| With the continuous expansion of construction scale in China,the repairing and grouting for old buildings and infrastructures have attracted much attention recently.And many repairing materials have been developed including cementitious-based repairing and grouting materials and widely used in the construction.However,the traditional cement mortar repairing materials also have the disadvantages of low bond strength and poor corrosion resistance.While epoxy resin has excellent mechanical properties,bonding properties,and corrosion resistance.Thus,the combination of the high performance of epoxy resin and low cost of cement mortar will have a wide application prospect in the repairing and grouting fields.In this paper,two epoxy resin systems were proposed to prepare the building repairing mortars: waterborne epoxy and anhydrous epoxy resins.And they were used to mix with cement and sands,respectively,and further prepared as the repairing materials for buildings.Meanwhile,in order to improve the pore structure and lower the cost of the repairing materials,an industrial solid waste,i.e.,copper slag,was used to partially replace siliceous materials to prepare repairing cementitious mortar.In addition,due to the fact that most of the currently used curing agents for epoxy resin are petroleum-based,toxic,and irritated,and have a high cost,a bio-based curing agent was synthesized using natural plant extractive,i.e.,oregano oil,and paraformaldehyde as raw materials.The mechanical properties,bonding properties,corrosion resistance,and microstructure of the developed epoxy-cement mortars were systematically investigated.The main research contents and conclusions are as follows.(1)Waterborne epoxy-cement mortar was prepared using waterborne epoxy resin,triethylenetetramine as curing agent,water,cement,and sand with a certain mixing ratio.The mechanical and corrosive resistance of the epoxy-cement mortar were evaluated,and the results show that with a resin to cement mass ratio of 10%,the 28 d compressive strength(41.75MPa)and flexural strength(7.99MPa)of the waterborne epoxy resin cement mortar meet the requirements of Chinese National Standard JC/T 2381-2016 Repair Mortar.Meanwhile,its bond strength(6.31MPa)to concrete is 122% higher than the required value by the specification of Repair Mortar;and the corrosion resistance is also much higher than the requirement value of Standard JC/T 2381-2016.The results of Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD),and hydration heat analysis show that the waterborne epoxy resin hindered the hydration process of cement,reduced the hydration heat release,decreased the content of hydration products,and delayed the setting time of cement.(2)In order to enhance the mechanical performance and lower the preparing cost of the waterborne epoxy-cement mortar,copper slag was used as a fine aggregate and a replacement for standard sand partially.The results show that the addition of copper slag has no significant effect on the mechanical properties and bonding properties of the mortar,but the compressive strength(28d compressive strength ≥ 41.75 Mpa,flexural strength ≥ 7.99MPa)meets the requirements of the specification of the Standard of JC/T 2381-2016,while the working performance and corrosion resistance of the mortar were enhanced.The results of water absorption and mercury intrusion experiment for the mortar indicate that the copper slag replacement effectively reduces the water absorption and porosity of mortar.A suitable addition of copper slag(10 wt%)can improve the pore structure of mortar and reduce the pore sizes of mortar,increase the harmless pore proportion of mortar(47.09%)and decrease the harmful pore proportion(2.07%),meanwhile it reduces the preparation cost of mortar.(3)The modified anhydrous epoxy-cement mortar was also prepared using copper slag,anhydrous epoxy resin,curing agent,diluent,accelerator,cement,and sand based on a certain mixing proportion.The addition of copper slag endows the mortar with excellent mechanical strength(28d compressive strength ≥ 100.53 Mpa,flexural strength ≥45.22MPa),bond strength(8.34MPa),and corrosion resistance,while reduces the preparing cost,and promotes the utilization of industrial solid waste.(4)The bio-based curing agent was synthesized using oregano oil,triethylenetetramine,and paraformaldehyde as raw materials,and it was further applied to prepare the anhydrous epoxy-cement mortar.The chemical characteristics of oregano oil and the synthesized curing agent were analyzed by using FT-IR and nuclear magnetic resonance spectroscopy(NMR).The results show that the functional groups including amino group and benzene group appeared in the spectra of the reaction products,confirming the successful synthesis of the oregano oilbased curing agent.The results of differential scanning calorimetry(DSC)and rheological tests for the curing agent indicate that the curing degree(94.14%)and mechanical properties of the anhydrous epoxy resins with the oregano oil-based curing agent were greatly improved.The results of the mechanical test for the mortar show that the 7d compressive strength(110.64 MPa)and 28 d compressive strength(113.42 MPa)of the mortar with 50 wt% oregano oil-based curing agent significantly increased by13.94% and 12.36%,respectively,compare with those with triethylamine as a curing agent only.And the mortar with oregano oil-based curing agent has excellent bonding performance to concrete and high corrosion resistance.The SEM images of the fractured section of the mortar show that the epoxy resin with oregano oil-based curing agent closely combined with aggregate,indicating a superior interfacial bonding between the resin and aggregate.The repairing materials of waterborne epoxy resin and anhydrous epoxy resin with oregano oil-based curing agent not only have high mechanical performance corrosion resistance,but also effectively utilize the solid waste and natural plant resources,thus lowering the preparation cost.They are low carbon-emissions materials and environmentally friendly,thus showing high economic and ecological benefits. |
PDF Full Text Request