Optimizing the setup of a flatbed color scanner for color measurement using full factorial design

The application of flatbed color scanners for the measurement of color in various industries, especially textile industry, has received a great deal of attention. The initial setup of a scanner and the investigation of factors with a significant effect on scanner outputs are necessary to measure a reliable color using the scanner. In the present study, the setup of a flatbed color scanner was optimized using a full factorial design technique. Three factors, including the scanning position on the glass surface of the scanner (A), cutting size of an image in pixels (B), and bit depth (C), at different levels as input factors, and signal‐to‐noise ratio and variance of the scanned image as the responses were considered for the evaluation of the reliability of the scanner color measurement. The results of analyzing the factorial design indicate that each of the three factors played a significant role in the scanner setup for the color measurement so that factor A demonstrated the most significant impact on the responses.     

Automated air void analysis of hardened concrete — a Round Robin study

The RapidAir is an automatic system for analysing the air void content of hardened concrete. The analysis requires polishing of the concrete surface as described in ASTM C 457 as well as a contrast enhancement of the surface. The system can automatically analyse the air void system according to the ASTM C 457 and EN 480-11 standards.The sample preparation includes contrast enhancement steps ensuring white air voids in black concrete (aggregate and paste). For a well-lapped sample of good quality concrete the contrast enhancement procedure requires approximately 5-10 min to perform. The air content can be analysed in less than 15 min traversing 2413 mm (95 in.) — a significant improvement compared to several hours normally required to perform a manual linear traverse analysis.This paper describes the method and technique required for automatic analysis using the RapidAir system as well as data from a Round Robin study. Three samples were circulated to 7 different laboratories for automatic air void analysis. Prior to the automatic analysis the samples were analysed manually using linear traverse and point counting methods. The results of the Round Robin study showed very good repeatability and reproducibility of the RapidAir system but large variations when using manually performed analysis.     

基于SPSS回归分析的气孔结构对引气混凝土强度影响分析

为便于高性能混凝土引气剂的开发和应用,采用定量体视学图像分析法,测定掺有9种引气剂的混凝土28d气孔结构参数（孔径范围10μm-1600μm）,运用统计分析程序SPSS对影响混凝土抗压强度比的分级孔隙率进行多元线性回归,得到相关系数高达0．971的多元线性回归方程及各分级孔隙率对抗压强度比的影响权重。     

Characterization of entrained air bubble systems in concretes by means of an image analysing microscope

The standard microscopic technique for the characterization of an entrained air bubble system in a concrete is a time consuming process. In this paper a sample preparation technique has been described for the use of an automatic image analysing microscope in the characterization of the air bubble system in concretes. In this technique the sample preparation takes about $\text{1}\text{1}\text{2}$ hours and the measurement of the air bubble characteristics takes about half an hour. The results obtained by this technique are identical to those obtained by using the standard (Rosiwal) technique. It has also been found that the air content, measured by this automatic image analysing technique in hardened concretes follows very closely to that measured in fresh concretes.     

Deicer-scaling resistance of phosphate cement-based binder for rapid repair of concrete

In this paper, a magnesium phosphate cement-based binder (MPB) was prepared by mixing MgO with mono-ammonium phosphate, borax and fly ash. The deicer-scaling resistance of MPB mortar and concrete and the bond strength loss between MPB paste and mortar with ordinary Portland cement (OPC) concrete were investigated. Experimental results show that MPB materials themselves have high deicer-frost resistance, which is not lower than that of OPC concrete with the air content of 4.5-6.5%. The bond strength loss between MPB materials and OPC concrete with the air-entraining agent is obviously lower than that between MPB and OPC concrete without the air-entraining agent, and the higher the air content in OPC concrete is, the smaller the loss is. Furthermore, the air-bubble parameters were analyzed, which indicate that MPB mortar and concrete can also obtain a reasonable air-bubble structure by chemical reactions.     

粉煤灰水泥基材料的水化产物

用热重仪-差示扫描量热仪、扫描电子显微镜、透射电子显微镜、X射线能量散射、高分辩电子显微镜、压汞仪,测定了粉煤灰水泥基材料水化产物的形貌特征、微观结构、化学组成及水泥石的孔结构,讨论了水化产物性质及水泥石孔结构随粉煤灰掺量的变化规律。结果表明：粉煤灰的大量掺加,可以改善凝胶的化学组成。水化后期,粉煤灰与Ca(OH)2及由熟料水化生成的高n(Ca)／n(Si)的水化硅酸钙(C—S—H)凝胶发生二次水化反应,生成低n(Ca)／n(Si)的C—S—H凝胶,此种凝胶的固碱能力强,可减少碱-集料反应的危害性。同时,二次水化产物能够填充那些对水泥石强度和耐久性极为不利的孔隙空洞,使水泥石的结构更加致密,优化水泥石的孔结构,对提高水泥基材料的耐久性作用极大,为进一步提高工业废渣利用的技术水平奠定了基础。     

Air void morphology in fresh cement pastes

Two different procedures are used in conjunction with low-temperature scanning electron microscopy to image the air voids in cement pastes at very early ages. The first procedure isolates the air voids from cement paste after less than 30 min of hydration, and allows them to be imaged apart from the paste. The second procedure involves quenching the fresh cement paste specimens in liquid nitrogen after 5 min of hydration. In both cases, a distinct air void shell is apparent even at these short hydration times. The shell appears to be made up of small (1-5 μm) mineral particles. The second method confirms the presence of a water-rich transition zone around the air voids in the quenched pastes, consistent with earlier studies. Foam stability studies show that sodium oleate gives more stable foams than sodium dodecyl benzene sulfonate, but is more sensitive to the presence of calcium ions.     

基于骨料-浆体两相组成的混凝土细观结构定量研究

骨料间浆体层厚度或距离是混凝土性能研究和配合比设计中的重要参数,其定量方法一般包括两类浆体层厚度的计算模型、平均自由程模型以及图像分析法。本文使用以上方法计算、测量了24组混凝土试样的浆体层厚度和骨料间自由程,通过对比试样结果间的差异与关系,来说明不同方法的适用性。结果表明:不同方法所得浆体层厚度与骨料体积分数之间呈幂函数关系,且不同方法的计算值或测量值之间具有较好的线性关系,说明它们均可用于定性分析混凝土性能与细观结构之间的关系;通过对比不同浆体层厚度定量模型的推导过程,得到了修正的浆体层厚度(MAPT_Ⅱ)模型,相比最大/平均浆体层厚度(MPT/APT_Ⅰ)模型,其具有更好的便利性和精确程度。     

Characterization of multi-scale porosity in cement paste by advanced ultrasonic techniques

The effectiveness of advanced ultrasonic techniques to quantitatively characterize the capillary porosity and entrained air content in hardened cement paste is examined. Direct measurements of ultrasonic attenuation are used to measure the volume fraction and average size of entrained air voids and to assess variations in intrinsic porosity - as influenced by water-to-cement ratio (w/c) - in hardened cement paste samples. For the air entrained specimens, an inversion procedure based on a theoretical attenuation model is used to predict the average size and volume fraction of entrained air voids in each specimen, producing results in very good agreement with results obtained by standard petrographic methods and by gravimetric analysis. In addition, ultrasonic attenuation measurements are related to w/c to quantify the relationship between increasing porosity (with increasing w/c) and ultrasonic wave characteristics.     

背散射电子图像分析在水泥基材料微观结构研究中的应用

自上世纪80年代,国外研究者成功将背散射电子图像分析（backscanered electron imaging and image analysis,BSE．IA）技术应用于水泥基材料微观结构的研究中,在微观定性研究及物相定量分析方面,都获得不同于其他研究方法的研究结果。介绍了BSE-IA技术在水泥基材料研究中的应用...     

Assessing the efficiency of entrained air voids for freeze-thaw durability through modeling

This paper models concrete's resistance to cyclic freeze/thaw using the solution of the poromechanical problem, which describes the freezing of an individual air void surrounded by hydrated cement paste. This enables calculation of the pore pressures and the volume of water expelled into the air void upon freezing. The model was applied to concrete specimens with entrained air voids with polydispersity in size, and subjected to water absorption, thereby simulating a cyclic freeze/thaw laboratory test. The mean and maximum pore pressures obtained by the simulation were compared to a series of experimental tests per ASTM C666, and results suggest the model may be used to predict satisfactory durability in the laboratory test. This framework may be useful tool to study the effects of porespace and entrained air void size distribution on concrete's freeze/thaw durability. Furthermore, it allows for a theoretical basis for assessing the entrained air void system parameters.     

Observations of air-bubbles escaped from fresh cement paste

Recent experimental work is presented using a new technique to observe bubbles that have escaped from cement pastes and suspended in the bleed water. These experiments suggest that the stability of an air-entrained bubble may be related to the integrity of the hydration shell. This paper also reviews literature dealing with changes to air bubbles with time in fresh air entrained cement paste and concrete and to the existence of a shell surrounding these bubbles.     

Microstructure of cement paste subject to early carbonation curing

Microstructure of Ordinary Portland Cement paste subjected to early age carbonation curing was studied to examine the effect of early carbonation on performance of paste at different ages. The study was intended to understand the mechanism of concrete carbonation at early age through the microstructure development of its cement paste. Early carbonation was carried out after 18-hour initial controlled air curing. The microstructure characterized by XRD, TGA, ²⁹Si NMR and SEM was correlated to strength gain, CO₂ uptake and pH change. It was found that early carbonation could accelerate early strength while allowing subsequent hydration. The short term carbonation created a microstructure with more strength-contributing solids than conventional hydration. Calcium hydroxide was converted to calcium carbonates, and calcium–silicate–hydrate became intermingled with carbonates, generating an amorphous calcium–silicate–hydrocarbonate binding phase. Carbonation modified C–S–H retained its original gel structure. The re-hydration procedure applied after carbonation was essential in increasing late strength and durability.     

Changes in the size of pores during shrinkage (or expansion) of cement paste and concrete

The often-argued and seldom-resolved issue of relating the bulk shrinkage of concrete to changes in the size of pores is analyzed using a simple model. It is shown that the pores in a composite containing both shrinking and nonshrinking solid phases can themselves either shrink or expand when the matrix shrinks, depending on the amount of restraint in the system. The analysis also applies to expansive deformations, which occur with some types of chemical attack of cement paste. A mathematical relationship between the degree of restraint in a composite and the relationship between bulk volume changes and pore volume changes is given. These observations provide guidelines for interpreting the meaning of gaps that often form between aggregate and paste in concrete.     

Characterization of elastic and time-dependent deformations in normal strength and high performance concrete by image analysis

Deformations in normal strength concrete (NSC) and high performance concrete (HPC) were examined using image analysis to better understand the distribution of strain in these materials as related to their composition and microstructure. Elastic strain, creep and shrinkage were shown to occur non-uniformly throughout the NSC and HPC microstructure and creep and shrinkage strain both increased with time, as expected. The non-uniformity in the strain measurements also increased with time, as a consequence of dissimilarities in time-dependent behavior of the paste and the aggregate. However, compared with NSC, the time-dependent strains in the HPC were lower and showed less variation, suggesting a more uniform microstructure. In both NSC and HPC, high-strain sub-regions were evident in the vicinity of the interfacial transition zone (ITZ), likely as a consequence of the strain mismatch between aggregate and paste. The thickness of the high strain sub-regions along the ITZ in HPC were approximately one half of those in NSC.     

磷铝酸盐水泥浆体的抗冻性研究

抗冻性是砼耐久性的重要方面,尤其影响北方地区砼工程的使用寿命。引气能提高砼的抗冻性,但同时又存在气泡的稳定性问题和砼其他性能的受损问题。若能提高砼中水泥浆体的抗冻性,则对提高砼耐久性更有意义。作者从宏观和微观两方面研究了磷铝酸盐水泥浆体的抗冻性,同时与硅酸盐水泥、硫铝酸盐水泥浆体进行了比较;采用压汞测孔方法测试了三种水泥浆体冻融前后的孔结构,并用分形理论分析了各自特征。结果证实:磷铝酸盐水泥具有优越的抗冻融性能,其自身优良的水化特性以及体系的低碱度是良好抗冻性的内在原因。     

Air‐void characterisation of foam concrete

The pore structure of cementitious material, predetermined by its porosity, permeability and pore size distribution, is a very important characteristic as it influence the properties of the material such as strength and durability. The pore parameter could therefore be a primary factor influencing the material properties of foam concrete and an in depth look into this aspect is required to establish relationships between this and material properties. In order to evaluate these relationships it was necessary to develop parameters to explain and quantify the air‐void structure of foam concrete. This paper discusses the investigations done to characterise the air‐void structure of foam concrete by identifying few parameters and influence of these parameters on density and strength. A camera connected to an optical microscope and computer with image analysis software were used to develop these parameters. It is found that out of the air‐void parameters investigated, volume, size and spacing of air voids have influence on strength and density. Mixes with a narrower air‐void size distribution showed higher strength. At higher foam volume merging of bubbles seems to produce larger voids, results in wide distribution of void sizes and lower strength. Air‐void shape has no influence on the properties of foam concrete.     

清水混凝土耐久性能的试验研究

本文以南京长江三桥不同标段清水混凝土为原材料,研究了粉煤灰、矿渣、减水剂、结构表面的浆体状况等对清水混凝土抗渗、抗碳化等耐久性的影响。应用压汞法试验分析了混凝土密实度、掺合料、孔结构性能的影响。研究结果表明,混凝土的密实度越高,混凝土的抗渗性能及抗碳化性能越好,采用聚羧酸盐高效减水剂配制的高性能混凝土具有良好的抗渗性;矿渣粉能显著提高混凝土的密实度及抗碳化性能;混凝土结构表面的浆体状况直接影响到混凝土结构的抗碳化性能。     

An acousto-ultrasonic approach for the determination of water-to-cement ratio in concrete

A novel nondestructive procedure for the evaluation of water-to-cement (w/c) ratio in concrete is presented. The experimental setup is based on the method of acousto-ultrasonics; data analysis, however, and recognition of concrete composition from the waveform transmitted through specimen thickness, are achieved by simple time and frequency domain schemes used in this work. Experiments were performed in a number of concrete specimens made at various w/c ratios and at a number of ages starting from 2 up to 90 days. Recognition results were satisfactory and the algorithm introduced was successful in identifying the correct w/c ratio in more than 90% of the test cases. The use of existing spectral analysis techniques such as the coherence function has also proved to be more efficient and fits the purpose. The possibility of water content determination in fresh paste is also discussed along with preliminary evidence from initial tests.     

透水混凝土冻融剥蚀成因分析

为探究透水混凝土冻融剥蚀是否来自水泥浆体劣化,选取2.5~10.0 mm粒径骨料,制备了水灰比为0.31的透水混凝土及同水灰比的水泥石,测量二者冻融循环下质量、强度及透水混凝土相对动弹性模量变化。采用压汞法(MIP)测量水泥石冻融循环下孔结构特征参数及孔径分布变化,并通过扫描电镜(SEM)观察透水混凝土骨料水泥界面形貌演变。结果表明,在水冻与盐冻环境下透水混凝土宏观性能指标均有不同程度下降,骨料水泥界面产生裂缝并随冻融次数增加不断扩展,而水泥石强度、质量及微观孔隙结构均无明显变化。这表明透水混凝土冻融劣化与骨料水泥界面劣化相关。