EARLY DETERIORATION MECHANISM AND PREVENT PRACTICE OF THE DEICING SALT ON CONCRETE
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The paper present the techno-measure of resisting early deterioration of concrete,resorting to the discussion on early detrioration mechanism and influencing factors of the deicing salt on concrete in cold region.Mixing air entraining agents and reducing water cement ratio were the most effective solution to improve resistance deicing salt scaling of concrete.Blast furnace slag can suppress alkali aggreate reaction caused by deicing salt.Setting up a rational drainage system,compacting concrete and improving concrete cover thickness were effective measures to protect bars.Keywords:
Air entrainment
Alkali–aggregate reaction
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Recently, the deterioration of concrete structures have been increased by the damage from salt, carbonization, freezing & thawing and the others. Therefore, the measures for the deterioration of concretes have been taken. Among them, it has been often used that surface treatment which cut off the deterioration factors of durability by protecting the surface of concrete. The water proof and repair materials for concrete mainly use organic materials such as epoxy, these materials excel in intial bonding force and resistance to chemical agents. But they cause difference in the modulus of elasticity and the rate of shrinkage and expansion of concrete, and thus result in such problems as scaling and spatting in the progress of time. Therefore in this study it develop the performance Improving agent of concrete surface that can block a deterioration cause such as gas, chloride ion and water from the outside and enhance waterproofing ability by reinforcing the concrete surface when applying it to concrete structures.
Waterproofing
Shrinkage
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Concrete pavement joints have shown the potential to deteriorate, thereby compromising the service life of an otherwise healthy pavement. It is proposed that this damage is due to fluid collecting at the joint. The collection of fluid makes concrete 1) susceptible to freeze and thaw damage when it reaches a critical degree of saturation and 2) susceptible to damage due to a chemical reaction between the salt and matrix. Currently, models that describe the rate of water absorption in concrete consider the concrete as uncracked. In service however, concrete can develop cracks that increase the rate of transport. The first part of this paper will begin by discussing water absorption in undamaged concrete. The second part of this paper discusses the influence of distributed cracking. The third part of this paper discusses a potential chemical reaction between cement and deicing salt that forms calcium oxychloride.
Service life
Degree of saturation
Saturation (graph theory)
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TO IMPROVE THEIR RESISTANCE TO DEICING SALTS AND FROST, CONCRETE SURFACINGS MUST CONTAIN AT LEAST 5% OF ENTRAINED AIR; COMPRESSIVE STRENGTH MUST NOT BE LESS THAN 350 KG/CM2 IF DYNAMIC STRESSES IMPOSED BY HEAVY VEHICLES ARE TO BE SATISFACTORILY SUPPORTED. TO ACHIEVE THESE RESULTS WITHOUT HAVING TO USE AN EXCESSIVE AMOUNT OF CEMENT, IT IS RECOMMENDED TO USE SODIUM ABIETATE AND A SULPHITE RESIDUE AS AIR-ENTRAINING AGENTS.
Air entrainment
Frost (temperature)
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This paper describes how concrete has performed well in bridge decks over the years. However, with increasing use of deicing salts and changes in concrete constituent materials, many decks are exhibiting distress that requires costly repairs. The distress may be the result of corrosion of reinforcement, freeze-thaw deterioration, alkali-aggregate reactivity, or sulfate attack. In each case, water and solutions penetrating into the concrete initiate the deterioration. Therefore, when exposed to these environments, concretes must have a high resistance to the penetration of water and harmful solutions if the concrete is to achieve longevity. This can be achieved with a low permeability concrete. In addition, for resistance to damage from freezing and thawing, a proper air-void system is needed.
Void (composites)
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A review of current literature on the effects of deicing salt and trace minerals, such as sulfate, on aggregate deterioration was conducted. Such deterioration in both Portland cement concrete, and bituminous pavements was reviewed. For Portland cement concrete, it was determined that current research on the effects of moisture and deicing salt on aggregates concrete matrix durability, with little discussion on the effects on aggregates. The effects of trace minerals in deicing salt are also rarely discussed. Pore size distribution, insoluble residue, absorption, and susceptibility to alkali-silica reaction all appear to affect aggregate durability in the presence of moisture of freeze-thaw. Based on available research, it is concluded that salt in solution exacerbates the damaging effects of moisture and freeze-thaw on aggregates. Several researchers currently are evaluating other features of aggregate deterioration by deicing salts. Moisture damage effects on aggregates in bituminous pavements have been widely studied. Damage potential is strongly related to the susceptibility of stripping of the bituminous covering from the aggregate surface. Research has been conducted on the use of various additives to reduce stripping, some of which consist of proprietary commercial formulations. There is also extensive research on testing procedures, which predict stripping potential of aggregates. However, the added effect of deicing salt has received relatively little attention. Some researchers have speculated that deicing salts may increase the brittleness of asphalt pavements thereby increasing susceptibility to moisture. Determining specific effects of deicing salts on aggregate may prove difficult because of the numerous properties that affect the stripping potential of aggregates for bituminous pavements. Mixture type, placement techniques and traffic, as well as aggregate properties, appear to be related to a bituminous pavement’s susceptibility to moisture damage.
Alkali–aggregate reaction
Stripping (fiber)
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The mechanism of the destructive effects of deicing salt on concrete structures is explored chemically and physically.The suggested anti erosion preventive measures include:to employ degassers,to control the water cement ratios,to mix in mineral admixtures and skeletal materials,and the combinations of the above measures.
Water–cement ratio
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This paper investigated a new type of admixture which can be used to enhance the resistance of concrete surface to deicing salt deteriorating. Physical and mechanical properties of concrete incorporating this salt-scaling resistant admixture were measured. Practical application on site has proved that this admixture is effective for concrete to resist salt-scaling action.
Salt solution
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With increased attention to service life, bridge decks are now being designed to perform for 75 to over 100 years without major repairs. In areas where deicing salts are used, sustainable and cost effective solutions utilize concretes with w/cm less than 0.4, concrete cover over the reinforcement greater than or equal to two inches, and/or additional corrosion protection measures such as corrosion resistant reinforcement or corrosion inhibitors. Concretes with w/cm less than 0.4 can be more susceptible to cracking, as well as requiring higher cement factors, even with the use of supplementary cementitious materials. The longer design life increases the risk of other degradation mechanism, such as alkali-silica reactions (ASR) which are expansive and can result in concrete cracking and deterioration. In this paper, data on an alternative solution, that could utilize more moderate cementitious levels, but still reduce chloride ingress, potentially raise chloride threshold levels, provide additional protection against ASR attack, and reduce differential shrinkage, by applying a very low surface tension organofunctional silane inhibitor to the surface, before exposure to chloride is discussed.
Cementitious
Service life
Shrinkage
Expansive
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凍結防止剤の使用より生じるコンクリートのスケーリングは、道路本体および付帯構造物において、かぶりコンクリートの断面の減少をもたらし、耐久性、美観のみならず耐力上の問題も引き起こしかねない。しかし、その有効な対策が確立されていないのが現状である。そこで本研究では、ASTM C 672に準拠し、普通コンクリートおよび高流動コンクリートを用い、各種配合条件を変化させた場合におけるコンクリートのスケーリング劣化の抑制について検討を行った。その結果、本研究の範囲内においては、スケーリングの抑制には、空気量を6～8％と高めにすることが極めて有効であること、前述の条件に加えて粗骨材の最大寸法を小さくすること、および振動締固めを行わない高流動コンクリートとすることによってスケーリング量が、さらに低減可能であることが確認された。
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Abstract In winter, a large number of chloride deicing agents are spread in northern China. The damage effect of chloride deicing agent on concrete has attracted great attention in the industry. It is of great significance to study the mechanism of salt freezing to improve the service life and safety of roads and bridges in cold regions. In this paper, using C30 and C50 concrete specimens commonly used in highway engineering, using water bath box, oven, cut-201 ultrasonic instrument and other instruments and equipment, on the basis of a large number of indoor tests, the mode and degree of concrete salt freezing damage under freeze-thaw cycle environment are studied in depth, including the influence of concrete quality loss rate, appearance, dynamic elastic modulus and strength The influence mode and degree of concrete salt frost damage are given, and the variation law of various performance parameters of concrete under salt freezing condition is analyzed, which provides the test basis for the proposal of relevant protection measures.
Frost (temperature)
Service life
Water–cement ratio
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