Papers by Author: Yi Bo Yang

Abstract: Since the gradation of cement-slag has significant influence on its properties, the optimal gradation of cement-slag was studied by imitating with limestone powder. From experimental results of the porosity and fluidity of limestone power and on the base of the RRB equation, the optimal gradation area was got and its rationality was confirmed by experimental results of cement-slag.

Abstract: The high contents of alkali ion and chloride ion in soda residue pollute environment. So how to treat the soda residue is an urgent problem to be solved in China. The soda residue can be used in inorganic binder stabilized materials. But the negative effect of soda residue is not studied. The impermeability, frost resistance, and chloride ion leaching of inorganic binder stabilize materials prepared by soda residue are studied. And the results as followings: (1) The permeability coefficients of cement/ mineral admixture-soda residue stabilized stone chip are very low, and they are good impermeable materials; (2) The frost resistance of cement-silica fume-soda residue stabilized stone chip is good, and silica fume is recommended to be used in cold area; (3) The mineral admixture has a better long-term immobilized effect on chloride ion than cement, and the ground granular blast-furnance slag is the best mineral admixture to immobilize the chloride ion.

Abstract: The soda residue pollutes the environment because of high contents of alkali ion and choleric ion in it. So how to treat the soda residue is an urgent problem to be solved. The mineral admixtures are added in traditional inorganic binder to improve the strength performance of inorganic binder stabilized materials and decrease the negative effect of soda residue is studied. And the results as followings: (1) Soda residue has different activated effect on mineral admixture; (2) Mineral admixture replace the cement with same dosage can improve the unconfined compressive strength greatly to meet the requirement of standard; (3) The choleric ion leaching rates of cement-mineral admixture-soda residue stabilized stone chip decrease with time. Mineral admixture has a better immobilization effect on the chloride ion except fly ash before 90d; (4) Ground granular blast-furnance slag is the best material to improve the strength performance of inorganic binder stabilized materials and decreases the negative effect of soda residue.

Abstract: Chloride resistant HPC and protective cover are two basic measurements to improve the durability of concrete in chloride environment. Though it provides crucial cover for concrete to resist chloride ions, spacer has limited chloride resistant ability, which is overlooked by past researchers. Cementitious spacers are easy access for chloride ions to penetrate into concrete resulting in reduction of structural durability. To improve cementitious spacers’ performance, a systematic study was conducted. Test results showed that there was major difference between mortar and concrete in terms of chloride coulomb electric flux but minor difference in terms of chloride ion diffusion coefficient, which implied using chloride ion diffusion coefficient as spacer’s durability indicator was preferable; parameters of mix design had a similar influence on mortar and concrete and, with the same mixing parameters, the strength and chloride resistant ability of mortar were weaker than concrete’s; it was feasible to develop the mix design of chloride resistant cementitious spacers based on concrete’s design method with certain adjustments, such as using stricter mix proportion, adding small-size coarse aggregate, lowering water-binder ratio and optimizing the binder proportion, to achieve higher strength and durability.

Abstract: Traditional PHC pile production adopts two-step curing with the disadvantages of high energy consumption, considerable carbon emissions, and easy cracking during construction. In addition, non-autoclaved pipe pile studies involve problems such as adoption of naphthalene based superplasticizer and lengthy coated curing duration, thus leading to their few applications. In order to solve the problems, the study on non-autoclaved PHC pile was conducted to systematically study the impacts of curing system, water-binder ratio, and admixture composition on concrete strength, ratio of tensile and compressive strength, and chloride ion resistance at different ages. Study results show that through the use of a polycarboxylate superplasticizer, an optimal 8-hour curing system and concrete mix ratio, the strength of non-autoclaved concrete reached 93.2MPa within one day, with the ratio of tensile and compressive strength of 6.07%, the coulomb electric flux of 85C, and the chloride migration coefficient of 0.54×10^-12m²/s.

Abstract: The usage of autoclaved PHC pile in chloride environment becomes common, so how to evaluate the resistance to chloride ion penetration of autoclaved PHC pile becomes urgent. This article Compare the resistance to chloride ion penetration of pile and pile concrete specimens based the Rapid Chloride Migration Synthesis Method and RCM. The results show that the Rapid Chloride Migration Synthesis Method is not suitable for pile, RCPT and RCM are suitable for pile; the resistance to chloride ion penetration of the pile inner and outer lateral concrete has a rather large different, so the sample must distinguish the direction when testing. Steel bar has little influence on the resistance to chloride ion penetration of autoclaved PHC pile, and the resistance to chloride ion penetration of pile outer lateral concrete is similar with pile concrete specimen, using pile concrete specimen to test the resistance to chloride ion penetration of autoclaved PHC pile is suitable. The chloride diffusion coefficient values have a good relationship with the electricity value, using the electricity value of square pile concrete specimen as commonly quality control way are suggested. The resistance to chloride ion penetration of pile can test the outer lateral concrete of pile or pile head, using the electricity value as daily quality control method and basis for project acceptance, and using RCM method as life assessment and basis for project acceptance.

Abstract: For reducing the consumption and pollution of the sodium chloride (NaCl), the effect of reducing the NaCl concentration on the result of coulomb electric flux were studied. Three typical proportions of concrete and mortar were used to investigate the effects on the results of coulomb electric flux when the NaCl solution is from 3.0% to 1.0% and 0.5% by mass, respectively. The coulomb electric flux for 6h and 18h and chloride ion penetration depth for18h were studied in this experiment. The results are as followings: (1) it is a little effect on the 6h and 18h coulomb electric flux value of concrete and mortar to use1.0% by mass NaCl solution instead of 3.0% by mass NaCl solution, and the error is less than 5%. It was suitable to use 1.0% NaCl solution by mass. (2)The influence of water-binder ratio (W/B) and test time on coulomb electric flux is related to the porosity and pore connectivity. The lower the W/B, the smaller the coulomb electric flux is; the ratio of coulomb electric flux of 18h to that of 6h was about 2.8 ~ 3.0, and the ratio increases with the water-binder ratio. (3) It is not suitable to use the test results of mortar specimens to count the results of concrete specimens, but can use the results of mortar specimens to estimate the anti-chloride performance of different binder. The suggested test method is that using 0.5% or 1.0% by mass NaCl solution, water-binder ratio is 0.38 and binder-sand ratio is between 1:1.5 and 1:1.8. The best binder-sand ratio and other test parameter need to be determined by more research.

Abstract: The pretreatment of concrete rapid chloride migration coefficient (RCM) method in different standard is different in China. However the influence of pretreatment on the experimental result is uncertain, which leads to poor comparability about the results between different standards and trouble in evaluating the durability of concrete structures. The influence of the pretreatment on the chloride diffusion coefficient was studied by contrastive method. On the base of the results a suitable pretreatment of RCM method was proposed. The results are as followings: (1) the influence of pretreatment on the chloride migration coefficient of concrete with 0.45 W/B is insignificant. The influence of pretreatment on the chloride migration coefficient of concrete with other W/B is significant, and the influence increase with the lower w/b.; (2) the chloride diffusion coefficient will increase after the ultrasonic bath and vacuum saturation, and the influence of the ultrasonic bath is larger. Considering the judgment to the durability of structure, the ultrasonic bath and the vacuum saturation are suggested to be used; (3) on the condition of the same anode and cathode solution, the chloride diffusion coefficient in accordance with JTG / T B07-01-2006 standard is usually higher than that in accordance with GB/T50082-2009 standard; (4) the relationship of the chloride diffusion coefficient between mortar and concrete specimens is uncertain under different proportion and curing system, so the mortar specimens can not replace the concrete specimens for the RCM method.

Abstract: Rock chips is a potential substitutable material for river sand, which can effectively solve the shortage problem of the river sand in concrete. At present most studies are about the rock chips concrete concentrate on the normal-strength concrete. The studies about rock chips as a substitution for river sand in C80 high-strength concrete were carried out. At first the basic physical properties of raw material are analyzed and the performance requirements of the concrete are confirmed. And then on the basis of the river sand concrete, the influence of the dosage of rock chips on the C80 high-strength concrete at the same water-binder ratio was studied. The particle size of rock chips larger than 4.75mm was considered as the coarse aggregate. The results showed that the C80 high-strength rock chips concrete can be prepared by increasing the dosage of superplasticizer and binder. The early age strength of high-strength rock chips concrete is higher than that of river sand concrete, while the contrary results of the long-term strength. Considering lots of fine powder in the rock chips, the coarse sand and rock chips are mixed to be used, the mixing ratio needs to be determined by experiments. In the high-strength concrete, the rock chips with good particle size distribution and with lower content of particle size larger than 4.75mm is better.

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.