Effect of Rice Husk Ash and Fly Ash on the workability of concrete mixture in the High-Rise Construction

Abstract

Abstract. The dense development of high-rise construction in urban areas requires a creation of new concretes with essential properties and innovative technologies for preparing concrete mixtures. Besides, it is necessary to develop new ways of presenting concrete mixture and keeping their mobility. This research uses the mathematical method of two-factors rotatable central compositional planning to imitate the effect of amount of rice husk (RHA) and fly ash of thermal power plants (FA) on the workability of high-mobility concrete mixtures. The results of this study displays regression equation of the second order dependence of the objective functions -slump conе and loss of concrete mixture mobility due to the input factors -the amounts RHA (x1) and FA (x2), as well as the surface expression image of these regression equations. An analysis of the regression equations also shows that the amount of RHA and FA had a significant influence on the concrete mixtures mobility. In fact, the particles of RHA and FA will play the role as peculiar "sliding bearings" between the grains of cement leading to the dispersion of cement in the concrete mixture. Therefore, it is possible to regulate the concrete mixture mobility when transporting fresh concrete to the formwork during the high-rise buildings construction in the hot and humid climate of Vietnam. Although the average value of slump test of freshly mixed concrete, measured 60 minutes later after the mixing completion, decreased from 18.2 to 10.52 cm, this value still remained within the allowable range to maintain the mixing and and the delivery of concrete mixture by pumping.

Effect of Complex Organo-Mineral Modifier on the Properties of Corrosion-Resistant Concrete

“…According to [8,9,13,14], сhecking the significance of the regression coefficients of the equation is performed by Student's criterion (t  (f 2 )). The coefficient b j is considered significant if:…”

“…According to [4,8,9,13,14], the adequacy of the regression equations is checked by means of the Fisher criterion. The calculated value of which is the following ratio (12):…”

“…In recent years organo-mineral modifiers such as superplasticizer an active mineral additive (natural pozzolan, rice husk ash, bottom ash and fly ash) obtained a wide circulation. The impact of various additives on the high performance concrete quality is studied [8,9]. This is associated with the pozzolanic reaction to form the secondary C-S-H gel of mineral additives in concrete mix design [10,11].…”

Effect of Aluminium Powder on Light-weight Aerated Concrete Properties

“…As can be observed in Figure 8, the fitting relationship between modulus of elasticity and the measured 28-day compressive strength of test aerated concrete was given by a linear regression equation (5). E = 0.633*(fcs) -3.453 where R 2 = 0.93975.…”

“…In recent years, the recycling of agricultural and industrial waste as modified additives for concrete and mortar mixtures both reduces capital investments and production cost in the production of construction materials products.. In addition, assisting the thermoelectric power industry to be more environmentally friendly [5,6].…”