Mathematical models for properties of mortars with admixtures and recycled fine aggregates from demolished concretes

In order to expand the engineering application of recycle aggregate mortars （RAM） with aggregates from demolished concretes, the models for the properties of RAM and the replacement rate of these recycled fine aggregates were proposed. First, different kinds of mathematical models for the basic properties （compressive strength, water retention rate, and consistency loss） of RAM with two kinds of admixtures, thickening powders （TP） and self-made powdery admixtures （SSCT） designed for RAM, and the replacement rates were established, while the average relative errors and relative standard errors of these models were calculated. Additionally, the models and their error analyses for the curves of drying shrinkage and curing time of RAM ＋ SSCT at different replacement rates were put forward. The results show that polynomial functions should be used to calculate the basic properties of RAM ＋ TP and RAM ＋ SSCT at different replacement rates. In addition, polynonfial functions are the most optimal models for the sharp shrinkage sections in the curves of drying shrinkage-curing time of RAM ＋ SSCT, while exponential functions should be used as the models for the slow shrinkage sections and steady shrinkage sections.

Studies on Strength and Related Properties of Concrete Incorporating Aggregates from Demolished Wastes: Part 1—A Global Perspective

The present study addresses the global concern of sustainability in building and construction engineering and how to an extent the use of demolished aggregate wastes in concrete production contributes towards ameliorating or minimizing the problem. The influence of demolished aggregate waste on the mechanical strength and stiffness of concrete are examined from the standpoint of the compressive, split tensile and flexural strengths as well as the modulus of elasticity of the concrete. In this respect the research carried out by previous investigators are noted. It is observed that in the Southern African region in general and Botswana in particular there is a paucity of studies on the subject, and consequently, it is concluded that further investigations need to be conducted utilizing aggregates derived from local wastes or sources.

Recycling of Crushed Demolished Concrete in Structures

Most important problems arising from industrial and technological developments are abundance and harmful effects of post-productive wastes. In most of the developed countries, these effects are avoided by orderly storing methods. Storing the wastes in random stacks in the site, and their effect on wide areas gives a rise to the risk of ground, air and under water pollution e.g., pollution of the surrounding environments. Therefore, in most engineering branches, effects and nature of harmful wastes are investigated and solution methods are developed. When structures made of concrete are to be demolished. Concrete recycling is an increasingly common method of disposing of the rubble. Concrete debris was once routinely shipped to landfills for disposal, but recycling has a number of benefits that have been made it a more attractive option in this age of greater environmental awareness, more environmental lows, and the desire to keep constant costs down. The purpose of this research is to study the effect of using demolished concrete as a reproducible coarse aggregate in fabricating normal and high strength concrete mixes. The effect of constituent materials in general and the recycled coarse aggregate in particular on the mechanical performance of the produced concrete mixes is investigated. The characteristics of using the by-pass product of cement industry as cementitious material in recycled concrete mixes with a percentage of 50% as a replacement of cement content is investigated too. Test results presented in this research leads to the promising use of crushed demolished concrete along with the by-pass product of cement as waste materials in producing concrete mixes as well as the optimistic results in enhancing the strength properties of plain concrete beside their benefits of the cost savings and reducing environmental impact.

Studies on Strength and Related Properties of Concrete Incorporating Aggregates from Demolished Wastes: Part 2—Compressive and Flexural Strengths

In an earlier study, a comprehensive and critical review of previous investigations into the assessment of the strength of concrete incorporating aggregates from demolished wastes was conducted and it was concluded that there was a stark absence of results from the South African sub-continent including Botswana. In the present study, recycled coarse aggregates (RCA) sourced from demolished wastes collected from a landfill site in Gaborone, Botswana was used in lieu of natural coarse aggregates for the manufacture of concrete. With reference to the natural coarse aggregate, RCA replacement levels of 0%, 20%, 40%, 60%, 80% and 100% were utilized and the results of hardened concrete tests for compressive and flexural strengths were obtained. It was found that in general the compressive and flexural strengths of the recycled aggregate concrete (RAC) decreased with increasing replacement levels of natural coarse aggregates using RCA. It was concluded that RCA could be employed as a substitute for natural aggregate in concrete only up to a certain limit or partial replacement. In this respect, it was also noted that the undesirable properties of RCA were primarily due to the quantity and quality of the adhering mortar.

Damage Mechanism of Al_2O_3 Ceramic Coatings Irradiated by CO_2 CW Laser

Rules and mechanism of damage in Al2O3 coatings irradiated by CO2 CW laser are studied in order to improve the ability of parts of equipment standing against the high power laser. Al2O3 coatings were sprayed by air plasma spray（APS） on the 45^# steel substrate, and then were irradiated by CO2 CW laser from 795 W/cm^2 to 31 830 W/cm^2. As the output power of the laser is increasing, its porosity is increasing and cracks are appearing and spreading quickly, And also the phase will transform from γ-Al2O3 to a-Al2O3 in the damaged areas. When the energy density is 17 507 W/cm^2, the coatings are destroyed completely. The thermal infection field on substrate is rather small. The laser energy is depleted by the phase transformation and cracks in Al2O3 coatings during the laser thermal shock.

A Corpus-Based Comparative Study on Synonyms in BNC: Taking Destroy, Ruin, Demolish as Examples

The discrimination of synonyms has always been the key and difficult points in language learning.By using the British Na⁃tional Corpus(BNC)to retrieve the standard frequency,registers and collocations of the three common words,DESTORY,RUIN and DEMOLISH,this paper analyzes their similarities and differences.Besides,this paper demonstrates the strong ancillary func⁃tion of corpus in synonyms discrimination as well as in English teaching and learning.

论老舍话剧The Spear that Demolishes Five Tigers at Once对《断魂枪》的改写

老舍英文话剧The Spear that Demolishes Five Tigers at Once是对其短篇小说《断魂枪》的改写。在剧本里,老舍不再像英译《离婚》时那样以批判中国文化为旨归,而是通过改写颂扬中国文化,并把文化传统中的"刚性文化"特质与西方新型的科学技术结合,从而建构他自1930年代就开始思考并不断丰富的中国精神文化现代化的"内涵"。

Elephants Used to Demolish Houses

【选注者言:我在上海《新民晚报》上看到一则印度人用大象摧毁非法建筑的消息,觉得很新鲜,在次日的因特网上读到此文,现发你们。读晚报短文,只获一笑,而读此文却可学到英语。本文最美的句子是:Officials decided to use theelephants after attempts to chase away the squatters(擅自占住者;在公地上定住者)resulted in clashes(冲突)that killed one person and injured dozens of police andforestry agents(林产代理人)。读者不妨细细体味其“End-weight”。】