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An experimental study on interpretation of core test results for assessment of concrete in-situ strength
No full textIn existing concrete structures, concrete cores may be extracted to assess the current condition of the structure. This is often done when there are concerns about the structural integrity or if the structure is undergoing renovations or modifications and to determine its ability to carry additional loads. This is generally done by taking cores at representative locations in the structure, to give a good overall indication of the strength. This helps ensure that the concrete meets the required strength and durability standards.
Core testing is therefore introduced in most local and international codes such as British, European and ACI Codes. The core test results should be carefully interpreted taking into account a number influencing factors such as diameter, aspect ratio (l/d), moisture condition of the core specimen, direction of drilling, etc. The factors considered in different standards and interpretation of the core results and influence of above factors are different.
In New Zealand, the technical standards NZS 3112:2 and NZS3109, have detailed how these tests should be carried out and the results analysed. In the New Zealand concrete construction standard NZS3109, the evaluation of core test results is determined by Technical Report No. 11 (TR11) from the UK Concrete Society. However, this document was withdrawn and replaced in the UK by Concrete Advice No. 68 (CA68), which is a summary of BS EN 13791.
In this research, an experimental study was undertaken to examine different factors affecting the interpretation of core test results, in particular comparing the methods described in TR11 and CA68. The experimental program involves four concrete test blocks. In total 24 concrete cores were taken with different length/diameter ratios in vertical and horizontal directions.
The compressive test results obtained from the cores are analysed and the influence of different factors are discussed. The results are evaluated in accordance with TR11 and CA68 codes, to compare and identify possible differences between the two methods in assessment of Concrete In-Situ Strength from core test results
Harnessing cold adaptation for postglacial colonisation: Galactinol synthase expression and raffinose accumulation in a polyploid and its progenitors
No full textAllotetraploid white clover (Trifolium repens) formed during the last glaciation through hybridisation of two European diploid progenitors from restricted niches: one coastal, the other alpine. Here, we examine which hybridisation-derived molecular events may have underpinned white clover's postglacial niche expansion. We compared the transcriptomic frost responses of white clovers (an inbred line and an alpine-adapted ecotype), extant descendants of its progenitor species and a resynthesised white clover neopolyploid to identify genes that were exclusively frost-induced in the alpine progenitor and its derived subgenomes. From these analyses we identified galactinol synthase, the rate-limiting enzyme in biosynthesis of the cryoprotectant raffinose, and found that the extant descendants of the alpine progenitor as well as the neopolyploid white clover rapidly accumulated significantly more galactinol and raffinose than the coastal progenitor under cold stress. The frost-induced galactinol synthase expression and rapid raffinose accumulation derived from the alpine progenitor likely provided an advantage during early postglacial colonisation for white clover compared to its coastal progenitor
The decision to buy genetically modified foods in China: What makes the difference?
No full textGenetically modified (GM) food products have been commercialized and promoted in China. Despite assurances from the China Ministry of Agriculture that certified GM food products are safe to consume, most consumers are reluctant to purchase GM foods. Given the benefits of GM foods, this study investigates Chinese consumers’ purchase intentions and purchase behavior toward GM foods and the associated influential factors. The theory of planned behavior with the consumers’ demographics and product-related factors supports our study. Data were collected from 477 Chinese consumers across 26 provinces in China. The study uses binary logit regression and ordinal logit regression to estimate the relationship among variables. The results reveal that Chinese consumers’ awareness, products’ available information, trust in sellers, long product life, GM foods’ taste and consumers’ experience in buying GM food products are positively related to their willingness to buy GM foods. The number of family members, the habit of checking GM labels and a preference for nutrition value are associated with Chinese consumers’ lower intention to buy GM foods. We demonstrate that product variety and trust are two determinants that could change Chinese consumers’ attitudes toward buying GM foods. Our study contributes new insights into Chinese consumers’ decision to purchase GM foods at the national scale. We consider a wide range of factors not tested in previous studies. Further, the study’s findings provide a better understanding of consumers’ GM foods purchases and purchasing behavior toward the Chinese government and entrepreneurs
Farmers’ perceptions, adoption and impacts of integrated water management technology under changing climate
Get PDFThis study investigates the correlations between Chinese banana farmers’ perceptions of integrated water management technology (IWMT) and their adoption behaviours and examines the impact of IWMT adoption on farm performance. The results revealed that farmers’ IWMT adoption correlates significantly with their perceptions of whether IWMT adoption can help reduce farm workload, fertilizer and water, the extent to which the technology is easier to operate, and the extent to which the technology can generate higher economic benefits than furrow irrigation technology. IWMT adoption significantly increases banana yields, gross revenue, net returns and irrigation frequency, but does not significantly affect irrigation expenditure
Global evidence on the association between environmental, social, and governance disclosures and future earnings risk
No full textMotivated by growing stakeholder demands for environmental, social and governance (ESG) disclosures and enhanced information transparency, this study investigates the relationship between ESG disclosures and future earnings risk in a globally diverse sample of firms. Using fixed-effects panel regression models and endogeneity controls, we show that ESG disclosures exhibit a substantial negative impact on earnings risk. The sub-dimensions, except governance, of ESG disclosures also reveal a negative impact on earnings risk. Notably, the social dimension's impact is economically more pronounced than the other ESG disclosure dimensions, indicating that social issues carry more value in reducing the uncertainty surrounding the future earnings risk of a firm. Besides, higher ESG reporting firms benefit more from reducing future earnings risk than low-reporting firms. Our findings suggest that enhancing information transparency can help alleviate the agency problem arising from information asymmetry between corporate managers and shareholders. Moreover, higher disclosure in various ESG dimensions can address stakeholders' concerns regarding firm's social and environmental impacts
Plant responses to nitrate and ammonium availability in Australian soils as measured by diffusive gradients in thin-films (DGT) and KCl extraction
Get PDFDetermining soil nitrogen (N) availability is essential in agriculture to minimise over-application, maximise growers’ returns and reduce potential environmental consequences. The present study assesses soil mineral N (nitrate-N and ammonium-N) using the diffusive gradients in thin-films (DGT) technique against the conventional potassium chloride (KCl) extraction. The DGT technique has demonstrated reliable predictability for plant-available P, Cu and Zn. However, the use of DGT to quantify soil N bioavailability is underreported and N measurements made with DGT have not been compared to plant growth responses or N uptake. A pot trial using wheat was performed to determine the suitability of the DGT technique to predict N plant uptake and plant biomass. Four contrasting soil types from South Australia were used, and four rates of N were applied to the soil. DGT devices and KCl extraction were used at sowing to measure soil mineral N. These data were then compared with plant relative yield (YR) and N uptake after harvesting the plants. Soil mineral N, as measured by both the DGT and KCl extraction techniques, demonstrated a significant positive correlation with YR, with an R² value of 0.6; however, DGT-N extracted comparatively more nitrate (NO₃-, >87 % of CN) than KCl-N (65 % of EN). Mineral N and NO₃- extracted by both DGT and KCl significantly correlated with plant N uptake albeit this correlation was stronger for KCl (R² = 0.8) than DGT (R² = 0.6). The same parameters also positively and significantly correlated with YR, however in this case, both correlations were similar and only modest (R² < 0.6 in all cases). These results are explained in terms of the differences between the pools of N accessed by these techniques and limitations related to soil N dynamics. In conclusion, KCl showed similar or better predictive ability for N uptake and yield response (YR) in wheat compared to DGT across four Australian soils. Given its low cost and ease of application, KCl presents a competitive advantage in this study
Host genetics shapes Pinus radiata phenotypic plasticity under drought and is linked with root-associated soil microbiome shifts
No full textUnder current and future climate scenarios, identifying drought-resistant tree species, tree genotypes, and beneficial interactions between trees and their root-associated soil microbiomes is becoming more imperative for maintaining tree health and sustaining increasingly vulnerable forests. We designed a genotype x soil x watering x time glasshouse experiment using Pinus radiata as a model tree to assess the magnitude of the effect of host genotype and root-associated soil microbiome on the phenotype response (functional traits, metabolome, nutrients) under drought. We identified the shikimate pathway as a critical metabolic pathway for Pinus radiata drought resistance, with the shikimic acid intermediate being one of the strongest drought signals, besides downstream metabolites such as flavonoids and phenylpropanoids. Overall, we found that the host genotype diversity was a key actor in the observed phenotype response of P. radiata to drought. In contrast, the microbiome was attributed a minor supporting role. Contrary to our hypothesis, dry soils could not support drought-sensitive genotypes under drought stress. Instead, the drought-resistant genotype was able to leverage locally adaptive bacteria to match local selective drought pressures at the expense of tree growth. This highlights the significance of finding specific combinations of tree genotype and mutualistic microbial communities that would thrive under future environmental pressure
The impacts of ecological disturbances on the diversity of biosynthetic gene clusters in kauri (Agathis australis) soil
Get PDFBackground The ancient kauri (Agathis australis) dominated forests of Aotearoa New Zealand are under threat from a multitude of ecological disturbances such as forest fragmentation, biodiversity loss, climate change, and the spread of the virulent soil pathogen Phytophthora agathidicida. Taking a wider ecosystem-level approach, our research aimed to explore the impacts of forest disturbance and disease outbreaks on the biosynthetic potential and taxonomic diversity of the kauri soil microbiome. We explored the diversity of secondary metabolite biosynthetic gene clusters (BGCs) in soils from a range of kauri forests that varied according to historical disturbance and dieback expression. To characterise the diversity of microbial BGCs, we targeted the non-ribosomal peptide synthetase (NRPS) and polyketide synthetase (PKS) gene regions for sequencing using long-read PacBio® HiFi sequencing. Furthermore, the soil bacterial and fungal communities of each forest were characterized using 16 S rRNA and ITS gene region sequencing.
Results We identified a diverse array of naturally occurring microbial BGCs in the kauri forest soils, which may offer promising targets for the exploration of secondary metabolites with anti-microbial activity against P. agathidicida. We detected differences in the number and diversity of microbial BGCs according to forest disturbance history. Notably, soils associated with the most undisturbed kauri forest had a higher number and diversity of microbial NRPS-type BGCs, which may serve as a potential indicator of natural levels of microbiome resistance to pathogen invasion.
Conclusions By linking patterns in microbial biosynthetic diversity to forest disturbance history, this research highlights the need for us to consider the influence of ecological disturbances in potentially predisposing forests to disease by impacting the wider health of forest soil ecosystems. Furthermore, by identifying the range of microbial BGCs present at a naturally high abundance in kauri soils, this research contributes to the future discovery of natural microbial compounds that may potentially enhance the disease resilience of kauri forests. The methodological approaches used in this study highlight the value of moving beyond a taxonomic lens when examining the response of microbial communities to ecosystem disturbance and the need to develop more functional measures of microbial community resilience to invasive plant pathogens
Differential structure and function of phosphorus-mineralizing microbial communities in organic and upper mineral soil horizons across a temperate rainforest chronosequence
Get PDFMicrobial community structure and function were assessed in the organic and upper mineral soil across a ∼4000-year dune-based chronosequence at Big Bay, New Zealand, where total P declined and the proportional contribution of organic soil in the profile increased with time. We hypothesized that the organic and mineral soils would show divergent community evolution over time with a greater dependency on the functionality of phosphatase genes in the organic soil layer as it developed. The structure of bacterial, fungal, and phosphatase-harbouring communities was examined in both horizons across 3 dunes using amplicon sequencing, network analysis, and qPCR. The soils showed a decline in pH and total phosphorus (P) over time with an increase in phosphatase activity. The organic horizon had a wider diversity of Class A (phoN/phoC) and phoD-harbouring communities and a more complex microbiome, with hub taxa that correlated with P. Bacterial diversity declined in both horizons over time, with enrichment of Planctomycetes and Acidobacteria. More complex fungal communities were evident in the youngest dune, transitioning to a dominance of Ascomycota in both soil horizons. Higher phosphatase activity in older dunes was driven by less diverse P-mineralizing communities, especially in the organic horizon
Possibility of using dry ryegrass as a partial substitution of Portland cement to produce concrete for reducing carbon footprint of cement
No full textCement production has a significant impact on the environment due to its high carbon footprint during production processes. Altering composition of concrete by reducing proportion of cement could be a way to contribute to climate change mitigation initiatives. This study aimed to investigate the possibility of using dry ryegrass as a partial replacement for cement to produce concrete. Seven concrete samples were prepared by mixing dry ryegrass with varying proportion (i.e., 0.0, 0.2, 0.5, 1.0, 2.0, 5.0 and 10.0%) with a readymade mix of concrete having a 10 to 20% cement ratio. The 28-day mechanical property (compressive strength) of the concrete samples was compared with the 28-day characteristic compressive strengths of the normal strength grades specified in NZS 3109. Samples with 2.0, 5.0 and 10.0% of dry ryegrass mixture did not have enough strength to withhold the compression test and quantifiable measurements could not be obtained. Samples with 1.0% of dry ryegrass mixture had negligible compression strength. The low compressive strength of the sample with 1.0, 2.0, 5.0 and 10.0% of dry ryegrass mixture was associated with the higher water retention by the grass present in the concrete mixture which prevented the curing process. The higher water retention also reduced the effective binding of the aggregate. Average compressive strength of the samples with 0.2 and 0.5% dry ryegrass mixture had 28.13 and 21.58 MPa, respectively. Sample with 0.2% dry ryegrass mixture can be applicable in heavy applications while sample with 0.5% dry ryegrass mixture can be applicable in light applications. Manufacturing a kg of cement produces a kg of CO2 thus, if 0.5% dry ryegrass mixture is used in concrete production, 0.5% CO₂ emission can be reduced. However, even at 0.2% dry ryegrass mixing the strength reduced by 39%. So, it might not be reasonable to go for 0.5% carbon emission reduction at the cost of 40% strength reduction. The results confirmed that the use of dry ryegrass as a partial component of cement for the preparation of concrete is not justifiable