Hydraulic and strength properties of unexposed and freeze–thaw exposed cement-stabilized soils

A total of 108 specimens were prepared to examine the hydraulic performance and strength performance of nine different cement-stabilized soils under unexposed and freeze–thaw exposed conditions. Specimens from each mix design were evaluated under two levels of curing conditions (i.e., immature versus mature). Hydraulic conductivity and unconfined compressive strength (UCS) measurements were performed to assess changes in the performance of specimens after 12 cycles of freezing at −10 ± 1 °C and thawing at 22 ± 1 °C. Measured mass losses of the specimens from a standard brushing test were also monitored at different freeze–thaw cycles, and results were compared with the changes in the hydraulic performance for each mix design. Hydraulic conductivity measurements on unexposed mature specimens showed that the lowest values likely occurred at water contents slightly wet of optimum water content (OWC). The UCS values showed a general decreasing trend with the increase in the water content for both immature and mature specimens under unexposed conditions. After freeze–thaw exposure, specimens showed minor reductions as well as increases of up to 5250 times in hydraulic conductivity values. Increases of up to 14% and reductions of up to 58% in compressive strength were also observed, compared with unexposed conditions. For most cases, mature specimens resulted in a higher degree of damage compared with immature specimens. Results from the brushing tests showed this test method is not a suitable indicator for predicting changes in the hydraulic performance of cement-stabilized soils. Hydraulic conductivity measurements after a period of post-exposure healing showed damaged specimens have some potential in recovering parts of the increased hydraulic conductivity value due to the healing process. </jats:p

Examining Freeze/Thaw Cycling and Its Impact on the Hydraulic Performance of Cement-Treated Silty Sand

Cement-based solidification/stabilization (s/s) is a remediation technology that has been widely used for treatment of a range of contaminants. Currently there is limited published data on changes in hydraulic performance of cement-treated materials subjected to cycles of freezing/thawing (f/t). Fourteen sets of tests were performed to examine the influence of factors such as number of f/t cycles, freezing temperature, curing time, and mix design on hydraulic conductivity and unconfined compressive strength (UCS) of a cement-treated silty sand. Results showed an increase of up to three orders of magnitude in hydraulic conductivity as well as decreases in UCS values after exposure to four to twelve f/t cycles. Analysis of variance (ANOVA) performed on the results of a factorial experiment considering the effect of freezing temperature, curing time, and number 22 of f/t cycles showed that all of these factors are significant in affecting the measured changes in the hydraulic conductivity and UCS values. Monitoring of damage using the impact resonance method showed that changes in the resonant frequency of specimens was consistent with changes in hydraulic conductivity and UCS after f/t exposure and also allowed monitoring of damage for intermediate cycles with minimal effort

THE EFFECT OF FREEZE/THAW CYCLES ON THE PERFORMANCE AND MICROSTRUCTURE OF CEMENT-TREATED SOILS

In this paper, the performance and structural changes in cement-treated soils under influence of freeze/thaw (f/t) exposure are investigated. Specimens from plastic and compacted soil-cement mix designs were exposed to different f/t scenarios to study the influence of f/t dimensionality (i.e., one-dimensional vs three-dimensional exposure) and specimens' age at the time of f/t exposure on changes in their performance. Changes in hydraulic conductivity, unconfined compressive strength, and longitudinal resonant frequency of the specimens were studied under each exposure scenario. An examination of the microstructure of the f/t exposed and control specimens using transmitted light optical microscopy was also performed to evaluate how the soil-cement matrix was disrupted after exposure to f/t cycling. Observations showed increases in water content of the mix design (when wet of optimum water content), as well as increased specimen age at the time of exposure may increase f/t susceptibility. Contrary, comparison of the performance of the specimens exposed to one-dimensional and three-dimensional f/t exposure did not show any significant variation. Microstructural analysis of petrographic thin section samples from control and f/t exposed specimens showed that while optical microscopy can detect matrix disintegration for highly damaged specimens, it is not able to identify structural degradation at early stages of damage development

The effect of freeze/thaw cycles on the performance and microstructure of cement-treated soils

In this paper, the performance and structural changes in cement-treated soils under influence of freeze/thaw (f/t f/t) exposure are investigated. Specimens from plastic and compacted soil-cement mix designs were exposed to different f/t f/t scenarios to study the influence of f/t f/t dimensionality (i.e., one-dimensional versus three-dimensional exposure) and specimens’ age at the time of f/t f/t exposure on changes in their performance. Changes in hydraulic conductivity, unconfined compressive strength, and longitudinal resonant frequency of the specimens were studied under each exposure scenario. An examination of the microstructure of the f/t f/t exposed and control specimens using transmitted light optical microscopy was also performed to evaluate how the soil-cement matrix was disrupted after exposure to f/t f/t cycling. Observations showed increases in water content of the mix design (when wet of optimum water content), as well as increased specimen age at the time of exposure may increase f/t f/t susceptibility. On the other hand, comparison of the performance of the specimens exposed to 1D and 3D f/t f/t exposure did not show any significant variation. Microstructural analysis of petrographic thin section samples from control and f/t f/t exposed specimens showed that while optical microscopy can detect matrix disintegration for highly damaged specimens, it is not able to identify structural degradation at early stages of damage development

AKAPs integrate genetic findings for autism spectrum disorders

Contains fulltext : 115371.pdf (publisher's version ) (Open Access)Autism spectrum disorders (ASDs) are highly heritable, and six genome-wide association studies (GWASs) of ASDs have been published to date. In this study, we have integrated the findings from these GWASs with other genetic data to identify enriched genetic networks that are associated with ASDs. We conducted bioinformatics and systematic literature analyses of 200 top-ranked ASD candidate genes from five published GWASs. The sixth GWAS was used for replication and validation of our findings. Further corroborating evidence was obtained through rare genetic variant studies, that is, exome sequencing and copy number variation (CNV) studies, and/or other genetic evidence, including candidate gene association, microRNA and gene expression, gene function and genetic animal studies. We found three signaling networks regulating steroidogenesis, neurite outgrowth and (glutamatergic) synaptic function to be enriched in the data. Most genes from the five GWASs were also implicated-independent of gene size-in ASDs by at least one other line of genomic evidence. Importantly, A-kinase anchor proteins (AKAPs) functionally integrate signaling cascades within and between these networks. The three identified protein networks provide an important contribution to increasing our understanding of the molecular basis of ASDs. In addition, our results point towards the AKAPs as promising targets for developing novel ASD treatments