Study On Bonding Performance Of Polymer-modified Cement-based Bonding Composite

Polymer-modified cement-based bonding composite(PCBC) is defined as that polymer powders or latex, some time with additive or mineral admixture, are incorporated to modify property of common concrete, mortar or paste hugely and improve its performance markedly, which is used as new-to-old concretes or mortars bonding materials. This dissertation focuses on the systemic experiments and theoretical analysis on the bonding performance of some PCBC, especially Styrene-Butadiene-Rubber(SBR) PCBC. The main research content and innovative achievements can be summed up in the following aspects:1. The more proper proportion of polymer-modified cement-based bonding mortar(PCBM) is brought forward to research on its short-time bonding performance, based on systemic proportion of mortar in the experimental investigation, by giving priority to achieve a better short-time bonding effect. The interfacial bonding performance of PCBM to the old mortar is affected under the conditions of different curing systems, bond methods, aging, bonding materials’ proportion and variety, admixture and mineral additive. It is found experimentally and theoretically that:(1) Change in the proportion of PCBM, such as polymer cement ratio P/C, water cement ratio W/C and sand cement ratio S/C, inflects markedly mortar’s strength, including bond strength. The short-time bonding performance of some PCBM is improved observably by using high efficiency water reducing agent at the same time, hardly improved by using mineral additives, such as UEA and SF, and improved differently by combining FDN, SF and UEA together.(2) The short-time bonding performance of PCBM with proper proportion and in well curing environment is almost improved with contrast to that of common mortar while it is different between before and after mortar harden.2. Long-time and short-time bonding performance of PCBC are researched systematically, involved of curing systems, bond methods, aging, bonding materials’ proportion and variety, additive and mineral admixture, bond strength, body flexural strength and body compressive strength,5years age in out-door bonding. As a result, some new building bonding materials are found. SBR modified mortar has good bonding performance. Acrylic latex, pure acrylic latex and chlorobutyl latex modified mortar have good bonding performance while they are in the fitting bonding conditions. Liquid epoxide resin can solidify in damp environment or in water so that its well bonding performance is validated by test. Bond strength of poly-oxane polymer powder(denoted as NP) modified mortar is reformed markedly while its body strength does not become below with contrast to that of common mortar.3. The long-time interfacial bonding mechanism of Styrene-Butadiene-Rubber(SBR) latex modified cement-based concrete/mortar/paste used and strengthed in RC structure is studied by some tests in this paper. The findings indicates that SBR latex modified cement-basedd mortar has achieved a good result of long-time interfacial bonding performance. The slanting shear、flexural、direct shear and direct axle tension tests are adopted to approach SBR latex modified cement-based paste resistance to the breaking stress in strengthed RC structure. At the same time, splitting strength of SBR latex modified cement-based concrete is high too. Semi-adiabatic exothermal hydration test is used to study the hydration interaction between SBR and cement in the mortar. The dry shrinkage and heating deformation tests are utilized to research characteristic of SBR latex modified cement-basedd mortars encountered with temperature and humidity change. Scanning electron microscope(SEM) is employed to read the microscopic structure of bonding interfacial transitiation zone(BITZ) in SBR latex modified cement-based mortar strengthed in RC structure. After microhardness test is utilized to research microhardness of bonding interfacial transitiation zone(BITZ) in SBR latex modified cement-based mortar strengthed in RC structure, weakness extent and weakness index for microhardness of BITZ are brought forward and made use of. It is confirmed again that there is long-time good bonding performance and function to self-repair and to self-perfect in the bonding interfacial transitiation zone(BITZ) of SBR latex modified cement-based mortar. Long-time interfacial bonding mechanism is thoroughly discussed to base on data of these associated tests. Research on long-time interfacial bonding mechanism of SBR modified cement-based composite help to understand its long and short-time bonding performance. The model for new-to-old bonding interface of SBR modified mortar is brought forward and used.