Abstract
The aim of this study was to analyze the influence mechanism of aeolian sand on the mechanical property of concrete and establish the time‐varying compressive strength model. Test studies on the development of concrete’s compressive strength with aeolian sand from the Mu Us Desert were carried out. Influence mechanism of aeolian sand on the strength of concrete was revealed by using the nuclear magnetic resonance (NMR) to analyze the pore ratio and structures of aeolian sand concrete (ASC) and using the X‐ray single crystal diffraction (XRD) to calculate the relative contents of hydration products semiquantitatively. Results show that the strength first increases and then decreases with the increase of aeolian sand content, where 20% was the best replacement ratio. With less than 20% content, it promoted the strength by changing the pore structure of concrete and accelerating the cement hydration speed based on its filling effect and chemical activity; when the content was more than 20%, it led to a decrease of strength because of an increase of harmful pore ratio and a weakening of the interface transition zone (ITZ), where the stress concentration and damage when loading are easier to occur. At last, a time‐varying compressive strength model of ASC considering the harmful pore ratio variation and heterogeneous nucleation effect was established based on the discussion, published date, and American Concrete Institute (ACI) model, which agrees well with the experimental results and can easily predict the strength of concrete.
Highlights
Sand is widely used as a fine aggregate material of concrete, and mainly river sand is used since a long time
Samples were removed at 3, 7, 14, 21, 28, 35, and 42 days, and the compressive strength was tested with a microcomputer electrohydraulic pressure testing machine (YAW-2000B) according to Chinese testing code GB/T50081-2002 [16] to analyze the macroscopic mechanical properties. e porosity and pore size distribution were measured by nuclear magnetic resonance (NMR)
(2) e physical and primary mechanism why aeolian sand improved the strength of concrete can be attributed to the change of the internal pore structure and the width of interface transition zone (ITZ) in concrete, especially the content of the harmless pores
Summary
Sand is widely used as a fine aggregate material of concrete, and mainly river sand is used since a long time. With the continued increase in the scale of global infrastructure construction, there is insufficient sand of appropriate quality for construction, making it difficult to meet the needs of engineering construction. In China, there has been more than 20-fold increase in the annual use of construction sand in the past 30 years; the use is expected to grow at an annual rate of more than 20% [1]. The increased need has led to a shortage of river sand. E government has issued restrictions on the use of river sand, but the increased regulation has further aggravated the imbalance of supply and demand. Exploiting new sources of sand for construction to meet growing demand is an urgent problem in China and the world. Aeolian sand has a good application prospect [3,4,5]
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