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This white paper provides a broad overview of the concreting process before going on to discuss common deficiencies and degradation mechanisms in hardened concrete structures that require petrographic examination for root cause analysis.
The context of this paper is geared toward cast-in-place concrete, but much of the content is also applicable to pre-cast.
Lightweight steel frames can be designed using the principals of Eurocode 3 (EC 3) however this gives much more conservative values than BS 5950, which it superseded. EC 3 allows design by testing which can result in value engineering and a much more economic design. As there is no standard covering the scope of testing required to simulate the load situations in which the panels will be used, similar standards have been adapted based on loadbearing wall tests. Adopted by industry, these tests provide a standardized test program which enables the performance of individual systems to be compared.
Design using cross laminated timber (CLT) panels falls within Eurocode 5 (EC 5): Design of timber structures, but is considered by many to fall between timber and masonry design with a panel acting as solid planes with no need for infill. Design by standard often provides a much more conservative result than design by testing. As there is no standard covering the scope of testing required to simulate the load situations in which the CLT can be used, similar standards have been adapted based on load-bearing wall tests. These tests are primarily for timber construction however customized tests have been developed where none were available. Industry has adopted these methods; they provide a standardized test program which enables the performance of all systems to be compared.
There are various routes to market for manufacturers of construction products; this is dictated by availability of appropriate standards and the category in which the products fall into under the Construction Products Regulations (CPR).
Depending upon which category products fall into, will determine whether it is mandatory or possible for products to be CE marked.
Precast concrete wall panels are load bearing wall, roof or floor panels, containing an insulated core. Currently, precast panel systems fall outside of any European or British Standard test specification or test methods. There is a European Technical Approval
Document, ETA 023 for 'Prefabricated Buildings' but this is not a mandatory document and is viewed as a costly process and concentrates on the finished system, including floor finishes and fittings which are not relevant to a panel manufacturer.
As there is no standard covering the scope of testing required to simulate the load situations in which the concrete panels will be used, similar standards have been adapted based on loadbearing wall tests. These tests have been adopted by industry and provide a standardized test program which enables the performance of individual systems to be compared.
Structural Insulated Panels (SIPs) are load bearing wall, roof or floor panels, containing an insulated core. Currently, SIPs fall outside of any European or British Standard test specification or test methods. As there is no standard covering the scope of testing required to simulate the load situations in which the SIPs will be used, similar standards have been adapted based on loadbearing wall tests. These tests are primarily for timber construction however customized tests have been developed where none were available. Industry has adopted these methods; they provide a standardized test program and enable the performance of all systems to be compared.
Redeveloping existing buildings is an important and valuable operation to bring old buildings, often with historical significance, back into use. Inspection and testing is crucial to ensure the safety and suitability for a change of use. Top Ten Tips covers some of the most important points to consider when planning on-site inspection and testing programmes.
Digital Image Correlation (DIC) is a technique which can deliver video film of the strain development on the surface of a material due to loading or other actions. Lucideon has recently used the technique on concrete masonry for the first time with some extraordinary results. This paper describes the technique and how it was used on two projects. The first project was to study the strain development in masonry walls made from Autoclaved Aerated Concrete (AAC) and dense aggregate concrete and subjected to a single concentrated load. The results illustrate clearly that the material beneath the point of load application was the most heavily compressed and that the pressure is gradually dissipated from the point of load application with contours of equal principal compressive stress in ‘bulb’ shapes. On failure the heavily compressed zone beneath the loading plate effectively became “part of the loading plate” in a similar way as soil under a foundation. The second project studied walls made from storey-height panels of AAC, jointed vertically by mortar, and subjected to a concentrated vertical load. In this case, the load effects were transmitted across the vertical joint indicating that more than one panel resisted the load until just prior to failure, which was by the joint failing in shear. The results were used to improve design provisions for walls subjected to concentrated loads.
Drying is an important and often necessary unit operation for many processes. It can determine the quality of the final product, determine its shelf life or expose imperfections and lead to defective products. It is also very energy intensive and time consuming, so a lot of attention should be paid to optimizing the drying step in order to make the overall process competitive.
Drying is the removal of water or other solvents from the product, firstly from the surface, then from the pores and cracks. If done too quickly, the solvent leaves a weak structure behind and this could cause fractures or imperfections, as seen in the ceramic industry. If done at too high of a temperature, it could degrade the product, a common issue in the pharmaceutical and food industry. Moreover, drying can be a hazardous step as the removal of the solvent (when drying paints and coatings for example) can create an explosive atmosphere.
In recent years, Lucideon has seen large numbers of wall, floor and roof systems passing through its laboratories, usually for testing to one ETAG or another; the scopes are often rather unclear. The focus, however, is nearly always on the testing of the panels and rarely whole assemblages. The purpose of this paper is to show some examples where the results from whole building tests have demonstrated distinct improvements in performance due to particular details or elements, or simply overall robustness, not evident from tests on sub-assemblies. The aim is to raise awareness that despite there being established testing regimes for potential offsite or pre-manufactured approaches, a test on the complete assemblage may provide surprisingly beneficial results.
Digital Image Correlation (DIC) is a non-contact, non-interferometric measurement technique that uses high-resolution machine-vision digital cameras to accurately measure surface deformation in two or three dimensions. This measurement is presented graphically in a number of ways such as a 2D strain map overlaying the test specimen, or a 3D displacement map showing the specimen surface and how it moves throughout the test. Early development of this technology began in the mid-1980s in the mechanical engineering department of the University of South Carolina. Since then it has gone on to revolutionize mechanical testing on both the macro and micro scale. The applications of DIC are vast, from eyeball pressure testing to earthquake analysis; this adaptable and highly capable system will transform design, validation and testing methods for anything from dental implants to wind turbines.
The Building Regulations in the UK are aimed at, amongst other things, ‘securing the health, safety, welfare and convenience of persons in and about buildings’. The legal requirements are quite simple and general, for example, in relation to the conservation of fuel and power the regulation includes the wording: “Reasonable provision shall be made for the conservation of fuel and power by: limiting heating gains and losses through thermal elements and other parts of the building fabric.”
Digital Image Correlation (DIC) is a full-field image analysis method which employs high resolution digital cameras to track displacement occurring on the surface of an object. It has gained recognition for the potential that it possesses for a number of industries, not least among them the construction industry. This white paper focuses on potential applications for the construction industry drawing on examples of previous testing applications and highlighting the advantages DIC offers over conventional structural and materials testing methods.
There has been little direct research into how and why lime improves the properties of mortar, both during mixing and whilst in service. This guide provides a review of the scientific literature around the benefits of using lime in cement-based mortars, in both the fresh (as mixed) and hardened state. The guide also evaluates existing information and highlights the direct benefits to mortar in general use, and specifically the durability and performance characteristics of mortar in service.
The guidance given in this document is aimed at showing ways in which appropriately qualified persons can produce structures using Porotherm blocks that have an equivalent level of safety to that when using British Standard Codes of Practice and will therefore meet the requirements of the Building Regulations.
The most slip-resistant surfaces can become slippery if not correctly maintained. This document provides guidance around the implementation of an effective cleaning and maintenance regime to preserve the original slip resistance of a floor surface. Several factors must be considered and accommodated in order for a schedule to be efficient and effective, these include the floor environment; pedestrian traffic; suitable detergents; and appropriate cleaning methods and procedures.
BS 8300:2001 - Design of buildings and their approaches to meet the needs of disabled people - Code of Practice, recommends the use of surfaces with contrasting lightness to assist visually impaired people in their search and navigation tasks, within and around buildings. The greater the difference in the light reflectance values (LRV) between adjacent surfaces, the more likely it is that the visually impaired will identify such differences. To assist in the selection of appropriate surfaces the LRV may be measured by a relevant method which will assign a value to a given material.
The Workplace (Health, Safety and Welfare Regulations) 1992 require that floors must not be slippery so as not to put people's safety at risk. Prevention of accidents, caused by slipping, is down to correct choice of flooring media and good management (i.e. contamination prevention, cleaning regimes, type of footwear worn and an assessment of the surrounding environment). In order for management systems to be effective it is important that floor materials are suitable for the application and environment in which they are used, and an appropriate
measuring method employed.
This Design Guide has been developed from an extensive series of tests on full size walls, generally 8m
x 5m (length x height) and reinforced at intervals up their height. The walls were made from concrete
blockwork and, in the case of plain walls, were reinforced by bond beams located approximately one
third and two thirds of the wall height. The bond beam course was a trough type concrete masonry unit
containing two 16mm reinforcing bars, placed horizontally one above the other in the ‘trough’. The bars
fitted into metal cleats fixed to columns at their ends and were concreted into the trough. At specified
intervals, vertical shear transfer rods connected the bond beam to the courses above and below it. For
walls with window or door openings, the bond beams were installed at window head and sill level or at
door head height respectively.
With the construction industry facing one of its toughest times to date, anyone involved in design and build, whether for new construction projects or for the refurbishment of existing buildings, is looking to reduce costs, particularly costs associated with materials and length of construction.
This white paper examines the valuable role that testing can play in relation to reducing such construction costs. The advantages of testing over following traditional Codes of Practice are outlined and examples from Lucideon given as to how testing can be implemented throughout the design, construction, handover and refurbishment stages.