洛阳理工学院毕业设计论文
[15]美国金属协会主编.金属手册8（9），失效分析与预防 北京：机械工业出版社，1986，[4]～143
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[18]尹路，郭天文，越野，等．表面镀膜纯钛牙膏磨刷后表面粗糙度研究．实用口腔医学杂志，2008，24(1)：65—68．
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洛阳理工学院毕业设计论文
外文资料翻译
The Effect of High Fly Ash Content on the Compressive
Strength of Foamed Concrete
E.P. Kearsleya , P.J. Wainwright b,*
aDepartment of Civil Engineering, University Pretoria, Pretoria 0001, South
Africa
b
Department of Civil Engineering, University of Leeds, Leeds LS2 9JT,
England, UK
Received 26 June 2000; accepted 18 September 2000
Abstract
A study has been undertaken to investigate the effects, on the properties
of foamed concrete, of replacing large volumes of cement (up to 75% by weight) with both classified and unclassified fly ash. This paper reports only on the results of the compressive strength of concretes cured under sealed conditions and shows that up to 67% of the cement could be replaced without any significant reductions in strength. There appears to be little difference in the performance of the ungraded and the graded fly ashes used in this investigation. Equations based on effective water/cement (w/c) ratio and binder ratio have been developed to predict the strengths up to 1 year, of foamed concretes made with densities ranging from 1000 to 1500 kg/m3. The calculated results compare well with the experimental results. ?2001 Elsevier Science Ltd .All rights reserved.
Keywords:Foamed concrete; Compressive strength; Fly ash
1 Introduction
Foamed concrete consists of cement paste and voids and the properties of both these components will have a measur-able effect on the properties of the
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洛阳理工学院毕业设计论文
combined material.Literature reviewed [1 ± 5] indicates that replacing up to 60% (by mass) of cement with fly ash (pfa) can enhance the properties of cement paste. The main aim of this investiga-tion was to determine whether the use of unclassified fly ash as replacement for large percentages (i.e. up to 75%) of the cement in foamed concrete has a significant influence on the compressive strength of the material.Properties of mortars containing different percentages of fly ash were compared to cement paste with the same water/ binder ratio to determine the effect of fly ash replacement.Thereafter, the properties of mortars containing fly ash were compared with those of mortars containing ungraded ash (Pozz-fill). Once the effect of high ash content had been determined, the effect of adding foam to the mortar was established. The target casting densities used in this investigation were 1000, 1250 and 1500 kg/m3 unless stated differently. The water/binder ratio was kept constant for the different casting densities and the compressive strength of the mixtures were determined after 7, 28, 56 days, 3, 6, 9 months and 1 year [6]. 2. Materials
Tests have shown that the production of foamed concrete with predictable densities and strengths is only possible with prefoamed protein foams [7]; this investigation was there-fore conducted using only this type of foaming agent. All the materials used are produced or manufactured in South Africa, and only one source of foaming agent, cement and ash was used.
Foamed concrete is produced under controlled conditions from cement, filler, water and a liquid chemical [8] that is diluted with water and aerated to form the foaming agent.The foaming agent used was ``Foamtech,'' consisting of hydrolyzed proteins and manufactured in South Africa. The foaming agent was diluted with water in a ratio of 1:40 (by volume), and then aerated to a density of 70 kg/m3.
The cement used in this investigation was rapid hardening Portland cement from Pretoria Portland Cement(PPC),
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洛阳理工学院毕业设计论文
Table 1
Properties of cementitious constituents
Hercules, Pretoria. The cement can be classified as CEM I 42,5R according to the South African specification SABS EVN 197-1:1992 [9]. Both the fly ashes used in this investigation were obtained from the Lethabo power station in South Africa. One was a graded ash (pfa) complying with SABS 1491 [10] and the second was an ungraded ash (Pozz-fill) from the same source. The chemical properties and the particle size distributions of all three binders are shown in Table1 and Fig. 1, respectively.
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洛阳理工学院毕业设计论文
Fig. 1. Particle size distribution of cementitious constituents.
3. Composition of mixtures
Twenty-seven mixtures were cast with cement, ash, water and foam contents as listed in Table 2. The water/cement (w/c), ash/cement (a/c) and water/binder ratios as shown in Table 2 are weight ratios, and the binder content is taken as the sum of the cement and the ash.The first three mixtures contained only water and cement with different w/c ratios and these mixtures were used to determine the cementing efficiency of the ash used.Mixture numbers 4 to 15 contained classified fly ash while mixtures 16 to 27 contained the unclassified ash( Pozz-fill). The first three mixtures cast for each type of ash were used to establish the effect of ash content on the properties of cement paste while the remaining nine mixtures cast with each ash type were used to establish the effect of varying foam contents. 4. Tests conducted
The compressive strength of foamed concrete was deter-mined from 100-mm cubes. The cubes were cast in steel moulds, demoulded after 24 ? 2 h, wrapped in polythene wrapping and kept in a constant temperature room at 22°C up to the day of testing. Before testing each cube was unwrapped and
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