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  1. Home
  2. Browse by Author

Browsing by Author "Marangu, Joseph M."

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    Characterization of composite material from the copolymerized polyphenolic matrix with treated cassava peels starch
    (Heliyon, 2020-07) Kariuki, Stephen W.; Wachira, Jackson M.; Kawira, Millien; Murithi, Genson L.; Marangu, Joseph M.
    Conventional binders in the particleboards formulation involve use of formaldehyde resins. Epidemiologic studies show that formaldehyde is carcinogenic. Efforts to reduce formaldehyde emissions by use of scavengers has not been proven to reduce the emission. Molecular bonding of biobased adhesive molecules with lignocellulose materials provides an alternative way of producing composite material. In this study, maize stalk (MS), rice husks (RH) and sugarcane bagasse (SB) were used as sources of lignocellulose materials for particleboard formulation. SB, MS and RH were collected from their respective sites, sorted and dried. MS and RH were ground. Lignin content determination was done by drying lignocellulose material at 105 C. Lignocellulose materials were prepared by hydrolysis of dried lignocellulose material with sodium hydroxide. Oxidized starch was prepared by oxidation of cassava peel starch using alkaline hydrogen peroxide. Particleboards were formulated through starchlignocellulose polymerization at 60 C compressed with 6.5 Nmm 2 pressure. Characterization of raw materials and formulated particleboards was done using XRD for mineralogical analysis, FTIR and NMR for elucidation of functional groups transformation. The results showed that esterification is the main process of chemical bonding in the particleboard formulation due to reaction between COOH from starch and and OH- from lignocellulose. Etherification between hydroxyl groups from starch with hydroxyl groups from lignocellulose material. RH combined more through silication process with cassava peels starch than RH and SB showing materials containing high cellulose and hemicellulose content are more compatible. Composite materials formulated were used to produce medium density particleboards that can be used for making furniture and room partitioning.
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    Physicochemical Performance of Portland-Rice Husk Ash-Calcined Clay-Dried Acetylene Lime Sludge Cement in Sulphate and Chloride Media
    (Hindawi, 2019-03) Wachira, Jackson M.; Thiong’o, Joseph K.; Marangu, Joseph M.; Murithi, Leonard G
    This paper reports leach and/or intake of SO42−, Cl−, Ca2+, Na+, and K+ from and/or into cement mortar cubes made from a novel cementious material in naturally encountered environmental simulated media. The paper also reports changes in pH of the media over time of exposure to the cement mortar cubes. The compressive strength changes of the test cement in simulated media are also reported. The novel cement, labelled PCDC, made from intermixing ordinary Portland cement (OPC) with waste materials which included rice husks, waste bricks, acetylene lime sludge, and spent bleaching earth was previously tested and found to meet the Kenyan Standard requirements for Portland pozzolana cement (PPC). 100 mm mortar cubes were prepared, and their compressive strengths were determined after exposure to the sea water. The media included sea water, distilled water, and solutions of sulphates and chlorides separately for a period of six months. The tests were carried alongside commercial PPC and OPC. The results showed that the PCDC exhibited comparable selected ions intake and/or leach to PPC in sea water, sulphate solutions, and distilled water. In chloride solutions, the cement exhibited the highest leach in the selected ions except K+ and Na+ ions. The results further showed that PCDC exhibited lower pH in all the media compared to OPC and PPC. The tests showed that the novel cement can be used for general construction work in the tested media in a similar manner to PPC.
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    Properties of activated blended cement containing high content of calcined clay
    (Elsevier, 2018-08) Marangu, Joseph M.; Karanja, Thiong’o J.; Wachira, Jackson M.
    This paper presents findings of an experimental investigation on sodium sulphate (Na2SO4) activated calcined clay e Portland cement blends in sulphuric acid media. Calcined clays were blended with Ordinary Portland Cement (OPC) at replacement levels of 40% 45% and 50 % by mass of OPC to make blended cement labelled PCC40, PCC45 and PCC50 respectively. Initially, pozzolanicity and setting time tests were conducted. Mortar prisms measuring 40 mm 40 mm 160 mm were cast using 0.5M Na2SO4 solution and their compressive strengths determined on the 2nd, 7th, 28th and 90 th day of curing. The 28th day cured mortar prisms were subjected to porosity test. Moreover, 5 5 5 cm mortar cubes were also prepared and their weight and strength loss was taken as a measure of their acid resistivity after an immersion time of 7, 14, 28, 56, 84 and 120 days in 3 % of sulphuric acid at 23 1 C. OPC, commercial Portland Pozzolana Cement (PPC) and PCC40, PCC45 and PCC50 cement were cast using water and similarly investigated for comparison purposes. The results obtained showed that chemically activated cements exhibited higher pozzolanic activity, lower porosity, shorter setting times and higher resistance to acid attack compared to non-activated cements. However, OPC was found to be non-pozzolanic.
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    A Review on Pyroprocessing Techniques for Selected Wastes Used for Blended Cement Production Applications
    (Hindawi, 2020-08) Nalobile, Protus; Wachira, Jackson M.; Thiong’o, Joseph K.; Marangu, Joseph M.
    Pyroprocessing is an important stage in cement manufacturing. In this process, materials are subjected to high temperatures so as to cause a chemical or physical change. Its control improves efficiency in energy utilization and hence enhances production for good quality assurance. Kilns used in cement manufacturing are complex in nature. *ey have longer time constants, and raw materials used have variable properties. *ey are therefore difficult to control. Additionally, the inclusion of various alternative fuels in burning makes the process more complex as the fuel characteristics remain inconsistent throughout the kiln operation. Fuel intensity standards for kilns using fuel oil are very high, ranging from 2.9 GJ to 7.5 GJ/ton of clinker produced. Grinding of clinker consumes power in the range of 2.5 kWh/ton of clinker produced. *ese and other pyroprocessing parameters make cement production costly. *e pyroprocessing process in kilns and the grinding technologies therefore have to be optimized for best processing. *is paper discusses the cement manufacturing and grinding processes. *e traditional kiln technologies and the current and emerging technologies together with general fuel and energy requirements of cement manufacturing have been discussed. From the discussion, it has been established that the cement manufacturing and grinding technologies are capitalintensive investments. *e kiln processes are advanced and use both electricity and natural fuels which are expensive and limited factors of production. *e raw materials used in cement manufacturing are also limited and sometimes rare. *e calcination of the raw materials requires external energy input which has contributed to the high cost of cement especially to low-income population in the developing countries. Self-calcining materials, in which the pozzolanic materials burn on their own, are potential pozzolanic materials with great potential to lower the cost of cement production. Such materials, as shown from the previous research study, are rice husks, broken bricks, spent bleaching earth, and lime sludge. *ere is a need, therefore, for research to look into ways of making cement using kiln processes that would use this property. *is will be cost-effective if successful. It can be done at microand small-scale enterprise.

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