To examine the application and significance of 3D printing technology in pavement maintenance engineering, a review of the current developments in principles, types, materials, and equipment for 3D printing was conducted. A comparison and analysis of traditional methods and 3D printing for asphalt pavement maintenance led to an investigation of 3D asphalt printing technologies and equipment. As a result, the following suggestions and conclusions are proposed: 3D printing technology can increase the level of automation and standardization of pavement maintenance engineering, leading to effective improvements in worker safety, climate adaptability, repair accuracy, etc. For on-site repair of cracks and minor potholes, utilizing material extrusion technology a mobile 3D asphalt printing robot with a screw extrusion device can be used for accuracy and flexibility. For efficient repair of varying cracks, material jetting technology with a UAV equipped with a 3D printing air-feeding device can be employed.

Old cement pavement directly overlaid with an asphalt layer produces many reflection cracks. Using microcrack homogenization technology to treat old cement pavement can effectively reduce the occurrence of reflection cracks. Micro-crack homogenization is relatively mature at the technical level; however, there is relatively little research on its mechanism. To evaluate the microcrack effect of old cement pavement, we conducted core sampling on a project road section after the appearance of microcracks. The core samples were sliced by X-ray tomography (X-ray CT). The mesostructure of the core samples was obtained. The core sample was further divided into microscopic cracks and macroscopic cracks according to the length and width of the crack. The development characteristics of cracks were subdivided into type I-III microcracks and type I-IV cracks. The core-drilling sample was divided into 5652 CT images. The statistical results showed that there were 3582 type-I microcracks, 3197 type-II microcracks, and 1835 type-III microcracks. Among the specimens, the minor proportion of microcracks was 32.87%, the most significant proportion was 100.00%, and the average ratio was 47.51%. Furthermore, the cracks development law and formation mechanism were analyzed based on CT images and cracking statistics. The results showed: (1) The microcrack homogenization process produced many microcracks in the test section and achieved a specific microcrack effect. (2) The cracks produced by the microcrack homogenization process tended to develop along the transition zone of the aggregate–cement mortar interface. The development of microcracks was mainly related to the aggregates’ shape and gradation, as well as the energy required to generate cracks. The research conclusions of this paper can be used as a theoretical basis for the optimization and improvement of the microcrack homogenization process.

Granular materials are used directly or as the primary ingredients of the mixtures in industrial manufacturing, agricultural production and civil engineering. It has been a challenging task to compute the porosity of a granular material which contains a wide range of particle sizes or shapes. Against this background, this paper presents a newly developed method for the porosity prediction of granular materials through Discrete Element Modeling (DEM) and the Back Propagation Neural Network algorithm (BPNN). In DEM, ball elements were used to simulate particles in granular materials. According to the Chinese specifications, a total of 400 specimens in different gradations were built and compacted under the static pressure of 600 kPa. The porosity values of those specimens were recorded and applied to train the BPNN model. The primary parameters of the BPNN model were recommended for predicting the porosity of a granular material. Verification was performed by a self-designed experimental test and it was found that the prediction accuracy could reach 98%. Meanwhile, considering the influence of particle shape, a shape reduction factor was proposed to achieve the porosity reduction from sphere to real particle shape.

Purpose: Research on social media frequently analyze social media usage (SMU)'s positive consequences for organizations and individuals; however, recent innovation studies caution that SMU may not always lead to positive new product development (NPD) outcomes. The competing streams of research highlight a fundamental tension that exists in the social media literature exemplified by the question: Is SMU good or bad for NPD? In this manuscript, the authors suggest that a more appropriate question as follows: What are the positive and negative indirect effects of SMU on NPD performance? The purpose of this paper is to discuss the aforementioned points in detail.Design/methodology/approach: A literature review provides the model and hypotheses. Using a sample of 168 Chinese firms, the authors conducted an empirical test following multiple regression analysis.Findings: The results demonstrate that SMU facilitates business analytics (ability) and social legitimacy (opportunity) but impairs entrepreneurial proclivity (motivation). These three constructs in turn mediate the effect of SMU on NPD performance. Moreover, this paper explores how technological turbulence moderates SMU's effects on business analytics, entrepreneurship proclivity and social legitimacy.Research limitations/implications: The results may be affected by both the context (solely in China) and type (cross-sectional) of the data set. Future research might take a decompositional approach to study SMU's effect on innovation in different NPD stages. Furthermore, with widely varying purposes (e.g., marketing, information searching, partner collaboration, new product launch, etc.), there is certainly a need for more clarity and understanding of how firms can leverage each of these different social media activities for successful NPD.Practical implications: First, we suggest that managers in China should be explicitly aware of the double-edged sword effect of SMU on NPD performance. Second, this study encourages managers to use social media carefully when technological turbulence becomes intense.Originality/value: Drawing on the ability–motivation–opportunity framework, this is one of the first studies to simultaneously examines the benefits and costs of SMU for NPD. In addition, this paper bridges the separate literatures on social media, business analytics, entrepreneurial proclivity and social legitimacy and contributes to the NPD research.