Documents published in Scipedia

• How Environmental Circumstances Influence Water Repellent Treatment Efficiency – A Case Study of Bentheim Sandstone

  X. Chen, T. De Kock, V. Cnudde, N. Van Den Bossche

  DBMC 2023.

  
  

  Abstract

  Water repellents are widely applied directly to the outer surfaces of existing buildings to increase the hydrophobicity and durability of historic facades. Nevertheless, there is little control over the initial moisture content inside masonry and boundary conditions in practice. The fluctuating temperature and moisture content of a wall are inevitable when applying the treatment under natural climatic conditions, therefore the efficiency under realistic application approaches may not be as optimal as in the lab. This research aims to understand how application circumstances affect the hydrophobic efficiency of a siloxane-based water-repellent solvent on sandstone. Samples with different moisture content were treated and cured under different temperature to simulate various field climate conditions in practical applications. The experiments indicate that application temperature and relative humidity have little effect on water-repellent efficiency. The water-repellent product is also effective on saturated walls.

  Abstract
  Water repellents are widely applied directly to the outer surfaces of existing buildings to increase the hydrophobicity and durability of historic facades. Nevertheless, there [...]

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• Holism vs. Sustainability in Construction

  T. Szkuta

  DBMC 2023.

  
  

  Abstract

  Introduction, motivation: almost 40 years of observation, work and cooperation with investors, designers, contractors, manufacturers, distributors, authorities directly in the construction, rescue of monuments, problem solving, design, implementation, maintenance of facilities is a field of research. I have been there to see how and why construction facilities are implemented, used and protected. The title holism is a good method for analyzing problems but also a tool for predicting the necessary characteristics of what we want to create. Holism is a way of thinking about a problem. Where it is applied it gives good results, especially in the long term. It allows one to see the consequences of the flow of time more easily than reductionism. The study of the causes of a problem is broader which allows us to better diagnose and solve it. It makes you always analyze the effects on the whole object and its environment. It places each problem in the context of nearer, farther, sometimes very far and the passage of time. An important element is the analysis of human behavior during the creation and life of the object. Most of the ways to research and determine the condition of objects are obviously known and used. The problem is to determine them (almost) all and the details. Understanding Aristotle's "The more you know, the more you realize you don't know." is crucial here. The point is to explore and come to a conclusion without "closing the door" to more sometimes diametrically opposed knowledge as you go along. Holism in construction can be formulated, describing principles so as to facilitate broader analysis. Such an approach is desirable, which will give the opportunity to benefit from the results to people with different levels of competence, that is, the majority. The purpose of the paper is to try to systematize the approach and show, with examples, why it is worth using. Method: shown in the table are the elements of the research method used in the appraiser's practice. Some areas and elements should be analyzed for the recognition and determination of conditions, impacts and behaviors of construction objects are described. It was determined how to situate the problem in the broadest possible context, with particular attention to typical human behavior. As it turns out, this context is underestimated here. Due to the small volume of the text, examples were limited to the analysis of two relevant elements: lime mortar brick masonry and monolithic reinforced concrete. Objects from the appraiser's practice were selected. For masonry, a school building from the early 20th century and a farmhouse from the mid-19th century. For reinforced concrete, the school swimming pool erected in 1968 and the building of the printing house from 1972, both in emergency condition. Results: The time caesura is important for the results of the conducted research. The indicated errors in the selection of repair methods and materials are due to simplistic methods of analyzing problems. Overlooking the longevity of existence under different conditions and the most important influence of human behavior at each stage of the establishment, use and existence of building structures prove to be crucial.

  Abstract
  Introduction, motivation: almost 40 years of observation, work and cooperation with investors, designers, contractors, manufacturers, distributors, authorities directly in [...]

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• Corrosion Initiation Period for Stainless Steel Reinforcement in Concrete Structures

  L. Abreu Araujo, I. Helices Arcila, N. Rebolledo Ramos, J. E. Torres Martín, S. Chinchón-Payá, J. Sánchez Montero, B. B. Raggiotti, V. Matres

  DBMC 2023.

  
  

  Abstract

  The designed service life of reinforced concrete structure is often shortened when disposed in aggressive environments. In certain situations, stainless steel reinforcement may be an appropriate replacement to attain a higher level of durability. This paper presents the findings of an experimental study conducted to determine the critical chloride threshold for two types of stainless steel reinforcement (UNS S40977 and UNS S32001). For each steel grade, a prediction model for the corrosion initiation period was obtained, applying the electrochemical test data in a Monte Carlo analysis. Results show that if the initiation period is taken as the corresponding for a 7% corrosion probability, that will occur at 6.5 years of age for carbon steel and over 150 years for UNS S32001 stainless steel.

  Abstract
  The designed service life of reinforced concrete structure is often shortened when disposed in aggressive environments. In certain situations, stainless steel reinforcement [...]

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• Assessing Different Insulation Strategies for Historic Wooden Facades Based on Modeled Mold Growth Risk

  M. Zhao, H. M. Künzel

  DBMC 2023.

  
  

  Abstract

  Wood makes up a considerable proportion of applied construction materials in Chinese historic building envelopes. With increasing awareness of preserving historic heritage by promoting their further use and occupation, it becomes necessary to improve the current poor indoor thermal environment in abundantly existing historic buildings in southern China. One common approach for improvement is to install insulation materials on historic building envelopes, which can additionally improve their sustainability by reducing buildings’ energy demand for heating and cooling. However, this measure of deep retrofits requires cautious design regarding the hygrothermal performance of insulated wooden facades, since an improper construction way would lead to mold growth in wooden materials, causing problems of durability and indoor hygiene. Therefore, this study investigates the mold growth risk of different insulation systems for historic wooden facades in the Chinese HotSummer-Cold-Winter zone based on a parameter study. The considered parameters are internal and external insulation systems, vapor-open (mineral wool) and vapor-tight (XPS) insulation materials, a U-value of 0.8 W/(m²K) as well as a lower U-value of 0.24 W/(m²K) for the insulated walls, different capabilities and positions of an additional vapor control layer, as well as different cooling/dehumidification conditions in the warm period of a year. The hygrothermal performance of insulated wooden facades is simulated with WUFI®Plus software, while the mold growth risk is assessed with mold index values of the Viitanen mold model. The results of this paper will provide a quantitative evaluation of different insulation strategies for historic buildings in southern China regarding the mold growth risk in wooden materials, which is of essential importance for the durability of construction materials. This study can also give instructions for deeply retrofitting wooden historic buildings in China.

  Abstract
  Wood makes up a considerable proportion of applied construction materials in Chinese historic building envelopes. With increasing awareness of preserving historic heritage [...]

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• A Dose-response Approach for Predicting Frost Damage with Hygrothermal Simulations

  K. Janssens, C. Feng, V. Marincioni, N. Van Den Bossche

  DBMC 2023.

  
  

  Abstract

  Freeze-thaw degradation is one of the most prominent degradation risks of brick facades. Considering the difficulties of repairing freeze-thaw damage without replacing the materials, which may not always be an option due to heritage values, it is highly important to quantify the risk of frost damage in advance. Hygrothermal simulations have proven to be a valuable tool to assess the risk of deterioration of building facades. The performance criterion method generally applied today quantifies the number of critical freeze-thaw cycles (FTCcrit) as described by Mensinga et al (2010). This method is based on frost resistance tests that adopt high moisture contents and extremely low frost temperatures. However, building facades often experience milder frost temperatures and lower moisture contents rather than these extreme conditions. A journal article published by Feng et al. (2019) investigated the relationship of frost damage with temperature and moisture content, which enables a dose-response approach that goes beyond the existing threshold level criteria. The experimental study tested freezing temperatures from -2°C to -20°C and moisture saturation degrees from 0.1 to 1.0. This paper studies freeze-thaw risk using this advanced approach, and investigates whether the dose-response approach can lead to a clarification at what number of FTCcrit actual deterioration occurs and how this can be predicted by the use of hygrothermal simulations. Thereby, an attempt is made to derive a more representative performance criterion for frost damage.

  Abstract
  Freeze-thaw degradation is one of the most prominent degradation risks of brick facades. Considering the difficulties of repairing freeze-thaw damage without replacing the [...]

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• Why the Quality of Concrete Construction for Infrastructure Contracts Must Not be Undermined by Inappropriate Design Code Assumptions

  S. R. Curtis

  DBMC 2023.

  
  

  Abstract

  The concept of a draft international project specification (DIPS) has long been under consideration in relevant fib Task Groups, - even before the framework Standard, ISO 22966 (Execution of concrete structures) was published (2009). However, the quality requirements of ISO 22966 were developed from the product quality inspection principles of the Eurocodes and ISO 9001:2000; and the author has explained why these principles cannot be applied directly to contract works. Furthermore, these principles do not demand the necessary level of high-performance concreting and supervision to produce defect-free structures and the 100 plus year service life which Owners expect. The original ISO 9001:1987 was a simple, contractually effective model quality system specification which “aimed primarily at preventing nonconformity,” (the fundamental purpose of quality assurance). Its most powerful element was ‘process control’ (including ‘special processes’), and it demanded that all processes which could adversely affect quality must be addressed by effective documented preventive procedures in the Contractor’s Project Quality Plan (PQP). The Contractor had to document exactly how he would perform each (special) concreting process and then demonstrate that his proposed procedures worked. Since 2000, this powerful combination of mandatory quality planning requirements has been removed from most specifications for concrete works; but this is precisely what needs to be restored if Owners’ and Designers’ durability expectations are to be consistently achieved. The author now proposes an amended draft version of the International Project Specification, - hoping that it will soon be used on a trial basis on selected construction contracts for reinforced and prestressed concrete bridgeworks in China, Australia, United States and Europe.

  Abstract
  The concept of a draft international project specification (DIPS) has long been under consideration in relevant fib Task Groups, - even before the framework Standard, ISO [...]

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• Validation Exercise at European Level on Natural Chloride Diffusion Test and Natural and Accelerated Carbonation Testing

  C. Andrade

  DBMC 2023.

  
  

  Abstract

  The work summarizes the results of the interlaboratory testing made in the committee CEN/TC51/WG12 on the standardized procedures for carbonation (EN 12390 – 10 and part 12) and chloride diffusion (EN 12390-12). The exercise was made by 13 different laboratories on 8 different concrete compositions with w/c ratios of 0.4, 0.5 and 0.6. The results indicated repeatability of 10-22% for natural carbonation (outdoors protected from rain and controlled chamber respectively), of around 5% for accelerated carbonation (at 4% of CO2 concentration), and 23% in the Apparent diffusion coefficient for natural chloride diffusion and 13% for the chloride surface concentration.

  Abstract
  The work summarizes the results of the interlaboratory testing made in the committee CEN/TC51/WG12 on the standardized procedures for carbonation (EN 12390 – 10 and part [...]

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• Link between Durability Defects and Construction Failures

  S. R. Curtis

  DBMC 2023.

  
  

  Abstract

  Over thirty years ago enthusiastic and dedicated materials scientists and structural engineers initiated a series of research projects and draft International Standards which has now revolutionised the design approach to durability of concrete structures. Concrete mix design is dominated by the contractual requirement for the concrete supply not to exceed specified limiting values of the nationally favoured durability criteria. The specifying Authorities are striving to ensure that structures achieve their design service life (ideally 100 years+). Concrete research and development is their primary hope. During the 1990s, the concrete construction industry was also working hard to develop better specifications and contract management procedures to address the pressing problems of not only durability but also safety. Central to all the work of the construction industry was the principle that all concreting operations were ‘special processes’ (as universally acknowledged for welding processes), and therefore they had to be documented, trialled, verified and implemented in compliance with the process control requirements of ISO 9001:1987/1994. Procedures had to be prepared, approved and implemented for all processes which were identified as being potentially ‘adverse to quality’ (which included most processes involved in concreting and prestressing operations (including grouting)). The critical question to answer in preparing a procedure is HOW the process will be carried out and verified. However, equally critical questions may be WHEN, WHERE and BY WHOM. The Project Specification must ask these questions in the tender documents and the Owner and/or his Designer must satisfy themselves that all the identified problems have been resolved – both technical and administrative – before relevant design/construction commences. These questions must be answered by all subcontractors, including designers and checkers of falsework structures. Example are given, based on recent fatal bridge collapses largely caused by Owner and Designer failings to control subcontracting of temporary works design and checking.

  Abstract
  Over thirty years ago enthusiastic and dedicated materials scientists and structural engineers initiated a series of research projects and draft International Standards which [...]

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• Electrical Resistivity Measurements on Hardened Concrete Exposed to Various Curing Conditions

  S. Gao, R. Douglas Hooton, K. Li, T. Hao, X. Feng

  DBMC 2023.

  
  

  Abstract

  Evaluating concrete quality and performance, especially determining the resistance of concrete to fluid and ion ingress, is fundamental to estimating concrete’s durability and predicting the service life of concrete structures. Both bulk and surface electrical resistivity tests have gained increasing interest as rapid and repeatable indicators of concrete’s resistance to fluid ingress. In this study, concrete electrical resistivity was measured at the ages of 56 and 91 days on specimens from five concrete mixtures exposed to different curing environments and storage solutions. Both bulk and surface resistivity of concrete in each curing condition are compared, and the effect of curing methods on electrical resistivity is discussed. The results show that conditioning in a highly-conductive storage solution, such as a simulated pore solution, led to a lower concrete resistivity measurement than when stored in saturated limewater. The effect of mixture compositions on measured resistivity revealed that for the same cementitious materials, the electrical resistivity increased as the w/cm ratio decreased, and a linear correlation between the w/cm ratio and concrete electrical resistivity was obtained.

  Abstract
  Evaluating concrete quality and performance, especially determining the resistance of concrete to fluid and ion ingress, is fundamental to estimating concrete’s durability [...]

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• Application of Service Life Planning to Existing Buildings – Perspectives on Condition Appraisal, Performance and Cost

  K. P. Bourke, A. Silva, P. L. Gaspar

  DBMC 2023.

  
  

  Abstract

  ISO 15686 on Service Life Planning of Constructed Assets provides guidance which is applicable to both new and existing constructed assets and their parts. However, there has been limited exposition of the applicability of the guidance to existing buildings. This paper provides perspectives on practical application of the principles to condition assessment (survey and appraisal) of the long-term performance of existing buildings, in particular in respect of the building envelope and how maintenance interventions and life cycle costs are predicted or estimated. The authors are currently actively involved through CIB W080 and ISO TC59/SC14 in preparing for the revision of the ISO 15686 standards to take account of experience over the last 20 years, including the development of the factor method and its applicability, and guidance on life cycle costing of existing buildings. The paper will develop key themes from the series of ISO 15686 standards, which are particularly relevant to assessment of existing buildings and other constructed assets.

  Abstract
  ISO 15686 on Service Life Planning of Constructed Assets provides guidance which is applicable to both new and existing constructed assets and their parts. However, there [...]

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