The present work consisted in carrying out a study on the effective formulation of concrete for an optimal resistance to compression (fc28) between 20 and 30 MPa for the sites animated by the actors of the informal an...The present work consisted in carrying out a study on the effective formulation of concrete for an optimal resistance to compression (fc28) between 20 and 30 MPa for the sites animated by the actors of the informal and semi-informal sectors of the construction. Studies have been carried out on projects under construction, by taking samples of fresh concrete in order to evaluate their real compressive strengths. These surveys show that there is a problem in the concrete formulation, as nearly 2/3 of the results show the lack of technical knowledge on concrete formulation practices. Indeed, on eight sites surveyed and whose fresh concrete samples were taken, only two sites (7 and 8) report fairly consistent results. Their 28-day compressive strength values are respectively 35.36 and 22.18 MPa. In addition, various formulations proposed with aggregates from different quarries or extracts from the bed of the Congo River, were determined in the laboratory. This study allowed us to obtain fairly objective results overall, which is characteristic of concretes of required quality. Of the six (06) formulation proposals, average resistances of 19.6 MPa at 07 days and 25.28 MPa at 28 days were obtained. These results at 28 days are in the range of 20 to 30 MPa, set as objective in this study. These formulations can be a reliable source for concrete manufacturers in these construction sectors. Similarly, the statistical study based on principal component factor analysis tests has shown that the most appropriate formulation, in terms of mechanical resistance, is that proposed with sand extracted from the Congo River (formulation 3). This is justified by the fact that this sand is consistent and has a good granular distribution.展开更多
Despite the intention of minimum wage policy to maintain the living standards of low-income groups in the formal sector, this paper has found that the actual result of this policy produces the ＂big push＂ impact on C...Despite the intention of minimum wage policy to maintain the living standards of low-income groups in the formal sector, this paper has found that the actual result of this policy produces the ＂big push＂ impact on China＇s economy under certain conditions, i.e. it is conducive to achieving the equilibrium of high wage, high consumption and formalization. The result shows that the elasticity of income growth from raising the minimum wage standard is greater for formal sector employees than for informal sector employees and is characterized by a U-shaped pattern in terms of quantiles. Thus, minimum wage hikes have widened wage gaps between and within sectors. Rising minimum wage standards greatly stimulate consumption with each 10% increase expected to bring about an additional urban household consumption of about 1.167 billion yuan in the surveyed four provinces. With local minimum wage hikes, the formal sector of wholesale and retail, hotel and catering services expands and the informal sector contracts, while the real estate sector experiences a ＂reverse formalization＂ trend. Based on the ＂big push theory＂, this paper concludes that against the backdrop of extensive, frequent and substantial minimum wage hikes, demand and sector TFP growth are the major causes of sector heterogeneity.展开更多
文摘The present work consisted in carrying out a study on the effective formulation of concrete for an optimal resistance to compression (fc28) between 20 and 30 MPa for the sites animated by the actors of the informal and semi-informal sectors of the construction. Studies have been carried out on projects under construction, by taking samples of fresh concrete in order to evaluate their real compressive strengths. These surveys show that there is a problem in the concrete formulation, as nearly 2/3 of the results show the lack of technical knowledge on concrete formulation practices. Indeed, on eight sites surveyed and whose fresh concrete samples were taken, only two sites (7 and 8) report fairly consistent results. Their 28-day compressive strength values are respectively 35.36 and 22.18 MPa. In addition, various formulations proposed with aggregates from different quarries or extracts from the bed of the Congo River, were determined in the laboratory. This study allowed us to obtain fairly objective results overall, which is characteristic of concretes of required quality. Of the six (06) formulation proposals, average resistances of 19.6 MPa at 07 days and 25.28 MPa at 28 days were obtained. These results at 28 days are in the range of 20 to 30 MPa, set as objective in this study. These formulations can be a reliable source for concrete manufacturers in these construction sectors. Similarly, the statistical study based on principal component factor analysis tests has shown that the most appropriate formulation, in terms of mechanical resistance, is that proposed with sand extracted from the Congo River (formulation 3). This is justified by the fact that this sand is consistent and has a good granular distribution.
基金Major project of National Social Sciences Foundation"Characteristics and Policy Orientation Research on the New Normal of China's Economic Growth"(Grant No.15ZDA008)Major project of National Natural Sciences Foundation"Research on the Mechanism and Policy of Promoting Industrial Upgrade in Economic Developed Regions"(Grant No.71333002)
文摘Despite the intention of minimum wage policy to maintain the living standards of low-income groups in the formal sector, this paper has found that the actual result of this policy produces the ＂big push＂ impact on China＇s economy under certain conditions, i.e. it is conducive to achieving the equilibrium of high wage, high consumption and formalization. The result shows that the elasticity of income growth from raising the minimum wage standard is greater for formal sector employees than for informal sector employees and is characterized by a U-shaped pattern in terms of quantiles. Thus, minimum wage hikes have widened wage gaps between and within sectors. Rising minimum wage standards greatly stimulate consumption with each 10% increase expected to bring about an additional urban household consumption of about 1.167 billion yuan in the surveyed four provinces. With local minimum wage hikes, the formal sector of wholesale and retail, hotel and catering services expands and the informal sector contracts, while the real estate sector experiences a ＂reverse formalization＂ trend. Based on the ＂big push theory＂, this paper concludes that against the backdrop of extensive, frequent and substantial minimum wage hikes, demand and sector TFP growth are the major causes of sector heterogeneity.
