Prediction Of Concrete Workability Based On Water Film Thickness Theory And Compressible Packing Model

Concrete workability is an important guarantee of the quality and safety of structural construction,there is no unified method or theory to accurately concrete workability,in water conservancy projects,more than the use of trial mix for concrete workability prediction,due to insufficient research on the mechanism of action of the concrete materials,resulting in the concrete mix design,which requires a lot of human and material resources.At the same time,with the massive use of new admixtures such as mechanism sand,fly ash and silica fume,the traditional mix design method based on close stacking theory and empirical data is increasingly unable to meet the demand of high performance concrete mix design.Therefore,efficient and reasonable prediction of the working properties of concrete is particularly important for the formulation of comprehensive performance and concrete.Thesis carried out the tests of net mortar and mortar pile compactness under different ratios by wet measurement method,studied the relationship between water reducing agent and fly ash on the change of pile compactness of mixed materials,analyzed the release mechanism of water reducing agent on flocculated water,and established the modified water film thickness model considering polycarboxylic acid water reducing agent.The effects of fly ash filling effect and lubrication effect on the workability of net slurry and mortar were elucidated,and the mechanism of water film thickness on the workability of net slurry and mortar was analyzed.The river sand was sieved to form different particle sizes with cement and fly ash,and the compressible pile model was used to study the influence of material particle size and the grade of river sand on the pile compactness of the mix,and the compressible pile model considering water reducing agent was established,and the calculation was programmed based on this model,which saved the time required for concrete mix ratio design.The results show that both fly ash and water reducing agent can increase the stacking compactness of neat mortar.The modified water film thickness model considering polycarboxylic acid water reducing agent has a linear relationship with the expansion of neat mortar.The compactness of materials is calculated by the compressible packing model considering water reducing agent.The results show that the calculated values of the model agree well with those of wet test.In addition,the critical expansion degree of mortar segregation is defined as 400 mm.Through the linear fitting between water film thickness and mortar expansion,it is found that when the water film thickness is less than 0.6 μ m the water film thickness has a linear relationship with mortar expansion.Based on this,the flow chart for predicting the workability of neat mortar and mortar is obtained,and the matlab calculation program is established.Based on the film thickness theory and compressible stacking model,thesis successfully proposed a method to predict the workability of net paste and mortar,which can reflect the mechanism of the influence of aggregate stacking and admixture on the workability of concrete,and can provide a theoretical basis for the ratio design of high performance concrete in practical engineering.