Rheological Behaviors of Fresh Cement Pastes with Polycarboxylate Superplasticizer

The rheologicalbehaviors of fresh cement paste with polycarboxylate superplasticizer were systematically investigated.Influentialfactors including superplasticizer to cement ratio（Sp/C）,water to cement ratio（w/c）,temperature,and time were discussed.Fresh cement pastes with Sp/Cs in the range of 0 to 2.0% and varied W/Cs from 0.25 to 0.5 were prepared and tested at 0,20 and 40 °C,respectively.Flowability and rheologicaltests on cement pastes were conducted to characterize the development of the rheologicalbehavior of fresh cement pastes over time.The exprimentalresults indicate that the initialflowability and flowability retention over shelf time increase with the growth in superplasticizer dosage due to the plasticizing effect and retardation effect of superplasticizer.Higher temperature usually leads to a sharper drop in initialflowability and flowability retention.However,for the cement paste with high Sp/C or w/c,the flowability is slightly affected by temperature.Yield stress and plastic viscosity show similar variation trends to the flowability under the abovementioned influentialfactors at low Sp/C.In the case of high Sp/C,yield stress and plastic viscosity start to decline over shelf time and the decreasing rate descends at elevated temperature.Moreover,two equations to roughly predict yield stress and plastic viscosity of the fresh cement pastes incorporating Sp/C,w/c,temperature and time are developed on the basis of the existing models,in which experimentalconstants can be extracted from a database created by the rheologicaltest results.

Variation of Starch Property and Its Relationship with Dry White Chinese Noodle Quality in Common Wheat

In total, 185 wheat cultivars and lines from major Chinese wheat regions, Australia and USA in two trials, sown in four and two environments, respectively, were used to investigate starch property and its relationship with dry white Chinese noodle (DWCN) quality. Significant variations were observed in all starch parameters and DWCN quality. High pasting viscosity cultivars include Sunstate, Hartog, Eradu, Cunning-han, Gamenya, Karl92, Sunco, Yangmai5, Yangmail58, Mianyang26, Een1, Yumai41, Yumai49, Zheng81-1, Yumai54, Yumai2. Yumai47, Lu955159, Lumai15, Lumai21, Shaanyou225, Guanfeng2, Ji5099, Bainong4, and Jinmai2. Wheats from Australia, USA, South China Autumn-sown Spring Wheat Region and Yellow and Huai Valley showed better starch properties and DWCN quality than those from North China Plain. High peak viscosity, breakdown and flour swelling volume were significantly associated with good DWCN quality. A relatively high frequency of Wx-B1 null alleles was detected in Chinese wheats. Cultivars with null for Wx-Bl GBSS performed higher pasting viscosity and flour swelling volume, and better DWCN quality than normal type.

Effects of Nitrogen Fertilizer on Grain Quality of Different Cultivars of Japonica Rice

Three cultivars of Japonica rice:hybrid Japonica rice,inbred Japonica rice and soft Japonica rice,were used to study the effects of recommended nitrogen fertilizer on grain quality including milling,appearance,nutrition,cooking and eating quality,pasting property and their relationships in direct seeding rice.Recommended nitrogen fertilizer improved the brown rice rate,the milled rice rate,and the protein content;increased the chalky grain rate and the chalkiness,and reduced the amylose content,palatability and pasting viscosity.The nitrogen fertilizer caused the appearance,the cooking and the eating quality to deteriorate.Lower amylose content and protein content were found in soft Japonica rice compared to those in hybrid Japonica or inbred Japonica rice under the condition of the recommended rate of nitrogen fertilizer,contributing to high cooking and eating quality.Correlation analysis indicated that palatability was negatively correlated with amylose content,protein content,hardness and gelatinization temperature,and was positively correlated with stickiness,peak viscosity and breakdown.Therefore,the decreased amylose and protein content of the soft Japonica rice cultivar planted under the condition of the recommended rate of nitrogen fertilizer is beneficial to achieving high taste quality.