Deterioration of concrete

Roberts, D. J., Nica, D., Zuo, G. Davis, J. L. (2002). Quantifying microbially induced deterioration of concrete initial studies. International Biodeterioration and Biodegradation, 49, 227-34. 

The processes of deterioration of concrete and corrosion of reinforcement are closely connected (Figure 3.1). The former provoke destruction of the concrete cover or cause microcracking that compromises its protective characteristics. On... 

In this chapter, only a few of the most common forms of physical and chemical deterioration of concrete wiU be mentioned (effects of freeze-thaw cycles, acid solutions, pure water, sulfates and aUcaH aggregate reactions). Other forms of deterioration, such as the action of certain aggressive liquids, while important in specific cases, wiU not be dealt with. For more details, the reader is referred to the classic Hterature on degradation of concrete, which has formed the source of usefiil information for many decades [1, 2]. Modern reference texts and standards rely for a large part on these classic sources [3, 4]. 

In the following section, microbial deterioration of concrete will be studied in more detail. 

The possible impact of nonbacterial species such as algae on the biological deterioration of concrete has been explained in a previous section (see Section 4.5.1.2.1.1) and the related references given there, and it will not be repeated here. However, the impact of microorganisms on MID will be briefly described. 

D.J. Roberts, D. Nica, G. Zuoo, J.L. Davis. Quantifying microbially induced deterioration of concrete Initial studies. International Biodeterioration Biodegradation, Vol. 49, pp. 227-234, 2002. 

Since the permeability significantly influences the deterioration of concrete, evaluation of water permeability in cracked HPFRCC seans a key factor to describe the durability performance of given materials. Superior impermeability of HPFRCC has been observed by several researchers. Lepech and Li (2005) studied the water permeability of cracked HPFRCC and reinforced mortar specimens. When subjected to identical tensile deformation, the HPFRCC and reinforced mortar specimens exhibited very different cracking patterns and widths. They found that the cracked HPFRCC exhibits nearly the same permeability as sonnd concrete, even when strained in tension to several percent (Figure 6.8). Homma et al. (2009) also evaluated the water permeability of cracked... 

The thermal treatment of concrete can cause the detrimental effect of delayed ettringite formation, resulting in the deterioration of concrete elements. The problem of delayed ettringite formation belongs to the internal corrosion of concrete and will be discussed in the chapter relating to this corrosion. 

This classification has a long tradition and reflects rather the problems to be resolved by the specialists in the field of cement chemistry, with aim to improve the durability of concrete in the more fiequently occurring aggressive enviromnents. The sulphate corrosion is here a typical, common example, which led to the invention of calcium aluminate cement by Bied (ciment fondu). The deterioration of concrete by de-icers, used in millions tons (for example in the USA in winter 1966/1967 6.3 milliont [62]), became a serious problem. The cost of bridges repairs in USA in 1975 was 200 million [63]. 

The deterioration of concrete can be the consequence of the presence of some aggregates components which, for example, as iron sulphide, decompose to give iron(lll) hydroxide and sulphuric acid [71]. This phenomenon will be presented later. Let us discuss now the studies of concrete deterioration mechanism caused by alkali silica reaction, the most important in practice. The two types of reactions can be distinguish ... 

In spite of numerous experimental works there are several unresolved questions and matty controversial opinions deahng with this problem. Some anthors support a view that the deterioration of concrete is the effect of alkah-aggregate reaction and the crystallization of ettringite occnrs later, in the microcracks thus produced [148]. 

This reaction is linked with a decrease of volume however, as the crystalhzation of gypsum is taken into account, the overall volume is increasing and can be estimated as 18 cm /mole of AFm. But the crystallization of gypsum is less probable in the concentrated solution of chlorides and rather the formation of anhydrite will be more probable, with the decrease of total volume. These examples are showing that the effect of chloroaluminate hydrate on the formation of microcracks and deterioration of concrete is negligible. 

The granulated silica fume, when used in concrete production, can be a source of reactive silica, causing the reaction with sodium and potassium hydroxides and leading to the deterioration of concrete [166]. 

In order to quantify microscopic damage, distribution of pore radii was also measured by the mercury intrusion method from concrete fragments at the three sites. After determining the pore distribution, the volume of pore radii over 0.5 pm was determined. This is because microvoids over 0.5 pm are dominantly responsible for deterioration of concrete. 

The deterioration of concrete due to leaching has been reported in Sweden when a dam deteriorated because of soft water in the 1920s, and in Scotland... 

The most common cause for the deterioration of concrete results from contact with inorganic and organic acids. Those that form soluble salts with calcium oxide or calcium hydroxide are the most aggressive. Typical compounds that can cause problems include sour milk, industrial wastes, fmit juices, some ultrapure waters, and organic materials that ferment and produce organic acids. Typical chemical families found in various types of chemical processing industry plants and their effect on concrete are shown in Table 18.1. 

Fibres may also prevent the occurrence of large cracks, thus preventing percolation of water and contaminants into ceramic materials such as Portland cement mortars and concretes. So, corrosion of steel reinforcement or potential deterioration of concrete may be reduced with the addition of a variety of fibres to the Portland cement matrices. In addition, other enhanced... 

The primary cause for deterioration of concrete bridge components is the chloride-induced corrosion of the reinforcing steel. Wedging action resulting from the production of voluminous corrosion reaction products causes cracking and delamination at the steel rebar/concrete interface, ultimately leading to spalling of the concrete. 

In summary, according to the above analysis the appearances of long term field tests did not show convincing evidences to support "salt weathering" causing the deterioration of concrete partially exposed to sodium sulfate environment. 

Water is considered to be the universal solvent. Given the right set of circumstances, water will over time dissolve or cause the deterioration of concrete, masonry, metals, wood, and plastic. 

Deterioration of concrete may result from chemical attack, corrosion of the reinforcing steel, structural movement, and wear and tear. Various methods are available to identify possible causes for deterioration of concrete ... 

---