Advanced Materials Research Vols. 168-170

Abstract: Mixing three different fiber composites into concrete specimens respectively, compressive strength, splitting tensile strength and flexural strength for fiber-reinforced concrete was done. The results show that the strengths of fiber reinforced concrete are improved to some extent. Due to the addition of fiber, the fiber concrete bears some of the force in tension, thus the time from the initial crack to damage is more prolonged comparing with normal concrete. Fiber concrete specimens did not get the collapse and lower intensity suddenly. Compared with normal concrete, the maximum increase of the reinforced concrete with steel fiber SQB -32 (Ⅱ) is listed, which compressive, tensile and flexural strength are increased by 30%, 40% and 24%, respectively.

Abstract: In general, in the evaluation of a test method, the repeatability tests must be performed to establish upper and lower bounds for the precision of a test method. The repeatability is calculated as a standard deviation and relative error of test results. In order to evaluate the repeatability of the workability tests used in self-consolidating concrete (SCC) applications, an SCC mixture proportioned with 0.38 w/cm, Type MS cement, 480 kg/m3 of binder , and crushed aggregate with MSA of 12.5 mm was used. The dosage rate of the HRWRA of the SCC was adjusted to secure two initial slump flow consistency levels of 630 ± 10 mm and 700 ± 10 mm for the repeatability tests. For each consistency level, the concrete was batched five times (for a total of 10 mixtures). Each test was repeated five times by the same operator in order to establish the single-operator precision values. Furthermore, five different operators were used to perform each of the workability tests in order to assess the multi-operator error that could occur during testing. Based on the relative errors obtained in the repeatability tests, relatively low error values were obtained for the slump flow, J-Ring flow, and L-box blocking ratio tests. Relative errors for recommended SCC workability test methods were also summarized.

Abstract: With the gob-side entry retaining technology in coal mining project, the materials research of backfill for mine gateway side and development to become the focus of attention. This study is based on the need of Jining well to adopt 42.5R portland cement, Tj-1 early strength agent, Tj-1 super plasticizer, prepared from 8 hours to form removal, 16 hours strength of up to 6.2MPa, 24 hours strength of 12MPa, 28 day strength to 43MPa, and the construction of super-excellent early strength pumping concrete, and obtained satisfactory results through engineering.

Abstract: Some precast, prestressed beams can reach heights of 2.4 m or more necessitating special considerations for lateral pressure to ensure formwork tightness. In order to investigate the initial form pressure of the precast, prestressed self-consolidating concrete (SCC), an experimental program was undertaken. Sixteen non air-entrained and four air-entrained SCC mixtures with a slump flow of 680 ± 20 mm were evaluated. These mixtures were made with 440 to 500 kg/m3 of binder, Type MS cement or HE cement and 20% Class F fly ash, 0.34 to 0.40 water-cementitious material ratio (w/cm), viscosity modifying admixture (VMA) content of 0 to 100 mL/100 kg of binder, and 0.46 to 0.54 sand-to-total aggregate (S/A) volume ratio. Two high-performance concrete (HPC) mixtures with 0.34 and 0.38 w/cm and slump of 150 mm were also investigated. Moreover, decay in lateral pressure with time was also determined in order to evaluate the rate of pressure drop and the time required for pressure cancellation. Test results indicated that SCC proportioned with higher binder content developed higher relative initial pressure for the 2.0-m deep section. For a given binder content, the more viscous mixtures made with 0.34 w/cm exhibited lower relative initial pressure and longer duration before pressure cancellation. It is worthy to note that air-entrained SCC exhibited higher initial pressure. Finally, a good correlation was established between the final setting time and pressure cancellation time.

Abstract: In this paper, the differential equations of composite laminated box beams are established based on the principle of minimum potential energy and the variational method. Considering shear lag and shear deformation effects, elastic stiff matrix, geometric nonlinearity stiff matrix and equivalent nodal forces vector of composite laminated box beam element are given. And a finite element program is developed, then a new computing analysis theory for composite laminated box beam is given, both considering shear lag, shear deformation and geometric nonlinearity effects.

Abstract: The ethylene diamine, acetone and dibutyl phthalate are used as the curing agent, diluent and flexibilizer in the researches about epoxy mortar. But in fact these materials are difficult to be bought in market because of the toxicity. The influence of the additives on the workability and mechanical properties of epoxy mortar are investigated by using the orthogonal experimental design method in this work, and all the additives can be bought easily from the market. The results are as followings:(1) the influence of curing agent on the initial setting time, the toughness and the 1d, 3d compressive strength of epoxy mortar is significant; (2) the influence of diluent on the workability of epoxy mortar is significant; (3) the influence of flexibilizer on the 7d compressive strength is significant; (4) the interface bonding of epoxy mortar and cement mortar is good; (5) the optimum proportion by mass for epoxy mortar is, epoxy resin: curing agent: diluent: fumed silica =1:0.5:0.1:0.05:0.01.

Abstract: The chemical shrinkages of alkali-activated slag cement (AASC), and the effect of fly ash, MgO burnt at 900°C and the curing solutions were studied. The shrinkages were compared with that of ordinary portland cement (OPC). The results show that the chemical shrinkage of AASC is lower than that of OPC. Adding fly ash and light-burnt MgO reduced the early age chemical shrinkage, while the shrinkage-reduction effect decreased with the age. The alkality of the curing solution has significant effect on the hydration and shrinkage of AASC. The chemical shrinkage of AASC increased with the alkali concentration of the curing solution. The mechanisms of fly ash, MgO and curing solution on the shrinkage were discussed.

Abstract: Through the anti-bending performance of the normal section experiment on four complex high titanium heavy slag reinforcement concrete beams and two ordinary RC beams, we compare them with concrete strength and longitudinal reinforcement ratio as parameters, and explore the performance of complex high titanium heavy slag reinforcement concrete beams on supporting capacity, crack, stiffness and ductility. The results show that, under the same conditions designed, the performance of complex high titanium heavy slag reinforcement concrete beams on the cracking moment, ultimate moment, the average crack width, stiffness and ductility is better than that of ordinary RC beams, presenting a typical normal section destruction. The findings of the present study provides reference to the application of complex high titanium heavy slag concrete into engineer structuring.

Abstract: The systematic study various kinds disasters which are likely to meet in civil engineering and construction of Guang dong Science Center. The research includes the study of environmental geotechnical engineering, the technology for treatment of large -area soft soil, the art of seismic isolation, the fire resistance, and the study of wind resistance of large-span shell structures. Based on these theoretical and experimental results, the authors have put forward some new technique for the key problems in design and construction.

Abstract: The expansion performance of expansive agent in cement-HCSA-fly ash cementitious materials and its coordination with strength were studied by orthogonal test. Shrinkage-compensating mortars were prepared. The results show that the restrained expansion rate (RER) of mortars cured moistly, RER residue and expansion decline rate of mortars stored drily after 7d are well consistent with each other to assess the expansion performance of expansive agent. Increase of expansive agent content and decrease of fly ash content can lead to the growth of RER. The impacts of all the factors on RER of moistly-cured mortars are becoming steady when the age is longer than 7days. The 7-day RER of 6.35×10-4 is the critical value to judge whether the shrinkage of expansive mortar occurs after it moved from moisture into dry air at 7d. The expansive agent content has no need to exceed 10% in view of compensation efficiency unless slight improvement of expansion performance is desired. 35~50%, 20~50% and 20~35% of fly ash content are recommended respectively for water-binder ratio of 0.32 0.36 and 0.40 to obtain better coordination of expansion and strength.