外文翻译--辅助性胶凝材料对混凝土水化热的改善作用

1、外文原文： The effects of supplementary cementing materialsin modifying the heat of hydration of concreteYunus Ballim Peter C. GrahamReceived: 23 February 2008 / Accepted: 17 September 2008 / Published online: 23 September 2008AbstractThis paper is intended to provide guidanceon the form and extent to wh

2、ich supplementary cementing materials, in combination with Portland cement, modifies the rate of heat evolution during the early stages of hydration in concrete. In this investigation, concretes were prepared with fly ash,condensed silica fume and ground granulated blastfurnace slag, blended with Po

3、rtland cement in proportions ranging from 5% to 80%. These concretes were subjected to heat of hydration tests underadiabatic conditions and the results were used to assess and quantify the effects of the supplementary cementing materials in altering the heat rate profiles of concrete. The paper als

4、o proposes a simplified mathematical form of the heat rate curve for blended cement binders in concrete to allow a design stage assessment of the likely early-age timetemperature profiles in large concrete structures. Such an assessment would be essential in the case of concrete structures where the

5、 potential for thermally induced cracking is of concern.Keywords: Heat of hydration _ Fly ash _ Silica fume _ Slag _ Concrete1 IntroductionSupplementary cementing materials, such as ground granulated blastfurnace slag (GGBS), fly ash (FA) and condensed silica fume (CSF), are now routinely used in st

6、ructural concrete. Used judiciously, these materials are able to provide improvements in the economy, microstructure of cement paste as well as the engineering properties and durability of concrete. They also alter the rate of hydration and can influence the timetemperature profile in large concrete

7、 elements. This paper is aimed at an improved understanding of the way in which the early-age heat of hydration characteristics of concrete are altered by the addition of supplementary cementing materials (SCM), in combination with Portland cement, as a part of the binder. Importantly, in the design

8、 and construction of large concrete elements, where the extent of temperature rise is of concern, our ability to reliably predict the early-age temperature differentials in the concrete requires a careful understanding of the rates at which heat is evolved during hydration 13. In essence,the intenti

9、on of this paper is to provide guidance on the form of the heat-rate function for concretes containing supplementary cementing materials. This is essential input information in the design and construction of large dimension and/or high strength structures where thermal strains are likely to lead to

10、deleterious cracking and/or loss of durability. In the investigation reported here, concrete samples containing combinations of Portland cement with GGBS, FA or CSF were tested in an adiabatic calorimeter in order to determine their heat of hydration characteristics. The test programme was limited t

11、o binary blends of the materials, i.e., each test was limited to a combination of Portland cement and one supplementary material and all concretes were prepared at the same water:binder (w/b) ratio. For each type of supplementary material, concreteswere prepared with supplementary material replacing

12、 between 5% and 80% of the Portland cement, depending on the type of SCM. Concrete samples with a volume of approximately 1 l were tested in the adiabatic calorimeter. The adiabatic calorimeter that was used in the test programme is based on the principle of surrounding a concrete sample with an env

13、ironment in which the temperature is controlled to match the temperature of the hydrating concrete itself, thus ensuring that no heat is transferred to or from the sample and the rise in temperature measured is solely due to the heat Mevolved by the hydration process. This calorimeter has been descr

14、ibed in detail by Gibbon et al. 4. Since the rate of evolution of heat during theMhydration of cementitious materials is influenced by Mthe temperature at which the reaction takes place, there is no unique adiabatic heat rate curve for a particular cement or combination of cementitious materials. Co

15、mparisons of the heat rate performances of materials must, therefore, be made on the basis of the degree of hydration or maturity. In this paper, the results are expressed in terms of maturity or t20 h, which refers to the equivalent time of hydration at 20_C. This form of expression of the heat rat

16、e function and the justification for its use, is described by Ballim and Graham 1.2 Concrete materials and mixtures Concrete materials which are commonly used and readily available in South Africa were used in these tests. The Portland cement complied with SABS EN197-1, type CEM I class 42.5 5 and t

17、he GGBS, fly ash and silica fume complied with SABS 1491 Parts 1, 2 and 3 68, respectively. The oxide contents of the binder materials were determined by XRF analysis and the results are shown in Table 1. The range of replacement levels by each of the three supplementary materials used, together wit

18、h the concrete mixture proportions. The concrete mixture proportions were kept the same throughout, except that the composition and relative proportion of the binder was changed as required. All the concretes therefore had a w/b ratio of approximately 0.67 and the water content was sufficient to com

19、pact the concrete by manually stamping the sample holder. All the mixture components, including the water, were stored in the same room as the calorimeter at least 24 h before mixing. This allowed the temperature of the materials to equilibrate to the room temperature, which was controlled at 19

20、77; 1_C. A 1.2 l sample of each concrete was prepared by manual mixing in a steel bowl and the adiabatic test was started within 15 min after the water was added to the mixture. All the tests were started at temperatures between 18 and 20_C and temperature measurement in the calorimeter was continue

21、d for approximately 4 days.The silica sand used in the concretes was obtained in three size fractions and these were recombined as needed for the mixing operation to ensure a uniform sand grading for each concrete. The stone used in the concrete was a washed silica, largely single-sized and 9.5 mm i

22、n nominal dimension. 3 Conclusions The intention of the project reported in this paper was Nto quantify the effects of supplementary cementing materials on the rate of heat evolution in Portland cement concretes. In particular, the focus was on providing information on the rate of heat evolution in

23、a way that would allow improved prediction of the internal concrete temperature profiles during construction of large or high-strength concrete elements. In this regard and given the parameters of the concretes used, the study has shown that:The peak rate of heat evolution in GGBS or FA blended bind

24、ers decreases linearly with increasing addition of GGBS or FA; Except for FA replacements as high as 80%, the time to reach peak rates of heat evolution is reduced with increased proportions of GGBS or FA in the binders. If the proportion of fly ash is increased to 80%, there is a significant increa

25、se in the time required to reach the peak rate of heatevolution. Up to a replacement level of 15%, the addition of CSF in Portland cement binders does not significantly alter the heat-rate profile of concrete. The most significant effect noted was an approximately 9% increase in the peak rate of hyd

26、ration when 15% of the Portland cement was replaced by CSF. However, the addition of 10% and 15% CSF had a marked effect in reducing the time to reach the peak rate of hydration.The presence of the SCMs assessed in this investigation have the effect of stimulating the hydration of the CEM I in the b

27、lended binder This stimulated hydration results from the consumption of calcium hydroxide, the dilution effectand hydration nucleation site effect. This stimulation of hydration is strongest with the addition of CSF, moderate in the case of GGBS and weak in the case of FA.In the absence of a more re

28、liable heat-rate curve for concrete containing supplementary cementitious materials, the model proposed in Eqs. 68 can be used to provide a first-estimate of the temperature profiles at the design stage of a temperature-sensitive concrete structure.References1. Ballim Y, Graham PC (2003) A maturity

29、approach to the rate of heat evolution in concrete. Mag Concr Res 55(3). doi:2. Koenders EAB, van Breugel K (1994) Numerical and experimental adiabatic hydration curve determination. In: Springenschmid R (ed) Thermal cracking in concrete at early ages. E&FN Spon, London3. Maekawa K, Chaube R, Ki

30、shi T (1999) Modelling of concrete performance. Spon Press, London4. Gibbon GJ, Ballim Y, Grieve GRH (1997) A low cost, computer-controlled adiabatic calorimeter for determining the heat of hydration of concrete. ASTM J Test Eval 25(2):261266中文翻译： 辅助性胶凝材料对混凝土水化热的改善作用尤努斯巴林/王泽长格雷厄姆收稿日期：2008年2月23日/接受日期

31、：08年9月17日/发表日期：2008年9月23日摘要：这篇文章在形式和程度上，对结合波特兰水泥的辅助性凝胶材料，在混凝土水化作用早期阶段热演化速率的改善进行了指导。在这次调查中，混凝土由粉煤灰，硅灰和地面浓缩粒化高炉矿渣，兑入5至80比例的波特兰水泥来制备。这些混凝土在高温条件下进行绝热水化试验，试验结果被用来评估和量化辅助性胶凝材料对混凝土水化放热速率改变的作用。该文件还提出了混凝土混合水泥粘合剂热率曲线的简化数学公式，使大型建筑早期时间的温度近似分布可以进行评估。这种评估在混凝土结构具因热而至开裂的情况是必不可少的。关键词：水化热、粉煤灰、硅粉炉渣的混凝土1、介绍辅助胶凝材料，如GGBS

32、（地面粒化高炉矿渣），FA（粉煤灰）和CSF（浓缩硅粉）的，这些都是现在常规使用的材料。用得好的，这些材料能够在经济，微观结构以及水泥浆体的工程性质及混凝土的耐久性上提供改善。他们还改变了水化的速度，可以影响到大型混凝土构件上随时间变化的温度分布。本文的目的是为更好地理解SCM（辅助性胶凝材料）作为粘结剂，并与波特兰水泥的组合而成的添加剂如何来改变混凝土早期水化放热特性的。重要的是，在设计和建造的大型混凝土构件，那里的温度上升幅度令人关注，我们有能力可靠地预测混凝土的早期温差，但需要对水化放热的速度进行仔细了解。从本质上说，本文的目的是为提供含辅助性凝胶材料的混凝土放热效率函数。这是在设计和建

33、设大型建筑或高强度结构时必须的基本信息，由于热应变有可能导致有害的开裂和/或耐久性损失。在这份调查报告里，由SCM（辅助性胶凝材料）GGBS（地面粒化高炉矿渣），FA（粉煤灰）和CSF（浓缩硅粉）混合组成的混凝土样本在绝热的量热仪钟进行试验，来确定它们的水化放热的特性。测试方案受限于材料，即二元共混体系，每个测试仅限于波特兰水泥和一项补充材料组合，所有混凝土是在同一水配制：水与粘结剂的比值。对于每个类型的辅助材料，混凝土制备了辅助材料取代波特兰水泥5至80，取决于辅助性凝胶材料的类型。在绝热量热仪用有大约1升体积的混凝土样品进行检测。在测试程序中使用的绝热量热仪是根据，使样品混凝土周围的温度能

34、够控制的与混凝土水化时的温度一致，来确保没有任何热量转移至样品或是没有任何热量从混凝土转移至周围环境，测得提升的问题完全是来自于混凝土水化作用的放热过程。吉本等人已经详细描述了这量热仪。由于胶凝材料水化时放热速率受温度变化的影响，所以没有唯一的绝热热率曲线和凝胶材料的组合。对材料放热速度性能的比较必须建立在水化程度的基础之上。在这个文件中，结果表示在条件成熟或时间20小时时，其中提到的水化等效时间在20。巴林和格雷厄姆以这样方式描述了热率函数和使用它的理由。 2、混凝土材料及混合物在南非混凝土作为常用的和现成的材料使用于这些测试。粘合剂材料的氧化物含量的由XRF测定分析，结果如表1所示。在更替水平范围内的三个辅助性材料混凝土的配合比。 具体混凝土混合比例整个保持不变，除了粘结剂组成和相对比例需要更改。因此，所有的混凝土w/ b(水与粘合剂)比值约为，水含量都足通过手动冲压样品以压缩混凝土。所有的混合物组成部分，包括水，被存放在同一个房间作为量热仪，过至少24小时后混合。这使得该材料在温度达到19±1的平衡室温下。每个升的混凝土样品通过手工搅拌制作与一个钢的容器中，然后在绝热测试开始后15分钟内加水的混合物。所有的测试都是开始于温度18到20摄氏度之间，并且量热仪要持续测量大约4天的时间。二氧化硅在混凝土用砂，得到3个大小不同组分，这些都是作为重组混合操作的必