This article talks about the best operation condition of the astringency elimination by the cyclodextrin of the lotus root juice:as a mixture make up by 3∶7 of the α,β-cyclodextrin by mass ratio.The dosage is 2.5g/L;the pH is 8.0;the temperature is 70 centigrade;the stirring speed is 1000r/min and react time:3 hours.As a result,the quality of the lotus root juice improved definitely after the process,and the stability rose efficiently.
Pore solution of hardened alkali-activated fly ash paste was extracted by the steel-die method. The aqueous phase composition of pore solution was analyzed using ICP-OES analysis technique. The results show that the concentrations of Si, Al, Ca, K and OH - decrease with curing time regardless of the curing temperatures (40°C/60°C) and alkaline activators (sodium hydroxide with/without sodium silicate). On the contrary, the concentration of S increases with curing time. A higher temperature curing decreases the solubility of Si, Al, Ca and K in the alkali-activated fly ash, while it doesn’t show much influence on the solubility of S. The plot of the concentration of Al versus the concentration of Si displays a quasi-linear logarithmic relationship. This relationship implies congruent removal of Si and Al from the frameworks of fly ash.
High Performance Concrete (HPC) has been defined as concrete with improved overall performance compared to conventional concrete. The high density of the microstructure is responsible for high strength and improved durability. However, the dense microstructure may have an adverse effect on the fire resistance. The formation of vapor goes along with expansion and the built-up of large stresses in the pore system, since the dense microstructure does hardly permit any pressure relief through the pores. The capillary pore structure, particularly the connectivity of the pores, plays a dominant role in this respect. In this contribution, a 3-D pore structure of cement paste, simulated with the numerical simulation program HYMOSTRUC, will be presented. The specific geometrical parameters, including the pore size distribution and the connectivity of capillary pores, can be deduced from the program. The potential of the program for analyzing the susceptibility of high performance concrete to spalling if subjected to fire loads will be discussed.
Multiscale modeling for cement-based materials, such as concrete, is a relatively young subject, but there are already a number of different approaches to study different aspects of these classical materials. In this paper, the parameter-passing multiscale modeling scheme is established and applied to address the multiscale modeling problem for the integrated system of cement paste, mortar, and concrete. The block-by-block technique is employed to solve the length scale overlap challenge between the mortar level (0.1-10 mm) and the concrete level (1-40 mm). The microstructures of cement paste are simulated by the HYMOSTRUC3D model, and the material structures of mortar and concrete are simulated by the Anm material model. Afterwards the 3D lattice fracture model is used to evaluate their mechanical performance by simulating a uniaxial tensile test. The simulated output properties at a lower scale are passed to the next higher scale to serve as input local properties. A three-level multiscale lattice fracture analysis is demonstrated, including cement paste at the micrometer scale, mortar at the millimeter scale, and concrete at centimeter scale.
Chloride-induced corrosion of reinforced concrete is one of the main deterioration mechanisms leading to shortening of the service life of concrete structures. Therefore, assessment of the resistance of concrete to chloride ingress plays an important role in predicting the service life of such structures. The Rapid Chloride Migration (RCM) test is one of the accelerated test methods commonly used in Europe. It is commonly assumed that for a properly cured Portland cement concrete without degradation, the chloride migration coefficient should decrease with increasing curing age due to on-going hydration and microstructure densification. However, recent experiments show that the rapid chloride migration coefficient of Portland cement concrete decreases at early curing age, but increases at later curing ages up to 5 years. In this paper, the evolution of the rapid chloride migration coefficient of Portland cement concrete during long-term curing periods up to 5 years is discussed. The test conditions for the RCM test and the test results obtained from RCM tests are described. Finally, possible causes for the increase in DRCM that occurred during late curing of the samples are investigated in order to explain this increase.
This research explored the microstructure formation and strength development of blended cement pastes prepared with municipal solid waste incineration (MSWI) bottom ash. A new sample preparation approach involving water treatment of MSWI bottom ash was developed to prevent sample cracking caused by the presence of metallic aluminum (Al) in bottom ash. The result showed that ions released during water treatment of MSWI bottom ash delayed cement hydration but promoted ettringite formation in blended cement pastes during the first day. Due to water treatment, the compressive strength of MSWI bottom ash blended cement paste increased to a level similar to that of Class F coal fly blended cement paste after 28 days. Blending water-treated MSWI bottom ash (WMBA) with cement promoted clinker hydration at later stages. The reaction products of WMBA in blended cement system were C-S-H gel and sodicgedrite, which contributed to strength development by filling the capillary pores.
The lattice fracture model is presented in this paper, which is intended to simulate the fracture processes in multiphase materials to obtain the mechanical behavior in terms of load-displacement diagram and the cracks propagation. The basic procedures of lattice fracture analysis is that imposing a prescribed displacement on a lattice structure, finding the critical lattice element with the highest stress/strength ratio, removing it from the system and repeating until the system fails globally. One of the challenges in computer implementation of 3D lattice fracture model is the huge demand for computer memory. Matrix free technique is adopted to solve this problem.
