Surface Roughness Slip Resistance And Relationship To Floor Cleaning

Summary: Determination of slip resistance of flooring materials is of importance to both designers and specifiers when responding to client requirements, and to building owners, users and facility managers when buildings are commissioned and over the lifetime of the floor. Clearly, acceptable slip resistance of floorings is a significant safety requirement of any building with an industrial, or public service operation. Assessment can be made as a routine part of production, to ensure client satisfaction, or upon the floor in-service, to ensure the required slip resistance has been maintained during routine service life. Slip resistance is commonly measured in the UK using the TRRL pendulum tester but the use of surface roughness measurement to assess slip resistance is growing in popularity. This paper identifies a relationship between the surface roughness of flooring materials and the cleaning properties by presenting two case studies. The BRE studies examined in-service floor tiles that were retaining dirt, irrespective of the cleaning regime, or the traffic. The relationship between surface roughness and dirt retention enabled the identification, in one case, of areas where the cleaning regime was insufficient. Examination of the data produced from the two case studies suggests that the peak to valley distances of the sub-millimetre surface profile and the widths of the peak to valley elements are important parameters influencing dirt retention. These parameters can be measured using one of the instruments recommended in the Guidelines of the UK Slip Resistance Group (2000), although the measurement of the mean width peak to valley distances is not required when assessing slip resistance. Thus, in addition to providing information concerning slip resistance, the assessment of submillimetre surface profile characteristics may also be advantageous in quantifying cleaning properties, and provide valuable information both before installation and during service life

Associations of physical activity and cardiorespiratory fitness with cognitive function, self-control, and resilience in young people with attention deficit hyperactivity disorder

The aim of the present study was to investigate if physical activity and cardiorespiratory fitness influence cognition, self-control, and resilience in young people with ADHD. Fifty-four children with ADHD (12.8 ± 1.4 y) completed questionnaires to assess self-control and resilience, wore an accelerometer for 7 d to assess free-living physical activity, and completed a battery of cognitive function tasks and a multi-stage fitness test (cardiorespiratory fitness). Positive associations were found between cardiorespiratory fitness and attention, measured via performance on the simple Stroop task (r(52) = −0.386, p = 0.004) and the congruent Flanker task (r(52) = −0.302, p = 0.026), and inhibitory control, measured via performance on the incongruent level of the Flanker task (r(52) = −0.348, p = 0.010). Furthermore, a higher proportion of active time spent in highintensity activities (r(37) = 0.370, p = 0.021) were associated with higher self control. No associations were found between physical activity or cardiorespiratory fitness and resilience (all p > 0.05). These findings demonstrate the importance of physical activity and cardiorespiratory fitness for cognition and self-control in young people with ADHD

The distribution and behaviour of gold in soils in the vicinity of gold mineralization, Nickel Plate mine, southern British Columbia

Sampling of soils and till are conventional methods of gold exploration in glaciated regions. However, the exact nature of the residence sites and behaviour of gold within soil and till are poorly known. A gold dispersion train extending from the Nickel Plate mine, Hedley, southwest British Columbia, was investigated in order to determine the distribution and behaviour of gold within soils developed from till. Three hundred and twelve soil, till and humus samples (representing LFH, A, B and C horizons) were collected from fifty-two soil pits and thirty-four roadcut locations within the dispersion train. Soil and till samples were sieved into four size fractions; the resultant -212 micron (-70 mesh) fraction of each sample was analysed for Au by FA-AAS. Humus samples were ground to -100 micron powder and analysed for Au by INAA. Based on the analytical results, each LFH, A, B and C horizon was subdivided into anomalous and background populations. Detailed size and density fraction analysis was carried out on soil profiles reflecting anomalous and background populations, and a mixed group of samples representing the overlap between both populations. Samples were sieved to six size fractions; three of the size fractions (-420+212, -212+106, -106+53 microns) were separated into two density fractions using methylene iodide and analysed for Au by FA-AAS. The Au content of the -53 micron fraction was analysed by FA-AAS and cyanide extraction - AAS. Results indicate that the Au content of soil profiles increase with depth while decreasing with distance from the minesite. Heavy mineral concentrates and the light mineral fraction Au abundances reveal that dilution by a factor of 3.5 occurs within the till over a distance of 800 metres. However, free gold within the heavy mineral fraction is both diluted and comminuted with distance. Recombination of size and density fractions indicate that the Au contents of each size fraction are equivalent; variation in Au abundance is not observed with a change in grain size. Seventy percent of the Au in the -53 micron fraction occurs as free gold. Chemical activity has not altered the composition of gold grains within the soil profiles. Compositional and morphological differences between gold grains are not indicative of glacial transport distance or location within the soil profile. Relative abundances of gold grains between sample locations can be used as an indicator of proximity to the minesite. The sampling medium with the best sample representivity and contrast between anomalous and background populations is the -53 micron (-270 mesh) fraction of the C horizon. Geochemical soil sampling programs in the vicinity of the Nickel Plate mine should collect a minimum mass of 370 grams of -2000 micron (-2 mm) soil fraction in order to obtain 30 grams of the -53 micron fraction.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat

The susceptibility of various UK aggregates to alkali silica reaction

A group of lithologically varied UK aggregates have been incorporated into concrete prisms of variable alkali content to ascertain the alkali levels at which significant ASR first occurs at 38oC and 100% RH. Petrographical analysis was used to establish the source of reactivity. The results of these expansion tests showed that significant ASR can develop with certain aggregates at initial alkali levels as low as 3.5 kg/m3 Na2Oe. Similar prisms were made at initial alkali levels, well above, on and just below the alkali thresholds for each aggregate. These prisms were placed in salt solution to establish the effects of ASR. The results showed that an external source of NaCl does accentuate ASR in high alkali mixes. However, in low alkali mixes the ASR initiated was even greater than that developed by the high alkali mixes. It was proposed that an `initial alkali pessimum' existed for each aggregate type for specimens placed in salt solution. Electron microprobe analysis of the ASR gels from concretes immersed in salt solution, showed that two compositionally varied gel suites develop. The first suite was derived from ASR caused by the initial alkalis in a concrete mix and was identical to ASR gels derived from the various concretes when immersed in distilled water. The second suite was developed by alkalis derived from a reaction between NaCl and the C3A component of the cement paste. It was demonstrated that the `initial alkali pessimum' was probably due to a combination of these two ASR types at the alkali threshold point where both suites of ASR gel can develop. Equivalent mixes were made with a 25% replacement of the cement by pulverised fuel ash (pfa) to establish whether alkalis released from the pfa could initiate ASR in otherwise non-reactive low alkali mixes. The addition of air entrainment to reactive concrete mixes was also examined as a method of suppressing ASR