Evaluation of an Improved Rotavapor Aging Apparatus Using a Morton Flask for Simulation of Hot-Mixing on Modified Asphalts

A modified Rotavapor apparatus and method had been previously developed at the Universityof Florida for simulation of short-term aging of modified asphalts. Due to the great potentialof this aging procedure, further refining of this procedure had been undertaken. This paperpresents the evaluation of an improved Rotavapor aging apparatus using a Morton flask. Itwas observed that greater temperature uniformity was obtained in the oil bath when theMorton flask was used. The equivalent aging severity between the modified rotavapor agingprocess and the standard short-term aging methods (TFOT and RTFOT) was established

Improving Concrete Durability by Using Optimized Aggregate Gradation and Reducing Cement Content

"This study evaluated the effects of (1) reducing the cementitious content, (2) the use of optimized aggregate gradation (OAG) technique, and (3) the use of Portland limestone cement (Type IL) in Florida Class I pavement and Class IV structural concrete. The potential performance of the pavement concrete mixes was also evaluated using critical stress analysis using a 3D FEM model. The compressive strength, modulus of rupture, modulus of elasticity, Poisson’s ratio, splitting tensile strength, coefficient of thermal expansion, rapid chloride permeability, and surface resistivity of the concrete mixes using normal Portland cement (Type I/II) and the concrete mixes using Type IL cement were similar to one another. The results of critical stress analysis indicated that the pavement concrete using Type IL cement had a predicted performance similar to concrete using Type I/II cement. The predicted performance of the pavement concrete was improved when the OAG technique was used. The main findings from this study are as follows: (1) The cementitious content of typical Florida pavement and structural concrete can be reduced by as much as 10 to 15% without loss in workability of the fresh concrete, and without decreasing the strength and durability of the hardened concrete. (2) Portlandlimestone cement (Type IL) can be used as a substitute for ordinary Portland cement (Type I/II). (3) The OAG technique can be used to efficiently reduce the cementitious content of the concrete mixes and to improve their performance.

CHARACTERIZATION OF COLD RECYCLED ASPHALT MIXTURES

Increased interest in improving the quality of the cold-recycled paving mixtures has made it necessary to better understand the behavior of these mixes and to develop a suitable mix design method. In this study, the long-term behavior of the cold-recycled asphalt mixtures was investigated through nine experimental designs. The scope of the study covered two types of pavement material, three levels of oxydized condition of the old binder and one type of virgin aggregate. The added softening agents included a high-float asphalt emulsion AE-150, a foamed asphalt, and the rejuvenating agents, Reclamite, Mobilsol and DUTREX 739. Specimens of the recycled mixes were compacted with the gyratory machine, and gyratory indices were obtained during the compaction process. The resilient modulus, Hveem Stabilometer R-Value and Marshall parameters were obtained on the compacted recycled mixes. The Water Sensitivity Test was used to evaluate the resistance of the recycled mixes to water. The results of the study indicated that most of the rejuvenating action of the added binder on the old binder took place during the compaction process. The binders of the recycled mixes which underwent the initial softening during the compaction process generally increased in stiffness with increasing curing time. The results indicated that the gyratory stability index and the gyratory elasto-plastic index could be used to determine the optimum binder content of a recycled mix. However, they could not be used to estimate the resilient modulus or the Marshall stability of the mix. A higher compactive effort generally produced a higher resilient modulus and Marshall stability of the recycled mix. When the binder content is too high, a higher compactive effort generally produces a lower Hveem R-value. The structural performance of these recycled mixes was compared to that of an asphalt concrete using a linear elastic multilayer analysis. A mix design procedure for cold recycled asphalt mixtures was recommended from the results of this study

CEMENT CONTENT REDUCTION IN CONCRETE THROUGH AGGREGATE OPTIMIZATION AND PACKING: A SUSTAINABLE PRACTICE FOR PAVEMENT AND SEAPORT CONSTRUCTION

Based on the full-bodied scientific consensus that climate warming is occurring on Earth, significant environmental and economic benefits may be obtained from cement content reduction in concrete, naming reduction in CO2 emissions, energy consumption, and construction costs. In contrast, standard limestone aggregate may experience increase in mining rate. The objective of this study was to propose the reduction of cement content in concrete framed by aggregate optimization as a viable alternative to reduce environmental effects from the cement industry. It was concluded that the higher the concrete volume in construction, the more environmental benefit can be obtained by reducing cement content in concrete. A 25 % cement reduction in a concrete pavement led to a decrease of 80.000 tons in CO2 emission, while a seaport construction displayed a decrease of 17.000 tons of CO2. The higher the designed cement per volume of concrete, the more budget savings in case of reduction in cement content. Port construction presented a reduction of 20,10 USD per m3 of concrete in cement costs against 11,04 USD per m3 in pavements. A 11,5 % increase in aggregate mining is expected when concrete contains less cement in its composition, targeting South Florida (U.S.A.) quarries

CEMENT CONTENT REDUCTION IN CONCRETE THROUGH AGGREGATE OPTIMIZATION AND PACKING: A SUSTAINABLE PRACTICE FOR PAVEMENT AND SEAPORT CONSTRUCTION

Based on the full-bodied scientific consensus that climate warming is occurring on Earth, significant environmental and economic benefits may be obtained from cement content reduction in concrete, naming reduction in CO2 emissions, energy consumption, and construction costs. In contrast, standard limestone aggregate may experience increase in mining rate. The objective of this study was to propose the reduction of cement content in concrete framed by aggregate optimization as a viable alternative to reduce environmental effects from the cement industry. It was concluded that the higher the concrete volume in construction, the more environmental benefit can be obtained by reducing cement content in concrete. A 25 % cement reduction in a concrete pavement led to a decrease of 80.000 tons in CO2 emission, while a seaport construction displayed a decrease of 17.000 tons of CO2. The higher the designed cement per volume of concrete, the more budget savings in case of reduction in cement content. Port construction presented a reduction of 20,10 USD per m3 of concrete in cement costs against 11,04 USD per m3 in pavements. A 11,5 % increase in aggregate mining is expected when concrete contains less cement in its composition, targeting South Florida (U.S.A.) quarries

Advancing the Structural Use of Earth-based Bricks: Addressing Key Challenges in the East African Context

The research discussed in this paper is a subset of a bigger, NSF funded research project that is directed at investigating the use of sustainable building materials. The deployment context for the research is the hot and humid climate using selected cases from the East African region. The overarching goal for the research is advancing the structural use of earth-based technologies. Significant strides can be made through developing strategies for countering the adverse factors that affect the structural performance of the resulting wall, especially ones related to moisture dynamics. The research was executed in two phases. The first phase was a two-day NSF supported workshop which was held in Tanzania in July 2009. It provided a forum for sharing best practices in earth-based building technologies and developing a research and development roadmap. The priority research areas were broadly classified as optimizing the physio-mechanical properties of earth as a building material and managing socio-cultural impediments. In the second phase of the research, the authors collaborated with researchers from East Africa to conduct experimental work on the optimization of physio-mechanical properties. The specific research issues that have been addressed are: (1) characterizing the chemical reactions that can be linked to deterioration triggered by hygrothermal loads based on the hot and humid context, and; (2) developing a prototype for a simpler, portable, affordable and viable compressed brick production machine. The paper discusses the results from the characterization work that ultimately will be used to design bricks that have specific properties based on an understanding of how different stabilizers affect the hydration process. It also describes a cheaper, portable and more efficient prototype machine that has been developed as part of the follow-up research activities