Research On Mechanical Properties And Constrained Shrinkage Crack Behaviour For Waterborne Epoxy Mortar

Epoxy is a thermo-plastic polymer,and is used extensively as adhesive and coating material.Epoxy has excellent physical features with strong inter-reaction forces and highly compact molecular structure,which make epoxy pose good mechanical properties.In addition,epoxy enjoys very small shrinkage.Therefore,waterborne is widely used in construction materials.Waterborne epoxy is made on the basis of epoxy by water-compatible treatment.It contains far less volatilized components and non-flammable,so it is much more environmentally friendly.It is also easy to store and transport.Currently under the theme of environmental protection,waterborne epoxy enjoys a tremendous advantage over traditional epoxy and the market demand is huge.In the industry of construction materials,one major application of waterborne epoxy is to serve as an additive into cement based mortar that can be used as a repair material or as building components.This type of waterborne epoxy mortar will meet certain specifications,among them the shrinkage is a key index which can lead to material cracking.As such,how to measure the shrinkage performance is a issue related to the durability,and has received high attention.Also,waterborne epoxy mortar still needs many researches to support its advancement,and this thesis is just doing this.Therefore,the significance of this thesis is to propose and conduct the shrinkage study on waterborne epoxy mortar.The strength index is also fundamental and they are included in the thesis.Five tests are suggested: 1.Fluidity Test or Flow Test;2.Compressive Strength Test;3.Flexural Strength Test;4.Restrained Ring shrinkage Test and 5.Restrained externally squared eccentric ring shrinkage test.The mortar proposition is of the ratio: 0.4(water): 1.(cement):2.5(sand)that serves as the base specification with 5%,10%,15%,20%,25% and 30% added waterborne epoxy against the cement weight as to evaluate the effect of waterborne epoxy.Total 7 material propositions are implemented to make test specimens that each contains three samples.The experimental results show that waterborne epoxy mortar exhibits overall good performance in against base mortar with impressive enhancement in crack resistance,which provide a substantial technical support for promoting waterborne epoxy mortar.The inherence of material shrinkage is a focus point among the construction material community.There are two types of test methods on shrinkage,one is non-destructive,and the other is destructive.For the latter,there is only one called restrained ring shrinkage test which enjoys many benefits and widely accepted.But this test method lacks of identifying crack position and shows the large scattering of measured cracking time.This thesis conducts an improved restrained shrinkage test named externally squared eccentric ring test developed by Han Zhu in Tianjin University,China,which provides the pre-determined cracking position and shortened cracking time,resulting in the enhancement for measuring of restrained shrinkage behaviour of the intended material.It is the first time that this thesis employs Zhu’s method in testing waterborne epoxy mortar and obtains good results.