Cross-scale Study on the Mechanical Properties and Frost Resistance Durability of Aeolian Sand Concrete

Abstract

Many researchers have been searching for the alternative for natural river sand as fine aggregate for concrete preparation. Thus, whether it is feasible to replace natural river sand by aeolian sand in concrete partially or totally is studied. At the macroscale, a universal testing machine and concrete rapid freeze-thaw equipment are applied in testing mechanical properties as well as frost resistance durability, respectively. At the mesoscale, a scanning electron microscope has been taken for observing and analyzing the interfacial transition zone in aeolian sand concrete. At the microscale, nuclear magnetic resonance is used for testing pore structure evolution. Simultaneously, the macro- and microrelationships between compressive strength and total and interval porosities are established. The grey correlation model is adopted to analyze the main microscopic pore parameters that affect aeolian sand concrete's frost resistance durability. Results show that the workability and mechanical properties of aeolian sand concrete first increase and subsequently reduce as aeolian sand content increases, and the optimum content is 30%. The influence mechanism is that aeolian sand particles with different contents change the linear packing density of fine aggregate and affect the aggregate gradation and pore structure. The compressive strength has a negative linear relation to total porosity and porosity of more harmful pores (>200 nm) and an insignificant correlation with the porosity of non-more harmful pores (<200 nm). A medium and low content of aeolian sand (10%–60%) partly improves concrete frost resistance, whereas a large content (80%–100%) significantly improves concrete frost resistance. Grey correlation analysis shows the most important microstructural factor influencing the macroscopic frost resistance durability in aeolian sand concrete should be the relative proportion of more harmful and harmless pores. The findings of this research expand aeolian sand concrete's application in cold areas and provide a new way for the reuse of waste resources.