Importance of consistent cement quality for a sustainable construction

The EN and SLS specifications for Portland cement have largely similar provisions on physical and chemical parameters of cement. However, consistency of cement within standards specifications is significantly high and it affect to standard deviation of concrete. In order to obtain good concrete quality, concrete users need to target a low standard deviation of concrete strength. In order to reduce the strength standard deviation of concrete strength, the material properties variations need to be lowered. This paper discusses variation in cement properties from 5 different cement suppliers. Cement from given suppliers varies between batches/ shipments. It is well understood that there are significant differences in mortar strength, chemical composition, fineness, setting times of same cement type (Type 1) from different suppliers. Experiments were conducted with 48 cement samples of 5 different cement suppliers collected over 10 months time from January 2011 to October 2011. It was found that as all cement brands comply with EN and SLS standards. However, coefficients of variation (COVs) of most parameters, especially strength, are significantly high. This paper answers two key questions; are all nominally similar cements the same? Does cement from same supplier always behave consistently? Finally it recommends cement users and specifies a systematic way to select a consistent cement supplier for an economical and sustainable construction

Pervious concrete – a sustainable choice in civil engineering and construction

Pervious concrete (no-fines concrete) is a concrete containing little or no fine aggregate; it consists of coarse aggregate and cement paste. It seems pervious concrete would be a natural choice for use in structural applications in this age of ‘green building’. It consumes less raw material than normal concrete (no sand), it provides superior insulation values when used in walls, and through the direct drainage of rainwater, it helps recharge groundwater in pavement applications. The first pervious concrete has been used in Europe and the United Kingdom since 1930s for the building of single story and multistory houses, but had found little acceptance in rest of the world. In recent years, however, due to increased awareness of the need for conservation of nonrenewable mineral resources, increased consideration is being given to the use of pervious concrete in most countries. Even though, it is not yet widely used in Sri Lanka, pervious concrete is generally used for light-duty pavement applications, such as residential streets, parking lots, driveways, sidewalks, channel lining, retaining walls and sound walls. This paper discuss the art of pervious concrete; materials and possible mix proportions, properties such as compressive strength, flexural strength, shrinkage, permeability with initial tests done at Innovation & Application Center of Holcim (Lanka) Limited, and the principal advantages, major disadvantages and principal applications in Sri Lankan construction industry

Water balance and renewal time of rekawa lagoon, Sri Lanka; a restorative approach

Rekawa Lagoon is a chocked and shallow coastal water body located in the southern coast of Sri Lanka. It is relatively unusual in that the major freshwater input, Kirama-oya river connects through the constricted channel much closer to the inlet at seaward end. A causeway was constructed, around 700 m from the lagoon inlet to the inland, across the constricted channel with an effort to link a secluded Kapuhenwala village with the rest of the area which in turn greatly reduced the volume and speed of water entering and leaving the lagoon system. Construction of the causeway led to many environmental problems with poor flushing efficiency and hampering to and fro movement of the prawns in the lagoon. The aim of this study was to evaluate the present situation and propose alternative management scenarios for improvement of water flow and lagoon ecosystem. The implications of different development stages of the causeway were discussed in terms of field measurements supported by modeling to describe the water balance and the water renewal time. The alternative of modifying the existing causeway was proposed to increase the free water flow at the inlet that favors recruitment of juvenile shrimp species

Knowledge, attitude and practices related to leishmaniasis among healthcare workers in an endemic area in southern Sri Lanka

NA

Behavioural indicators of welfare in farmed fish

Behaviour represents a reaction to the environment as fish perceive it and is therefore a key element of fish welfare. This review summarises the main findings on how behavioural changes have been used to assess welfare in farmed fish, using both functional and feeling-based approaches. Changes in foraging behaviour, ventilatory activity, aggression, individual and group swimming behaviour, stereotypic and abnormal behaviour have been linked with acute and chronic stressors in aquaculture and can therefore be regarded as likely indicators of poor welfare. On the contrary, measurements of exploratory behaviour, feed anticipatory activity and reward-related operant behaviour are beginning to be considered as indicators of positive emotions and welfare in fish. Despite the lack of scientific agreement about the existence of sentience in fish, the possibility that they are capable of both positive and negative emotions may contribute to the development of new strategies (e. g. environmental enrichment) to promote good welfare. Numerous studies that use behavioural indicators of welfare show that behavioural changes can be interpreted as either good or poor welfare depending on the fish species. It is therefore essential to understand the species-specific biology before drawing any conclusions in relation to welfare. In addition, different individuals within the same species may exhibit divergent coping strategies towards stressors, and what is tolerated by some individuals may be detrimental to others. Therefore, the assessment of welfare in a few individuals may not represent the average welfare of a group and vice versa. This underlines the need to develop on-farm, operational behavioural welfare indicators that can be easily used to assess not only the individual welfare but also the welfare of the whole group (e. g. spatial distribution). With the ongoing development of video technology and image processing, the on-farm surveillance of behaviour may in the near future represent a low-cost, noninvasive tool to assess the welfare of farmed fish.Fundação para a Ciência e Tecnologia, Portugal [SFRH/BPD/42015/2007]info:eu-repo/semantics/publishedVersio

Aquatic Plant and Benthic Macroinvertebrate Diversity in Headwaters of Sapugahadola Stream, Walasmulla

Headwater regions of the streams consist an array of unique biological communities, and these ecosystems are considered the most sensitive element of river ecosystems. The significant role played by these ecosystems are well documented but the information relevant to Sri Lankan water bodies is very limited. Thus, the present study was designed to study the vegetation and benthic macro- invertebrates in relation to their habitats at upstream Sapugahadola in Walasmulla. Four sites were selected in the headwater region from upstream to downstream (S1, S2, S3 and S4) and each site was visited two consecutive months in 2018. Distribution of aquatic plants was observed along a transect (7-13 m) which placed perpendicular to the stream bank. Benthos were collected at each four sites using Surber sampler. Water quality parameters (Temperature, pH, Conductivity, Dissolved Oxygen (DO)) were measured using water quality meters while Total Suspended Solids (TSS), Biological Oxygen Demand (BOD), nitrate and phosphate contents of water were measured using the standard analytical procedures. Soil pH, soil conductivity, soil nitrate, soil phosphate and soil organic carbon were measured as soil properties. Eleven macro- invertebrate families were found in the sampling sites representing eight orders, including nine insect families. Leptoceridae, baetidae and potamonidae were the most dominant families. Benthos diversity increased towards downstream and it was noticed in the Shannon-Wiener Index (SWI). The SWI of S1, S2, S3 and S4 were 1.49, 1.72, 1.70 and 1.88 respectively. Eighteen aquatic plant species were found in the stream sites, and out of those species, Taxiphyllum sp, Bryum sp and Homaliodendron flabellatum were dominant. The most dominated phylum was bryophyte and nine species were recorded. The highest SWI for plant was found in site 3 while it was statistically similar for other sites. Benthos diversity was strongly correlated with dissolved oxygen content (r=0.85, p<0.05), soil nitrate content (r=0.95, p<0.05) while the vegetation diversity was strongly correlated with total suspended solids (r=-0.74, p <0.05) and biological oxygen demand (r=0.89, p<0.05). Although the relationship between macro-invertebrate diversity and soil quality parameters were significant, vegetation diversity was independent from soil properties. Most of the vegetation were found on rocky surfaces that were above the water level of the stream.Keywords: Vegetation, Macro- invertebrates, Diversity, Soil properties, Water qualit

The Current status of density stratification of Koggala lagoon

A field observation was conducted on 22nd November 2011 to estimate the present state of density stratification of Koggala lagoon. Vertical variation of salinity, water temperature and dissolved oxygen were measured with neap and ebb. The same measurements were taken from inflow streams. The observations indicate that main water body of the lagoon is salinity stratified despite the strong or partial mixing at the mouth. Particularly, strong saline stratification is prominent in the deep central part of the lagoon. Firstly, the current hydraulic state and then bulk parameter of Koggala lagoon is analysed. The relationship between the mixing state and the values of parameters of Koggala lagoon agree with Fisher’s plot. The effects of modification of lagoon mouth are discussed based on these parameters. Temporal and spatial complexities of lagoon mouth affect transport and mixing of saline water and intrusion into the lagoon. In future, a modified bulk parameter will be needed for better understanding of stratification behaviour of the Koggala lagoon

High performance concrete incorporating fly ash, nano-silica (nano-SiO2) and micro-silica (micro-SiO2)

High performance concrete (HPC) exceeds the properties and constructability of normal concrete. Normal and special materials such as fly ash, micro silica and nano silica are used to make these specially designed concretes that must meet a combination of performance requirements. There are many good reasons to view fly ash, micro silica and nano silica as blended materials in concrete. In many cases, concrete made with fly ash, micro silica and nano silica performs better than concrete made without them. In this paper, an effort was made to evaluate the effect of nano-silica (nano-SiO2), micro-silica (micro-SiO2) and fly ash in improving the properties concrete. Firstly, compressive strength of concrete with different percentage of nano-silica (nano-SiO2), micro-silica (micro-SiO2) and fly ash was studied. Secondly, compressive strength of concrete with Ordinary Portland cement (OPC) and Portland fly ash cement (PPC) was studied. Thirdly, compressive strength of concrete with combination of fly ash and micro silica (micro-SiO2) was studied