Optimum mix design of concrete made with dune sand as fine aggregate

The use of dune sand for replacing ordinary fine aggregate in concrete has environmental benefits and the feasibility has been demonstrated in China and some Middle East countries. However, the use of dune sand tends to decrease the engineering properties (compressive strength and workability) of concrete. To improve engineering properties of dune sand concrete (DSC), the current paper is to check which strength andslump levels can be obtained by optimization of mix proportions. Results show that the ratio of cement to sand (C/S) has significant influence on the engineering properties of DSC. At low C/S ratio, the engineeringproperties of DSC are inferior to those of concretes made with normal sand (NSC). However, when C/S ratio exceeds 0.75, DSC has comparable or even better engineering properties compared to NSC. In the range ofinvestigated C/S ratio, DSC has comparable tensile splitting strength and elastic modulus to its reference NSC.Based on the experimental results, the Australia dune sand can be used as fine aggregate whenever mix proportions are properly controlled.

The properties of fly ash based geopolymer mortars made with dune sand

Geopolymer cement utilises industrial by-products and is associated with low CO2 emissions. The use of dune sand as fine aggregate could reduce the environmental impact of mining activities. The present study is to examine the feasibility of using dune sand in geopolymer-based construction materials. The geopolymer mortars made with dune sand (DSM) were prepared by using alkali activators of different cations(Na, K and Na/K). In order to compare, the corresponding geopolymer mortars made with normal sand (NSM) were also prepared. It was found that dune sand has little influence on the strength of geopolymer mortars, especially for K based mortars. However, the alkali cation has significant influence on the compressive strength of geopolymer mortars. This influence was found to be correlated to porosity. Low compressive strength is associated with high porosity. For all investigated alkali cations, the tensile strengths of DSM compare favourably to those predicted by the relevant Standards for construction materials. Based on the experimental results, Australian dune sand can be used as fine aggregate for the production of geopolymer based construction materials.

The properties of fly ash based geopolymer mortars made with dune sand

This paper reports the properties of fly ash based geopolymer mortars made with dune sand. The geopolymer mortars of different cation type, namely sodium based (Na), potassium based (K) and a mixed Na/K, were prepared with dune sand (DS) and river sand (RS). The corresponding geopolymer pastes were also prepared. A series of tests including compressive strength, modulus of elasticity, splitting tensile strength, microanalysis (using scanning electron microscopy), porosity (using mercury intrusion porosimetry), sorptivity and air void (using section analysis method) were carried out. The results showed a strong correlation between strength and porosity of geopolymeric materials. The addition of DS had influences on the chemical compositions and physical properties of geopolymer mortars. These influences were dependent on the type of cation. Based on the results of mechanical properties, DS can be utilised as the fine aggregate for the production of geopolymer based construction material.

Effects of beacon administration on energy expenditure and substrate utilisation in Psammomys obesus (Israeli sand rats)

Objective: To investigate whether beacon administration affects substrate utilisation, physical activity levels or energy expenditure in Psammomys obesus. Design: Pairs of age- and sex-matched Psammomys obesus were randomly assigned to either beacon-treated (15 µg/day for 7 days (i.c.v.)) or control (i.c.v. saline) groups. Measurements: Indirect calorimetry on day 0 and day 7 to measure oxygen consumption and carbon dioxide production, which were used to calculate fat oxidation, carbohydrate oxidation and total energy expenditure. Physical activity in the calorimeter was measured using an infrared beam system. Food intake and body weight were measured daily. Results: The administration of beacon significantly increased body weight compared to saline-treated control animals. This body weight gain was primarily due to increased body fat content. Average daily food intake tended to be higher in beacon-treated Psammomys obesus, but no effect of beacon administration on substrate oxidation, activity or energy expenditure was detected. Conclusion: The effects of beacon on body weight are due to increased food intake, with no detectable effect on nutrient partitioning, physical activity or energy expenditure.

Changes in vegetation sand floristics under a powerline easement and implications for vegetation management

Utility corridors such as powerlines are widespread linear easements of highly modified vegetation which often fragment natural areas of conservation significance. Vegetation management along these easements is aimed at modifying vegetation structure by the removal of all tall shrubs and trees, which may have adverse impacts on flora and fauna diversity. Victoria's Bunyip State Park is bisected by a high voltage powerline easement which is managed by a four year slashing cycle. Repeated slashing has altered plant species composition and structure of the drier slope and ridge vegetation compared to unslashed adjacent Open Forest vegetation, but Wet Heath within the management zone has remained largely unmodified. At a broad level, plant species diversity in the easement is increased, and higher vegetation density has created small mammal habitat. The powerline easement did not appear to facilitate weed invasion. Vegetation management by repeated slashing has altered the vegetation, but does not appear to have had adverse conservation impacts on local plant and small mammal diversity.

Absorption and desorption characteristics of fluoride in the calcareous and siliceous sand sheet aquifers of south-west Victoria, Australia

This study assessed the sustainability of utilising groundwater systems to
manage an aluminium smelter's fluoridated trade wastewater stream. Replacing ocean discharge of the wastewater with land irrigation is one option. Using a groundwater model (developed using MODFLOW incorporating parameter estimation software (PEST-ASP)), we found that most of the groundwater flow takes place through surface sands. Fluoride is adsorbed in these sands during the drier summer months, but desorption is rapid when winter rain flushes the aquifer. Underlying clays and other layers prevent significant contamination of the deeper aquifer.

Climate change and community response in the Borough of Queenscliffe

The Borough of Queenscliffe (BoQ) occupies a unique place among coastal Victorian locations. Situated at the tip of the Bellarine Peninsula, the Borough has approximately 3000 permanent residents, one third of who are over 60 years old. The Borough is also the smallest in Victoria, covering a total area of 13 square kilometres. BoQ is also unique because of its location. The Borough is almost totally surrounded by water and much of this is classified as maritime national park. The Swan Bay Marine Reserve is a Ramsar site and is therefore a wetland of international significance. The Borough relies heavily on tourism for its economic livelihood.

This paper begins with an overview of the BoQ in geographic, demographic and economic terms and then discusses the possible effects and impacts of climate change, as they relate to this small community. These sections are viewed from environmental, economic and social perspectives. Environmental impacts include the erosion of the coastal sand dune system and the loss of habitat for the orange-bellied parrot. Social impacts include the health effects and dangers of flooding for low-lying housing. Various indicators of community response are described, particularly the activities of the local climate change action group. Their strategy can essentially be described as a ‘push upward and downward’ approach. Innovative actions to implement this strategy are described in the paper.

Can sand slugs in rivers deliver conservation benefits? The biodiversity value of tributary junction plug wetlands in the Glenelg River, Australia

Restoration works are carried out to alleviate human impacts and improve habitats within ecosystems. However, human impacts may also create new (anthropogenic) habitat for species to exploit.A dilemma arises when proposed restoration works would remove anthropogenic habitat and the assemblages it supports. Sediment input into the Glenelg River has formed tributary junction plug wetlands at confluences. Sand slug removal is proposed as part of river rehabilitation, but would also drain plug wetlands. We sampled four plug wetland, four river run and three river pool sites to determine whether plug wetlands influence water quality and add to the biodiversity of macroinvertebrates in the Glenelg River.Water quality and macroinvertebrate diversity were similar in plug wetlands, river runs and river pools.Assemblages were distinct among all sites, regardless of type, so there was no characteristic ‘plug-wetland fauna’. Therefore, although removal of plug wetlands would not cause a dramatic loss of invertebrate biodiversity, it would destroy anthropogenic habitat that supports a similar range of species to natural habitats in a river subject to multiple degrading processes. Gains from rehabilitation should be weighed against the value of anthropogenic habitat and the extent of similar habitat lost elsewhere in the ecosystem.

Fish assemblage response to rehabilitation of a sand-slugged lowland river

The impact of excessive sediment supply on river channels has been  described in many areas of the world. Sediment deposition disturbance alters habitat  structure by decreasing channel depth, changing substrate composition and burying woody debris. River rehabilitation is occurring worldwide, but information is scant on fish assemblage responses to rehabilitation in sedimentdisturbed lowland rivers. Sediment removal and large woody debris (LWD) replacement  were used to experimentally rehabilitate habitat along a 1500m stretch of the Glenelg River in western Victoria, Australia. Using an asymmetrical before-after control-impact (BACI) design, fish were captured before and after the reach was rehabilitated, from two control reaches and from a ‘higher quality’ reference reach. After two years post-rehabilitation monitoring, the fish assemblage at the rehabilitated reach did not differ from control reaches. Temporal changes in taxa richness and the abundance of Philypnodon grandiceps, Nannoperca spp. and three angling taxa occurred after rehabilitation (winter 2003) compared with the before period (winter 2002), but these effects did not differ between rehabilitated and control locations. Highest taxa richness and abundances occurred at the reference location. High salinity coincided with the timing of rehabilitation works, associated with low river discharges due to drought. The negative effects of other large-scale disturbances may have impaired the effectiveness of reachscale rehabilitation or the effects of rehabilitation may take longer than two years to develop in a lowland river subjected to multiple environmental disturbances.

Sand pads : a promising technique to quantify human visitation into nature conservation areas

In many places the expansion of urban areas has brought recreationists into close proximity to nature conservation areas, sometimes leading to conflict where recreation and sensitive environmental or natural values are incompatible. An important first step in managing these conflicts is to assess the degree and nature of the problem. We describe the application, and methodological considerations, associated with the use of an innovative, low-cost, practical technique to monitor human intrusions into a wetland reserve which has been designated as ‘off-limits’ to the general public. The use of seven frequently monitored sand pads over 13 weeks enabled us to determine that intrusions occurred in every week (3–14 per sand pad), deep inside the reserve during most weeks, and also identified the key access points. Most intrusions occurred during holiday periods and were by walkers or cyclists. We also conducted a series of simple experiments to examine the utility of sand pads. Our sand pads maintained their shape well and held footprints for over 1 month, they were rarely avoided by people and provided reliable indices of the level of human activity. Sand hardness varied with rainfall, and hardened sand was frequent (53.8% of 26 days) and potentially prevented detection of people. We conclude that the sand pad technique is an effective and efficient tool to measure recreational use of off-limits areas and other conservation and recreation areas, provided human traffic is not too intense, and that checks are made reasonably frequently.