Study On Performance Of Premixed Wet Mortar

With the rapid development of Chinese new urbanization, the number of urbanmunicipal infrastructure and housing will be substantially increased, whilethe overallbuilding energy consumption has occupied a considerable part.Building mortar as abulk building materials after the wall materials and the concrete, the annual amount isup to hundreds of millions of tons.On the current domestic situation,theextension ofready mixed mortar as green building materials will be imperative. But compared withthe developed countries, research on the premixed wet mortar in China started late andthe extension is not popular, therefore the study on how to preparegoodworkabilityanddurability of premixed wet mortar and how to maintainits performancepersistence is very necessary.This paper mainly studies the effect on the performance of premixed wet mortar, inthe selection of cement sand ratio, also studied on wet mortar properties of differentcomponents for admixtures and secondary water addition at different time. The mainresearch contents are as follows:Firstly, it studies the influence of cement sand ratio on the impact property ofcement mortar and different components on performance of ready mixed mortar. Theresults show that, with the cement sand ratio decreases, mortar stratification,consistency of the loss and the dry shrinkage of mortar increased gradually;28dcompressive and flexural strength gradually reduce; the setting time increases.Whencement sand ratio is1:3,with CaCO3instead of sand in the mortar, fly ash replacingcement or lime paste replacing cement can improve some performances of mortar,butthe volume of replacing has an optimum range,including CaCO3substituted amountshould not exceed30%the sand,fly ash and lime paste should not exceed20%of thecement.Secondly, it studies the effect of admixtures on performance of premixed wetmortarwith different components. Incorporating water reducing agent, water retainingagent and retarderin different components mortar can improve the water retention ofmortar, dry shrinkage, consistency and setting time of the loss.The amount of admixtureis not the more the better, but existsa relatively optimum range,the saturated content ofretarders in different cementitious material system is not same at all.Finally, remix thepremixed wet mortar withdifferent components through with secondary water addition at the different timeto study its effect on performance of readymixed mortar in different cementitious material system.In terms of mechanical properties, secondary wateraddition mixing decreases themortar compressive strength of28d in different levels: cement-lime plaster-sand>cement-sand> cement-fly ash-sand> cement-CaCO3-sand;In terms of durability, secondary wateraddition mixingalso has different levels ofweakening thedurability:cement-lime plaster-sand> cement-fly ash-sand> cement–sand>cement-CaCO3-sand. Therefore,“thecement-lime-sand”and “cement-flyash-sand” wet mortar should try to avoid the secondary water addition mixxing, if therehasto remix through secondary water addition, we can choose cement-CaCO3-sandmortar system to offset weakened performance because of the secondary water addtionmixing properly.Finally, integrated the setting time-the penetration resistance curve analysis, thepenetration resistance value and operation time has a certain relationship, when thepenetration resistance between0-0.5N, mortar is easy to handle; when the penetrationresistance between0.5-1N, operation feels worse gradually; when the penetrationresistance is more than1N, mortar has no operating handle.The incorporation of theadmixture can be extended to some degree of mortar penetration resistance valuereaches1N or so, so as to prolong the operation time of mortar.Generally speaking, thegrowth trend of mortar penetration resistance has two flat areas and two growth areas,namely the mortar by penetration resistance in0-1N,7-10N interval growth is relativelyslow; penetration resistance in the range of1-7N,10N growth rate obviously, and theinterval after10N growth isfaster than in the range of1-7N.