scispace - formally typeset
Search or ask a question
Author

Samson Ngambi

Other affiliations: Gifu University
Bio: Samson Ngambi is an academic researcher from Coventry University. The author has contributed to research in topics: Cement & Cementitious. The author has an hindex of 11, co-authored 28 publications receiving 272 citations. Previous affiliations of Samson Ngambi include Gifu University.

Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, the authors revisited the problem of sudden packing transition from a micro-physico-mechanical viewpoint (i.e. collapse imetan terms of structure-based effective stress).

44 citations

Journal ArticleDOI
TL;DR: RoadCem (RC) is an additive produced based on nanotechnology and comprises of synthetic zeolites and alkali earth metals as some of its components as discussed by the authors, and the geotechnical properties of a soil stabilized by adding RC to partly replaced cementitious materials are studied.
Abstract: RoadCem (RC) is an additive produced based on nanotechnology and comprises of synthetic zeolites and alkali earth metals as some of its components. The geotechnical properties of a soil stabilized by adding RC to partly replaced cementitious materials are studied. Various combinations of the additives were investigated with the objective of reducing the amount of OPC by 50% by an inclusion of RC and ground granulated blast furnace slag (GGBS) in the stabilized soil. Laboratory studies involving index property testing, oedometer swell-deformation, unconfined compression tests and microstructural examinations were carried out on both the natural and 7-& 28- day cured samples of the stabilized soil. The influence of RC on the mechanical properties of the stabilized soil was examined by comparing the performance of the stabilized soil mixtures that contain the RC and the mixtures without the RC added. Results indicated the positive effect of RC as noticed by the tremendous strength gain in 7 days with the OPC reduced by 50% in the stabilized soil. Swelling decreased significantly to 0% after 28 days curing with the settlement also reasonably reduced for nearly all the percentages of the OPC substituted. The stabilized soil’s microstructure revealed the mechanism of cementation observed as an encapsulation or “wrapping effect” as a result of the presence of RC. A comparison of the RC-modified soil containing the by-products GGBS and PFA indicated that GGBS was more effective in the enhancement of engineering properties than PFA. Overall, as well as meeting some of the standards set for road pavement applications, the results obtained from this research are very promising for the ongoing discussions on reducing carbon foot-printing by OPC replacement.

42 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of high plasticity on swell potential, swelling pressure and micro-structural characteristics of kaolinite-bentonite mixed clays was presented, and the results showed that reduction in plasticity index resulted in decreased swell potential and swelling pressure of the mixture.
Abstract: This study presents the effect of high plasticity on swell potential, swelling pressure and micro-structural characteristics of kaolinite-bentonite mixed clays. Five different mix ratios of kaolinite bentonite mixture of 100:0, 90:10, 75:25, 50:50 and 25:75 in % by weight of dry kaolinite were used. All five synthesised soils were then mixed with 0%, 5% and 8% of cement by weight of dry soil, cured for 28 days and subjected to the Atterberg limit, one-dimensional oedometer and scanning electron microscope test. The inclusion of 5% and 8% cement reduces the plasticity index of the treated soils as the percentage of bentonite increases. The effects on plasticity of treatment with 5% and 8% cement after a 28-day curing period was evaluated, and the results show that reduction in plasticity index resulted in decreased swell potential and swelling pressure of the kaolinite-bentonite mixed clays. The results of microstructural analysis of 5% cement-treated soils show formation of flocculated fabric and cementation of soil particles, and filling with cementitious compounds of the voids of flocculated fabric in the soil. The reduction in swell can be attributed to the resulting compacted and dense mass of treated soils due to cementation of soil particles and cation exchange. The complex swell behaviour of high-plasticity kaolinite-bentonite mix is explained using the one-dimensional oedometer test, by further experimental study and examination of the microstructure of treated soils.

36 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the unconfined compressive strength (UCS) of weak soil materials for construction purposes, and developed mathematical and graphical models for prediction of UCS for use in design and construction.
Abstract: This paper presents the possible inclusion of pulverized fuel ash (PFA) and ground granulated blast slag (GGBS) in cement deep soil mixing for enhancement of unconfined compressive strength (UCS) of weak soil materials for construction purposes. The main focus of this paper was to investigate the UCS of cement-, cement/PFA- and cement/PFA/GGBS-improved soils, and development of mathematical and graphical models for prediction of UCS for use in design and construction. Samples of cement, blends of cement and PFA, and cement/PFA/GGBS were prepared using 5 %, 10 %, 15 %, and 20 % by weight of dry soil and tested for UCS after 7, 14, 28, and 56 days. A multiple regression analysis was conducted using the SPSS computer program. The results showed that soil materials with lower plasticity show higher strength development compared to those of higher plasticity for cement improvement. The study has also revealed that the inclusion of PFA and GGBS can cause a reduction in the amount of cement in deep soil mixing, which can result to reduced cost and emission of carbon dioxide (CO2) during construction. The developed mathematical and graphical models could give reliable predictions of UCS for weak soil materials with initial UCS less than or equal to 25 kPa and for water to binder ratio of unity based on the observed agreement between experimental and predicted data. The developed multiple regression models have also been validated using different mixtures of 6 %, 8 %, 12 %, and 16 % of binders.

33 citations

Journal ArticleDOI
TL;DR: In this paper, a detailed examination of the core mineralogy, microfabric, grain size and suction response of expansive clays during moisture ingress can be explained by an examination of their core mineralogical properties.
Abstract: The complex swelling mechanism in expansive clays during moisture ingress can be succinctly explained by an examination of their core mineralogy, microfabric, grain size and suction response. This note has attempted to investigate these influential factors on five different expansive clay samples to enable further understanding of swell behaviour. Laser diffractometry tests were performed on the expansive clays to determine the clay-sized particle structure (

28 citations


Cited by
More filters
01 Apr 2009
TL;DR: In this paper, a conceptual model is presented for the provenance and dispersal patterns of small dust that falls on Europe, and three simple deposition zones can be recognized; a D1a zone where sufficient dust is deposited to form a discrete soil layer (not well classified as a Rendoll), in the extreme south of Europe; the D1b zone where the airborne dust simply provided a silty admixture to soil systems across Middle Europe; and a northern zone D1c where the dust is a fugitive cloud, but very occasionally forms noticeable deposits.
Abstract: Abstract A conceptual model is presented for the provenance and dispersal patterns of small dust that falls on Europe. Generally its sources are in North Africa, and it is distributed across all Europe. Several key sources can be distinguished: ‘Sahelian’ dust comes largely from the old Lake Chad region—this is a clay-rich unimodal material. ‘Saharan’ dust comes from the great sand sheets—it contains small monomineralic particles and may have a bimodal size range. Three simple deposition zones can be recognised; a D1a zone where sufficient dust is deposited to form a discrete soil layer (not well classified as a Rendoll), in the extreme south of Europe; a D1b zone where the airborne dust simply provided a silty admixture to soil systems—across Middle Europe; and a northern zone D1c where the dust is a fugitive cloud, but very occasionally forms noticeable deposits. Two particle formation methods can be noted. Particle control in Sahelian dust is via the sedimentation in the original lake. This gives an open structure which can be modelled using a simple Monte Carlo approach. The open structure ensures that only small particles are produced; size control is via particle packing. A chipping mechanism can produce fine quartz particles from sandy deserts. The aeolian energy is, by and large, not sufficient to cause major impact fracturing but small mineral chips can be produced in the small dust size (fine and very fine silt), which go into high-level suspension and travel to Europe and beyond. The Saharan material can have a wider, more variable size distribution than the Sahelian material. The Canary Islands ‘loess’ is largely Sahelian material; the Cape Verde Islands deposits, from the nearby sandy regions, are Saharan deposits. Large dust has fallen on Europe, and produced widespread loess deposits. Large dust is essentially an ‘in-continent’ deposit; small dust comes from outside—from Africa.

155 citations

Book
01 Jan 1999
TL;DR: In this article, the authors present a collection of reports written by about 35 internationally recognized authorities, covering a range of interests for geotechnical engineers, including fundamentals for mechanics of granular materials, continuum theory, and discrete element approaches.
Abstract: This textbook compiles reports written by about 35 internationally recognized authorities, and covers a range of interests for geotechnical engineers. Topics include: fundamentals for mechanics of granular materials; continuum theory of granular materials; and discrete element approaches.

113 citations

Journal ArticleDOI
TL;DR: In this article, the potential for effective loess stabilization using nanoclay, an engineered nanomaterial, both in the laboratory and in the field at the Gonbad dam irrigation channel site was investigated.

101 citations

01 Jan 2016
TL;DR: The the foundation engineering handbook is universally compatible with any devices to read and is available in the digital library an online access to it is set as public so you can get it instantly.
Abstract: Thank you very much for downloading the foundation engineering handbook. As you may know, people have search numerous times for their favorite readings like this the foundation engineering handbook, but end up in infectious downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they cope with some harmful bugs inside their desktop computer. the foundation engineering handbook is available in our digital library an online access to it is set as public so you can get it instantly. Our book servers spans in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Merely said, the the foundation engineering handbook is universally compatible with any devices to read.

87 citations