Search

The Oryctocephalus indicus biozone (Wuliuan, Miaolingian) is recognised in the Sumna Valley, in the southeastern part of the Spiti region in the Himalaya, based on the first appearance datum and last appearance datum of Oryctocephalus indicus. The biozone is approximately 5.6 m thick (17.8–23.4 m), and it contains the trilobites Oryctocephalus indicus, Pagetia significans and Kunmingaspis pervulgata. Comparative studies of the lithological variations across the Cambrian Series 2–Wuliuan (Miaolingian) transition in the Parahio and Sumna valleys (southeastern part of the Spiti region) show that the Wuliuan (Miaolingian) deposits transgressed over the undulatory surface of Cambrian Series 2. The uppermost part of the Cambrian Series 2 deposits in the southeastern part of the Spiti region is characterised by a reddish-brown ferruginous, very coarse grained sandstone unit, which indicates a diastem prior to the Wuliuan (Miaolingian) transgression.

This study investigated the potential of incorporating crushed brick powders (CBPs) and hydrated lime (HL) as additives in concrete production. Various tests were conducted on mortar, paste, and concrete samples to evaluate the performance of different blend types. The results reveal that among 3%, 6%, 9%, and 12% HL additive in the cement-CBP blend, 6% HL addition yields a significant increase in compressive strength of up to 16% compared to the control mortar. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) indicate improved hydration and reduced calcium hydroxide content in CBP-blended pastes, particularly in the blend with 6% HL. The concrete blend incorporating crushed bricks (C-CB) with 6% HL (C-CB-6HL) demonstrates superior early strength gain, surpassing the control blend by approximately 2.1% at 28 days and exhibiting the highest compressive strength at 90 days. It also shows enhanced moisture resistance, with a reduction in water absorption percentage of up to 10.6% compared to the control blend, reduced water permeability, improved resistance against chloride permeability, and better durability against acid attack compared to other blends. Overall, the C-CB-6HL blend shows the most promising durability characteristics, highlighting the potential for sustainable concrete production. Its outcomes have implications for shaping technical standards and promoting sustainable practices in the construction industry, aligning with environmental conservation goals. [ABSTRACT FROM AUTHOR]

The strength and durability properties of the recycled aggregate concrete (RAC) have been affected by the cracks and the weak interfacial transition zone (ITZ) of the recycled coarse aggregates (RCA). However, the mechanical and physical features of RCA can be improved by microbially induced calcite precipitation (MICP). Therefore, immobilization techniques were used to protect and maintain the high efficiency of Bacillus bacteria for the formation and precipitation of calcium carbonates in self‐healing concrete over a period of time. The objective of the present study was to show the viability of the immobilized bacterial consortium‐enhanced RCA to form self‐healing cracks. Further, the self‐healing capability of enhanced RCA was investigated along with two other immobilization methods, that is, RCA and hydrated lime and brick powder (HBr)‐immobilized bacteria. The experimental results show that the increase in the bio‐deposition time improved the physical and mechanical properties of the RCA. Further, subsequently 56 days of the healing incubation period, the immobilized consortium‐enhanced RCA concrete specimens completely healed the cracks of width 0.58 mm. However, the equivalent cracks of width 0.56 mm were also recovered by the HBr immobilized bacterial cultures. Furthermore, the field emission scanning electron microscope (FESEM), energy dispersive spectroscopy (EDS) and X‐ray diffraction (XRD) analysis revealed that the existence of precipitation at the crack surface was calcium carbonate with a regular cubic‐shaped and lamellar layer morphology. The outcomes of the current study show that consortium‐enhanced RCA has promising potential to develop self‐healing concrete with self‐repaired and improved durability properties in the concrete construction field. [ABSTRACT FROM AUTHOR]

Concrete is an important material for the construction of buildings, and highways. However, natural resources are being depleted by using natural coarse or fine aggregates for the production of concrete. The substitution of natural coarse aggregate (NCA) with recycled coarse aggregate (RCA) efficiently manages construction waste and preserves natural resources. In the present study, 50 and 100% NCA have been replaced with RCA for the preparation of recycled aggregate concrete (RAC) with blended hydrated-brick powder (RAC-HBr). Additionally, cement was replaced by 10 and 20% of blended HBr in the preparation of RAC mixes. To investigate the strength and durability properties of RCA-HBr mixtures, compressive strength, water permeability, chloride penetration test, and ultrasonic pulse velocity (UPV) tests were conducted. The outcomes indicate that the optimum percentage of blended HBr enhances the compressive strength of RCA mixes. However, blended HBr positively influenced the RCPT, water permeability, and ultrasonic pulse velocity of the RCA concrete mixes. Further, the RCPT outcomes show that the chance of corrosion was reduced by 20%, while the UPV value confirms that the density of the RAC-HBr mixes was enhanced by 28.7% at the age of 56 days. Furthermore, based on the FESEM and EDS analysis, the pozzolanic materials have densified the concrete matrix by reducing the pores and voids of RAC-HBr mixes. Thus, practically, 100% RCA with blended hydrated lime and brick powder can be used to create M35-grade concrete. The current paper investigates the effect of blended HBr on the properties of RAC. 10% HBr was an optimum percentage which has significantly enhanced the strength and durability characteristics of RAC mixes. CSH gel CH crystals densify the concrete matrix. CSH gel and CH crystals were confirmed from the microstructure analysis through FESEM and EDS analysis. [ABSTRACT FROM AUTHOR]

Our study compares the sensitivity, specificity and cost of visual acuity screening as performed by all class teachers (ACTs), selected teachers (STs) and vision technicians (VTs) in north Indian schools. Prospective cluster randomized control studies are conducted in schools in a rural block and an urban-slum of north India. Consenting schools, with a minimum of 800 students aged 6 to 17 years, within a defined study region in both locations, were randomised into three arms: ACTs, STs or VTs. Teachers were trained to test visual acuity. Reduced vision was defined as unable to read equivalent of 20/30. Optometrists, who were masked to results of initial screening, examined all children. Costs were measured for all three arms. The number of students screened were 3410 in 9 ACT schools, 2999 in 9 ST schools and 3071 in 11 VT schools. Vision deficit was found in 214 (6.3%), 349 (11.6%) and 207 (6.7%), (p <.001) children in the ACT, ST and VT arms, respectively. The positive predictive value of VT screening for vision deficit (81.2%) was significantly higher than that of ACTs (42.5%) and STs (30.1%), (p <.001). VTs had significantly higher sensitivity of 93.3% and specificity of 98.7%, compared to ACTs (36.0% and 96.1%) and STs (44.3% and 91.2%). The cost of screening children with actual visual deficit by ACTs, STs and VTs, was found to be $9.35, $5.79 and $2.82 per child, respectively. Greater accuracy and lower cost favours school visual acuity screening by visual technicians in this setting, when they are available. [ABSTRACT FROM AUTHOR]