旧水泥混凝土路面碎石化处理技术

介绍了旧水泥混凝土路面碎石化处理技术的基本原理、适用情况、主要措施,以及碎石化处理的技术要求和质量控制评价等,指出其应用于破损严重的水泥混凝土路面改建具有重要意义。     

旧水泥混凝土路面加铺沥青混凝土浅析

简单介绍了旧水泥混凝土路面使用现状及改善行车条件的必要性,分析了在旧水泥混凝土路面上加铺沥青的可行性,具体阐述了加铺沥青前的技术准备和对路面的技术处理及病害预防措施,以指导实践。     

Experimental study and field application of calcium sulfoaluminate cement for rapid repair of concrete pavements

The fast-track repair of deteriorated concrete pavement requires materials that can be placed, cured, and opened to the traffic in a short period. Type III cement and Calcium Sulfoaluminate (CSA) cement are the most commonly used fast-setting hydraulic cement (FSHC). In this study, the properties of Type III and CSA cement concrete, including compressive strength, coefficient of thermal expansion (CTE) and shrinkage were evaluated. The test results indicate that compressive strength of FSHC concrete increased rapidly at the early age. CSA cement concrete had higher early-age and long term strength. The shrinkage of CSA cement concrete was lower than that of Type III cement concrete. Both CSA and Type III cement concrete had similar CTE values. Based on the laboratory results, the CSA cement was selected as the partial-depth rapid repair material for a distressed continuously reinforced concrete pavement. The data collected during and after the repair show that the CSA cement concrete had good short-term and long-term performances and, therefore, was suitable for the rapid repair of concrete pavement.     

Identification of the sources of organic compounds that decalcify cement concrete and generate alcohols and ammonia gases

This study identifies the emission sources of various types of airborne organic compounds, which deteriorate cement concrete by penetrating into the concrete together with moisture. The study used high-performance liquid chromatography and gas chromatograph mass spectrometry. The results show that the types of organic compounds contained in decalcified cement concrete were very similar to those found in the total suspended compounds in the air, and that the source of the emissions was particles of exhaust from diesel vehicles and radial tires used in summer. Such organic compounds include substances suspected of having endocrine disrupting properties. Hydrolysis occurs when these substances penetrate into highly alkaline cement concrete, and leads to deterioration of the cement concrete and the release of alcohols and ammonia gases which pollute indoor air and may be a cause of the sick building syndrome.     

高等级公路水泥混凝土路面破损分析

分析了造成水泥混凝土路面发生破损的原因,典型和机理,提出了预防措施。指出路面破损原因复杂多样,而且一旦出现裂缝难于修复成原有的整体效果,因而必须树立“以防为主,防重于治”的观念。     

Risk assessment of exposure to volatile organic compounds in groundwater in Taiwan

The purpose of this study is to assess the risks from exposure to 14 volatile organic compounds (VOCs) in selected groundwater sites in Taiwan. The study employs the multimedia environment pollutant assessment system (MEPAS) model to calculate the specific non-cancer and cancer risks at an exposure level of 1 μg/L of each VOC for a variety of exposure pathways. The results show that the highest specific non-cancer risk is associated with water ingestion of vinyl chloride (VC) and that the highest specific cancer risk is associated with indoor breathing of VC. The three most important exposure pathways for risk assessment for both non-cancer and cancer risks are identified as water ingestion, dermal absorption when showering, and indoor breathing. Excess tetrachloroethylene (PCE), trichloroethylene (TCE), dichloroethylene (DCE), and VC are detected in the groundwater aquifers of one dump site and one factory. However, the study suggests that the pollutants in the contaminated groundwater aquifers do not travel extensively with groundwater flow and that the resulting VOC concentrations are below detectable levels for most of the sampled drinking-water treatment plants. Nevertheless, the non-cancer and cancer risks resulting from use of the contaminated groundwater are found to be hundred times higher than the general risk guidance values. To ensure safe groundwater utilisation, remediation initiatives for soil and groundwater are required. Finally, the study suggests that the current criteria for VOCs in drinking water might not be capable of ensuring public safety when groundwater is used as the primary water supply; more stringent quality criteria for drinking water are proposed for selected VOCs.     

The effect of ventilation on indoor exposure to semivolatile organic compounds

A mechanistic model was developed to examine how natural ventilation influences residential indoor exposure to semivolatile organic compounds (SVOCs) via inhalation, dermal sorption, and dust ingestion. The effect of ventilation on indoor particle mass concentration and mass transfer at source/sink surfaces, and the enhancing effect of particles on mass transfer at source/sink surfaces are included. When air exchange rate increases from 0.6/h to 1.8/h_, the steady‐state SVOC (gas‐phase plus particle phase with log K_OA varying from 9 to 13) concentration in the idealized model decreases by about 60%. In contrast, for the same change in ventilation, the simulated indoor formaldehyde (representing volatile organic compounds) gas‐phase concentration decreases by about 70%. The effect of ventilation on exposure via each pathway has a relatively insignificant association with the K_OA of the SVOCs: a change of K_OA from 10⁹ to 10¹³ results in a change of only 2–30%. Sensitivity analysis identifies the deposition rate of PM_2.5 as a primary factor influencing the relationship between ventilation and exposure for SVOCs with log K_OA = 13. The relationship between ventilation rate and air speed near surfaces needs to be further substantiated.     

Deterioration of cement-based materials due to the action of organic compounds

Due to the growing extent of the sources of aggressive media, the concrete structures may be exposed to the action of organic species.The paper presents the results of the long-term study on the action of various organic substances on the cement-based material. The results obtained show the different aggressivity of the solutions of phenols, carboxylic acids and sulphonic compounds. Petroleum and mineral oil have been shown as unaggressive media. Observed increased expansions followed by crack propagation at the action of some media were adjudged to the cooperation of the mechanism of acidic attack and dispersive effect of surface activity of organic substances.     

谈水泥混凝土路面施工中混凝土的病害与防治

分析了水泥混凝土路面的缺陷及其成因，就混凝土路面的断板、缺边掉角、裂纹、脱皮等病害，提出了相应的防治措施，以使道路表面平整，满足设计要求。     

高寒地区防冻混凝土配制技术与性能研究

本文从外加剂入手,研究了不同外加剂以及不同粉煤灰掺量对混凝土不同龄期的力学性能及抗冻性能的影响。结果表明:混凝土受冻强度随粉煤灰掺量的增加而降低,故在高寒地区或冬季施工时,应该控制粉煤灰掺量;适应性好的外加剂复掺(也即防冻引气早强成分的外加剂复掺),不管对混凝土早期强度还是后期强度来说,都比只掺一种外加剂时的强度高,且28d强度提高10MPa左右,适宜用于高寒地区的实际施工。     

低温条件施工对水泥混凝土路面质量的影响

水泥混凝土路面是典型的板状结构,浇筑时混凝土的温度、基层温度、模板温度、环境温度、相对湿度以及风速等对混凝土的浇筑、压实、饰面以及长期路用性能影响较大.低温条件对早期混凝土质量如工作性、凝结时间和早期强度以及体积稳定性和耐久性的影响不可忽视.在总结低温条件对混凝土质量影响的基础上,认为控制混凝土的浇筑温度和浇筑后数日的养护温度对路面的长期性能至关重要.对目前通常采用的控制混凝土浇筑时温度的措施如改善配合比、提高混凝土组分温度、掺加特种外加剂和采取合理的养护措施等作了详细介绍.     

沥青路面在既有水泥路面改造中的应用

在既有水泥路面上铺设沥青面层是水泥路面改造的重要手段,但要防止改造后路面出现反射裂缝,影响使用性能。设置应力吸收层是防治反射裂缝的主要方法,应力吸收层中改性沥青的作用极其重要。本文通过对三种应力吸收层进行介绍,阐明应力吸收层防治反射裂缝的原理,从而解决既有水泥路面改造中加铺沥青面层的技术难题。     

Shrinkage properties of compacted sand concrete used in pavements

Compacted sand concrete is being researched for potential usage in road construction because of shortage in gravel resources in many countries. However, one of the problems for this material with such application is shrinkage cracking. This paper presents the results of the unrestrained shrinkage test performed on three different compacted sand concrete mixes. Two existing shrinkage prediction models, namely the ACI 209 and the CEB 90, were used to fit the measured shrinkage data. The CEB 90 model with an application of a correction factor was found to perform well with compacted sand concrete. Based on the results of the shrinkage tests, joint spacing between compacted sand concrete slabs was calculated.     

混凝土外加剂对水泥的适应性

通过外加剂在不同厂家水泥中的应用效果对比及外加剂对水泥的适应性的影响分析,提供解决外加剂对水泥适应性的改进方法,提出外加剂在混凝土应用中的几个问题。     

冻融环境再生混凝土结构耐久性模糊综合评估

根据寒冷地区再生混凝土结构的破坏特征,分析了影响钢筋混凝土结构耐久性的主要因素,综合运用模糊数学法与结构的实际调查分析,初步建立了钢筋混凝土结构耐久性评估等级,并给出了相应的工程评估算例,为寒冷地区再生混凝土结构耐久性评估提供了参考和依据。     

高寒地区混凝土桥梁裂缝成因及预防

介绍混凝土桥梁裂缝形成的主要原因、裂缝的形式与特征,并依据裂缝形成的内因,提出混凝土裂缝的预防与处理方法。     

寒冷地区运煤栈桥结构混凝土耐久性试验

为掌握寒冷地区运煤栈桥结构混凝土的性能退化规律,利用运煤栈桥主要构件实际施工时的材料及配合比制作了一批混凝土试件,并进行了耐久性试验,结果表明:栈桥主要构件混凝土抗压强度均达到了设计强度等级;厂区外山下栈桥主要构件冻融损伤最为严重;粗骨料不存在碱—硅酸反应危害。     

高寒地区混凝土构筑物裂缝成因及预防

针对青藏高原季节性冻土区恶劣的自然环境条件特点,分析了青藏铁路部分桥涵裂缝的成因,提出了预防或减缓混凝土裂缝的具体措施。以引起后续工程施工的重视,确保其混凝土结构的长期耐久性能。     

寒冷地区道路混凝土渗透性与强度的关系

通过试验,分析了寒冷地区不同水胶比的道路混凝土强度与渗透性的关系,指出普通混凝土的抗压强度与渗透性有较好的相关性,而掺加粉煤灰、硅灰及引气剂的混凝土强度与渗透性相关性较差。     

Compressive strength loss and reinforcement degradations of reinforced concrete structure due to long-term exposure

Degradations due to long-term weathering actions on a reinforced concrete structure were investigated. Compressive strength and reinforcement corrosion developments of a prototype RC structure were monitored for 6 years using destructive and non-destructive tests which include periodic coring, compressive strength, rebound hammer, ultrasonic pulse velocity, carbonation, half-cell and tensile strength tests. Eventually, results have shown that more than a quarter of peak compressive strength can be lost within 5 years of continuous exposure. Corrosion of the exposed bars within the range of the testing period was also observed to be quite alarming. Thus, defects caused by prolonged actions of environmental factors may pose serious threats on the integrity of partially completed structures especially abandoned projects.