Research On The Relationship Between The Composition Of Fresh Concrete Material Parameters And Resistivity

The mix proportion design parameter of concrete is an important parameter of concrete quality. Rapid measurement of fresh concrete compositions can effectively monitor the on-site concrete quality management, and it play a great role in quality control. We study the variation of fresh concrete resistivity with the aid of electrodeless cement concrete resistivity meter, and discuss the impact of fresh concrete resistivity under different varieties of cement content, water-binder ratio mineral admixture, chemical admixtures dosage on. We establish the functional relationships between resistivity and the fresh concrete material parameters. The studies show that:There is a linear relationship between the fresh concrete resistivity and compositions. Resistivity method can be used to test fresh concrete constituents quickly, there is provided a convenient method for the rapid testing in fresh concrete quality control.The main conclusions are as follows:(1) With the resistivity values of fresh concrete setting and hardening process and constantly changing, the resistance rate of the slurry after mixing the slurry to reduce, then the resistivity gradually increases with time;(2) There are great impact on the fresh concrete resistivity that the amount of cement, water-binder ratio, mineral admixture type and admixture contents. The use of mineral admixtures significantly increase the electrical resistivity of concrete under the same water-binder ratio conditions, the smaller of mineral admixtures particle size, the better the dispersion of cement, and the greater of concrete resistivity is.(3) The fresh concrete resistivity increase with the decreasing of water-binder ratio, the fresh concrete resistivity increases with the increasing of material content. Under the same mineral admixtures content condition, the resistivity of fly ash concrete slurry is lower than the resistivity concrete of slag slurry; The content of superplasticizer have less effect on the early resistivity of fresh concrete;(4) There is a good linear relationship between the fresh concrete resistivity and compositions. It achieved the purpose of rapid detection. The relationship equation of resistivity in testing 10 minutes is:Y= 7.89593-0.00733X1 +1.30652X2+2.62820X3-5.13611X4 (R2=0.792); The relationship equation of resistivity in testing 20 minutes is:Y=7.53522-0.00697X1+1.30792X2+2.58552X3- 4.73389X4 (R2=0.791),The X1, X2, X3, X4 represent the unit amount of cement, the unit amount of fly ash, the unit amount of slag and water-binder ratio respectively. The earlier the test is made, the more accurate the results we can get. The test can be finished in 20 minutes, and it’s achieved the object of rapid detecting and real-time monitoring on fresh concrete.