Papers by Author: Chong Zhi Li

Abstract: A modified agent GHPC-1 for green high-performance concrete was composed of the strength-increasing groups of organic alcohol amine, the slump-retaining groups of carboxylate polymer and the workability-stabilizing groups of amide. It could be used through substituting some of polycarboxylate water-reducers or combining with polycarboxylate water-reducers to modify the workability of fresh concrete and to increase the strength of hardened concrete. The adaptability tests of cementing materials with admixtures show that the dispersing ability was almost not influenced but the retaining ability of paste flowing was evidently enhanced if the substitution of polycarboxylate water-reducers have been to 20 %. The comparative tests of concrete indicated that as 20 % content of GHPC-1 was added in polycarboxylate water-reducers, it could modify the concrete workability. If adding 0.6 % with polycarboxylate water-reducers it could save water by 5 % and cement 10 % and simultaneously modify the workability and to enhance the strength, or to reduce water by 2.5 % and increase the strength of 28 d by 5~8 MPa.

Abstract: Material composition, mix proportion and physical properties of a low carbon cement with 90% of industrial refuse, properties of the cement was measured according to chinese national standard GB1346-2001 and GB175-2008. It is seen that the cement had good soundness, long setting time, low water requirement for standard consistency, good initial fluidity and high final strength as well, the properties are beneficial for the construction of highway engineering, underwater engineering and large volume concrete engineering.

Abstract: Two kinds of the representative artifactitious aggregates, namely the calcium-base and silicon-base, were chosen in the experimental study. Through analysis of SEM, it was found that the former’s main chemical component is calcium carbonate with a structure of crystal granules, the later might be a rock of silicon-base in a state of sandwich. Through experiments of the paste fluidity, ZETA potential and concrete test with different water-reducers, it was shown that the calcium-base aggregate, which could be easily used to prepare high workability and high strength concrete with the polycarboxylic water-reducer, bears a lower water-sobbing ability and has a well adaptability with any water-reducer, and that the silicon-base aggregate, a higher water-sobbing ability, a higher ZETA potential value of its powders, a bad adaptability that there might be a problem of producing HPC though using the high property polycarboxylic water-reducer.

Abstract: Charge passed of mortars with different aggregate volume fractions was tested according to ASTM C1202, and the differential expression of the Ohm law was introduced to explain the relationship between charge passed data and aggregate fractions.Cl- penetration depth of the corresponding mortars and concretes was measured to illustrate the influence of the aggregate volume fraction on their chloride permeability. It was shown that the charge passed of mortar was negatively correlated with aggregate volume fractions, and high aggregate fraction bearing concrete with low charge passed did not necessarily mean low permeability. As a result, the influence of aggregate fraction on charge passed should be taken into consideration when charge passed data was employed to evaluate Cl- permeability of concrete.

Abstract: A slow-release type carboxylic polymer(SLPC) is synthesized with the monomer mixture at a certain Molecule ratio of methacrylic acid, methoxy polyethylene glycol methacrylate and polyethylene glycol di-methacrylate. Test results of the fluidity, Zeta potential and adsorption in cement paste show that the polymer SLPC has the remarkable anti-adsorbing and high fluid-retaining ability for enhancing fluidity of cement paste as time elapsed, concrete experimental results indicated that it could be used to substitute 30～50% polycarboxylic type water-reducer in the same quality for preparing high workability concrete and controlling its slump loss.

Abstract: Mineral powders play positive role in improving the durability of concrete subjected to alkaline and saline corrosion, where sulphate ion and chloride ion coexisted may cause serious deterioration to the reinforced concrete structures. Metakaolin, slag, fly ash and natural zeolite mixed in appropriate proportion were tested in inhibiting the deterioration. It is found that the composite powder might decreased AAR and the charge passed of concrete effectively，the while the 7d and 28d strength of cement and concrete are improved as well.

Abstract: A series of polycarboxylate-type water-reducers (MPCs) had been developed and tested. Through molecular design, macromers of polyethylene glycol unsaturated carboxylic esters, and other derivative of unsaturated vinyl monomer containing the carboxylic groups，sulphonic groups， graft groups of alkyleneglycol was introduced as the chemical structure unit of MPCs. The copolymers MPC-2 contained long and short PEO chains and ionic groups, possessed a high dispersing and good slump retaining behavior. Therefore, MPCs can be used as high range water-reducers to prepare high-flowing concrete, high-strength high performance concrete and high-durability concrete.

Abstract: Sulphate ion and chloride ion existed in the alkaline saline soils may cause serious problems on the durability of reinforced concrete structures, while it is found that superfine mineral powder plays positive role in the precaution of the alkaline saline corrosion. A composite cement named high performance cement (H.P.C) composed of clinker, metakaolin and fly ash powder in appropriate proportions is developed with good performance in preventing concrete from alkaline saline soil corrosion. Mortar bar test and visual examination showed that the cement could effectively control AAR and sulphate ion related expansion, and the charge passed tested according to ASTM C1202 was decreased to “negligible” level for concrete with W/B ratio of 0.3, and “very low” grade for concrete with W/B ratio of 0.45 and 0.55 when the high performance cement was used. Other properties such as low hydration heat and anti-freezing properties, as well as the uniformity of the fresh concrete (with no bleeding and segregation), made it an important material in the construction of concrete structure in alkaline saline soils.