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.

No description available.

No description available.

Crop production systems which utilize the biomass produced by rye (<i>Secale cereale</i> ) to suppress weed growth and conserve soil moisture have been developed at Virginia Tech. The success of alternative, reduced-input crop production systems has encouraged research into the potential for breaking the traffic-tillage cycle associated with conventional tillage crop production systems. The fragile residues encountered in agricultural crop production, whether incorporated into the soil or distributed on the soil surface, provide minimal protection against compaction by wheeled vehicles. The potential of an intact cover crop to reduce machine-induced effects on soil properties that affect primary crop growth was the subject of this study. A randomized complete block experiment was conducted at the Whitethorne Farm in Montgomery County, Virginia. One set of plots was arranged on a terrace adjacent to the New River in a fine, mixed, mesic, Aquic Argiudolls. Another set of plots was arranged on an upland site, a river terrace tread, in a fine-loamy, mixed, mesic, Typic Hapludults. Three rye cover crop treatments were examined. In one, a live cover crop was completely undisturbed prior to tracking by a wheel-type tractor. In another, the cover crop was chemically desiccated, and in the third treatment, all above-ground biomass was removed from plots prior to machine traffic. The treatments permitted investigation of the effects of crop condition on machine-induced soil compaction and the contribution of root reinforcement to the alteration of soil response to machine traffic. A fall-tilled fallow treatment served as an experimental control. Three levels of traffic were investigated: one pass, three passes, and five passes. Undisturbed soil core samples were analyzed to determine machine-induced effects on dry bulk density, pore size distribution, and saturated hydraulic conductivity. The treatments affected soil response to machine traffic. The cover crop treatments altered the soil-plant microenvironment, affecting soil parameters that influence compactibility. Soil compaction was attenuated by the reinforcing effect of a network of undisturbed roots within the soil. There was no convincing evidence that above-ground biomass contributed directly to the reduction of machine-induced compaction effects. Soil response to machine traffic was limited to the uppermost 15 cm of the soil profile. / Ph. D.

M.S.

The main purpose behind this thesis was to study the variations of strength in a soil after it had been stabilized with various percentages of lime, cement, and combinations of the two. In both cases where the additives were added separately to the soil, the percentages used were 5 and 10 per cent by dry weight of soil. In the additive combination study, lime-cement percentage additions were 2-3, 3-2, 4-6, and 6-4 by dry weight of soil. The first two percentages, when added together, amount to 5 per cent stabilizing agent, while the latter two total 10 per cent. Since these two totals were the same as those used in the separate lime and cement studies, an analysis of strength changes when lime, cement, and lime-cement combinations were added to the soil could be made. Strength studies which were made consisted of unconfined compression immediately after compaction and after a four-day curing period in a 100 per cent humidity curing room. Atterberg limit tests were also run at the various percentages of additive. The laboratory test results indicate: 1. For cured specimens containing a stabilizing agent, the greatest four-day strengths will occur at or above OMC, in most cases. This may not always be true in the case of cement, since moisture condition is not as significant in cement stabilization as it is in other types. 2. Control of moisture at or near OMC during field compaction appears to be much more important in lime stabilization than in cement stabilization if maximum strengths are to develop. This statement is supported by a statistical analysis which was performed on the strength data. 3. The variation of' the lime-cement percentage trom 6-4 to 4-6 has no effect on four-day cured strengths. / M.S.

Master of Science

The main objective of this study was twofold: 1. To determine the effect of freezing and thawing on the loss in strength of lime-soil mixture. 2. To investigate the effect of the addition of an air entraining agent on the freezing and thawing durability of lime-soil mixtures. For the first part, twelve specimens were prepared for each of 0, 5, 10, 15 and 20 percent combination of lime-clay mixture, giving a total of 60 specimens. For the second part, twelve specimens were prepared for each of 0, 5 and 10 percent of lime, giving a total of 36 specimens. Those containing five percent were treated with 4, 6, 8, 10 and 12 drops of air entraining agent for each two specimen batch, while those containing 0 and 10 percent were treated with 4, 7, 10, 15 and 20 drops. All specimens were wrapped with aluminum foil and immediately sealed with paraffin and cured for two days at 120°F. Control specimens were placed in the 70°F environment for ten days while companion specimens underwent five and ten cycles of freezing and thawing. The results of this study indicated the following: 1. Addition of lime increases the strength of clay soil. 2. Maximum percent increase in durability of clay soil found to occur with addition of ten pero.ent lime. 3. The decrease in strength due to freezing and thawing mainly occurred during the first five cycles. 4. Seven drops of air entraining agent gave maximum strength of air entrained specimens. / Master of Science

Research was conducted to study the unconfined compressive strength of a mica soil stabilized with various percentages of lime, Portland cement, and combinations of calcium hydroxide and calcium carbonate. In order to trace the calcium carbonate and calcium hydroxide in the stabilized soil, x-ray diffraction analyses, differential thermal analysis, and thermagravimetric analyses were made. Results show the appearance of calcium carbonate and absence of calcium hydroxide. / Master of Science

The influence of calcium carbonate on the properties of four non-plastic lime-stabilized soils was studied. The four soils span a range in mica content and sand content. It was found that carbonate generally increased unconfined compressive strength and secant modulus of elasticity when included as part of the lime stabilizing agent. This effect was most pronounced with soils with a large sand content and low mioa content. A calcium hydroxide-calcium carbonate weight ratio of 3 to 1 was most effective for the case where six percent additive was used. It is hypothesized that the presence of carbonate enhances pozzolanic activity in lime-stabilized non-plastic soils by increasing the solubility of siliceous minerals at high pH levels. / Master of Science