CO2 absorption behaviour of four commonly used cement based building products: cement paste, concrete block, expanded polystyrene bead (EPB) and cement-bonded cellulose fiberboard are studied. Cement products are manufactured following industry formulation and process, and carbonation curing takes place in a chamber under a pressure of 0.5 MPa, at ambient temperature, for durations of mostly 2 to 8 hours with both pure carbon dioxide gas and flue gas. The flue gas of 13.8% CO2 content is collected from a typical cement kiln without separation. Influencing factors on carbon uptake, long-term strength as well as microstructure development are studied. / It is found that the CO2 uptake ability of those cement-based products follows the same order when exposed to either pure gas or flue gas: fiberboard has the highest uptake capacity, followed by cement paste, bead board and concrete. For fiberboard, the best CO2 uptake in flue gas is 8.1%, it reaches 23.6% if pure gas used. Introduction of cellulose fiber in the fiberboard significantly increases voids volume and cement paste surface area through dispersing the paste onto fiber surface, effectively increasing carbonation reaction sites and thus CO2 uptake. / For pure gas carbonation with high reaction rate, it takes longer time for carbonated products to further develop strength from subsequent hydration, due to the high water loss during carbonation, the densified cement matrix structures and even fast decalcified cement minerals. Fast carbonation with pure gas is detrimental to cement paste in its long-term strength. For flue gas carbonation, both immediate strengths and long-term strength of the products are comparable with those by pure gas carbonation, although with less CO 2 uptake ability. / Five CO2 uptake determination methods are evaluated. Weight gain method is suitable for both pure gas and flue gas carbonation systems. Mass curve method is more suited for pure gas carbonation. For flue gas carbonation, CO2 concentration method agreed well with the weight gain method. Pressure drop method is relatively less accurate because of water vapor generation during carbonation.

Carbonation curing of concrete products has shown potentials for CO2 capture and storage with environmental, technical and economical benefits in global greenhouse gas mitigation exercise. The primary objective of this study is to investigate the effect of early age carbonation on mechanical performance and pH of concrete in an attempt to understand the process and promote large scale applications. / It was found that significant early strength was developed in cement and concrete through early age carbonation curing. The early strength could be maintained and improved due to subsequent hydration. Twenty-eight-day strength of carbonated cement and concrete was comparable to that of hydrated reference if subsequently cured in the air in a sealed bag, but was lower if subsequently cured in water. Treatment with either internal curing using lightweight aggregates or chemical admixture can effectively enhance late strength development in carbonated concrete. / For three typical cement-based products including cement paste compacts, concrete compacts and precast concrete, two-hour carbonation reduced pH value from 12.8 to 11.8 as the lowest and subsequent 28-day hydration could slightly increase pH by 2% as maximum. At any time pH of early age carbonated concrete was always higher than 11.5, a threshold value under which the corrosion of reinforcing steel is likely to occur in concrete. The high pH in early-age carbonated concrete was likely attributed to the fact that early age carbonation was an accelerated hydration process, which was totally different from weathering carbonation in which pH of concrete could be neutralized due to the decomposition of calcium hydroxide and calcium silicate hydrates gel. Therefore, early age carbonation technology is applicable not only to concrete products such as masonry units and paving stones, but possibly to precast concrete with steel reinforcement as well.

Thesis (Ph.D) -- University of Western Sydney, Nepean, 1997. / Bibliography : Appendix IV, p. ii-vi.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 117-121). Also available via the Internet.

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Jacobs, Laurence J.; Committee Member: Kim, Jin-Yeon; Committee Member: Qu, Jianmin. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (M.Eng.(Civil and Biosystems Engineering))--University of Pretoria, 1985. / Summaries in Afrikaans and English. Includes bibliographical references.

Thesis (MScFor)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: This research focuses on the utilisation of de-inking sludge from a tissue mill to produce a wood-fibre inorganic composite called the Deviro panel. The study is based on the SA provisional patent 95/9594 by Ysbrandy and Gerischer' and the further research conducted by Crafford'. The patented Deviro panel contains up to 70% de-inking sludge. Cement and a cement extender serve to fortify the composite. The panel's fibre content of 25-30% is significantly greater than encountered in commercial fibre inorganic composites which contain 8-12% fibre by weight. The physico-mechanical characteristics of the Deviro panel compare favourably with resin bonded wood-fibre composites, but less favourably compared to conventional wood and wood-fibre inorganic composites. These properties are strongly dependent on panel density. For instance flexural strength being directly proportional while dimensional stability and hygroscopicity being inversely proportional to density. After confirming the results from the preceding work by Crafford, further improvements were investigated through chemical and curing enhancements. For instance, an autoclaving treatment during the curing period showed an increase in flexural strength. Addition of water glass could be associated with bulking of the panel, which resulted in increased flexural strength and a slight reduction of density. Panel density could be significantly reduced by the addition of Perlite, while inhibiting the concomitant reduction in strength. In addition a pilot production process was developed to produce 1m2 panels, which exhibited similar curing characteristics as the smaller panel units. / AFRIKAANSE OPSOMMING: Hierdie navorsing handeloor die gebruik van ontinkingsslyk van 'n sneespapier meule om die Deviro paneel, 'n houtvesel anorganiese saamgestelde produk, te produseer. Die studie volg uit die SA voorlopige patent 95/9594 deur Ysbrandy en Gerischer en verdere narvorsing deur Crafford'. Die gepatenteerde Deviro paneel bevat tot 70% ontinkingsslyk. Sement en sement-byvoegmiddels dien om die saamgestelde produk te versterk. Die paneel bevat 25-30% vesel wat aansienlik meer is as ander kommersiële anorganiese saamgestelde produkte wat 'n vesel inhoud van 8-12% het. Die megamese eienskappe van die Deviro paneel is vergelykbaar met houtvesel saamgestelde produkte waar hars as kleefiniddel dien, maar vergelyk minder gunstig teenoor konvensionele hout en houtvesel anorganiese saamgestelde produkte. Die paneel se eienskappe is afhanklik van sy digtheid Buig sterkte is eweredig terwyl dimensionele stabiliteit en hygroskopisiteit omgekeerd eweredig aan die digtheid van die paneel is. Die voorafgaande werk van Crafford is eers gestaaf voordat veranderinge aan die chemiese samestelling en drogingsmetodes van die paneel nagevors is. Daar is byvoorbeeld bevind dat, deur die paneel te outoklaveer gedurende die set periode, dit lei tot 'n toename in buig sterkte. Die byvoeging van water glas kan swelling laat plaasvind wat 'n afname in buig sterkte en 'n afname in digtheid tot gevolg het. Digtheid kan ook aansienlik verlaag word deur die byvoeging van Perlite terwyl 'n dienooreenkomstige verlaging in buig sterkte tot 'n mate voorkom word. 'n Loods produksie proses is ook ontwikkel om 'n 1m2 paneel te vervaardig wat dieselfde eienskappe toon as die kleiner paneel.

In this dissertation the effects of different types of Pulverized Fuel Ash (PF A)-types on the workability of cementitious pastes containing relative large amounts of PF A were investigated. The different types of PF A were produced at the same source thus they were chemically similar but differed in terms of average particle size and size distribution (grading). By using a two-point measurement technique based on flow through a J-shaped tube it was possible to detect relative small differences in workability between pastes. It was found and concluded that the different types of PFA had a significant effect on the workability of pastes containing cement and PFA as well as PF A alone. The physical differences between the PF A-types were quantified and their effects on workability investigated. It was concluded that PF A with a broader particle size distribution range produced pastes with higher workability at constant water content. It was found that compressive strength as measured after 28 days were solely a function of the water/cementitious ratio for the curing regime employed. It was concluded that for curing conditions used the type of PF A used could have a significant effect on compressive strength when constant workability is required. / Dissertation (MSc (Transportation))--University of Pretoria, 2006. / Civil Engineering / unrestricted

No description available.

Thesis (PhD (Civil Engineering))--University of Stellenbosch, 2007. / ECC (Engineered Cement-based Composites) is a type of HPC (High Performance Concrete) that was engineered to overcome the weaknesses of ordinary concrete. It shows high ductility as it can resist the full tensile load at a strain of more than 3 %. This superior response is achieved with multiple cracking under tensile loading which has a pseudo strain hardening phenomenon as result. The purpose of the research project reported in this dissertation is to investigate and characterise the time-dependant behaviour of ECC and create a constitutive model to numerically simulate the static and time-dependant behaviour of ECC. To investigate the time-dependant behaviour experimentally, rate and creep tests were done on the meso- and macro-level while rate tests were done on the structurallevel. The meso-level was represented by the pull-out testing of fibres embedded in the cement-based matrix and direct tensile tests were done for the macro-level. Flexural tests on thin beams were done to simulate the structural-level. Strong time-dependant behaviour was found on all three these levels. On the meso-level, the most prominent finding is that the failure mechanism can change with a change of strain rate, i.e. fibre pull-out at a low pull-out rate, while with a high pullout rate, fibre rupture can occur. Even though the strength of a tensile specimen on the macro-level showed a dependence on the strain rate, the ductility remained constant over four orders of magnitude of the strain rate. On the structural-level, however, a reduction of the flexural ductility was found with an increase of the ...