CN108564287A - A kind of heavy haul railway bridge pier sulphate corrosion risk evaluating method - Google Patents

Abstract

The invention discloses a kind of heavy haul railway bridge pier sulphate corrosion risk evaluating methods, belong to science of bridge building field.Three broad aspect of environmental factor, raw material factor and Surface layer's concrete qualitative factor is considered.Environmental factor is divided into Climate Dryness/Wetness, underground water and soil sulfate ingredient and three subclass of content；Raw material factor is divided into three tricalcium aluminate content in cement, flyash and fine slag contents subclass；Surface layer's concrete quality is indicated with interconnected pore rate；Corresponding subitem risk index is assigned to above each factor, integrated risk index is obtained by the adduction of each subitem risk index, and passes through its corrosion risk of the integrated risk index assessment.The present invention can be used for heavy haul railway concrete pier and be evaluated by sulphate corrosion risk, and method is relatively simple, calculate simplicity, and distinction is strong.

Description

A risk assessment method for sulfate corrosion of heavy-duty railway bridge piers

technical field

The invention relates to a corrosion risk assessment method, in particular to a sulfate corrosion risk assessment method for heavy-duty railway bridge piers, which belongs to the field of bridge engineering.

Background technique

Concrete engineering is widely used all over the world. Although concrete is considered as a durable building material in ordinary environments, its durability problems are becoming more and more prominent in harsh service environments. Chemical corrosion is a relatively serious corrosion category faced by concrete, and sulfate corrosion is the most common form of chemical corrosion. my country has a vast territory, and there are many saline-alkali lands in the northwest and eastern coastal areas, especially the sulfate erosion in the inland salt lakes in the northwest and the Yellow River Delta in the east (including near the old course of the Yellow River). Some transportation infrastructure and power infrastructure have been severely corroded after being in use for more than ten years or even a few years, and have to be reinforced and rebuilt or demolished and rebuilt, interrupting the use of facilities and causing adverse social impacts. my country's heavy-haul railways were built earlier. At that time, the understanding of durability was not sufficient, and durability issues were often not considered in engineering design. On-site investigations showed that the corrosion of concrete piers in the eastern saline-alkaline area has become prominent. After searching the literature, no risk assessment method for sulfate corrosion that comprehensively considers the environment, materials and concrete quality has been found at home and abroad. The present invention aims to provide a comprehensive evaluation method.

Contents of the invention

In order to solve the above-mentioned problems existing in the prior art, the present invention provides a kind of heavy-duty railway pier sulfate corrosion risk assessment method, through the assessment of the environment of the concrete engineering, the raw materials used and the mix ratio, and the quality of the surface layer concrete, A comprehensive corrosion risk evaluation index is obtained, which has reference significance for judging the risk of sulfate corrosion of concrete.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

A risk assessment method for sulfate corrosion of heavy-duty railway bridge piers, which comprehensively considers three major aspects: environmental factors, raw material factors and surface concrete quality factors, and divides environmental factors into three subcategories: climate environment, groundwater and soil sulfate composition and content; Raw material factors are divided into three subcategories of tricalcium aluminate content in cement, fly ash and slag admixture; the surface concrete quality is represented by connected porosity k; wherein, the soil sulfate composition and content subcategory includes soluble Sulfate content and the relative concentration of soluble sulfate components in the soil, which in turn is divided into concentrations of magnesium sulfate, sodium sulfate, and calcium sulfate in the soil; the fly ash subcategory includes concrete mix The percentage of the amount of primary fly ash in the mass of all cementitious materials in the ratio; the slag addition subcategory includes the percentage of the amount of granulated blast furnace slag in the mass of all cementitious materials in the concrete mix ratio; assign corresponding values to the above factors The sub-item risk index, the comprehensive risk index is obtained by summing the sub-item risk indexes, and the corrosion risk is evaluated through the comprehensive risk index.

Preferably, for the climate environment, if the climate environment is an arid area, then the sub-item risk index R ₀ =0; if it is a humid area, then the sub-item risk index R ₀ =1; if it is a dry-wet alternate area, Then the sub-item risk index R ₀ =2;

For groundwater, if the groundwater has no groundwater, the sub-item risk index R ₁ =0; if the groundwater is shallow stagnant water, then the sub-item risk index R ₁ =1; Index R ₁ =2;

For the soluble sulfate content p in the soil, if p≥4000mg/Kg, then the sub-item risk index R ₂ =3; if 2000mg/Kg<p<4000mg/Kg, then the sub-item risk index R ₂ =2; if 400 mg/Kg<p≤2000mg/Kg, then the sub-item risk index R ₂ =1; if p≤400mg/Kg, the sulfate corrosion risk can be ignored, and the comprehensive risk index R=0;

For the concentration of magnesium sulfate, sodium sulfate and calcium sulfate in the soil, the concentrations of magnesium sulfate, sodium sulfate and calcium sulfate in the soil are respectively recorded as C _Mg , C _Na and C _Ca , if C _Mg >max{C _Na , C _Ca }, then the sub-item risk index R ₃ =3; if C _Na >max{C _Mg ,C _Ca }, then the sub-item risk index R ₃ =2; if C _Ca >max{C _Mg , C _Na }, then the sub-item risk index R ₃ =1;

For the content of tricalcium aluminate in cement, if the content is greater than 9%, the sub-item risk index R ₄ =2, otherwise the sub-item risk index R ₄ =1;

For the percentage of the amount of primary fly ash in the concrete mix ratio to the mass of all cementitious materials, if the percentage is greater than 25%, then the sub-item risk index R ₅ =1; otherwise, the sub-item risk index R ₅ =2;

Regarding the percentage of the amount of granulated blast furnace slag to the mass of all cementitious materials in the concrete mix, if the percentage is greater than 60%, the sub-item risk index R ₆ =0; otherwise, the sub-item risk index R ₆ =1.

For concrete quality, if the connected porosity k>0.12, then the sub-item risk index R ₇ =2; if 7≤k≤12, then the sub-item risk index R ₇ =1; if k<7, the sub-item risk index R ₇ =0.

Preferably, for the quality of concrete, cores should be drilled at the parts susceptible to sulfate corrosion, the diameter of the drilled holes should not be greater than 50 mm, and the drilled depth should not be less than the thickness of the concrete protective layer; the core samples should be washed with clean water and put into the concrete vacuum Saturate the machine with water so that the reading of the vacuum pump is less than 0.1 atmospheric pressure, keep the vacuum and inject distilled water, and continue vacuuming for 48 hours; take out the core sample and wipe off the water on the surface, and immediately weigh it with an electronic scale with an accuracy greater than one tenth of a gram , record the mass as m ₁ , put the core sample in an environment of 80°C to 90°C and bake for 72 hours, weigh it with the same electronic scale, record the mass as m ₂ , and calculate k=2.4×(m ₁ -m ₂ )/m ₂ .

Preferably, the comprehensive risk index Check the risk level according to Table 1:

Table 1

Compared with prior art, the beneficial effect of the present invention is:

1. This method can be used for a comprehensive qualitative evaluation of the sulfate erosion risk of heavy-duty railway concrete piers.

2. This method combines on-site investigation and laboratory test, and the consideration factors are relatively comprehensive, and the required experimental instruments are few, and the operation is simple.

3. The method is relatively simple, the calculation is concise, and the distinction is strong.

Detailed ways

The present invention will be described in further detail below in conjunction with specific examples, but not as a limitation of the present invention.

A railway bridge pier in Dongying City, Shandong Province is in an alternating dry and wet environment, and the sub-item risk index R ₀ =2; the groundwater is shallow stagnant water, and the sub-item risk index R ₁ =1; the soluble sulfate content in the soil is 3860mg/Kg, The sub-item risk index R ₂ =2; the concentration of sodium sulfate in the soil is higher than the concentration of magnesium sulfate and calcium sulfate, the sub-item risk index R ₃ =2; the content of tricalcium aluminate in the cement chemical components is 8%, the sub-item risk index Item risk index R ₄ =1; the percentage of primary fly ash to all cementitious materials is 30%, sub-item risk index R ₅ =1; no slag is added, sub-item risk index R ₆ =1; Coring is drilled at three different parts of the same pier, k=8.2 is calculated according to the above process, and the sub-item risk index R ₇ =1. Calculated comprehensive risk index R = 11, look up Table 1 as extremely high risk. In fact, the pier was identified as a dangerous pier by experts in August 2012 and has been reinforced and reconstructed.

The above-mentioned embodiments are only enumerations made to illustrate the technical solutions of the present invention more clearly, and are not intended to limit the present invention. Any modification of the technical solutions of the present application by those of ordinary skill in the art according to the common knowledge in the field is also within the scope of protection of the present application. In a word, the above-mentioned embodiments are merely examples, and the scope of protection of the present application shall be subject to the scope of the appended claims.

Claims (4)

1. a kind of heavy haul railway bridge pier sulphate corrosion risk evaluating method, it is characterised in that：Consider environmental factor, former material Environmental factor is divided into climatic environment, underground water and soil sulfate by three broad aspect of material factor and Surface layer's concrete qualitative factor Three subclass of ingredient and content；Raw material factor is divided into tricalcium aluminate content in cement, flyash and slag and adds three Subclass；Surface layer's concrete quality is indicated with interconnected pore rate k；Wherein, the soil sulfate ingredient and content subclass Include the relative concentration of soluble sulphate ingredient in soluble sulphate content in soil and soil, and it is soluble in soil The relative concentration of sulfuric acid salt component is divided into as the concentration of magnesium sulfate, sodium sulphate and calcium sulfate in soil；The flyash subclass The percentage of all cementitious material quality is accounted for including level-one flyash dosage in concrete mix；The slag adds subclass The percentage of all cementitious material quality is accounted for including granulated blast-furnace slag dosage in concrete mix；Above each factor is assigned Corresponding subitem risk index obtains integrated risk index by the adduction of each subitem risk index, and passes through the integrated risk Its corrosion risk of index assessment.

2. a kind of heavy haul railway bridge pier sulphate corrosion risk evaluating method according to claim 1, it is characterised in that：

For climatic environment, the climatic environment is if arid area, then itemize risk index R₀=0；If moistening ground Area, then itemize risk index R₀=1；If alternation of wetting and drying area, then itemize risk index R₀=2；

For underground water, if the groundwater condition is without underground water, subitem risk index R₁=0；If then underground water is shallow-layer Backwater, then itemize risk index R₁=1；If circulating water, then itemize risk index R₁=2；

For soluble sulphate content p in soil, if p >=4000mg/Kg, itemize risk index R₂=3；If 2000mg/Kg<p<4000mg/Kg, then itemize risk index R₂=2；If 400mg/Kg<P≤2000mg/Kg, then risk of itemizing Index R₂=1；If p≤400mg/Kg, sulphate corrosion risk is negligible, directly takes integrated risk index R=0；

For the concentration of magnesium sulfate, sodium sulphate and calcium sulfate in soil, magnesium sulfate, sodium sulphate and calcium sulfate in the soil Concentration, be denoted as C respectively_Mg、C_NaAnd C_CaIf C_Mg>max{C_Na,C_Ca, then itemize risk index R₃=3；If C_Na>max{C_Mg, C_Ca, then itemize risk index R₃=2；If C_Ca>max{C_Mg,C_Na, then itemize risk index R₃=1；

For tricalcium aluminate content in cement, if the content is more than 9%, itemize risk index R₄=2, wind of otherwise itemizing Dangerous index R₄=1；

Level-one flyash dosage in concrete mix is accounted for for the percentage of all cementitious material quality, if the percentage More than 25%, then itemize risk index R₅=1；Otherwise subitem risk index R₅=2；

Granulated blast-furnace slag dosage in concrete mix is accounted for for the percentage of all cementitious material quality, if the percentage Than being more than 60%, then itemize risk index R₆=0；Otherwise subitem risk index R₆=1.

For concrete quality, if interconnected pore rate k>0.12, then itemize risk index R₇=2；If 7≤k≤12 are divided Item risk index R₇=1；If k<7, subitem risk index R₇=0.

3. a kind of heavy haul railway bridge pier sulphate corrosion risk evaluating method according to claim 2, it is characterised in that：It is right For concrete quality, Ying Yi is not more than 50mm by sulfate attack position boring and coring, bore diameter, and drilling depth is not Less than thickness of concrete cover；Core sample is cleaned with clear water, water of satisfying is put into the full water dispenser of concrete vacuum, keeps vacuum pump reading small In 0.1 atmospheric pressure, keeps vacuum degree to inject distilled water, persistently vacuumize 48 hours；It takes out core sample and dries surface water mark, immediately It is more than 1/10th grams of electronic scale weighing with precision, note quality is m₁, then core sample is put into 80 DEG C~90 DEG C of environment and is dried 72 hours roasting, with the same electronic scale weighing, note quality is m₂, calculate k=2.4 × (m₁-m₂)/m₂。

4. a kind of heavy haul railway bridge pier sulphate corrosion risk evaluating method according to claim 3, it is characterised in that：

The integrated risk indexIt is looked into according to table 1 and takes risk class：

Table 1