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Urease were known to catalyze the conversion of urea to ammonia and carbon dioxide. Microbial urease has demonstrated its benefits in wide biotechnological, agricultural, medicinal and engineering application. There are number of diverse microbial species contribute to urease activity in different natural habitats like soil, ocean and in various geological formation. For this study, urease bacteria were screened and isolate from acidic peat in Sarawak, Malaysia. Five distinct and diverse bacterial strains that were able to produce urease constitutively were selected to be characterized with respect to morphology, biochemical test, growth conditions and urease activity. The selected strain showed their capability to precipitate calcium carbonate (CaCO 3 ). Hence, the isolates could be potential source of acid ureases that can be use in various industrial utilizations. 16S rRNA sequencing and phylogenetic analysis found that the selected isolates belong to the genus of Bacillus . [ABSTRACT FROM AUTHOR]

• Replacing coarse aggregate of adsorbent pervious concrete with iron slag improved the mechanical and physical properties. • Mechanical strength of adsorbent pervious concrete is reduced by substituting coarse aggregates with zeolite. • Using adsorbents in pervious concrete decreases the volume of waste in the environment. • Adsorbent pervious concrete could be an effective approach for wastewater post-treatment. Using low-cost industry waste and mineral adsorbents to produce Adsorbent Pervious Concrete (APC) is a sustainable solution with manifold environmental advantages. This study investigates the engineering properties of APC to widen the potential of its further utilization as a post-treatment step in refinery and wastewater treatment plants. For this reason, coarse aggregate in pervious concrete was replaced by coarse iron slag and zeolite in portions of 25%, 50%, 75%, and 100% by volume. The statistical analysis of variance (ANOVA) and visualization of the microstructure of APC using Scanning Electron Microscopy (SEM), and Energy Dispersive X-Ray Spectroscopy (EDS) were also presented. Experimental results showed that replacing coarse aggregate with iron slag increased the APC's strength, and the maximum value of compressive strength (16.80 MPa) occurred at 75% of replacement. Alternatively, increasing the zeolite proportion caused the strength reduction of APC, and the minimum compressive strength (9.40 MPa) happened in a sample with only coarse zeolite. The effect of cementitious paste thickness (CPT) on the compressive strength indicated that the iron slag did not markedly change the average of CPT, only a minor reduction compared to the control sample (0.30–1.5 mm), while zeolites caused considerable increase of average CPT (0.00–2.1 mm). Hence, increasing the average CPT resulted in reducing the APC compressive strength. Also, the specific gravity, resistance to compression, rectangular shape, and micropores on the surface of adsorbents affected the mechanical properties, porosity, and permeability of APC. All APC samples had a satisfactory porosity (more than 15%) and permeability (more than 1.17 mm/s), and the APC sample containing 75% of iron slag had the highest values. The role of adsorbents shape affects the porosity and permeability of APC, especially in the replacement portion of 50% and less, while for samples with more than 50% of adsorbents due to homogenization of the mix and having the same size as aggregates, the void content and infiltration rate approached the value of the control sample. Eventually, iron slag and zeolite based APC could potentially be used in wastewater treatment plants for post-treatment of wastewater as a new cleaner production. [ABSTRACT FROM AUTHOR]

In the paper, we present newly developed hydro-mechanical hypoplastic model for partially saturated soils predicting small strain stiffness. Hysteretic void ratio dependent water retention model has been incorporated into the existing hypoplastic model. This required thorough revision of the model structure to allow for the hydro-mechanical coupling dependencies. The model is formulated in terms of degree of saturation, rather than of suction. Subsequently, the small strain stiffness effects were incorporated using the intergranular strain concept modified for unsaturated conditions. New features included degree of saturation-dependent size of the elastic range and an updated evolution equation for the intergranular strain. The model has been evaluated using two comprehensive data sets on completely decomposed tuff from Hong-Kong and Zenos Kaolin from Iran. It has been shown that the modified intergranular strain formulation coupled with the hysteretic water retention model correctly reproduces the effects of both the stress and suction histories on small strain stiffness evolution. The model can correctly predict also different other aspects of partially saturated soil behaviour, starting from the very small strain range up to the asymptotic large-strain response. [ABSTRACT FROM AUTHOR]

The adverse effects of hostile marine environment on concrete structure have inevitably resulted in huge economic loss and may contribute to catastrophic failure. Concrete is susceptible to weathering, particularly under wetting-drying action (WDA), although its current state of the art is well established. The diverse characteristics of WDA at different site locations have compromised the reliability of laboratory works. The objective of this study is to review the impact of WDA on concrete and to provide an overview of the research trend, aiming to identify the research gap. Concrete deterioration mechanisms in marine environment in respect of WDA are identified. The influential factors of WDA are analyzed. The physical and mechanical properties and corrosion resistance of concrete exposed to WDA are discussed. WDA aggravates concrete deterioration by hastening intrusion of inimical compounds such as chloride, sulphate and carbon dioxide. Chloride convection zone can be expanded by two to three times to cause a significant concrete cover loss. Physical damage of concrete starts with efflorescence staining, followed by mortar delamination, aggregate detachment and concrete spalling, leading to loss of mechanical properties. The use of mineral admixtures such as fly ash and silica fume improves concrete resistance against corrosion, but its refining effect may lead to over-accumulation of chloride, risking the long-term durability. Limited research works are identified on synergy between physical and chemical deteriorations, validation of simulated experiment, volume expansion, mass change and tensile strength of concrete. • Wetting-drying action accelerates intrusion of chloride, sulphate and carbon dioxide. • Wetting-drying behavior, ion, temperature and loading impact deterioration mechanism. • Damage includes efflorescence stain, mortar and aggregate splitting and strength loss. • Increased moisture transfer expands chloride convection zone and hastens corrosion. • Shortfalls of test disparity, simulation difficulty and lack of guidelines are noted. [ABSTRACT FROM AUTHOR]

• Concrete incorporated with silicomanganese (SiMn) slag, marine sand and seawater was studied. • SiMn slag reduced concrete compressive and tensile strengths by 9.2% and 17.5% respectively. • SiMn slag concrete exhibited comparable durability in the long term. • Marine sand had advantageous effect on durability of concrete. This experimental investigation has validated the feasibility of utilizing silicomanganese (SiMn) slag, marine sand and seawater in concrete production. Compressive and splitting tensile strengths of concrete were evaluated. Assessment was also performed on concrete durability which included water absorption, sorptivity, chloride penetration and sulphate resistance. SiMn slag was found to reduce concrete compressive and tensile strengths by 9.2% and 17.5% respectively. Nevertheless, the concrete exhibited comparable durability to conventional concrete at 90-day age, though it showed reduced value at 28-day age. The research also illustrated that marine sand improved concrete durability by at least 42.3% and 11.5% in aspect of sorptivity and chloride penetration respectively, while seawater showed little effect. More durable concrete can be produced by utilizing SiMn slag, marine sand and seawater for potential industrial application. [ABSTRACT FROM AUTHOR]