Concrete used in pavements has to be durable to withstand the load and wear imposed by vehicles moving across it and the effects of drying shrinkage and thermal changes. Failure of the pavement by either excessive cracking or degradation of the surface results in poor riding quality and low skid resistance. The inclusion of Pulverised Fuel Ash (PFA), otherwise known as fly ash, generally improves the quality of pavement concrete and thus extends its useful life. The PFA used for the thesis was from the Lethabo power station's second electrostatic precipitator field (Lethabo Field 2 PFA). This Field 2 PFA has a very close resemblance to the expected classified commercial Lethabo PFA of the future. PFA is characterised by its fineness. The Field 2 PFA had 7.7 percent retained on the 45 micron sieve. This was considerably finer than the current commercial Matla PFA with about 12 percent retained. It was thus expected that the higher quality Lethabo Field 2 PFA could be used to produce higher quality concrete. The other mix materials were those commonly used in the Western Cape. The aggregates used were Cape Flats Dune sand and Malmesbury shale (hornfels). The dune sand typically has very little fines content, causing severe bleeding problems in normal concrete mixes. The crushed coarse aggregate was 13 mm and flaky in shape. Ordinary Portland cement (OPC) was obtained from the De Hoek cement factory. The investigation was carried out in two parts. First was the development of a wide range of mixes, varying 28 day design strength (10, 20, 30, 40, 50 MPa), percentage of PFA as part cement replacement (OPC only, 15% PFA, 30% PFA, 50% PFA and 70% PFA) and the coarse aggregate content to give under-, average- and over-sanded mixes. Over this wide range of mixes, the fresh properties and development of the compressive strength were observed. Secondly, properties affecting pavement quality concrete were observed on a similar range of mixes. These properties were flexural strength, surface wear resistance by wire brush, sand blasting and ball race abrasion and the drying shrinkage.

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Pavement concrete joints are the weakest locations in concrete pavement systems. They are man-made cracks to accommodate concrete slab expansion and contraction due to temperature fluctuations. Sealant is usually used in pavement joints to prevent roadway debris, deicing chemicals, and moisture from entering the joint. When sealant fails, the pavement deteriorates rapidly; and when joint sealant performs adequately, the pavement preserves its intended performance. In the field, joint sealant undergoes two types of mechanical loading simultaneously. The sealant is experiencing tension or compression as slabs contract (low temperature) or expand (high temperature), respectively. Sealants also experience shear as heavy trucks travel over the joint and deflect the ends of the pavement slabs. In addition, sealants may also be exposed to a variety of environmental conditions, such as moisture, ultraviolet light, and jet fuel, which in some cases could be detrimental to their performance. In this study, the effects of vehicular and environmental loading on joint sealant performance were evaluated. To simulate the sealed joint performance, specimens were constructed by sandwiching a sealant between two 50.8 mm Portland cement concrete (PCC) cubes. Prior to mechanical loading, specimens were subjected to partial immersion in distilled water, partial immersion in jet fuel, and/or exposure to UV-A light. The specimens were then subjected to static horizontal tension, simulating slab contraction, and cyclic deflection-controlled shear, simulating heavy trucks travelling over the joint. The cycle consists of one 0.2 second period of sinusoidal loading (total 6.4 mm deflection) followed by a 0.4 second relaxation. The mechanical loading was applied using a special fixture developed at Virginia Tech, which is connected to a closed-loop servo-hydraulic loading machine. Two types of sealants (preformed neoprene and field-molded silicone with a primer) were tested using PCC mixes with two different aggregate types. In, addition, two different joint widths were evaluated for each sealant type. From the results of the cyclic testing and environmental conditioning, it was shown that the use of a primer greatly enhances the performance of the silicone sealant used with concrete containing limestone aggregate. In addition, severe swelling occurs when silicone sealant is exposed to jet fuel, and the failure of the field-molded silicone initiated at the bottom of the sealant and propagated upward. The preformed neoprene sealants proved very durable despite any combination of environmental conditioning, provided that the sealant remained in compression. / Master of Science

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Typescript (photocopy). / Digitized by Kansas Correctional Industries

Thesis (M.S.)--Clemson University, 2006. / Includes bibliographical references (p. 133-136). Also available online.