Papers by Julius Ndambuki
Impact of mine closure on groundwater resource: Experience from Westrand Basin-South Africa
Physics And Chemistry Of The Earth, Parts A/b/c, Oct 1, 2023
Recycling and reuse of waste materials remains a major option for waste reduction, preserving the... more Recycling and reuse of waste materials remains a major option for waste reduction, preserving the natural resources from further depletion and reduction in greenhouse gases emission thereby contributing to sustainable green environment. In this study, focus on the reuse of waste soda-lime glass crushed into coarse aggregate sizes as a substitute for natural coarse aggregate in normal concrete was investigated. The variables in this study is coarse aggregate while the cement, sand and water-cement ratio were held constant. The crushed waste glass was varied from 0-100% in steps of 25% by weight to replace the coarse aggregate in the concrete mix. Concrete mixes were prepared using a mix proportion of 1:2:4 (cement: sand: granite) at water-cement ratio of 0.5 targeting a design strength of 20 MPa. Slump tests were carried out on fresh concrete mixes and tests were also carried out on total number of 60 concrete cube specimens of size 150 x 150 x 150 mm and 60 concrete cylinder specimens of dimension 100 mm diameter by 200 mm height after 3, 7, 28 and 90 days of curing. Results on the slump tests shows a decrease in the concrete workability as the glass content increases. Test results also indicated that the compressive and split tensile strength of the hardened concrete decreases with increasing waste glass content compared with the control. However, concrete mix made with 25% waste glass content compared significantly well with the control and can be suitably adopted for production of normal concrete.
Crystals, Dec 3, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Application of geographical information systems and FARSITE in fire spread modelling
International Journal of Environment and Sustainable Development, 2014
Wildfires are a perennial problem in the Northwest of USA. Wallowa Whitman National Forest fires ... more Wildfires are a perennial problem in the Northwest of USA. Wallowa Whitman National Forest fires are quite frequent as a result forest completes between 10,000 and 15,000 acres of burning in a year. According to research, it was reported that the study area experienced fires from 1970 to 2006 with total burning of 149 fires and total burnt area of 7,583 hectares per year which observed to be between June and October. In Wallowa County, over 80% of fire starts are caused from lightning and 20% are attributed to human-caused fire starts. A GIS proved to be used effectively to map forest fire risk zone with the aid of LANDSAT satellite images and high resolution Google Earth images. FARSITE was used to predict fire intensities across a landscape. Results indicated that using GIS and FARSITE, one can generate a reliable management strategy, hence, minimising both life and property loss.
Polymers, Oct 20, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
IntechOpen eBooks, Mar 25, 2020
Vulnerability to cracks is one of the major flaws of concrete infrastructure. The need to reduce ... more Vulnerability to cracks is one of the major flaws of concrete infrastructure. The need to reduce the repair cost of this defect birthed the need for self-healing concrete. The incidence of cracks on concrete structures is a big threat to the stability of bridges, concrete roads, and other concrete infrastructures. This review assessed the use of self-healing technology on concrete using sustainable material as an active method of healing crack. This was done with the view of improving the stability, strength, and sustainability of infrastructure for national growth. The outcome of the review showed three prominent methods used in self-healing technology, which include autogenous healing, encapsulation of polymeric material, and microbial production of calcium-carbonate (biotechnological approaches). The review also revealed that calcium carbonate is a versatile material that can be used in crack healing for the filling of voids and improves the porosity of the concrete. The success of using the autogenous healing method depends on the diameter of the crack induced in the concrete structure. Additionally, this method can operate independently in different conditions regardless of the crack position. Correspondingly, lowering the water-cement ratio improves the autogenous healing process. The use of encapsulation of polymeric material and microbial production of calcium-carbonate methods showed that the presence of water and humidity is a critical factor to be considered. However, biotechnology using microbial action is prone to the production of ammonium ions (NH4+) through ureolytic activity, which results in nitrogen oxide emission into the atmosphere. Congruently, this may affect the durability of the concrete. Based on the uniqueness of this technology, it is recommended for the construction of sustainable infrastructure now and in the foreseeable future.
Environmental Greening Through Utilization of Glass Waste for Production of Concrete
Social Science Research Network, Jan 20, 2014
The amount of glass waste generated by glass manufacturing and recycling companies creates seriou... more The amount of glass waste generated by glass manufacturing and recycling companies creates serious environmental challenges. The utilization of glass waste in concrete to mitigate such challenges involved the adaptation of the material with respect to the fundamental requirements. This research involved the beneficial use of two types of soda-lime glass wastes in concrete, as partial replacement of cement and fine aggregate, in order to enhance the greening of the environment. The glass wastes were produced in large quantities by glass recycling companies in Gauteng, South Africa. Low alkali cement, CEM V/A 32.5N, a composite cement with 25% Fly Ash (FA) and 18% Ground Granulated Blast-furnace Slag (GGBS) was used. The two types of glass waste, namely, Superfine Waste Glass Sand (SGW), a fine residue of glass recycling processes and Ceramic Stone and Porcelain (CSP) glass waste, cullet contaminated with ceramics, stones and porcelain; were respectively used as sand and cement replacements. As collected, SGW was sieved and blended with fine sand in line with the recommendations of the South African National Standard (SANS) for sieve analysis. CSP was sorted from contaminations, through decantation, dried in the oven at 104 oC for 24 hours, grounded into powder with rod and ball mills successively; and sieved through 75µm mesh. The tests conducted include sieve analysis, particle relative densities, compacted bulk densities and loose bulk densities; in accordance with the Cement and Concrete Institute (CC the second set consisted of 10%, 20% and 30% of glass powder (GLP) replacement of cement; the third set consisted of 10% GLP in combination with 20%, 40%, 50% and 60% of SGW, respectively; the fourth set consisted of 20% GLP in combination with 20%, 40%, 50% and 60% of SGW, respectively; and the fifth set consisted of 30% GLP in combination with 20%, 40%, 50% and 60% of SGW, respectively. Subsequently, cube specimens were tested at 3, 7 and 28 days for compressive strength, according to the SANS recommendations. It was found that, the glass waste were effectively adapted in concrete. SGW was adequate for blending with fine aggregates as it improved the gradation of the blend. SGW and GLP increased the workability of the fresh concretes and significantly reduced the weight of the hardened concrete by 6.5%. Glass powder reacted as early reactive pozzolanic material, as it enhanced the 3 days compressive strength of the concrete by 14% when compared to the control mix with natural aggregates. Compressive strengths obtained from the laboratory tests ranged between 18.8 MPa and 32.7 MPa, which were 65% above that of the control mix. Up to 30% of glass wastes used as cement and fine aggregate replacement, respectively, did not impair the 28-day compressive strength of the concrete. The blend with 20% GLP and 40% SGW exhibited the same 28-day compressive strength as that of the control mix value with a value of 25.86 MPa. The mix with 20% GLP and 20% SWGS exhibited the highest strength at 28 days with a value of 32.7 MPa which represented an increase of 26.5% of the compressive strength of the control mix. The research demonstrated the beneficial use of glass waste as partial replacement for cement and sand in concrete. This will appreciably reduce the amount of glass waste dumped to the landfill sites and enhance the greening of the environment, with the added advantage of preservation of virgin materials for posterity.
Assessment of the effects of climate change on the performance of pavement subgrade
African Journal of Science, Technology, Innovation and Development, Mar 4, 2015
This research investigated the effects of future climate change on pavement life in South Africa ... more This research investigated the effects of future climate change on pavement life in South Africa by simulating prolonged moisture presence in the pavement subgrade. The study was conducted on roads P435 and P443 within uMkhanyakude District Municipality. Climatic data were collected from the Council for Scientific and Industrial Research (CSIR) and Climate Systems Analysis Group (CSAG) from 1940 to 2001 and simulated from 2012 to 2062. Sampling was done using the standard procedure described in Technical Methods for Highways (TMH) 5 and soil laboratory tests carried out according to TMH 1. Results of laboratory tests classified the materials as G10 based on their California bearing ratio (CBR) and plasticity index (PI). Relative compaction of 91.4 and 94.3% were obtained from the CBR test on the subgrade layers of roads P435 and P443 respectively. The research showed that 50 years into the future will bring a climate change signal that will be minimal in terms of precipitation. However, natural weather variability threatens to be the dominant signal. The pavement life has been shown to decrease in a way that would threaten the road category and design reliability.
Multimodeling Approach to Assess the Impact of Climate Change on Water Availability and Rice Productivity: A Case Study in Cauvery River Basin, Tamil Nadu, India
Phytoremediation of Water Using<i>Phragmites karka</i>and<i>Veteveria nigritana</i>in Constructed Wetland
International Journal of Phytoremediation, Jul 7, 2015
Constructed wetland is an innovative and emerging ecological technology for wastewater treatment.... more Constructed wetland is an innovative and emerging ecological technology for wastewater treatment. This study was conducted to investigate the effectiveness of a Vegetated Submerged Bed Constructed Wetland (VSBCW) for removal of heavy metals from industrial wastewater in a steel manufacturing company. A pilot Effluent Treatment Plant (ETP) consisting of equalization basin, two VSBCW basins and a storage tank was constructed. The VSBCW was constructed using 10-30 mm round granite for the different zones. This was overlaid by 200 mm deep granite and 150 mm washed sand with Phragmites karka, Vetiveria nigritana and Cana lilies as macrophytes. Irrigation of macrophytes using effluent from the industry was done after 3 months of planting and ETP monitored. Industrial wastewater samples were collected and analyzed for heavy metals such as zinc (Zn), lead (Pb), iron (Fe), manganese (Mn), magnesium (Mg) and chromium (Cr) to know the treatment efficiency of the ETP. Results indicated that the removal efficiencies of the VSBCW for Pb, Mg and Cr were 15.4%, 79.7% and 97.9% respectively. Fe and Mn were seen to increase by 1.8% and 33% respectively. The ETP using locally available macrophytes is effective in the phytoremediation of heavy metals, particularly Cr from the wastewater.
Impact of Mine Closure on Groundwater Resource: Experience from Westrand Basin-Sa
Social Science Research Network, 2022
A review on Africa energy supply through renewable energy production: Nigeria, Cameroon, Ghana and South Africa as a case study
Energy Strategy Reviews, Nov 1, 2021
Environmental Impact of Wastewater Dry Sludge-Based Concrete: A Case Study of Limpopo Sludge in South Africa
Social Science Research Network, 2022
Sustainable usage and the positive environmental impact of wastewater dry sludge-based concrete
Results in materials, Dec 1, 2022
Revision of the Macro Climatic Regions of Southern Africa
Social Science Research Network, Oct 21, 2013
Factors influencing pavement designs are divided into two, namely controllable and non-controllab... more Factors influencing pavement designs are divided into two, namely controllable and non-controllable. Controllable factors include engineering design, selection of materials, construction quality and control, standards and progress. Uncontrollable factors include climate, terrain and geological conditions such as surface and sub-surface hydrology. Therefore there are many influential factors that the engineer cannot control and hence understanding risk and reliability is a key aspect of design to cater for uncertainties. It is believed that by the year 2100, world climate will have changed in ways that are difficult to imagine - as difficult as it would have been at the end of the 19th century to imagine the changes of the 100 years since. The current heat, drought, floods and rainfall spurts are evident of the effects of climate change. The response to climate change is often seen as twofold; adaptation and disregard. Adaptation often viewed as the most essential part of the response to the threat of climate change whereas disregard comes from a poor understanding of the influential factors of the African climate. Severe lack of local weather data, particularly for central Africa is also part of the problem. This lack of knowledge makes it very difficult to predict with any degree of accuracy what will happen as a result of climate change at a country, or even sub-regional level in Africa. Extensive research has been done by climatologists on the subject of climate change. However, engineers and technologists have not yet adapted an approach that aims to address the topic within the engineering sector. Improvements ought to be made particularly on climate based parameters used in transportation engineering and designs. The Macro Climatic Regional Map of Southern Africa adopted from Weinert (1980) by Technical Recommendations for Highways (TRH4) (1994) is one of the most outdated weather based catalogues used in the industry. To date, even in light of the eminent threat of climate change, no credible advances have been made yet for any improvements on this over thirty year old design climatic regional map. Minor editions on the Weinert N-Values include up to ten percent adjustments on net cold binder whereby an increase is made on dry areas (N-value > 5) and reduction in wet/humid areas (N-value
Utilization of wastewater sludge for lightweight concrete and the use of wastewater as curing medium
Case Studies in Construction Materials, Dec 1, 2021
Abstract The increasing population have resulted in a higher generation of domestic and industria... more Abstract The increasing population have resulted in a higher generation of domestic and industrial wastewater sludge. The sludge ends up as a landfill in designated areas which makes the land unusable. The search for lightweight materials for construction has led to the use of sludge as a viable replacement for the basic composition of concrete due to its low density. The dry sludge collected from Polokwane Waste Water Treatment Works (WWTW) in Limpopo Province was used as a partial replacement of sand in concrete. The sludge content in the sand was varied from 2.5, 5, 7.5, 10, to 12.5 %. The outcomes of the analysis indicate that the partial replacement of sand with dry sludge in the concrete mix is viable and useful. The result showed that up to 7.5 % of sand could be replaced with dry sludge in concrete for structural applications. Also, wastewater can be used as a curing medium. The unit weight of the concrete decreased with increasing sludge content, which was attributed to the lower density of the sludge. The SEM image revealed a porous nature and irregular surface morphology of the sludge and the concrete.
Predicting Four Day Sub-Grade CBR Strength from Unsoaked Laboratory Specimens
Social Science Research Network, Oct 21, 2013
Most construction projects take place on soil and fewer projects are carried out on solid bedrock... more Most construction projects take place on soil and fewer projects are carried out on solid bedrock. Therefore the bearing capacity of any soil must be evaluated prior to the construction of any road. The bearing capacity or strength of granular materials for road construction is measured in terms of California Bearing Ratio (CBR). This test method has been used for the past seven decades with very limited improvements in its lifetime especially with regards to the time it takes to complete. It is considered one of the most fundamental tests of any granular material in road construction. It takes any soil laboratory a period of at least seven days to produce a comprehensive set of CBR and Indicator tests. The former is in essence a five day long test method. The waiting period means whatever progress that can be made with regards to construction on site will in the meantime be all based only on experience of site technical staff and very little scientific reliance. Therefore there is a need to make improvements on current test methods in order to expedite such a lengthy test procedure. The methodology followed in this research included extensive soil laboratory testing, particularly CBR tests on identical samples that are compacted at Optimum Moisture Content (OMC) and compressed after soaking at varying daily intervals. The results of such tests for all the specimen are then plotted on a graph to obtain a trend that will best represent the plotted data such that a formula can also be developed. An equation aimed at obtaining CBR strength of materials within a shorter timeframe than the current five day period it takes to soak and compress the soil specimen has been derived from the obtained data. Preliminary findings reveal that the equation is ideal for use on weaker gravels used as subgrade for road pavements as it has only been tested on such materials. These are materials that generally have a CBR strength ranging from 3% to 15%. Thus far, the formula has provided an impeccable correlation with the conventional four day CBR strength test method. The equation, similarly to other test methods such as DCP, provides a rapid and accurate way to determine the CBR of weaker materials. Ordinarily, the Maximum Dry Density (MDD) and CBR test alone would take five days to complete and the proposed formula shall drastically reduce that turnaround time as it manages to remove the entire four day soaking period. This means the CBR of such materials can be confirmed in two days, the same day as the actual MDD.
Civil and environmental research, 2014
Adsorption by activated sludge which plays a significant role in substrate removal has received a... more Adsorption by activated sludge which plays a significant role in substrate removal has received a lot of recognition. A number of studies have been conducted into understanding this mechanism. However, the impact of activated sludge preservation on the adsorption capacity test results has not been documented. Live activated sludge is usually preserved after sampling to maintain the original sludge characteristics in order not to alter its adsorption capacity. Preservation of the sludge is relevant when the sludge has to be transported over long distances before adsorption experiments can be conducted. This paper seeks to present the effects of preservation of activated sludge on its adsorption capacity. The preservation methods considered were pre-aeration and coldstorage of the sludge. Sludge samples were pre-aerated for periods of 4 and 24 hours at room temperature and some were stored at 4⁰C for 6 hours. Adsorption batch experiments were then carried out on both fresh and preserved activated sludge samples. Glucose was used as an external substrate in these experiments. The results revealed a difference between the adsorption capacity of the fresh and preserved sludge samples. Sludge preaeration increased the adsorption capacity of the sludge. There was however, no significant difference in the adsorption capacities for 4h and 24h pre-aerated sludge samples. Adsorption capacity of the 6h cold-stored activated sludge was poor compared to that of the fresh sludge.
Groundwater Level Trend Analysis and Prediction in the Upper Crocodile (West) Basin, South Africa
Disasters related to climate change on our water resources are on the rise in terms of scale and ... more Disasters related to climate change on our water resources are on the rise in terms of scale and severity. Therefore, predicting groundwater levels (GWL) is a crucial means to aid adaptive capacity towards disasters related to climate change in our water resources. In this study Gradient Boosting (GB) regression modelling approach for GWL prediction as a function of rainfall and antecedent GWL is used. Firstly, we sought to demonstrate the effects of rainfall changes on our groundwater resources through a Mann-Kendall trend analysis. Secondly, we evaluated the relationship between the input and response variables and determined the optimal lag times between the variables using autocorrelations and cross-correlations. Lastly a predictive model was developed for eight groundwater stations in the Upper Crocodile. 50 % of the groundwater stations revealed declining trends, while 25% had no trends and the other 25% showed an increasing trend. Generally low cross-correlation maximum (CCma...
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Papers by Julius Ndambuki