Recycling of Silicon Carbide Sludge on The Preparation and Characterization of Lightweight Foamed Geopolymer Materials

This study used silicon carbide sludge (SCS) to prepare lightweight foaming geopolymer materials (FGPs) by the direct foaming method. Results showed that when the SCS replacement level was 10%, the bulk density of the lightweight FGPs with added foaming agent amounts of 0.5% and 2.0% was 0.59 and 0.49 g/cm3, respectively; at a curing time of 28 days, the lightweight FGPs with amounts of added foaming agent of 0.5% and 2.0% had bulk densities that were 0.65 and 0.58 g/cm3, respectively. When the SCS replacement level was 10%, and the amount of added foaming agent was 2.0%, the porosity ratio of the lightweight FGP increased from 31.88% to 40.03%. The mechanical strength of the lightweight FGPs with SCS replacement levels of 10% and 20% was 0.88 and 0.31 MPa, respectively. Additionally, when the amount of foaming agent increased to 2.0%, the thermal conductivity of the lightweight FGPs with SCS replacement levels of 10% and 20% were 0.370 and 0.456 W/m×K, respectively. When the curing time was 1 day, and the amount of added foaming agent was 0.5%, the reverse-side temperature of the lightweight FGPs with SCS replacement levels of 10% and 20% were 286 and 311 °C, respectively. The k value of the O2 reaction decreased from 2.94 × 10−4 to 1.76 × 10−4 because the reaction system was affected by the presence of SiC sludge, which was caused the reaction to consume O2 to form CO2. The results have been proposed to explain that the manufactured lightweight FGPs had a low thermal conductivity (0.370−0.456 W/m×K). Therefore, recycling of silicon carbide sludge in lightweight foaming geopolymer materials has potential as fire resistance material for the construction industry.

Determination of the Level and Trend of Fertility in Four Provinces in South Africa

Relevance of the research: Th e study of fertility and mortality is of great importance because it shows the dynamics of the population and the need for eff ective planning measures required to be put in place to avert catastrophe. It is therefore important for South Africa also to check whether its fertility is heading toward the same trajectory seen in these developed countries. Purpose of the article: This study seeks to determine the level and trend of the fertility in South Africa using four provinces, Mpumalanga, Kwazulu-Natal, North West and Limpopo, for the years 2011, 2012, 2013 and 2014, as case studies. Th us, the study aims to determine: (a) Whether the fertility rate was changing in the provinces during the years 2011, 2012, 2013 and 2014. (b) What is the trend? And; (c) Whether the fertility is falling below replacement level or not. Scientifi c novelty of the article: Th e study shows that fertility in South Africa has indeed declined with some provinces having the level of fertility below replacement level. Th e decline seen in this study is mainly due to the fertility of the black majority population. Th e high population growth rate was mainly due to the fertility of the blacks, therefore, when recent fertility levels in the country are low, the implication is that the fertility of the blacks has gone down, and in fact this is what this study is showing, and advises that unless measures are put in place, the fertility of the blacks or fertility in South Africa will go down below replacement level. Fertility levels have declined worldwide, including South Africa. But the extent to which South Africa’s fertility has declined is not very clear because data from two previous censuses on fertility and mortality were very poor. South Africa (SA) had reliable data on the White popula-tion of the country, but with the new dispensation since 1994, data collection, especially from the black population that forms majority, has not been easy. Th e quality of data from the black population that accounts for over 80 percent of the population has not been good and reliable, probably because of the low level of education of this segment. Fertility and mortality data from the two previous censuses, 2001 and 2011, were not reliable when compared with data from vital statistics and national population register. Th us, estimates made from these censuses’ data on these events are questionable. South Africa, however, has data from the General Household Surveys (GHS), and this study uses data from these surveys to attempt to fi nd the level and trend of fertility. Th e GHS is an annual household survey which measures the living circumstances of South African households. Demographic and statistical methods are used to calculate measures, like the UN age ratio scores, to assess the quality of the data from four provinces, namely, North West, Kwazulu-Natal, Mpumalanga and Limpopo provinces, for the period 2011 to 2014. Th e four provinces are selected as a case study to compare rural and urban fertility characters. Th e results show that the quality of the survey data is fairly good and reliable with KwazuluNatal province having the most reliable data. Th e fertility levels were lowest in the more urbanized and educated provinces of Kwazulu-Natal and North West, and highest in the less educated and rural provinces of Limpopo and Mpumalanga. Th e study further shows that fertility in all the provinces has been declining since 2012, with the gross reproduction rate falling below replacement level; with implication that the fertility of the black population is declining fast. Th e decline in the fertility level could be attributed to quite a number of factors including education, urbanization, and improvement in primary health care. Because of the sharp decline in the fertility level in the recent years, the study calls for proper policy intervention to avoid population “extinction”.

Studies on Impact Resistance of Self-Compacting Concrete with mechanically treated Recycled Coarse Aggregate

Self-compacting concrete (SCC) is an extraordinary type of concrete that is extremely flowable and spreads into the formwork without the need of external vibration. In order to attain self-compatibility SCC obliges extensively surplus quantity of fine particles as compared to conventional concrete. Recycled Coarse Aggregate (RCA) obtained by crushing of old concrete is used in the investigational analysis. Nan-Su method is used to design the SCC mixes A and B (M35 and M45). The current experimental study aims to evaluate the impact energy of Recycled Coarse Aggregate (RCA) based self- compacting concrete by replacing with Natural Coarse Aggregate (NCA) (25%, 50%, 75%, and 100%) in unprocessed and processed states for various number of revolutions (500R, 1000R, 1500R, 2000R). Tests were carried out with a constant mass of hammer (16.38 kg). The impact energy determined for the Mixes A and B is compared with respect to replacement level and processing of RCA. The impact energy calculated is maximum for mix-A (1500 and 2000 revolutions) and mix-B (2000 revolutions) at 75% and 100% replacement of RCA respectively. From the experimental results of obtained Coefficient of Variation (CoV) with respect to processing of aggregate, in both the mixes it is observed that RCA in unprocessed state and processed state (1500R) has good Coefficient of Variation. Comparing the results of Coefficient of Variation with respect to replacement level of aggregate it has a very good CoV at 25% replacement level of RCA for both the mixes.

Strength Properties of Foamed Concrete Containing Blends of Rice Husk Ash (RHA)

The present study was planned to study the influence of Rice Husk ash (RHA) on fresh and hardened properties of foamed concrete. The percentage replacement levels of RHA for fine aggregates (FA) were 0%, 5%, 10%, 15% and 20%. Production of light weight concrete was carried out with foam which was produced indigenously using a foaming agent (Foamtech). The theoretical density of foamed concrete containing 0% replacement level of Rice husk ash (RHA) was kept to be equal to 1300 ± 50 kg/m3. The actual density observed for foamed concrete containing 0% replacement level of RHA during experimental analysis was 1317 kg/m3. At curing age of 7, 14, 28, 56, and 90 days, the hardened foamed concrete cube specimens of size 100 mm × 100 mm × 100 mm were evaluated for compressive strength and 150 mm × 300 mm for split tensile strength. At a curing age of 28 days, the cube specimens were also examined for water absorption and dry density. For all of the foamed concrete mixes, the cement and fine aggregate content were kept the same. The water-cement ratio was maintained at 0.5. The only difference among all the mixes was the replacement level of RHA 5%, 10%, 15% and 20%. The amount of foaming agent was varied according to the replacement levels of RHA to ensure good workability of paste. All the results of various properties were compared with the control mix. It may be noted that 0% replacement level of RHA with FA has been considered a control mix. The maximum and minimum compressive strengths, split tensile strengths and dry densities were shown by control mix and mix containing 20% replacement level of RHA respectively. On the other hand, the minimum and maximum water absorption capacities were shown by control mix and mix containing 20% replacement level of RHA respectively.

Durability properties of self-compacting concrete (SCC) incorporating cassava peel ash (CPA)

Self-compacting concrete (SCC) is a highly flowable concrete with enhanced strength and surface finish. The production of SCC requires high content of Portland cement (PC), which in turn consumes a lot of energy and emits greenhouse gases like CO2 and CH4 to the atmosphere during its production. Also, environmental pollution arising from agricultural wastes such as cassava peels, groundnut shells, is a cause of concern. Cassava processing centres alone generate approximately 40 million tons of wastes per annum in Nigeria, while attempts to eliminate them through burning or natural decomposition is sometimes unsuccessful. It is important to reduce the CO2 emission during the production of PC and environmental pollution caused by cassava peels through partial replacement of cement in the SCC. This study assesses the durability properties of SCC produced with cassava peel ash (CPA) at 5 %, 10 %, 15 %, 20 % and 25 % replacement level of cement. The effects of water absorption, acid (H2SO4) and salt (MgSO4) attack and elevated temperature were investigated on the CPA-SCC specimens. It was revealed that the CPA improves the resistance to H2SO4 and MgSO4 degradation while the performance is poor when subjected to elevated temperature compared to the control specimen. Also, an optimum of 5% cement replacement is recommended for grade 35 compressive strength of CPA-SCC. However, the rate of water absorption reduced to a minimum when CPA is used in SCC as a result of an improved pore structure of the CPA-SCC specimen.

The level of replacement of employees with PhD degrees in the Republic of Belarus and the prospects of its improvement

Based on the available statistical data, an approach to the quantitative assessment of the replacement level of employees with PhD degrees in the Republic of Belarus is proposed in the article. The practical application of this approach made it possible to determine the inefficiency of the postgraduate education system in terms of the annual replenishment of the number of employees with an academic degree. The quantitative parameters of the performance of postgraduate education system which necessary to stabilise the number of employees with PhD degrees in the economy are determined.

Physical Properties of Cement-Sand Brick Made by Kenaf Core: Discovering the Optimal Formulation

In this study, the effect of replacing the river sand with industrial waste and cellulosic waste was investigated. The cellulosic waste use in this study only focuses on kenaf core, while the industrial waste use in this study is quarry dust. The fine aggregate formulation is adjusted with a different percentage of kenaf core. While the quarry dust is fixed at 50% replacement level. The water-cement ratio set for the formulation is 0.75, and the cement-sand ratio fixes at 1:8. The physical properties are measured through compressive strength and density at 28 days. The result shows that 10% is the maximum replacement of sand with kenaf core to produced brick that using 50% of quarry dust. The compressive strength value of the 10% of kenaf core at 28 days is 8.16 N/mm2 while for density is 1830 kg/m3 at 28 days. All the result shows that kenaf core has the potential to be used as a lightweight fine aggregate. But kenaf core needs to combine with other materials that contribute to the strength.

STRENGTH, DURABILITY AND MICROSTRUCTURE INVESTIGATIONS OF CONCRETE CONTAINING EMPTY PALM OIL FRUIT BRUNCH ASH (EPO-FBA)

Understanding of the internal arrangement of the constituents of structural concrete, at the microscopic level, and its strength behavior, as well as its ability to result in durable concrete, are necessary in order to enhance its innovative and sustainable application. This paper presents the results of investigation conducted to ascertain the strength characteristics, microstructure configuration and durability traits of concrete with its ordinary Portland cement (OPC) fraction replaced partially with empty palm oil fruit brunch ash (EPO-FBA). The compressive strength properties were assessed with 150 x 150 x 150 cube specimens while 100 x 100 x 100 cube specimens were used to assess the durability properties. An insight into the morphology and the microstructure of samples with EPO-FBA was obtained through Scanning Electron Microscopy (SEM). The results showed that EPO-FBA is a good supplementary cementing material up to 10% replacement level, however, the samples with EPO-FBA showed a significantly improved compressive strengths development and good durability characteristics at latter ages, at the replacement level beyond 10%.