Advanced Materials Research Vols. 250-253

Abstract: Earlier laboratory test results showed a possibility of utilizing GFRP beam as a mid-beam in foundation pit support. This paper presents the development of a new-style GFRP mid-beam with I-section and double webs. Loading tests show that the new-style GFRP middle beam can satisfy the requirements for the globe and local stabilities, and simultaneously the material strengths of the middle beam can also be fully utilized. Beam tests with bolted connections show that a combined use of steel bolts and GFRP splice plates improved the stiffness and strength of the beam by 17.9% and 45%, respectively.

Abstract: Self-repairing concrete is that adhesive agent is composited inside the concrete to form the self-repairing system and automatically repair the damaging materials. It can solve some problems that are difficult to be solved by the traditional methods. The development background of the self-repairing concrete and the present research at home and abroad were reviewed. The existing problems of the present studies were also elaborated. Moreover, the development trend and the application prospect of the self-repairing concrete were forecast.

Abstract: The morphology and elements enrichment in the vicinity of interfacial transition zone was investigated with employment of SEM, EDS and BEI. Results indicated that the morphology of products of hydration in ITZ area and cement matrix was similar but differed in amount, size and crystal features. Elements Ca, Si, Al and Mg had tendency to enrich in ITZ zone but differed in accumulation extent in orders. MgO was non-uniformly distributed in concrete, fully mixed in construction though, richer in cement matrix than in ITZ, yet MgO later inclined to migrate to ITZ area and the gap in between was mitigated with in-depth hydration.

Abstract: Polycarboxylate copolymers (PCs) with poly(ethylene oxide) (PEO) side chain were synthesized using first an esterification reaction technique and second a free radical polymerization in aqueous solution. The resultant PCs have been characterized by Fourier transform infrared (FTIR) spectrum and gel permeation chromatography (GPC). The molecular structural parameters of PCs were determined from GPC and ion chromatography (IC). The dispersibility of PCs having different degree of polymerization (DP) of PEO side chain was investigated in cementitious system. Also, the mechanism of dispersion was discussed via the respect of electrostatic repulsion and steric hindrance effect. The results show that the PCs possessing an appropriate DP of PEO side chain can exhibit a higher dispersibility.

Abstract: Self-healing concrete is a kind of smart concrete, and becoming one of research focus both in material and civil engineering field, in the paper, main self-healing methods concluded and partial technical problems of the self-healing facing, aim to these problems designed a kind of novel self-healing system, and experimental analyzed mechanism of self-healing.

Abstract: Palm oil fuel ash (POFA) has been used successfully as a supplementary cementing material in various types of concrete. In the present study, self-consolidating concrete (SCC) was produced by using POFA as a partial replacement of ordinary portland cement (OPC). In total, sixteen SCC mixes were prepared by varying water to binder (W/B) ratio, POFA content, and high-range water reducer (HRWR). POFA was used by replacing 0–30% of OPC by weight at the W/B ratios ranging from 0.25 to 0.40. The filling ability, passing ability and segregation resistance of various SCC mixes were investigated. The filling ability was determined with respect to slump flow, 50-cm slump flow time, inverted slump cone flow spread and time, and V-funnel flow time. The passing ability was examined with respect to J-ring flow. In addition, the segregation resistance was assessed with regard to sieve segregation index and column segregation factor. Based on the data obtained, the correlations for the fresh properties of SCC were sought. The experimental findings showed strong correlations between most of the fresh properties of SCC.

Abstract: Impact property of concrete containing nano-particles (TiO₂ or SiO₂) for pavement is experimentally studied and compared with that of plain concrete, concrete containing PP fibers and concrete containing both nano-TiO₂ and PP fibers. The test results indicate that the impact property of concrete is enhanced when the amount of nano-particles is smaller. However, the impact property of concrete is reduced when the amount of nano-particles is larger. The impact property of concrete containing PP fibers is improved, and the impact property of concrete containing both nano-TiO₂ and PP fibers is decreased. There is a significant linear relationship between impact property and flexural strength of pavement concrete.

Abstract: Based on the compaction test and unconfined compression test of cement soil, the optimum water content is ascertained. The relationship is studied about cement content, curing time and unconfined compression strengths, ultimate strain of compacted cement soil in this paper. The results indicate that the unconfined compression strengths increase in linear with the increase of curing time and cement content on the whole, and the ultimate strains decrease with the increase of cement content and curing time. The results provide theoretical basis for rational construction mixture ratio and parameter which have been successfully used to a project and achieved good economic benefit.

Abstract: In this paper, the performance of concrete is studied through different water-cement ratio, different air-content, different mineral admixtures, different admixture contents, examined the mechanical properties of concrete, electric flux and chloride ion penetration depth of different mix concrete. The results show that, decreasing w/c ratio, proper air content, adding mineral admixtures can improve the resistance of chloride-permeation. Within some contents, the chloride-permeation resistance using silicides is better than that of fly-ash or slag. On this basis, the proper scheme of mix ratio used in saline area is recommended: the air-content is 3%～5%, the content of fly-ash or slag is 20%～30%, the content of silicides is 6%～8%, and double mixed with silicides.

Abstract: This paper describes the optimal design of ductile fiber reinforced cementitious composite (DFRCC) under fatigue loading. First of all, fatigue tensile experiments of the DFRCC under constant strain amplitude were conducted, and the degradation of bridging stress was measured. The test results were employed to verify the micromechanics-based theoretical model developed in this research. The model accounts for the loss of fatigue ruptured fibers of which fatigue rupture is based on S-N relationships. According to the parametric study from the theoretical model, we found that the optimal choice of design variables, such as fiber length, is varied according to the maximum strain level and the number of cyclic loading. Therefore, it is required to design DFRCC optimally under given loading conditions to make the most of its excellent material properties and the developed model enables such a design.