Key Engineering Materials Vols. 302-303

Abstract: The appearance of buildings and towns is ruined by graffiti drawn on walls made of concrete or brick. Much money and labor are spent in removing graffiti from such rough surface. This paper is a comparative study of the laser irradiation method and the high-pressure water jet method for removing graffiti from the surface of concrete. The former uses a YAG laser beam and the later uses water containing sodium bicarbonate particles. The graffiti were drawn in nine colors on the surface of concrete specimens using oil spray paint and emulsion spray paint. The main results of this study are as follows: Graffiti drawn with oil paint is easier to remove than that with emulsion paint. Yellow and orange colors are harder to remove compared to other colors. In both methods (laser irradiation and water jet) of removal, the surface of concrete is damaged only slightly. Overall, the laser irradiation method appears to be more effective for graffiti removal than the water jet method.

Abstract: The influence of pre-wetted time on strength of shale ceramsite concrete is studied.Microstructures of both cement paste and interfacial zone between aggregate and paste of concrete are observed by scanning electronic microscope (SEM). The results show that, if the pre-wetted time of the shale ceramsite increased, the decline degree of early strength of concrete will be greater than strength at a longer age, and the growth rate of concrete strength may obviously increase. The pore characteristics of concrete at different ages is examined. The change tendency of concrete strength at different ages is revealed from the point of view of microstructure.

Abstract: Soil-cement concrete can be manufactured by mixing portland cement, water and on-site soil and has been studied by the authors. This study deals with compressive strength and density of soil-cement concrete where the portland cement was partially substituted with fly-ash. Saturated surface-dry condition of on-site soils has never been taken into account in the conventional mix design whereas experiments of determining the saturated surface-dry conditions were carried out with the help of the concept of effective water content to assure the quality and the designed strength. Effects of fly-ash on the strength and density of soil-cement concrete were studied by altering cement-fly-ash ratio, soil-sand ratio, binder-water ratio and age under a constant unit water content

Abstract: Self-compacting concrete (SCC) has the environmentally friendly effect. The SCC can be prepared by using the technical approaches of “Double adding” (adding mineral admixtures and chemical admixtures and) low W/B (the ratio of water to composite binder). According to the requirements of design and construction, SCC of C30～C60 can be produced by selecting materials used and adjusting the amount and composition of composite binder, the dosage and composition of high performance chemical admixture as well as W/B, based on the reasonable component of SCC with volume. It had been applied successfully in some construction works in several, such as concrete filled steel pipe column and strengthening of concrete structure.

Abstract: Supercritical water (SCW) has both the solvent power approximate to liquids and the transport properties common to gases. It is therefore expected as an excellent solvent for industrial waste treatment. In this study, various building materials were treated with SCW, and their morphological changes after treatment were observed. The effects of SCW treatment on the pore structure and compressive strength of cement concrete and mortar were also investigated. In the range of this study, after SCW treatment, inorganic materials and organic materials can be recovered as solids and liquids, respectively. Under sub-critical and super-critical temperature and pressure conditions, compressive strength of mortar decreases, while the effective pore volume increases.

Abstract: According to abalone’s growth characteristics, artificial abalone reefs are invented in this paper. The trace elements are added in concrete. The proportion is fixed by test. Ocean alga adheres to reefs with them very well. The craft, matching optimization, curing terms in the island environment and concrete long-term stability in the ocean current are studied to solve the durability of reefs in the marine environment. It shows the durability of fishing reef by high performance, high function, and ecological concrete technology is reliable. Its strength is still increasing for one year and no damage has been found. It is feasible to use the complex admixture, high-quality fly ash, ultrafine silicon powder, surface-soaking-into water-hating material made by our own, adhering-shaking-compact molding equipment made by ourselves and solar-energy-curing technology. Ten thousands of large-scale artificial abalone reefs have been done. A large amount of marine organisms covered the reefs only after 40 days using.

Abstract: Based on experiments, the effect of various types and content of mineral admixtures and steel fiber on flexural strength and compressive strength of reactive powder concrete (RPC) have been studied. The low-cost green RPC is made with the replacement of quartz sand, quartz powder and partial silica fume by natural fine aggregate and fly ash. The preparation techniques of RPC was also improved.

Abstract: Presence of crumb rubber can change the concrete characteristics in a significant way. This article presents some experience of building crumb rubber concrete (CRC) test sites, and the data of on-site measurement with respect to slump and air content of fresh CRC samples.

Abstract: The Badong highway bridge over the Yangtze River is a grand bridge in Enshi, Hubei Province of China. Its deck pavement consists of C40 polypropylene fiber concrete, 100 millimeters thick. Experiments show that C40 concrete incorporating polypropylene fibers at dosage of 1.35 kg/m3 has the excellent properties against cracking, permeation, impact, wearing, etc. Thus polypropylene fiber concrete as deck pavement can extend service life of the deck and decrease the maintenance cost and traffic inconvenience for reparation. It can be widely applied in construction of deck pavement and road pavement.

Abstract: This paper has summarized generally the progress of multifunctional, intelligent concrete, and the concept of intrinsic intelligent materials is put forward on the point of materials, in addition the research and development direction of multifunctional and intelligent concrete is advanced.