Physical and Mechanical Properties of Cemented Soil Fill At Liquid and Hardened States

Cemented soil fill is a new backfilling technology developed for the problems of narrow foundation trenches and uncompacted backfilling. It has good fluidity before solidification and higher strength and stiffness after solidification. This type of fill materials makes full use of the waste soils. The proportioning test was carried out on excavated soil on a construction site. Liquid property tests and unconfined compressive strength tests was carried out. The results show that the cemented soil fill can meet the requirement of foundation trenches backfilling, which has great prospect for future applications.

Influence of Curing Time on the Microbiological Behavior of Bulk-Fill Nanohybrid Resin Composites

This in vitro study aimed to evaluate the influence of curing time on surface characteristics and microbiological behavior of three bulk-fill resin-based composites (RBCs). Materials were light-cured for either 10 s or 80 s, then finished using a standard clinical procedure. They were characterized by surface morphology (SEM), surface elemental composition (EDS), surface roughness (SR), and surface free energy (SFE). Microbiological behavior was assessed as S. mutans adherence (2 h) and biofilm formation (24 h) using a continuous-flow bioreactor. Statistical analysis included a two-way ANOVA and Tukey’s test (p < 0.05). Materials differed substantially as filler shape, dimension, elemental composition and resin matrix composition. Significant differences between materials were found for SR, SFE, and microbiological behavior. Such differences were less pronounced or disappeared after prolonged photocuring. The latter yielded significantly lower adherence and biofilm formation on all tested materials, similar to conventional RBCs. Improved photoinitiators and UDMA-based resin matrix composition may explain these results. No correlation between surface characteristics and microbiological behavior can explain the similar microbiological behavior of bulk-fill materials after prolonged photocuring. This different performance of bulk-fill materials compared with conventional RBCs, where surface characteristics, especially surface chemistry, influence microbiological behavior, may have important implications for secondary caries occurrence and restoration longevity.

Waste utilization to enhance performance of road subbase fill

Purpose The purpose of this study is to use waste materials in construction to create sustainable practices. This will contribute towards circular economy which has gained momentum in recent years throughout the world. Design/methodology/approach Waste materials cause enormous environmental problems that can have an adverse effect on the environment. Recycling of waste consists an important part of the circular economy. Therefore, researchers have been investigating the economic use of a variety of waste materials for reducing their environmental impact. One potential usage is in road subbase fill materials where wastes can be incorporated in large quantities. In this study, the engineering properties of road subbase fill materials (i.e. kaolinite) mixed with Granite Waste (GW), coal Fly Ash (FA) and lime are investigated. Kaolinite was replaced with 15% lime and FA, whereas the GW replacement varied from 10% to 20%. Testing included strength of the various soil compositions subjected to different curing times. Also the microstructural analyses and phase changes of samples were conducted using scanning electron microscopy and x-ray diffraction techniques, respectively. The results obtained indicate that GW can be incorporated in road base materials to improve its bearing capacity. The mixture consisting of 15% lime, 15% FA, 20% GW and 50% kaolinite resulted in maximum dry unit weight and optimum moisture content. Using GW exhibited a noticeable increase in the California Bearing Ratio of more than eight times at 1 day and 28 days curing regime compared with the control sample. Findings This study shows that GW and FA can be used for road subbase materials and can contribute toward a better and cleaner environment. Originality/value In this study, the engineering properties of road subbase fill materials (i.e. kaolinite) mixed with GW, coal FA and lime are investigated. This are value added in circular economy.

Theoretical analysis on stress distribution characteristics around a shallow buried spherical Karst cave containing fill materials in limestone strata

The prime objective of the article is to present the spatial characteristics of stress distribution around a shallowly buried spherical Karst cave containing fill materials in limestone strata. Firstly, considering the external load effects, stress field in the Earth’s crust, internal filling, and the Karst landform characteristics in China, a spatial axial-symmetrical model was established. Concurrently, combining available work and the concept of elasticity, the boundary conditions were determined. Subsequently, Love displacement method was introduced, in addition to the expressions of stress components were gained. The diagram characteristics of each stress component were summarized, which are affected by various influencing factors. Finally, in order to prove the rationality of the general solution, a comparison between numerical simulation result and theoretical calculation result was carried out, as well as the maximum error between theoretical calculation value and numerical simulation value is less than 5%. Thus, the analytical solution could represent the spatial characteristics of stress distribution around a shallowly buried spherical Karst cave containing fill materials in limestone strata.