# Performance Evaluation of Bedding Sand and Load Transfer Characteristic of Concrete Block Pavements
###### Abstract  
Concrete block pavement is used as a modern pavement type owing to its economic benefits. The physical properties, mechanical properties, and functional characteristics of bedding sand and joint sand, the main components of concrete block pavements, should be accurately understood. Owing to the discontinuous structure of these pavements, load transfer efficiency (LTE) is the most important index from the perspective of performance. The factors that affect LTE are bedding sand (type, grading, and thickness), joint sand (type and grading), and concrete block (shape and pattern). Therefore, the optimal design for concrete block pavements can be achieved by analyzing each factor. In this study, three types of sand (river, quartz, and manufactured) were selected to examine the mechanical properties via direct transfer experiments. It was observed that the shear strength of river sand was the highest. It was also found that the difference between the shear strength and the internal friction angle (according to the content of 0.6 mm in the grading of bedding sand) was not large, and the shear strength and the friction angle increased as the content increased to 0.075 mm. In addition, the load transfer characteristics of the joint and rotational interlocking of the block were evaluated through a non-destructive test using the degree of joint filling, block shape, and construction pattern as variables. As a result, the degree of joint filling had the greatest effect on the load transfer characteristics of the joint and rotational interlocking of the block. The effect of the block shape was larger than that of the construction pattern. When a heavy load is applied, the LTE between blocks must be maintained at 50% or more, and the rotation of blocks at 0.6\({}^{\circ}\) or less, if 75% or more of the joint must be filled for preventing excessive vertical deformation. concrete block pavement; load transfer efficiency; joint sand; bedding sand +
Footnote †: journal: Applied Sciences  
**Problems:**  
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To increase the interlocking effect between blocks and provide a level surface at the bottom, the bedding layer of concrete block pavement is used to fill the empty space at the bottom of the joint to minimize damage caused by the concentrated load. It also levels the lower layer of the concrete block pavement and its finished surface [5]. The thickness of the bedding layer is set to 20-50 mm. The bedding sand layer of a concrete block pavement is not used to secure the bearing capacity, but to make the base and surface layer level with each other. However, when used in a roadway, the bedding sand layer may be crushed by repeated traffic loading, thus affecting the performance of the concrete block pavement. The thicker the bedding layer is, the higher the probability of rutting [6]. Depending on the pavement hierarchy, the requirements of the median particle diameter (600 \(\upmu\)m) and fine powder content (75 \(\upmu\)m or less) that determine the particle size of the bedding sand are different [7]. The bedding sand, having a low crushing resistance to an external load, is compacted and turned into powder; this reduces the friction between the block and bedding layer, causing the blocks to slide, which leads to the loss of joint sand. Owing to the enlarged joint width, the load transfer efficiency decreases between blocks. When rainwater infiltrates, fine powder of the bedding sand is lost, resulting in damaged concrete block pavement [8]. [PERSON] (1996) examined the difference in the durability of bedding sand using different rock types through the [PERSON] and [PERSON] experiment and found that silica sand was the most durable, followed by granite and limestone. Bedding sand can be evaluated in two ways: properties of sand and properties of materials with reasonable grading [9]. The larger the particle size, the higher the shear resistance, and the better the pavement performance is [10].