Effect Of Mineral Admixture On Creep Behavior Of Three-scales Cement-based Materials

Slag and fly ash can reduce the production cost of concrete, saving resources asmineral admixtures used in cement base material, can also reduce the slag and fly ashpollution from emissions to the environment. Therefore, slag and fly ash have become oneof the important components of cement base material, and widely promoted in practicalengineering popularization and application.The influence of creep to concrete, especially to the prestressed structure is very large.So creep as a long-term inherent deformation performance of cement base material, attractmuch attention from scholars both at home and abroad. In order to study the regular ofcement paste, mortar, concrete creep effect, and analysis the correlation among theregularity conduct, the test select specimen size is40mm×160mm×40mm, under astress of33%ultimate strength and the curing condition of temperature (20±2)℃andhumidity (60±5)%, under, with a water-binder ratio of0.37and different ground slagand fly ash two kinds of mineral replacements of0,30%and60%cement materialrespectively, a total of15set of creep experimental study on cement base material.The results show that the ability of cement base material to resist creep can beincreased with the aggregate join in, so that the creep time-varying characteristic ofcement mortar close to concrete; and cement paste vulnerable to influence of externalfactors due to lack of aggregate in, the creep have developed rapidly and stable for a longtime, and have a low similarity with the creep of concrete. The creep law of cement basematerial in different scales did not change with adding mineral admixtures, the mineraladmixtures to concrete and cement paste with the dosage of S30, S60, F30have the samecreep curve, maximum error less than15%, while in the F60cases there is a big differentwith mortar and concrete. To clarify the internal mechanism, combine with scanningelectron microscopy image to analysis the situation under the different dosage of mineraladmixtures and the matrix, find that when mixed with30%ground granulated slag, mixedwith60%ground granulated slag and mixed with30%fly ash, there is no obvious flaws,interface area denser relatively and mineral admixtures combined with the matrix in goodcondition, and when the dosage of fly ash is60%, interface combination of fly ashcombined with the matrix is poor, unpredictable influence will be brought to the creep law.Based on the experimental results in this paper, cement mortar can approximate simulate the creep law of concrete to study the effect of other factors on the concrete creep with ingood condition of the interface bonding, for carrying out extensive research on the laws ofthe creep.