Study On Crack Control Of Recycled Aggregate Concrete Brick Building

Cracks on top of masonry building walls are caused by the volume deformationdifference of the top wall and roof, most of cracks are commonly caused by temperaturechanges of temperature crack and drying shrinkage cracking of masonry wall.Firstly, the author investigate and analysis on the choice of materials and their basicproperties of recycled aggregate, then design many different groups of mixture ratio toconduct the orthogonal experimental,according to two main factors of the brickbat proportionof recycled aggregate and fine aggregate ratio of these, focusing on the effect of the dryingshrinkage of recycled aggregate gradation to recycled concrete porous brick. In the base of theexisting drying shrinkage prediction model of no-fired brick masonry, Through the dryingshrinkage test results for a single brick, the author propose the calculation method of the brickin the use phase of drying shrinkage of the equivalent temperature difference.Secondly, the drying shrinkage of non-load-bearing frame filled with wall is a changingprocess over time, Therefore, it will produce the phenomenon of stress relaxation in themasonry, the paper based on the theoretical basis for concrete creep and stress relaxation,With the premise of the basic assumptions,the mechanical model of both ends of the boundmasonry is proposed by considering the creep effect, Using the elasticity method to derive andget the stress relaxation coefficient by considering the effect of creep masonry,whencalculation, it prefers to stress relaxation coefficient of30days that is0.72.Thirdly, using the harmonic method calculate and get the expression of the temperatureeffect of the top wall and roof by the first boundary condition, though considering the fourconditions, calculating and getting the wall temperature load and the daily temperature load inthe different forms of wall and roof insulation, and on this basis, considered the masonrycreep and stress relaxation and combined with masonry drying shrinkage equivalenttemperature difference, can get a combination temperature load of the top wall.Lastly, For the temperature affection of the top wall is more obvious, this paper presentsthe stress analysis model of masonry building analogy framework, using the structuralmechanics and elastic mechanics to derivate the thermal stress of the top wall of the masonrybuildings to the simplify formula, and apply to get a combination of temperature load value,the projected top-level wall under what kind of mining and the top wall in which a form ofwall insulation, thermal stress is the maximum, then the wall will crack,and presents themeasures of cracks controlling for the top wall.