ARTICLE | doi:10.20944/preprints202007.0602.v1
Subject: Engineering, Civil Engineering Keywords: recycled crushed concrete aggregate; reclaimed asphalt pavement; unconfined compressive strength; Microstructure; scanning electron microscope; image analysis
Online: 25 July 2020 (11:07:49 CEST)
The reuse of recycled crushed concrete aggregate (RCCA) and reclaimed asphalt pavement (RAP) can provide a sustainable solution for the disposal of C&D materials instead of sending it to landfill. More importantly, it will save energy and reduce impact on the environment. Several states in USA are using RCCA and RAP as base materials for years, focusing on the quality of the recycled materials. The structure of Recycled Aggregate (RA) is more complex than Natural Aggregate (NA). RAs have old mortar adhered on them that forms a porous surface at interfacial transition Zone (ITZ) and prevents new cement mix from bonding strongly with the aggregates. The objective of this work was to correlate microstructural properties like micro-porosity, inter and intra aggregate pores with the unconfined compressive strength (UCS) of RAP and RCCA molds, mixed at different proportions. In this paper, the quantity of micro-pores and their effect on the strength of mixed materials is used as the basis of microstructural analysis of recycled concrete and reclaimed asphalt. Microstructural properties obtained from the analysis of scanning electron microscope (SEM) images were correlated with unconfined compressive strength. Intra-aggregate and inter-aggregate pores were studied for different ratios of cement treated mixture of RAP and RCCA. The results show that the number of pores in the mixture increases considerably by adding RAP, which eventually causes reduction in unconfined compressive strength. In addition, significant morphological and textural changes of recycled aggregates were observed by SEM image analysis.
ARTICLE | doi:10.20944/preprints202011.0739.v1
Subject: Medicine & Pharmacology, Allergology Keywords: knowledge; attitude; preparedness; COVID-19; gender; Bangladesh
Online: 30 November 2020 (16:12:02 CET)
Effective pandemic management requires understanding the level of community knowledge, attitude of people and preparedness towards COVID-19. This study aimed to assess the knowledge, attitude and preparedness toward COVID-2019 among Bangladeshi general people. A cross sectional survey was conducted from 20th March 2020 to 20th April 2020 among 1007 Bangladeshi adult people. A convenience sampling strategy was utilized and the data was collected through a self-administered questionnaire. Chi-square test was used to identify the gender differences regarding knowledge, attitude and preparedness towards COVID-19. Respondents predominately used social media to inform themselves about COVID-19 (68.10%) and female used social media more than male (p<0.001). Female had more correct knowledge about staying home with sickness and/or symptoms to contain the COVID-19 transmission (p=.02). While male had more negative attitude about staying out during the pandemic than female (<0.001) and men were less likely to take preventative measures than female counterparts. A number of people were still believing the myths like “COVID-19 can transmit via mosquito” (9.14%) and male had more incorrect knowledge regarding this (p<0.001). Moreover, 17.81% of the respondents thought that COVID-19 can spread in warm weather. Some findings are directing us to a knowledge gap among general population in Bangladesh which calls for uncovering those aspects. Adequate and effective communication are necessary so that general people can stay alert with positive attitude and hygienic practices to fight against this ongoing crisis.