Cement render

Abstract: Since the introduction of Portland cement in the early nineteenth century the number of buildings constructed from concrete or using cement mortars and renders has grown exponentially, and cement is one of the most common building materials in use today Consequently a significant proportion of the built heritage contains cementitious materials The relative youth of these buildings means that less research has been undertaken to understand how and why they deteriorate than for traditional buildings, and that the development of appropriate conservation methods and techniques is less advanced The primary aim of this research was to understand the causes and mechanisms of some of the types of deterioration commonly found in historic concrete and cement buildings and structures, with reference to the Second World War reinforced concrete and cement-rendered buildings at East Fortune airfield in East Lothian, Scotland Additional aims were to investigate the efficacy of the building repairs and maintenance regimes undertaken to date, and to make recommendations for the future conservation of the buildings East Fortune airfield contains a number of cement-rendered brick masonry buildings and a reinforced concrete air raid shelter The initial visual survey identified several types of deterioration, from which the blistering and flaking of the render; the cracking and delamination of the render; and the spalling of the concrete in the air raid shelter were selected for further research The research included time lapse photography, non-destructive testing, environmental monitoring and the physical, chemical and petrographic characterisation of the building materials Hypotheses regarding the causes of deterioration were tested in the laboratory, for example with linear variable displacement transducer measurements, and modelled using crack propagation theories and models for water transport through porous media It is demonstrated that the blistering and flaking of the render is caused by shale aggregate particles, which undergo sufficient expansion during freeze-thaw cycles to crack the surrounding render This phenomenon is termed ‘pop-outs’ in the concrete literature The more catastrophic cracking and delamination of the renders is also due to freeze-thaw cycling, which is shown to cause significant damage provided the moisture content of the render is above a certain threshold level This type of deterioration has occurred at an accelerated rate for some of the modern render repairs, due to an inadequate understanding of the properties of the original and repair materials In particular, the properties of the bricks are critical to the performance of the cement renders, and it is found that the sorptivity of historic bricks may vary considerably depending upon the orientation of the brick Finally, the diagnosis for the air raid shelter is that the corrosion of the steel reinforcements is caused by high levels of chlorides present within the raw materials used to make the pre-cast concrete sections The results of…

Abstract: In order to shed light on various decorative cement renderings, their characteristics, formulas, and application methods were studied. National and international plasterer and mason manuals, periodicals (mainly architectural), patents, and archival records (building specifications and estimations, plans, correspondence) were consulted. Chemical analyses of onsite lifted samples and testimonies of former plasterers revealed additional information. Several interwar period cement-based finishes that were poplar in Belgium will be discussed in this article, which contributes to knowledge about the material and decoration of cement-rendered facades and their care, to encourage the preservation of this special aspect of our modern architectural heritage.