Research On The Production Process And Durability Of Concrete Mixed With Alkaline-Activated Water

Concrete is a most widely applied composite construction material in civil engineering, composed of cement (commonly Portland cement) and other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate made of gravel or crushed rocks such as limestone, or granite, plus a fine aggregate such as sand), water and chemical admixtures. The content and properties of water in concrete, also known as the second component of concrete, have decisive influences on concrete performances. Generally, water is the activator of cement. Combining water with a cementitious material forms a cement paste by the process of hydration which is closely related with the activity of water. Currently, the main method to activate water used for mixing concrete is magnetization, from which magnetized water is obtained. Similar to magnetized water, a new type of activated water by the membrane electrolysis method. For its alkalescence reason, this type of water is named alkaline-activated water. Besides its high activity, alkaline-activated water also has the advantages of high PH value, low surface tension, reducing property and long life time, all of which contribute to concrete performances and increase its practical site convenience. This paper uses a small scale membrane electrolysis device to manufacture alkaline-activated water, and studied the performances and production techniques of alkaline-activated water concrete for the first time.In order to find out how electrolysis parameters influence the chemical and physical properties of alkaline-activated water, the experiment tested the pH value and surface tension of alkaline-activated water of different electric fields and flow velocities. Results show that pH value and surface tension of the derived water reach best at field strength of 280-320V/m and flow velocity of 60-80ml/s. Then the experiment uses the water derived at 320V/m and 80ml/s (pH value of 9.8) as a sample to test the preservation time of alkaline-activated water; the result is 3 months in sealed bottle, over 15 days in open bottle and more than 6 days in open container. Longer preservation time provides much convenience for concrete construction, especially for merchandise concrete.According to the results of the influences of alkaline-activated water on the performances of grout and mortar, It shows that alkaline-activated water reduces water usage at standard consistency, shortens initial and final condensing time of cement, greatly improves mortar workability and increases the compressive strength of mortar and mortar with 30% fly ash admixture for all ages. Compressive strength increasing of mortar and mortar with 30% fly ash admixture both reach max when the pH value of alkaline-activated water is 9.0-9.5. Therefore 9.0-9.5 is considered the best pH value for alkaline-activated water to improve mortar performances.Then the influences of alkaline-activated water with best pH value on concrete workability, compressive strength and pore structure etc were studied. Workability of alkaline-activated water concrete was improved. Compressive strength at all ages of alkaline-activated water concrete was elevated a lot. After 28 days, the compressive strength of concrete with cement P.032.5R increased by 21%, concrete with P·042.5R increased by 15%. Total porosity decreased by 20%, pore gradation of all curing ages improved significantly. It indicates that alkaline-activated water is of great importance to fly ash concrete engineering.By combining the attributes of alkaline-activated water and the theory of cement slurry hardening and comparing the SEM photos of 300,1000,3000 amplification and the backscattered electric image of 300 amplification of both common concrete and alkaline-activated water concrete, extensively focused on the principles of alkaline-activated water’s improving the performance of mortar and concrete.Since alkaline-activated has the advantages of high activeness and high pH value, this paper studied the impact that alkaline-activated water has on concrete carbonation property(C40 objected). Results show that carbonation property enhanced a lot that in the 28-day fast carbonation test the carbonation depth decreased by 16%. For the purpose of better studying the changing rules of concrete carbonation property, taking into account that carbonation depth of concrete has few measurements and high uncertainty, this paper adopts the grey system to study the basic methods of formulating concrete carbonation depth forecasting model. In order to sufficiently optimize the carbonation equation, a new mould for concrete specimen is designed. It enables the specimen to have smooth and continuous spherical concave surface and thus attains non-destructive tests for concrete carbonation specimens; tests on carbonation depth therefore gain the advantages of homogeneity, continuity, accuracy and multiple samplesThe paper briefly studied the workability and compressive strength of self-compacting concrete with alkaline-activated water. Results show that the workability of the self-compacting concrete mixed with alkaline-activated water is obviously higher than that of the concrete mixed with tap water, which at the 28th day of curing the advantage is approximately 15%. It proves that alkaline-activated water helps enhance the properties of self-compacting concrete, as well as other kinds of HPC.To ensure the properties of concrete with desalinated sea sand and at the same time conserving freshwater, this paper proposed a new process to manufacture desalinated sea sand concrete:First, by using the co-operating device of dual membrane electrodialyzers and membrane electrolyzers to desalinate sea water, it obtains the salinity qualified alkaline-activated sea water. Then sluice the sea sand with ample desalinated sea water by means of piling sand sluicing. What’ s more, adopting the desalinated sea sand and alkaline-activated water to mix the concrete. It’s shown that the sea water desalination device is handy and mobile, the desalination effect of sea water meets the requirements of sluicing sea sand and the piling sand sluicing is easy and effective. Results of the comparative experiment of standard concrete prove that concrete made from desalinated sea sand and alkaline-activated water show better dynamics properties and steel protection. Both alkaline-activated water and desalinated sea sand contain certain amount of OH- ions, which could reduce the Cl-/OH-ratio in concrete liquidoid; accordingly, Cl-ion corrosion and concrete carbonation are further inhibited, and concrete durability enhanced.