Research On Reduction Of Efflorescence Of Concrete In Qinghai-tibet Area

Firstly, according to the characteristics of concrete efflorescence, a evaluation method for its efflorescence degree was determined. Through a large number of experiments, the evaluation method was put forward, with efflorescence experiment by using the mortar of fresh concrete , measuring efflorescence surface area of specimen with image processing software ProPlus6.0 and evaluating the efflorescence of concrete by computing the percentage of efflorescence area of specimen that in its surface area.Secondly, the inhibitory effect of internal and external factors on the concrete efflorescence was researched respectively. Utilizing the characteristic of different porosity of different grain grading sand , the influence of different grading sand on concrete efflorescence in grading limit ofⅡdistrict was researched; Utilizing the pozzolanic activity of mineral admixtures, the effect of inhibiting efflorescence of fly ash, slag, silicon fume and zeolite powder was studied; Utilizing the characteristic of optimizing pore structure and reducing water of the air-entraining agent and water-reducing agent, the inhibiting efflorescence effect of the air-entraining agent and different water-reducing agent was studied. In addition, the influence of different curing way and waterproofer on concrete efflorescence was studied. After the above analyses, major results can be concluded as follows:①In the preparation of concrete, the sand close to intermediate grading ofⅡdistrict should be initially used, because the effect of inhibiting efflorescence of the concret preparing with it is slightly better.②The mineral admixtures can significantly inhibit concrete efflorescence, their effect of inhibiting efflorescence,from high to low, is silicon fume, zeolite powder , slag and fly ash from high to low.③Adding water-reducing agent and air-entraining agent to concrete, the efflorescence of concrete is obviously inhibited. When the quantity of admixtures reaches to its best, the inhibiting efflorescence effect of polycarboxylate water-reducing agent is superior to K12 powder air-entraining agent which is superior to naphthalene sulfonate water-reducing agent.④The effect of inhibiting efflorescence of concrete respectively cured by sprinkling, membrane, sack and membrane&sack in the shade of outside is inferior to the concrete cured in the standard condition. ⑤Waterproofer can significantly reduce the efflorescence degree of concrete. Among them, the best material of inhibiting efflorescence is Penetron cement-based capillary crystalline waterproofer, then, US-1510 cement-based capillary non-crystalline waterproofer and M1500 inorganic water-proofing agent in turn.Finally, after analysing reasons of the efflorescence of a bridge concrete in Qinghai-Tibet area, according to the above results, the method of adding silicon fume, slag, polycarboxylate water-reducing agent and air-entraining agent into concrete to produce C30 concrete inhibiting efflorescence was raised and proved to inhibit the efflorescence of concrete under laboratory conditions.