well as to the protection of environment.

In this study, basalt fiber-reinforced and polymer-modified magnesium phosphate cement (BFPMPC) mortar, a novel rapid repair material, is proposed for portland cement concrete pavements (PCCP). A practical mixture design was selected from the orthogonal experiments. The properties of this mixture under different environments were studied. Considering the horizontal load of vehicles, the bonding mechanism between magnesium phosphate cement (MPC) mortar and PCCP was studied through shear strength tests. The experimental results show that the BFPMPC mortar proposed has not only reliable compressive and flexural strengths but also good water resistance in the interfacial transition zone (ITZ) and good bonding performance with the old cement concrete. Additionally, the ITZ between the BFPMPC mortar and old concrete has good freeze-thaw resistance. Then, the salt freeze-thaw cycles were found more destructive to the repair interface than freeze-thaw cycles. The addition of the styrene-butadiene copolymer (SBC) emulsion in BFPMPC mortar was formed without new hydration components, which was observed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The ability to enhance the bonding strength with the addition of SBC was found by scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). In summary, the BFPMPC mortar can be used as a rapid repair material for PCCP in seasonally frozen areas.