Abstract
Dielectric constant is an important parameter for the nondestructive test of cement stabilized macadam base (CSMB) on road by ground-penetrating radar (GPR). However, few studies have been reported on the quantitative relationship between the dielectric constant and the compaction degree, strength indicators, and influencing factors of CSMB. To address the problem, groups of CSMB specimens, which were different in gradation of aggregate (fine or coarse), compaction degree, and curing time, were made and tested for dielectric constant and influencing factors with the help of the Swedish MALA GPR. The relationship between the dielectric constant of CSMB and the influencing factors such as the compaction degree, moisture content, percent residues of aggregate on the sieve of maximum particle size and curing age, and the relationship between the dielectric constant and the unconfined compressive strength were investigated based on several test data and theoretical analysis. The major findings are as follows. There is a good logarithmic correlation between the dielectric constant and the compaction degree of CSMB, and quantitative functions have been established. There is a good linear relationship between the dielectric constant and the unconfined compressive strength of CSMB, and quantitative functions have been established. A comprehensive equation between the dielectric constant of CSMB and the influencing factors such as the compaction degree, moisture content, percent residues of aggregate on the sieve of maximum particle size, and curing age has been established and validated with high significance and small error. The findings are a theoretical basis for the application of GPR to the test and quality assessment of CSMB on roads.
Highlights
Ground-penetrating radar (GPR) has been widely used in geophysical exploration and construction engineering in many countries [1–6], especially in nondestructive tests of structural layers such as cement stabilized macadam base (CSMB) in road engineering [7–9]. e compaction degree and strength of the cement stabilized macadam base, which is an important layer of the road base, are major indicators of quality of road construction
It is fast and economical in assessing the compaction degree, strength, and thickness of CSMB [18–21]. e interpretation and information retrieval of images of GPR-reflected waves depend on the dielectric property of CSMB, i.e., the accuracy of estimated thickness, compaction degree, strength, and moisture content depend on the dielectric constant of CSMB
Groups of fine or coarse CSMB specimens were designed, produced, and tested. e relationship between the dielectric constant of CSMB and the influencing factors such as the compaction degree, moisture content, percent residues of aggregate on the sieve of maximum particle size, and curing age, and the relationship between the dielectric constant and the unconfined compressive strength were investigated based on a number of test data and theoretical analysis. e main conclusions are as follows
Summary
Ground-penetrating radar (GPR) has been widely used in geophysical exploration and construction engineering in many countries [1–6], especially in nondestructive tests of structural layers such as cement stabilized macadam base (CSMB) in road engineering [7–9]. e compaction degree and strength of the cement stabilized macadam base, which is an important layer of the road base, are major indicators of quality of road construction. Ground-penetrating radar (GPR) has been widely used in geophysical exploration and construction engineering in many countries [1–6], especially in nondestructive tests of structural layers such as cement stabilized macadam base (CSMB) in road engineering [7–9]. As a nondestructive and continuous testing tool, GPR has been widely applied in the field of civil engineering [15–17] It is fast and economical in assessing the compaction degree, strength, and thickness of CSMB [18–21]. Groups of CSMB specimens with varying gradations and compaction degrees were collected and tested for the dielectric constants at different curing ages. Based on the radar test data, relationship models were established between the dielectric constant and the influencing factors, including the compaction degree, moisture content, percent residues of aggregate on the sieve of maximum particle size, and curing age. 13 specimens of good quality were selected out of 16 specimens and labelled from 1 to 13. e gradation design of the fine and coarse aggregate is as shown in Table 1 and Figure 1
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