Papers by Keyword: Compressive Strength

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Authors: F. Dombrowski, P.W. Garcia Caso, M.W. Laschke, M. Klein, J. Günster, Georg Berger
Abstract: The paper presented here deals with the investigations of orthophosphates (Q0) containing none or differing amounts of meta-(Q2) and diphosphate phases (Q1) for the use of 3-dimensional printing process in order to create porous, bioactive, nonloadbearing bone replacement scaffolds. The main ceramic phase in all cases is Ca10[K/N(PO4)7 hereinafter called 401545(100) consisting of 99,9% Q0 and 0,1% Q1-phase. The other phosphate ceramics i) 401545(40) consists of 75% Q0-phase, 22% Q1-phase and 4% Q2-phase ii) 401545(15) consists of 65% Q0-phase, 33% Q1-phase and 2% Q2-phase iii) 401545consists of 56% Q0-phase, 40% Q1-phase and 4% Q2-phase. The in-house produced ceramics where crushed and sieved to achieve particles of irregular shape in the range of 45-90µm. These powders show a quite good flowability and were used to generate cylindrical samples with a diameter of 5,5mm and a height of 11mm via 3-dimensional printing using a R1 printer from ProMetal company (USA). After drying the samples at T=125°C for 48 hours they were sintered at temperatures according to the thermal analysis results in the range of 900°C up to 1300°C. Afterwards the porosity, the linear shrinkage and the compressive strength were determined.
Authors: Yong Taeg Lee, Seung Hun Kim, Seung Ho Lee, Sang Ki Baek, Young Sang Cho, Seong Uk Hong
Abstract: As the industrial development brings the structures growth, the consumption of the natural aggregate is increasing annually. On the other hand, the amount of the potential aggregate is decreasing with the huge amount of construction waste from the concrete demolition. The annual total amount of natural aggregate consumption estimated 370million tons. And the experts are concerned about the depletion of aggregate which is presumed to be exhausted in 20 years, considering the annual consumption, which is approximately 250million(m³) in construction industry. Along with this issues, the government promotes to use recycled coarse aggregate from the construction waste in consideration of social, economic and environmental aspects. In conclusion, the purpose of this study is to promote to use of recycled coarse aggregate as a future substitute resource and to increase awareness of it as well. This study conducts the experiments by comparing high-strength concrete for the substitution of chosen two companies.
Authors: Yan Wen Li, Xiao Xue, Zhuo Yang, Zhong Yu He, Jie Qin, Wei Dong Zhang, Li Jin Xu, Jian Qu, Ru Feng Jia
Abstract: The mechanical properties, including the compressive strength, flexural strength and adhesion strength of the rapid setting conventional and polymer-modified waterproof mortars are systematically compared in this paper. The polymer modification is demonstrated to increase the flexural strength and adhesion strength of the rapid setting waterproof mortar whereas it reduces its compressive strength.
Authors: De Yu Kong, Jin Da Mao, Tong Yuan Ni, Jian Jun Zheng
Authors: Lu Jin, Zhu Ge Yan
Abstract: Porous concrete is one of the innovative and promising concrete products, which is featured with a relatively high water permeability rate. Compared with conventional concrete products, due to the lack of fine aggregates in the mix design of porous concrete, the void spaces between the coarse aggregates remains unfilled and causes a large amount of porosity in the hardened concrete mass. On the other hand, the strength of porous concrete is usually lower than that of the conventional concrete products due to the lack of fine aggregates. For the purpose of achieving a relatively high strength of porous concrete while maintaining a good permeability of pavements, the mix design of porous concrete is modeled as a Markov Chain Monte Carlo (MCMC) system and a Gibbs Sampling method based approach is developed to approximate the optimal mix design. The simulation results show that, by using the proposed approach, the system converges to the optimal solution quickly and the derived optimal mix design achieves the tradeoff between the compressive strength and the permeability rate.
Authors: Hai Bo Wang, Zi Zeng Lin, Zhong Yi He
Abstract: Series of experimental tests on the forming technique, sintering technique, performance and effectiveness of a new fired brick by mixing municipal sewage sludge and shale are carried out. Test results show that adding sludge properly in the process of manufacture shale fired common brick is feasible. Along with increase of sludge content, the compacting of uniformity of unburned brick decreased and its porosity increased. When shale-sludge mixtures were calcined, the heavy metal solidified, the ignition lost and organic substance volatilized that reduced the unconfined compressive strength (UCS) of the brick and improve its thermal insulation ability. The phase composition and leaching toxicity of sewage sludge-shale baked brick can be up to national standard. Good quality brick can be produced by blending mixture with the optimum moisture content (OMC) 18.0%-20.0%, drying at 105°C and sintering at 960°C. With all being considered in manufacturing brick, the content of sewage sludge shall be controlled within 9.0% that can make UCS of the new brick reach MU10 criterion and it has a superior heat preservation effect to normal brick from clay or shale alone.
Authors: Zheng Tao Hou, Ming Qing Sun, Bin Li, Xie Dong Zhang
Abstract: A new method is proposed to prepare carbon fiber reinforced concrete (CFRC) and carbon fiber (CF)/carbon black (CB) reinforced concrete in this paper. First, CF is dispersed in 0.4% carboxymethylcellulose sodium (CMC) water solution. Then, resolvable carbon fiber surfacing mat (RCFCM) is manufactured and cut into small patches. Finally, these patches are mixed with cement, sand, gravel, CB and water. During mixing, RCFCM patches are broken up once they meet with water. So, CF is dispersed into concrete. Results show that this method is feasible. CF/CB reinforced concrete possesses low resistivity (<100 Ω•cm), high compressive strength (≥35 MPa) and low contents of CF (0.3 Vol.%) and CB (0.6 Vol.%), so it can be used as a kind of conductive concrete for melting snow and deicing applications on highways. Both the mixing time and the curing period can affect the electrical and mechanical properties of CF/CB reinforced concrete.
Authors: E.F. Burguera, Francisco Guitián, Laurence C. Chow
Abstract: The progression of the setting reaction of a tetracalcium phosphate (TTCP) –dicalcium phosphate dihydrate (DCPD) rapid setting cement was investigated as a function of time. Compressive strength and extent of conversion to hydroxyapatite (HA) were obtained at different incubation times. The results indicated a rapid development of both strength and HA conversion in the early stages of the reaction, which slowed down after 4 h, presumably as a result of HA formation on the surface of the reactants. This hypothesis was supported by scanning electron microscopy examination of cement fracture surfaces.
Authors: Qiao Zhu, Lin Hua Jiang, Jin Xia Xu
Abstract: In this article, some empirical and theoretical models accounting the relationship between the strength and pore structure of cement-based materials is reviewed and analyzed. From the literature review and analysis, it can be found that the total porosity can be singly used to characterize the relationship between compressive strength and pore structure, but can not be applied into describe the relationship between pore structure and tensile strength. Another major parameter of pore structure - pore size distribution, will have a major impact on strength; the relationship between pore structure and tensile strength is for most models of cement paste, without the consideration of aggregate, and the application of the model must comply with the relevant assumptions. The research on the relationship between the tensile strength of concrete is still at a preliminary stage, requiring more theoretical and experimental study.
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