Research On Optimizing Mix Proportion Of Self-compacting Concrete Based On Paste Rheological Theory

Rock-filled concrete(RFC)is a novel large-scale concrete construction technology based on self-compacting concrete(SCC).RFC has been applied in many projects.SCC has many excellent performances,such as improving the environment during construction and increasing the construction speed.However,duing to high cost and weakness of robustness,it is difficult for promoting the application and quality control of SCC.This thesis mainly aims to optimize and improve the disadvantage of SCC.Through the establishment of a quantitative relationship between mix proportion and rheological characteristics of paste based on a rheological threshold theory,quantitative adjustment of mix proportion,optimization of cost and evaluation of robustness of SCC were completed.With water-powder ratio byvolume and dosage of superplasticizer by mass as mixture variables,the correlation between mix proportion variables and rheological characteristics of paste were determined based on a bilinear interpolation method and the test results of the reference mixtures.The distributions of the rheological characteristics of paste were obtained within the reference mixtures area.The accuracy and feasibility of the correlation was verified through a series of mini-slump flow tests.Then,the deviation of the correlation was amended through an iterative verification process.A self-compacting zone at paste level was defined and the obtaining method of this zone was introduced based on the correlationship and the rheological threshold theory of paste.The self-compacting zone provides the data basis for quantitative adjustment of mix proportion.A cost optimization method of SCC was proposed based on the self-compacting zone with fixed aggregates properties,thus the combined effects of water and superplasticizer on the flowability of SCC were fully considered.This cost optimization method was verified through a series of paste mini-slump flow tests with different combinations of powders and admixtures.Effective ways to reduce the cost were obtained.The cost optimization and analysis were also completed with different content and proportion of fine and coarse aggregates.Effects on costs by changing aggregate properties and the relative recommendations on aggregates were obtained.Then,a methodology to quantitative evaluate robustness of SCC was proposed based on the self-compacting zone.The tolerances of fluctuations in water content and the loss of superplasticizer were identified as evaluation indexes.Reducing water-powder ratio and increasing dosage of superplasticizer with a certain proportion simultaneously based on the self-compacting zone,the robustness of SCC would be effectively improved.This rule was verified through a series of paste mini-slump flow tests with different combinations of powders and admixtures.Approaches to enhance the robustness of SCC were obtained.A feedback methodology of mixture adjustments was proposed to improve mixture design efficiency.A mini-slump flow measurement tool was developed using the augmented reality technology based on image processing and smart phones.By correcting the error caused by the position of camera and determining the starting time of tests,the flow time of paste could be easily measured.The former complicated measurement procedure was improved.An information system for mix design and optimization of SCC was devised based on this measurement tool and the methods mentioned above,providing an efficient idea and solution for the design and optimization of SCC in the future.