Applied Mechanics and Materials Vols. 423-426

Abstract: Purpose: studied the mechanism of polycarboxylicacid plasticizing effect on α-calcium sulfate hemihydrate. Methods: the adsorbed amount was tested by ultraviolet visible absorption spectrum method, ζ potential was measured by micro-electrophoresis analysis, and the corresponding workability was studied. Results: firstly, polycarboxylicacid plasticizer was adsorbed on α-calcium sulfate hemihydrate by Van Der Waals force and the saturated adsorption quantity of polycarboxylicacid plasticizer (HC) was about 5.8mg/g; secondly, the decisive factor for polycarboxylicacid plasticizer to disperse α-calcium sulfate hemihydrate particles was the steric hindrance of polycarboxylicacid plasticizer, and the maximum ζ potential of α-calcium sulfate hemihydrate with polycarboxylicacid plasticizer was-9.360mv, much less than β-calcium sulfate hemihydrate under the same conditions; finally, the perfect mixing content of polycarboxylicacid plasticizer was 0.3%~0.6%; it increased fluidity by 66%, to the maximum 300mm.

Abstract: Moderate Heat Portland Cement is not only frequently-used cement for dam but also one of the largest amount of special cement as a main cementitious materials of concrete in hydraulic structure in China. Due to the high quality requirement and the complicated technology in the construction of dam, a series of measures are adopted to control the production quality of Moderate Heat Portland Cement used in the dam construction. In this paper, the measures of production quality control of the Moderate Heat Portland Cement are introduced, including controlling the raw materials such as the cement raw meal, fuel, clinker and gypsum, managing the discharge from the mill and the entrance test, which ensure that the various targets of physical and mechanical indexes are in accordance with the standard requirement. Moreover, the engineering quality of Roller Compacted Concrete (RCC) for the dam is effectively guaranteed through the lower pot temperature and the less hydration heat. The construction experience is available for the like-kind engineering interiorly.

Abstract: In some provinces in Indonesia, like West Java, fired clay and unfired soil lime bricks co-exist as non standard bricks. Low rise buildings and rural houses in Indonesia are often constructed with non-standard bricks. The paper discusses strength-time relation of unfired bricks reinforced with and without natural fibers. Untreated and treated coconut fibers with three different lengths (1 cm, 2.5 cm and 4 cm) were prepared for bricks reinforcements. The effects of 4% non-uniform fiber addition, which constitutes 1/3 part each of 1 cm, 2.5 cm and 4 cm average fiber length, was investigated. Absorption of the bricks was evaluated. For all type of bricks, up to 90 days compressive strengths are almost stable but bending strengths rapidly decrease with time. The results show that unfired bricks added with treated fiber resulted in better performances compared to those added with untreated fibers and without fibers.

Abstract: In this paper, the effects of using copper slag wastes on hydration, gelling properties, mechanical properties, pozzolanic activity and durability aspects of concrete are studied.. It has been found that copper slag have micro pozzolanic effect in the study. The concrete batches with copper slag addition presented greater mechanical and durability performance. The mechanism of copper slag powder in composite cementitious materials is filling effect, activity effect and acceleration effect. The filling effect of copper slag can make matrix denser and the accelerating effect can accelerate the early hydration. At the same time, the problems existed in the comprehensive utilization of copper slag have put forward, and the key research direction has been raised for the future study, and an entry point has been provided for future copper slag utilization research.

Abstract: According to the research on whole curves of strain-stress of concrete materials, the paper illustrates in evidence features of stages and shows that the discrete feature of curve often occurs in strain-softening stage. After chaotic dynamic analysis of testing datas, it presents that system of whole process of strain-stress evolves from ordered steady state to low chaotic state and then to high chaotic state along with increase of compressive strength. The linear relationship of strain-stress grows evident and the system evolves from strong ordered steady state to low chaos state. The strain-stress system before compressive strength peak is basically in weak chaotic state. Theis proposed to be the stability criterion of concrete features in different stress stages, and the is regarded as the representative value of the system stability degree. The calculation of example shows that the stability criterion definited by the proposed method is consistent with the actural situation.

Abstract: To study the dynamic modulus characteristic of LSPM mixes, dynamic modulus test was conducted for Large Stone Permeable Asphalt Mixtures (LSPM ) with neat asphalt and with modified asphalt and the range of dynamic modulus values for LSPM was determined and the dynamic modulus master curves were developed. The magnitude of the dynamic modulus decreased with an increase in temperature and increased with an increase in the frequency. The phase angle decreased as the frequency increased at low temperature. With temperature increase, there was a transition interval, where the phase angle increased up to frequencies of 0.5 Hz, and then it started to decrease as frequency increased. After the transition interval, the phase angle increased with an increase in frequency. Master curves developed by sigmoidal function showed that LSPM with modified asphalt exhibited higher dynamic modulus values at middle and high frequencies and lower dynamic modulus values at low frequencies.

Abstract: Green high performance fiber reinforced cementitious composites (GHPFRCC) is a new class of Engineered Cementitious Composites (ECC) with high volume fly ash based on the orthogonal experimental method. Focus is placed on the flexural failure properties of GHPFRCC, considering the influences factors like fly ash content, water-binder ratio, sand-binder ratio, PVA (Polyvinyl Alcohol) fiber and water reducing agent, et al. The experimental results indicate that the failure process of GHPFRCC beam can be divided into three stages including elastic stage, yield stage and failure stage. The multiple fine cracks appeared in the specimen can effectively dissipate energy.

Abstract: In this paper, we apply Fourier Spectral Element Method (SEM) to the dynamic analysis of large dams, and take advantage of its high numerical accuracy and exponential rate of convergence and excellent geometrical adaptability to improve the computational procedure, efficiency and results of dynamic problem of large dams in numerical calculation. Based on the governing dynamic equation of large dams with the boundary nonlinearity, this paper derives the Fourier spectral stiffness, mass, damping matrix and equivalent load vector in terms of discrete Fourier spectral series, so a spectral formulation of dynamic analysis of large dams can be reached. For the purpose of higher numerical efficiency, Fast Fourier Transform (FFT) is also adopted in this paper. Although SEM has few applications in the analysis of solid structures, this paper indicates that SEM could be used in solid construction such as large dams as good as other preferable fields.

Abstract: Temperature and humidity of the pavement affected the performance of the pavement structure as the key factor. In this paper, we used the classic migration theory of temperature and humidity, and considered the actual characteristics of the asphalt pavement structure，established a temperature and humidity coupled equations for the asphalt pavement and got the calculation model by discretization，determined the boundary conditions and calculation parameters。Compared the calculation results with the actual results, we found that the model has high accuracy，it was able to meet the requirement of the predictive analysis about internal temperature and humidity of asphalt pavement in the work of researching and designing.

Abstract: Concrete bridges are most widely used all over the world, it has important practical significance to research the durability. In this paper, research progress home and abroad of durability and maintenance decision for concrete bridge is summarized. The main problems in research are pointed out and future research tendency is discussed. The content of this paper has good reference value for correlation study.