This research investigated the chemistries and mechanisms involved in lead-cement systems through the study of a larger number of lead compounds.

After a major flooding disaster, construction materials will be scarce during early recovery stages and any material of reasonable quality would be useful. Instead of importing higher quality material from sites a considerable distance away, on-site material may be useable. This thesis explores usage of specialty portland cements, and in some cases polymer fibers, as stabilization additives to fine grained soils with elevated moisture contents. The primary objective of this thesis is to develop strength, modulus, and ductility trends for a variety of soil types, cementitious materials, cementitious material contents, and moisture contents, and to use the data to compare specialty grind portland cements to commercially available portland cement from the same production facility. The secondary objective is to evaluate the effect of polymer fibers combined with portland cement for the same mixtures. Over 1300 Unconfined Compression (UC) tests were conducted to complete these two objectives.

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Three main objectives have been set for this research. The first is to develop an accurate method for measuring the dielectric constant of PCC using a capacitor probe (C-Probe) that has been recently developed at Virginia Tech and validate it for field application to detect internal PCC flaws such as delamination. The C-Probe consists of two flexible conducting plates, connected to a Network Analyzer, with a specific separation between them. The second is to optimize the C-Probe design configuration for different PCC slab thicknesses. The third objective is to develop a predictive model that correlates the bulk dielectric constant of PCC with its critical parameters (cement, aggregate, and air content). Five calibration methods have been developed and evaluated for the C-Probe to measure the dielectric properties of PCC. This evaluation has demonstrated that open, short, Teflon material (OSM) calibration method is the most appropriate one for the C-Probe. The selected calibration method was used to validate the C-Probe fixture for field application by measuring 1.5 x 1.5 m PCC slabs prepared with different mix properties, thicknesses, and induced deterioration. The C-Probe has been proved to detect induced voids in the PCC slabs. In addition, the effect of steel reinforcement on measurements can be mastered by controlling the penetration of electromagnetic (EM) field in the PCC slabs. The effective penetration depth of the EM field for different C-Probe design configuration was optimized by computer simulation. The results have been used to develop a predictive model that correlates the effective penetration depth with the plates' size, separation between them, and the dielectric constant of the PCC under test. Thus, an optimum design for different desired penetration depth was achieved. Two experimental designs were developed to identify the critical parameters that affect the bulk dielectric constant of PCC. A computer simulation was used to identify the significance of each parameter. A predictive model has been developed to correlate the PCC bulk dielectric constant to the critical parameters. The estimated dielectric constant of PCC using the predictive model was correlated to that obtained by other theoretical mixture models; the predictive model has found to correlate well with Looyenga theoretical mixture model. / Ph. D.

In view of the fact that prestressed concrete is extensively used in bridge construction and that it holds potentialities for eventual use in pavement construction, and that methods must be investigated to utilize an otherwise rejected aggregate which cannot be used for its poor performance under natural weathering, it has become of paramount importance that further efforts be made to evaluate the effect of prestressing on the durability of concrete. The purpose of this thesis was twofold: 1) To study the durability of prestressed concrete made of poor-performing aggregate; 2) To compare the freezing and thawing effects on prestressed concrete with those on ordinary concrete. Two mix designs having different proportions of poor performing aggregate were used in this study. Half the number of specimens were post-tensioned after they had been cured for a period of 13 to 18 days in water, and were then replaced in the curing room for 24 hours, Level of prestress was 600 psi. Before transferring the specimens - both prestressed and non-prestressed - into freezing and thawing apparatus, they were tested for fundamental transverse frequency and initial weight and length measurements were recorded. Thereafter, transverse frequency, weight, length change and temperature change measurements were made periodically. The relative dynamic modules of elasticity and durability factor were then calculated for each specimen. On the basis of the results furnished by these tests, it may be concluded that prestressing improves the durability of concrete made of poor performing aggregate and that the magnitude of improvement in the durability ef concrete tends to diminish with increasing proportion of good performing aggregate. / Master of Science

The results of this investigation may serve as the basis for some conclusions with regard to the curing of Portland cement concrete. Some of the more important conclusions are as follows l. A concrete, if it may be classed as such, consisting of fine aggregate, cement, and water, is not subject to the extreme effects of freezing as is a true concrete containing a coarse aggregate. 2. Maximum loss of strength, which is evidently long-enduring is suffered by concrete frozen in an extremely green stage when frost enters mortar paste. 3. Freezing may be harmful at any time within the first week. However, in most cases a recovery is indicated. 4. Steam curing, if not carefully controlled at optimum conditions, will result in loss of strength in a concrete. 5. The expansion and drying which occur at the temperatures in the steam chamber apparently are the cause of harmful results in steam.curing. It must be borne in mind that the limitations of data gathered make these conclusions more indicative than conclusive. There is still much room.for further research at this institution along the line of both problems presented herein. / Master of Science

Based on the results of this investigation certain conclusions were arrived at relative to Portland cement concrete using Dolomitic limestone sand as the fine aggregate. The most important of these are as follows: 1. Fresh concrete continues to gain strength while in the frozen state. 2. Freezing and then thawing of fresh concrete does not have an appreciable effect on the twenty-eight day ultimate strength, and the concrete, if given time to recover, will compare favorably with concrete cured under normal conditions. 3. Freezing of concrete immediately after pouring has a greater effect on the twenty-eight day ultimate strength of the concrete than has freezing for the same period at a more advanced age within the twenty-eight days. 4. Concrete cured at 65°C. tends to increase its twenty-eight day ultimate strength, providing the water lost through evaporation is replaced. 5. High early strength concrete can be obtained by curing ordinary Portland cement concrete at high temperatures. Based on the results of compression tests performed in this investigation, Dolomitic limestone sand has been found to be satisfactory as the fine aggregate for Portland cement concrete; verifying what Messrs. Broyles and Brown had said in 1936 and 1937 respectively. What has been done in the way of concrete research at Virginia Polytechnic Institute is satisfactory for relatively new concrete using Dolomitic limestone sand as the fine aggregate; but it is wondered how this concrete will stand up over a long period of time. Professor Hartman and Dr. Holden have inaugurated some long time studies at the Institution, but there is still much room for further investigation. Dolomitic limestone rock has proven itself worthy when used as the coarse aggregate for Portland cement concrete. It is up to time and future research to prove the worth of its sand used as the fine aggregate. / Master of Science

University of Stellenbosch Business School / The objective of this study is to determine whether brands create value for shareholders and the extent to which such value can be quantified. The research methodology is based on a case study of Pretoria Portland Cement, South Africa’s leading cement producer, and seeks to demonstrate how a commodity like cement can be successfully differentiated and branded. Primary data was gathered by conducting unstructured interviews with business leaders and key personnel involved with the development and execution of the company’s brand vision. Secondary data is based on the results of a customer loyalty survey by IPSOS Markinor as well as on customer perceptions from Millward Brown’s BrandDynamics™ model. The results of both these surveys, together with historic market share data and the company’s financial performance over a 15-year period, is analysed and interpreted before conclusions are made about the brand’s contribution to value creation. The study concludes by attempting to make generally applicable findings about the value of brands and their overall contribution to shareholder value. One of the major limitations of the study is the inability to assign a definitive value to the PPC brand because of the vast number of credible brand valuation models available and the lack of consensus among academics and industry experts regarding the determination of brand value.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy