Comparison of Self-levelling Underlayment to Traditional Methods Used in Brazil

Between 2005 and 2015,the Brazilian real estate market experienced strong growth,driven by the stable scenario of the Brazilian economy and policies to encourage real estate credit.With this demand,the companies of the sector sought to be more competitive in the market.One of the measures adopted is the search for more efficient executive processes.While the traditional manual methodology for underlayment predominates in the country’s construction sites,a self-levelling underlayment presents a tendency towards mechanization of executive construction procedures.This paper aims to present a case study of a residential construction in Rio de Janeiro,which used self-levelling underlayment technology.Comparisons regarding cost and productivity of both methodologies were made to evaluate the viability of the self-levelling underlayment in future construction sites.Data obtained from other constructions were used to estimate the productivity and cost of the traditional underlayment levelling.The results demonstrate that the use of self-levelling underlayment has potential to be widespread and used in the constructions in Brazil.

Study on Performance Regulation and Mechanism of Quicklime and Biopolymer on Hemihydrate Phosphogypsum

In order to reduce the influence of impurities in hemihydrate phosphogypsum(HPG)on the environment and improve the workability of HPG,the effects of the content of quicklime and types of biopolymer(hydroxypropyl methylcellulose,xanthan gum,sodium polyacrylate(PAANa))on the compressive strength,softening coefficient and ultrasonic velocity of HPG were evaluated.When the content of quicklime was 1.5%and the content of PAA-Na was 0.2%,HPG had the best mechanical properties and workability,its water retention rate can be increased by 5.8%,and unconfined compressive strength of 3 days increased by 10.3%and 7 days increased by 13.1%.Through the analysis of scanning electron microscope and X-ray diffraction,it was found that the hydration reac-tion of HPG was more sufficient,the pores size and number decreased,the number of impurities on the crystal surface decreased obviously,and CaF2 and other substances were formed by the reaction after the addition of quicklime.After adding quicklime and PAANa,the indicators of gypsum self-leveling mortar prepared by HPG meet the requirements of the standard.