Freeze-thaw deterioration

In addition to the forms of attack already discussed, cracking and spalling of concrete due to acid-induced corrosion can also lead to and accelerate other forms of attack having other causes, most notably freeze-thaw deterioration. Prudil (30) found that concrete which normally withstood attack due to freeze-thaw cycling was subject to attack after exposure to acid solutions. 

For waterproofing, sodium silicate concentrations below 30% are adequate concentrations between 35 and 70% are used for strength improvement. Grouts having 35 vol % or higher silicate resist deterioration on freeze—thaw or wet—dry cycles. Water permeability of sands can be reduced from 10 to 10 cm/s. Unconfined compressive strengths of stabilized sand can vary from 103 to 4130 kPa (15—600 psi) the normal range is between 690 and 1380 kPa. 

Freeze-dried aequorin is also quite stable, but the process of drying always causes a loss of luminescence activity (see the last part of Section 4.1.2). All forms of aequorin are satisfactorily stable for many years at — 50°C or below, but all rapidly deteriorate at temperatures above 30-35° C. A solution of aequorin should be stored frozen whenever possible because repeated freeze-thaw cycles cause little harm to aequorin activity. 

In addition to being potentially less costly to construct, ET covers have the potential to provide equal or superior performance compared to conventional cover systems, especially in arid and semiarid environments. In these environments, they may be less prone to deterioration from desiccation, cracking, and freezing/thawing cycles. ET covers also may be able to minimize side slope instability, because they do not contain geomembrane layers, which can cause slippage.5-42 43... 

In a typical experiment, the Fe(n) derivative of (314) rapidly binds dioxygen in pyridine subsequent deoxygenation may be effected by freeze-thawing. Several such cycles can be performed with little deterioration of the system. Moreover, the Oz adduct in pyridine has a half-life of about 20 hours. Following this initial success, the 02-binding properties of a number of other related capped porphyrin derivatives have been investigated (Baldwin Perlmutter, 1984). 

It can be concluded from the assessment of the data in this section that inclusion into a concrete mix of a water-reducing admixture of the lignosulfonate, hydroxycarboxylic acid and air-entraining type should not lead to any deterioration in the durability of that concrete to freeze-thaw cycling. Indeed there are strong indications that, when used either as a means of reducing the water-cement ratio or, alternatively, of reducing the cement content, more durable concrete may result. 

It should be pointed out that deterioration under freeze-thaw conditions can also be caused by a mechanism other than the direct freezing of the non-evaporable water. The capillaries contain dissolved salts, such as hydroxides, sulfates and carbonates. As part of the water is frozen, the concentration of salts in the remaining water increases and water will flow by osmotic pressure from the gel pores to the capillary pores, setting up an additional disruptive pressure. 

In summary, the main cause for masonry deterioration is the presence of water in it. A dry wall will not effloresce, the salts contained in it will not be able to recrystallize and other deterioration processes such as freeze-thaw will also be avoided. 

ABSTRACT This research project aims to use reactive powder concrete, RPC. as a new repair material and evaluate its bond strength and bond durability to existing concrete. One accelerated aging environment, namely a freeze-thaw cycle acceleration deterioration test, was selected for the evaluation of bond durability of the repair materials. Before and after aging, the samples were evaluated by the compressive strength, bond strength (slant shear test), steel pull out strength, and relative dynamic modulus NDT tests. 

For concrete, deterioration due to freeze-thaw is caused bj freezing of pore water inside the concrete. If the pores are too small, then the expansion caused by freezing can exert stresses on the concrete that crack the concrete and thus cause deterioration. Air entrainment of 7-8 %, depending on the aggregate size, can essentially eliminate this freeze-thaw damage [3]. 

Concrete subjected to freeze-thaw cycling may suffer from micro cracks and surface scaling. Dynamic modulus of elasticity was measured to evaluate the degree of deterioration in the concrete cylinders. A decrease in dynamic modulus indicates that the concrete is internally deteriorating by micro cracks and/or surface scaling. 

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]. 

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