Advanced Materials Research Vols. 250-253

Abstract: A study on carbonation resistance of recycled aggregate concrete (RAC) subjected to different loading level was carried out. Three series of concrete mixtures were prepared with loading level of 0.5, 0.8, and 1.2 of ultimately tensive strength of concrete. The coarse recycled aggregate was used as 30%, 60% and 90% replacements of coarse natural aggregate and fine recycled aggregate as 10%, 20%, and 30% replacements of fine natural aggregate. Moreover, the fly ash and slag were employed as 15%, 25%, and 35% addition of cement. Although the action of the tensile stress had a negative effect on the carbonation resistance of RAC, it was found that the addition of fly ash and slag was able to mitigate this detrimental effect. The carbonation depth would increase with an increasing loading level and reduce when increasing the sand ratio.

Abstract: It’s necessary evaluating for quality of coarse recycled concrete aggregate (CRA) before it is used as feasible alternative of natural coarse aggregate (NCA). The factors affecting the quality of CRA, however, being multitudinous and complicated so much, associated to regional characteristic of CRA, led to a research on evaluating quality of CRA from China. First, the CRA was partitioned into three fuzzy quality classes corresponded to high, middle, and poor, respectively, whose applicable environment action grades and projects in terms of quality classes were suggested. Second, a fuzzy synthesis method how to evaluate quality classes was proposed. The present method used six indices, i.e., attached mortar content, bulk specific density, water absorption, Los Angeles abrasion loss, chlorid content and sulfate content. The weights for six indices were obtained based on credibility matrix and frequency statistic and the memberships based on optimum-intervel-style membership function. Using fuzzy weighted average operator, judgment matrix was calculated and synthetic membership score was considered as quality class judgment standard. Last, large numbers of engineering examples were computed using a program compiled in Matlab language. Computing results show that the present method is objective and reliable.

Abstract: In order to study the influence of modified polypropylene (PP) fiber on the physical and mechanical properties of curing sludge, the same amount of cement and different content of polypropylene fiber were mixed into the sludge. Unconfined compressive strength tests, water content tests and shear strength tests were carried out on different specimens with different curing time. The results show that the sludge curing effect is markedly improved by the addition of the polypropylene fiber. As to the curing sludge with the same curing time, when the content of the polypropylene fiber increases, the unconfined compressive strength and the cohesive strength greatly increase, and the internal frictional angle decreases.

Abstract: For the first time, a new kind of polycarboxylic acid high-performance water reducer, with ultra-high water reducing performance, was prepared through one-step polymerization, using new type polyether TPEG and acrylic acid as raw materials. Maximum water-reducing ratio of TPC may reach 50%. The most distinguishing characteristic of TPC was its reaction character at normal temperatures (30°C), which was of great practical significance for energy conservation and pollution reduction.

Abstract: Starch in architecture material industry has been paid much attention for its inexpensive price, good characteristics of bonding, forming property and good biodegradability. In the paper, the research progress of starch on architectural constructional materials is concluded in five aspects of green wood adhesive, coatings binder, mortars preparation, concrete water reducing agent and ceramic production. It is suggested that the new starch-based architectural gelled material should be prepared and replaces the traditional gelled material —cement in the future for the reasons of application limited of starch and problems caused by cement producing process, and the application prospect of starch-based adhesives in related field is also proposed in the end.

Abstract: Ethyl cellulose was hybridized with methyl methacrylate and butyl acrylate via mini-polymerization. The polymerization process was traced to obtain a stable reaction system. The effects of the EC content and viscosity on the monomer droplet size, the particle size and the monomer conversion were investigated. It was showed that the stability of the latex dispersion was strongly dependent of the EC content and viscosity. With investigation on ethyl cellulose series, initiator and crosslinker, the stable mini-emulsion with 10% ethyl cellulose was obtained under conditions of crosslinker and LPO as initiator.

Abstract: Fly ash (FA) and flue gas desulphurization gypsum (FGD) were blended in proportion into a new composite binder added with cement, lime and some modifiers. In the paper, the mix proportions of composite binder with low-quality FA and FGD were studied. FA-FGD more than 80% with FA:FGD 3:2 was suggested for mortar, plastering and slurry while FA:FGD 2:1 and FA-FGD 30~40% was recommended for middle-strength concrete. Hydration process of typical mixtures of FA-FGD paste was investigated through SEM and XRD tests. The conclusion could be made that FA showed much improved pozzolana activity especially at early ages due to the existence of FGD as an ideal sulfate activator, which also crystallized later to strengthen the hardened paste. The microstructure of hydrated FA-FGD paste was more excellent than that of neat cement stone or one blended with the same percentage of pure FA.

Abstract: The effect of the frost resistance on hybrid fibers reinforced lightweight aggregate concrete is investigated. And hybrid fibers reinforced lightweight aggregate is that steel fiber and polypropylene fiber are selected to incorporate into. The results indicate that, hybrid fibers reinforced lightweight aggregate concrete can improve the frost resistance. The weight loss rate of hybrid fibers reinforced lightweight aggregate concrete is not better. The research to establish a model for service life prediction of hybrid fibers reinforced lightweight aggregate concrete on experimental results has been done.

Abstract: Pumice, polypropylene fiber, steel fiber and fly ash were used to compound fiber reinforced lightweight aggregate concrete (LWAC). The effect of fibers on frost resistance durability of LWAC is studied, which including freezing-thawing in 5% Na₂SO₄ solution and in water. The test results show that the strength loss of LWAC is reduced with the increase in fiber fraction, but the impact of mass loss is not obvious by mixing fiber. LWAC freezing-thawing deterioration is even more serious in salt solution than in water. SEM photo show that polypropylene fiber has more stronger cementing bond with paste than steel fiber. the mass loss and strength loss are decreased significantly. By introduction silica fume can improve Interfacial Transition Zone（ITZ）and the frost resistance of fibers reinforcement LWAC dramatically.

Abstract: The rules of various factors influence the gypsum-based composite material(GBCM) performance are studied, using orthogonal experiment from the material components, retarder dosages and different w/c ratio. The results show that the strength and softness coefficient of GBCM are obviously higher than that of pure gypsum. The Portland cement can markedly accelerate the coagulation of GBCM, when its mixed amount is 10%-15%, it can enhance the strength and softness coefficient of GBCM, but overdosage will cause fall of the strength and softness coefficient of GBCM. The phosphate retarder changes the growth habit of dehydrate gypsum crystal and the aperture distribution of GBCM, which correspondingly makes the crystal thickening and the pore structure deteriorating and ultimately leads to reduce the strength