混凝土电阻系数的研究和分析

作者研究表明^[1-3]：混凝土电气加热蓄热冷却过程中温度（t）随时间（z）变化的客观规律可用吴震东方程精确描述和控制，文献[3,4]中各种不同形式的电极布置图可以满足混凝土冬季施工采用电极加热法的需求^[4，5]的基础上对极间电阻（R）和扩散电功率（P）的计算公式中混凝土电阻系数ρ的主要影响因素，作深入的研究和分析。     

不同加热方式下高温后防辐射混凝土的性能研究

以磁铁矿为骨料制备了防辐射混凝土,研究了不同加热方式（微波辐射加热、马弗炉加热）和温度（25～800℃）对防辐射混凝土外观形貌、抗压强度、超声波波速和屏蔽性能的影响。结果表明：在相同加热方式下,随着温度的升高,试件的外观形貌劣化程度加重,抗压强度、超声波波速、屏蔽性能均降低;与马弗炉加热相比,微波辐射加热在各个温度区间内对试件造成的损伤均较大。     

混凝土电极加热养护设计与施工要求

混凝土电气加热蓄热升温、恒温、降温三个养护过程温度变化规律可用吴震东方程精确地描述 ,从而使混凝土在电极加热法有一套精确的热工计算公式。本文在文献〔5〕的基础上添补了电阻、电功率、计算公式一览表 ,对电极加热养护提出了设计与施工要求。     

快速加热商品混凝土的方法

快速加热商品混凝土的方法林学友，邢东明（中铁建筑工程公司，北京１０００３９）在室外温度为─１０℃的条件将入模施工温度保持在８℃以上，历来是混凝土拌合站急待解决的技术难题，尤其对连续流动的大批量砂石料快速加热及如何使砂石料冻结体迅速解冻，是决定混凝土搅...     

混凝土电气加热蓄热冷却计算理论的研究

本文在吴震东教授提出的非大体积混凝土蓄热冷却理论的基础上，对混凝土电气加热的时间ｚ和加热过程中平均温度ｔｐ的计算，依据不稳定传热理论，从瞬时动态角度出发，考虑实际影响电热蓄热的主要因素，提高广义的混凝土电热冷却定律，建立电热蓄热平衡微分方程，从而解得整套理论公式，电热蕹热微分方程可应用于非大体积混凝土冬季电热法的蓄热设计，也可应用于大体积混凝土的冬季电热法的蓄热设计，因此表面系数Ｍ可不受限制。     

沥青罐及加热设备的选用

沥青混凝土搅拌系统中的沥青罐（即沥青储罐和沥青高温罐）和导热油加热设备的合理选用,是降低投资成本和提高设备经济效益的关键。本文拟以涟水县公路管理站ＱＬＢ１０００型沥青混凝土搅拌设备为例,说明如何合理选配沥青罐及加热设备。沥青储罐和沥青高温罐的选用必须满足沥青混凝土搅拌设备连续生产的需要,还要避免投资过大,造成浪费,增加成本。应根据沥青耗量及储量合理确定。该搅拌设备日生产沥青量ｍ（ｔ）为：ｍ＝Ｐ·ｈ·ｋ＝８０ｘ１０ｘ５％＝４０式中Ｐ──沥青混凝土搅拌设备上限生产能力,ｔ／ｈｈ──日工作有效时间,设…     

珠海长陆公司在国内首推基于PWC的分布式混凝土站控制系统

模块化的水泥、沥青混凝土站采用分布式控制系统早已在欧美流行。在中国广大混凝土站机械设计工程师们也早已将机械部分模块化,但是电气系统都未能实现模块化装、卸。长陆公司作为国内称重自动化技术一流的制造商,推出可编程称重控制器（PWC）平台可方便实现分布式电气控制系统。     

联合快速测定砂（石）含水（泥）量简法

文中较详细的介绍了检测操作方法，计算原理和砂（石）含水率，此法操作简单、易于掌握，不用加热烘干砂（石），约五分钟左右即可得到检测结果。它特别适宜建筑施工现场使用，可随时对进入施工现场的砂（石）做含水（泥）检测，用测得的数据科学指导调整混凝土或砌筑砂浆配合比，确保建筑工程质量。     

2001年第一季度发行的国家建筑标准设计图集

图集号００ＺＪ６１９００Ｇ５１４（三）～（四）００Ｇ５１４（五）９５Ｇ４１５（四）９５Ｇ４１５（六）、（九）９７Ｄ２６７００ＤＸ００１图集名称电动采光排烟天窗１２ｍ实腹式钢吊车梁（重级工作制 ,Ｑ２３５钢、Ｑ３４５钢）１２ｍ实腹式钢吊车梁（中级工作制 ,Ｑ２３５钢、Ｑ３４５钢）１２ｍ实腹式钢吊车梁（轻级工作制 ,Ｑ２３５钢）图集为１８～２７ｍ跨度预应力筋采用碳素钢丝的预应力混凝土折线形屋架施工图变压器室电气布置图、变压器室土建设计任务图和土建设计技术要求、设备构件安装图预应力混凝土折线形屋架预应力混凝…     

HLS120混凝土搅拌楼

HLS120混凝土搅拌楼是我公司吸收国内外各种机型的优点和先进技术．结台本公司多年生产混凝土搅拌设备的理论和实践经验而自行开发的大型混凝土搅拌设备．它由物料输送储存系统、计量系统、搅拌系统电气控制系统．摄像监视系统和钢结构等组成（见图1）．可广泛用于道路，桥梁．水坝机场、港口等大型工程及城市商品混凝土等需求量大的场所。     

Evaluating a polymer concrete coating for protecting non-metallic underground facilities from sulfuric acid attack

Deteriorating underground facilities built with cement concrete and clay bricks require rapid in situ rehabilitation, and using coating as a corrosion protectant is one method currently being adopted. The performance of a polymer concrete coating was evaluated using a combination of full-scale and laboratory tests. The polyester-based polymer concrete coating had a density of 1.75 g/cm³ (109 lb/ft³) and hardness in the range 38–45 (Barcol hardness). A full-scale test on coating applicability and performance on the concrete substrate was performed under an external hydrostatic pressure of over 103 kPa (15 psi) of water, simulating the groundwater condition. Coated concrete cylinders and clay bricks with holidays (pinholes) were used to study the chemical resistance of the coating under acidic environments to represent the worst sewer and accelerated test conditions (ASTM G 20). Bond strength between the coating and the concrete/clay brick substrates were determined using the modified ASTM D 4541 test. The performance of the polymer concrete coating material was studied for over 3 years. The polymer concrete coating was applied with ease on dry and wet concrete surfaces. Test results showed that the polymer concrete coating had good bond strength with clay bricks and wet concrete surface. No failure was observed in 3 years with coated clay bricks. The coating extended the lifetime of dry and wet concrete by a factor of 29 and 71, respectively. The weight change of coated concrete was modeled using a film model.     

Accelerated carbonation and testing of concrete made with fly ash

An accelerated carbonation test was carried out in order to assess the carbonation of fly ash (FA) concrete. The process of carbonation was accelerated using a controlled environment. The concrete mixtures made with 0, 50 and 70% replacement of normal Portland cement (NPC) with fly ash were prepared. Water–cementitious material ratios were ranged from 0.28 to 0.55. Some concrete mixture was also made with a superplasticizer. Comparisons were made to evaluate the influence of FA on the carbonation of concrete. The laboratory test results showed that FA concrete made with 70% replacement ratio was carbonated more than that of 50% FA replacement concrete and normal Portland cement (NPC) concrete. In contrast, 50% FA replacement concrete showed lower or similar carbonation to NPC concrete. Before exposing the concrete to the accelerated carbonation testing, the longer initial curing period resulted in lower carbonation depth. The effect is more marked with moist curing. The statistical analyses results showed a strong correlation between the carbonation depth and the strength of the concrete. The influence of the superplasticizer on the carbonation was found to be insignificant.     

高强玻璃纤维/碳纤维混杂复合材料加固混凝土梁的抗弯试验研究

以高强玻璃纤维 (SGF)布与碳纤维 (CF)布混杂加固混凝土梁 ,进行对比试验研究 ,结果表明 ,与单一CF布加固相比 ,SGF/CF布混杂加固不仅使梁的延性显著提高 ,加固成本大幅降低 ,而且承载力也略有提高 ,仅刚度略为降低。简要讨论了耐久性问题     

双掺超细活性混合材对高强混凝土性能的影响

对比研究了普通硅酸盐高强混凝土(PCC)、大掺量粉煤灰高强混凝土(HFAC)，以及双掺超细粉煤灰和矿渣混合料的高强混凝土(GGFAC)在不同养护方式下的强度发展特性。同时观测了各混凝土在7d龄期时的微观结构特征，对混合材的作用机理进行了初步探讨。     

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.     

Recycling of scale and steel chips waste as a partial replacement of sand in concrete

Modification of concrete properties by the addition of appropriate materials is a popular field of concrete research. This study is focusing on the use of selected waste of iron and steel industry (steel chips and scale) as a partial replacement for sand in the production of concrete. In this research study, concretes were made with steel chips scale (ScC) and (SchC) as substitution for raw sand. Sand was replaced by these waste in different proportions (25%, 50%, 75%, and 100%) by weight of sand.The aim of this study is to investigate the compressive strength and absorption properties for gamma radiation of concrete with steel chips and scale waste as a partial replacement for sand. The tests results obtained from concretes produced with scale and steel chips were compared with those in conventional concrete (CC-0).The experimental results indicate that, the addition of these waste to concrete enhances the absorption of gamma radiation without impairing other technical features of the investigated concrete. The data shows, that the concrete mixed with steel chips have better strength than conventional concrete, while in the case of concrete mixed with scale in excess of 25%, the strength become deteriorated. The linear attenuation coefficient of gamma radiation of concrete with a mixture of scale and steel chips with 75% and 100% was very good while the rest have good and satisfying radiation properties. Consequently, concrete prepared from the iron and steel industry solid waste containing steel chips and scale could be preferred for buildings as shielding concretes against gamma radiation. In this research the thickness of the concrete shield which can be used instead of the conventional concrete was also calculated.     

Effect of coarse aggregate characteristics on concrete rheology

In the present study, concrete was considered as a two-phase material, consisting of coarse aggregate (CA) and mortar. Coarse aggregate properties were characterized by fineness, uncompacted void and friction angle. The combined effects of CA characteristics and mix design on the rheological properties of the corresponding concrete were investigated using a portable IBB concrete rheometer. Experimental results indicated that a higher CA and fine aggregate content normally result in higher concrete rheological parameters (yield stress and viscosity). For a given type and amount of mortar, concrete yield stress and viscosity generally increase with the uncompacted void content and friction angle but decreased with the size (or fineness) of CA. Well graded CA, generally having low uncompacted void content, provides concrete with considerably reduced yield stress and viscosity when compared with single-sized CA. In addition, a multiple-parameter linear regression analysis was conducted to evaluate how different CA characteristics (fineness, uncompacted void and friction angle) and mix design parameters (mortar composition, and CA volume fraction) affect concrete rheological behavior.     

原位合成SAR表层处理混凝土的抗碳化性

采用含有引发剂、交联剂的丙烯酸和丙烯酰胺单体溶液浸渍混凝土表层,通过红外辐射引发原位合成吸水性树脂(SAR)对该表层进行处理,并与斥水型有机硅防水剂(AAS)表层处理的混凝土试件进行了对比;通过不同碳化时间下的平均碳化深度和碳化层内Ca(OH2),CaCO3的XRD特征峰变化规律表征了混凝土SAR表层处理前后的抗碳化能力;通过SEM分析了SAR改善混凝土抗碳化能力的机理.     

Effect of reducing coarse aggregates on concrete strength

This paper reports the results of experimental investigation carried out on the effect of reducing coarse aggregate (CA) quantity in mix proportions on the compressive strength of concrete. It also presents empirical formulas aimed at optimizing a concrete mix design for desert regions. Intensive laboratory experiment of 1350 samples of 30 different concrete mixes using three curing methods was carried out. The influences of the water/cement (W/C) ratio, coarse and fine aggregates (FA), CA/total aggregate (CA/TA) ratio, TA/C ratio, and curing methods (air curing, oven curing, and water curing) on the compressive strength of concrete were characterized and analyzed. Mathematical formula was developed for concrete strength as a function of CA quantity that ranges from the standard quantity to null, and another formula was developed for the quantity of FA as a function of compressive strength.     

Utilization of bagasse ash as a pozzolanic material in concrete

The physical properties of concrete containing ground bagasse ash (BA) including compressive strength, water permeability, and heat evolution, were investigated. Bagasse ash from a sugar factory was ground using a ball mill until the particles retained on a No. 325 sieve were less than 5wt%. They were then used as a replacement for Type I Portland cement at 10, 20, and 30wt% of binder. The water to binder (W/B) ratio and binder content of the concrete were held constant at 0.50 and 350 kg/m³, respectively.The results showed that, at the age of 28 days, the concrete samples containing 10–30% ground bagasse ash by weight of binder had greater compressive strengths than the control concrete (concrete without ground bagasse ash), while the water permeability was lower than the control concrete. Concrete containing 20% ground bagasse ash had the highest compressive strength at 113% of the control concrete. The water permeability of concrete decreased as the fractional replacement of ground bagasse ash was increased. For the heat evolution, the maximum temperature rise of concrete containing ground bagasse ash was lower than the control concrete. It was also found that the maximum temperature rise of the concrete was reduced 13, 23, and 33% as compared with the control concrete when the cement was replaced by ground bagasse ash at 10, 20, and 30wt% of binder, respectively. The results indicate that ground bagasse ash can be used as a pozzolanic material in concrete with an acceptable strength, lower heat evolution, and reduced water permeability with respect to the control concrete.