But material limitations, design and construction practices and severe exposure conditions can lead to deterioration of concrete, which can result in aesthetic, functional or structural problems. Concrete can deteriorate for a variety of reasons, and concrete damage is often the result of a combination of factors. Concrete deterioration can cause major headaches for building owners. It is important to correctly identify these defects early, and to plan appropriate repair strategies.
Concrete deterioration can occur through spalling, disintegration, erosion, reinforcement corrosion, delamination, spalling, alkali-aggregate reactions and concrete cracking. Concrete degradation can have several causes. Concrete can be damaged by fire, aggregate expansion, seawater effects, bacterial corrosion, calcium leaching, physical damage and chemical damage (from carbonation, chlorides, sulphates and non-distilled water). This process adversely affects concrete exposed to these damaging stimuli.
Corrosion is the deterioration of the steel reinforcement of concrete. Corrosion can be induced by chloride or carbonation. Corrosion can lead to the appearance of cracks in the concrete cover, delamination of concrete covers, etc. Disintegration is the physical deterioration (such as flaking) or breaking of concrete into small fragments or particles.
The freeze-thaw cycle also affects the soil. Soil sets differently in warmer months than when it is frozen. This setting can crack and break concrete foundations. Damage caused by weathering most often manifests itself in the form of cracks and potholes.
Adding new levels to a building, placing heavy machinery or building with heavy materials can induce too much stress in the concrete and cause severe damage. Stress can manifest itself in many forms: spalling, flaking and cracking. Future deterioration of concrete structures can stem in part from errors in concrete production, pouring or placement, and compaction. For example, inadequate curing can lead to the development of micro-cracks perpendicular to the surface of the concrete, due to drying shrinkage.
Mixing and segregation can be assessed by searching for domains in the cement paste with less or no (fine) aggregate at the microscopic level, accompanied by the assessment of the presence of cement or binder agglomeration, the distribution of coarse aggregate at the mesoscale level. In fluorescence mode, the effects of processes affecting capillary porosity, such as micro-bleaching, can be identified. Inadequate compaction can reveal local areas of poor adhesion of the cement paste to the aggregate particles and excessive voids (Fig. The most common causes of concrete deterioration are outlined here.
Recycling concrete is difficult and expensive, reduces its strength and can catalyse chemical reactions that accelerate deterioration. The world needs to reduce its concrete production, but this will not be possible without building more durable structures. Research carried out by Sakr and EL-Hakim (200) covered the comparison of the shielding properties of ordinary, barite and ilmenite concretes after heating to 950°C. Concrete has enjoyed a reputation as a "set it and forget it" building material since it became popular in the mid-20th century.
While considerable research has been carried out on ASR in concrete specimens, the published literature on the structural analysis of concrete bridge elements subjected to ASR expansion and subsequent deterioration is limited. Paramagnetic defects and optical centres form easily, but very high fluxes are required to displace a sufficiently high number of atoms in the crystal lattice of minerals present in concrete before significant mechanical damage is observed. Carbonisation of concrete is a slow and continuous process that progresses from the outer surface inwards, but slows down with increasing diffusion depth. Although TSA has long been recognised by concrete petrographers as an unusual deterioration mechanism274 , an investigation of severely degraded buried concrete elements of some motorway bridges in south-west England in 1998 (Fig.
Crammond and Halliwell320 highlight the role of finely divided carbonate filler in promoting the type of sulphate action of thaumasite, indicating that the type of aggregate can sometimes have an influence on the occurrence of that form of damage in concrete. In addition, a review of the following two papers is highly recommended in learning about concrete defects and deterioration (Reference 1 and Reference. Samarai,268 in experiments in Iraq using powdered gypsum in mortar bars, produced unacceptably high expansions with Portland cement concrete mixes containing total sulphate contents greater than 5 and mass of cement. And yet, many concrete structures of the last century - bridges, roads and buildings - are crumbling.
Secondly, fly ash can reduce the non-durable binder in concrete which makes it permeable and susceptible to chloride attack. Consequently, the bridge analysis presented in this case study is based on the fundamental principles of structural mechanics with material behaviour assumptions for the expansive pressures exerted within the concrete bridge elements. The conversation definitely made more sense and made me feel more informed about what needs to be considered in various concrete structures.