# Mechanical Properties of Sandstone Cement-Stabilized Macadam
## 1 Introduction  
Cement-stabilized macadam (CSM) is a family of compacted blends containing aggregates with appropriate grading, cement of 3-8% by weight of aggregates and water at optimum moisture content levels [1; 2]. CSM has been widely used in highway bases and sub-bases because of better bearing capacity and lower tensile stress or strain at the bottom of the bituminous layer [3]. With the rapid development of road construction, natural stone materials as aggregates of CSM are becoming depleted at an increasing rate, making them insufficient to meet the increasing construction demands [4]. The task of road construction in remote areas, in particular, is a challenge due to its very high demand for aggregate resources. However, the use of high-quality stone may cost more manpower and financial capital in most of these economically underdeveloped areas as a result of stone resource shortages. Hence, it is very significant to hunt for materials as aggregate replacements within a close range along highways to solve the problem of stone resource shortage. Soft rock is widely distributed along the highways in the southwestern region, South Central China, central China, and Shaanxi-Gansu-Ningxia regions [5], including a sequence of sedimentary rocks, such as mudstone, sandstone, argillaceous sandstone, sandy mudstone, and siltstone [6]. If these soft rocks are abandoned and high-quality rock is purchased from a long distance away, large increases in the construction costs will result, together with extended construction periods and environmental pollution problems caused by the disposal impacts of the abandoned rock. For example, \(14\times 10^{6}\) m\({}^{3}\) of red sandstone was converted into eligible roadbed materials in the construction of the Heng-ZaoExpressway in Hunan Province of China, which not only saved 842.5 hectares of farmland and 167.9 hectares of forest land, but also reduced millions related to the construction cost [7]. The use of widely distributed and not widely developed sedimentary rocks for CSM aggregates may be an effective means of addressing the shortages of high-quality stone, thereby simultaneously providing economic and environmental benefits. Compared with natural aggregates, sedimentary rocks are considered undesirable road materials because of their high-water absorption and large crushing value [8]. Construction and demolition waste (CDW) with the same characteristics has been used as aggregates in existing studies, such as crushed clay brick and recycled concrete [9]. The successful research on the use of CDW for concrete gravel is mostly concentrated in the United States and European countries [10]. [PERSON] and [PERSON] [11] studied the properties of concrete blends with CDW used as an aggregate. Although the mixtures have a lower dry density and higher moisture content as a mixture of aggregates than natural materials, they can still be used in road sub-bases. [PERSON] et al. [12] studied the properties of CSM mixtures with crushed brick as aggregate through laboratory tests and found that the physical and strength properties of the mixture meet the road requirements. In addition, the researchers [13] conducted unconfined compression tests, split tensile tests and flexural strength tests; it was concluded that road base materials containing recycled concrete aggregates could be used for high-grade road construction. With the shortage of resources and worsening of the environment, recycling has gradually become a concern of academic experts in China. The feasibility of using recycled concrete aggregates as substitutes for natural aggregates was evaluated in lime-fly ash crushed stone bases [14]. The UCS values are better than those of natural aggregates and meet the requirements of road engineering. Based on the above facts, sedimentary rock may be feasible as a substitute for traditional aggregates in road construction.