Thermal, mechanical and microstructural analysis of concrete containing microencapsulated phase change materials

This paper studies the thermal, mechanical and microstructural aspects of concrete containing different amounts of microencapsulated phase change materials (PCMs). In addition, numerical simulation is carried out to study the potential application of PCM-modified concrete for reduction in summer surface temperature. It is shown that increasing PCM content in concrete led to lower thermal conductivity and an increase in the heat storage ability of concrete. However, the compressive and flexural strength of concrete significantly decreased. Microstructural analysis showed that PCMs appear to remain intact during mixing; however, PCM particles appear to fail by bursting under loading, creating hemispherical voids and crack initiation points as well as possible entrapped air behaviour. The result of numerical simulation revealed that reduction in summer concrete pavement surface temperature by several degrees was possible, with implications for reduction in concrete thermal stresses, shrinkage and urban heat island effect

Research note: Describing average illuminance for P-class roads

Design criteria for lighting in subsidiary roads usually include a minimum average horizontal illuminance, widely assumed to be the arithmetic mean illuminance. Analyses of the illuminance distributions over thirty road sections shows that the distributions are not normal and hence the median is more appropriate than the arithmetic mean as a measure of central tendency: the medians are significantly lower than the arithmetic means but the two are highly correlated. Design recommendations should state whether it is the arithmetic mean or median and not just the ‘average’ that is required

The upgrading of fire safety in historic buildings

There is a seemingly continual erosion of our cultural heritage due to fires in historic buildings. Some of these fires result in partial loss of the asset, some result in total loss – in all cases irreplaceable historic fabric is destroyed. Accurate recording for fires in historic buildings is problematic, but such data as has been collated indicates that the level of loss is high. One of the key factors in achieving robust fire safety in historic buildings is the upgrading of physical fire protection measures. It has been suggested that we should assume a fire event is probable, and together with a context in which outside help might be some time in arriving, such measures are considered crucial in containing the fire and raising the alarm as quickly as possible. This article considers passive and active fire protection measures, using case study material to provide illustrative examples. Where it might be expected that conservation requirements, aiming to avoid negative impact to character and significance, might hinder disruptive physical interventions to improve fire protection, in fact a great deal can be achieved. Such a pragmatic approach is arguably necessary for the safety and preservation of built heritage, when the alternative might otherwise be yet another burnt-out shell

Biodegradability standards for carrier bags and plastic films in aquatic environments: a critical review

Plastic litter is encountered in aquatic ecosystems across the globe, including polar environments and the deep sea. To mitigate the adverse societal and ecological impacts of this waste, there has been debate on whether ‘biodegradable’ materials should be granted exemptions from plastic bag bans and levies. However, great care must be exercised when attempting to define this term, due to the broad and complex range of physical and chemical conditions encountered within natural ecosystems. Here, we review existing international industry standards and regional test methods for evaluating the biodegradability of plastics within aquatic environments (wastewater, unmanaged freshwater and marine habitats). We argue that current standards and test methods are insufficient in their ability to realistically predict the biodegradability of carrier bags in these environments, due to several shortcomings in experimental procedures and a paucity of information in the scientific literature. Moreover, existing biodegradability standards and test methods for aquatic environments do not involve toxicity testing or account for the potentially adverse ecological impacts of carrier bags, plastic additives, polymer degradation products or small (microscopic) plastic particles that can arise via fragmentation. Successfully addressing these knowledge gaps is a key requirement for developing new biodegradability standard(s) for lightweight carrier bags

Lighting for cycling in the UK : a review

While UK governments have recently sought to increase cycling activity, it remains a minority interest. One reason for this is the perceived danger of cycling on roads filled with traffic. There is statistical evidence to support this perception; for equal exposure, cyclists are more likely to be seriously injured than either drivers or pedestrians. Lighting has a role to play in reducing the hazards of cycling by enhancing the visibility and conspicuity of cyclists. Unfortunately, it is not at all clear that the current lighting regulations and recommendations for cycling and cyclists are the best that can be achieved or are even adequate for these purposes. A number of actions are suggested that should enable lighting’s contribution to the safety of cyclists to be realized

A novel approach of introducing crystalline protection material and curing agent in fresh concrete for enhancing hydrophobicity

A new line of research to enhance the performance of concrete under adverse (harsh) and normal (air cured) curing conditions is presented. A crystallising hydrophobic admixture and curing agents were added to fresh concrete to improve its resistance against severe environmental conditions. A two-stage approach was pursued by adding the crystallising admixture to fresh concrete followed by curing agents, in a wax and liquid forms, in a separate application process, followed by exposing concrete to normal and adverse curing conditions. Results obtained suggests that protecting concrete with the crystallising admixture followed by applying wax based curing agent improves concrete strength and its resistance to water ingress than concrete cured with the liquid curing agent. When following the crystallising-wax treating system under adverse curing conditions, a more conserved strength was noticed compared to that produced by the crystallising-liquid system. Using the liquid curing agent in concrete with high water to cement ratio (w/c) has increased the cracks in the internal structure, while water permeability has decreased, either under normal curing conditions or adverse conditions. Following this protection-curing system in industry would resolve the problem of applying protection on wet surfaces and increase concrete’s resistance to deterioration. A microscopic study of the crystallising material was attained with a Scanning Electron Microscope (SEM) to check crystal growth with time

Analysis of interfacial shrinkage stresses in patch repairs

This paper presents simple analytical expressions that predict the interfacial shrinkage stresses in a repair patch over time. Four repair materials (L2, L3, L4 and G1) were applied by spraying (gunite) to unpropped compression members of two highway structures, and their performance was monitored to approximately six months' age. The elastic moduli of all the repair materials, E rm , were greater than the elastic moduli of the substrate concrete, E sub . The mechanics of patch repair interaction with the substrate were established, and analytical models, based on an analogy of the bimetallic strip undergoing a drop in temperature, were developed. Basic properties of the repair material (elastic modulus, shrinkage and tensile creep) and substrate concrete (elastic modulus), and geometrical details of the repair patch, are required to analyse the interfacial stresses in the repair patch. Verification of the analytical procedures is based on the field data, and the results show a satisfactory correlation between the actual and predicted stress redistribution.</p

Shear behaviour of crushed concrete and bricks

Demolition waste materials mainly consist of concrete and bricks and arise from the demolition of existing structures and buildings. Environmental and economical reasons make their recycling necessary, but to date, their use is curtailed due to the lack of research in determining their properties. This paper reports on the efforts to understand the behavioural characteristics of three types of recycled material to determine their potential for engineering fill applications. For this purpose, their physical and mechanical characteristics were extensively investigated. Two types of crushed concrete, one obtained straight after demolition and the other processed to industry specifications, and one type of crushed brick were tested. An extensive large-scale shear box test regime was employed to determine the shear strength behaviour of the materials. The influence of the normal stress on the peak friction angle, the shear stress– horizontal displacement relationship and horizontal displacement– vertical displacement behaviour of the materials are discussed in this paper. The results showed that the behaviour of the three recycled materials during shear testing was similar to the behaviour exhibited by natural granular materials from literature. In conclusion, the shear box test results have shown that the specific demolition waste products exhibit considerable shear strength and can be utilised in construction as low-level engineering fill