Effect Of Functional Components On Concrete Release Agent And Surface Cement Hydration

With the development of the fair-faced concrete industry and the precast concrete component industry,concrete release agent has been widely used in the construction industry.With the increasing demand for release agents in construction engineering,the demand for functional release agents in the concrete industry gradually appears.As we all know,the erosion of concrete by the external environment is the main reason for the destruction of concrete buildings or structures.Due to the porous structure of concrete,corrosive ions will erode the microstructure of the concrete through the infiltration of water.Water in cement-based materials provides the necessary carrier and diffusion medium for the occurrence of these erosions,and some even directly participate in the erosion process.Therefore,it is very important to improve the durability of concrete by modifying its surface by physical or chemical means and enhancing its ability to resist water erosion.At present,to improve the surface compactness of concrete or endow its hydrophobic properties,it is generally done through the way of secondary brushing or impregnation.Few of the functional concrete release agents for cement-based material surface protection research exist.In addition,most researchers focus on the preparation process of the basic release agent,but few study the effect of the release agent on cement hydration on a concrete surface.In this paper,the functional component is added to modify the basic release agent and functionalize the concrete release agent.The functionalization of a concrete release agent is explored by testing its basic physical properties,release properties,and influence on the cement hydration of the concrete surface layer.Specific research results are as follows:（1）Study on an emulsion release agent prepared based on different types of base oil and its influence on the cement hydration of the concrete surface layer.Based on different types of base oils,the hydrophilic oil balance value（HLB）was determined according to the emulsification method.Different kinds of surfactants were selected to study the influence of stirring speed,stirring time,and reaction temperature on the emulsification effect and test the influence of using temperature on the demoulding effect.Finally,the influence of the demoulding agent emulsion on the hydration of cement and the porosity of the test block was tested.The results showed that the optimum technical parameters of the emulsion release agent were Span-80 23.5%,LAS-TEA 21%,OP-10 26.5%,and OP-4 29%,respectively.The stirring speed was 1200 r/min.The mass ratio of emulsifier to base oil is 1:10;the mass ratio of emulsified oil to water is 1:10～20,which can be used in large proportions of dilution.The emulsion release agent not only has good performance at room temperature but also has good performance at 60℃.Compared with an oil-based release agent,an emulsion release agent can compact the porosity of cement-based materials,and the overall porosity of the test block decreases from 20.51%to 17.18%.（2）Research into concrete release agent reinforcement component modification.The release agent of emulsion concrete was modified by using the non-model strengthening agent Ca（HCOO）₂.Through the testing of basic physical properties and demoulding effect,the prepared enhanced concrete demoulding agent emulsion has a good demoulding effect.When the mass fraction of Ca（HCOO）₂ is 3%of the mass of the release agent,it has the best effect on the surface strength of the test block,indicating that it has a good balance between the negative influence of the release agent and cement hydration.The effects of reinforcing components with different mass fractions on the hydration properties of surface cement were studied.The results show that when the mass fraction of Ca（HCOO）₂ is 2%of cement mass,the strength of mortar test blocks is the highest,and the strength of 3d and 7d blocks increases by 84.9%and 69.3%,respectively.The microcosmic test results show that the addition of Ca（HCOO）₂ has no obvious effect on the type of cement hydration products,but can accelerate the hydration reaction process of cement and reduce the porosity.（3）Study on concrete release agent modified by a hydrophobic component The effects of different mass fractions of hydrophobic modified silica submicron particles on the hydrophobic properties of concrete release agents were studied.The experiments showed that the hydrophobic materials had certain hydration activities compared to the cement-based materials.Under the premise of ensuring the release effect,the concrete surface had a better hydrophobic effect.The results show that the viscosity of the release agent increases with the addition of hydrophobic material.When the dosage is 3%,the effect of balancing the negative influence of the release agent on cement hydration is the best.The addition of 1%hydrophobic modified silica submicron particles can give the test block surface hydrophobic properties.The microscopic detection analysis can confirm that the mechanism of action is that,under the alkaline condition of cement hydration,silica sol particles combine with calcium hydroxide in cement to produce calcium silicate hydrate,which then prevents the cement-based material from absorbing water.