Panama City Pit

Our project is located in the village of Coclecito, Panama. Here we have proposed to relocate a village into a 1850’ x 1500’ by 400 deep mining pit that has been left behind by the mining company. Our thought is that with the terries left in the mine we can use them to create terries farming in which it can provide sustainable life to the people. With this the building would be set on stable volcanic rock, taking advantage of regional geology. We tend to use a concrete mixture with volcanic rock to create most of the structure

Coefficient of Thermal Expansion of Concrete Produced with Recycled Concrete Aggregates

This study presents a comparison between the coefficient of thermal expansion (CTE) of concrete produced with natural aggregate and that of concrete produced with recycled concrete aggregate. In order to achieve this, natural aggregate concrete (NAC) specimens were produced, tested, then crushed and sieved in the laboratory to obtain recycled concrete aggregates, which was then used in the production of recycled aggregate concrete (RAC) specimens. The RAC samples were then tested and compared to the NAC samples. The CTE testing was carried out using a AFTC2 CTE measurement system produced by Pine Instrument Company. In addition to CTE testing, the water absorption, specific gravity, and unit weight of the aggregates was determined. A vacuum impregnation procedure was used for the water absorption test. The recycled aggregate properties showed a significantly higher absorption capacity than that of the natural aggregates, while the unit weight and specific gravity of the recycled aggregate were lower than that of the natural aggregates. The average CTE results showed that both the NAC and the RAC samples expanded similarly. The results show that the CTE of RAC depends on the natural aggregate used in the NAC, which was recycled to produce the RAC. Also, there was no significant difference between the average CTE values of the RAC and that of NAC that could discredit the use of recycled aggregate in concrete

Fitness voter model: damped oscillations and anomalous consensus

We study the dynamics of opinion formation in a heterogeneous voter model on a complete graph, in which each agent is endowed with an integer fitness parameter k ≥ 0, in addition to its + or − opinion state. The evolution of the distribution of k–values and the opinion dynamics are coupled together, so as to allow the system to dynamically develop heterogeneity and memory in a simple way. When two agents with different opinions interact, their k–values are compared and, with probability p the agent with the lower value adopts the opinion of the one with the higher value, while with probability 1 − p the opposite happens. The winning agent then increments its k–value by one. We study the dynamics of the system in the entire 0 ≤ p ≤ 1 range and compare with the case p = 1/2, in which opinions are decoupled from the k–values and the dynamics is equivalent to that of the standard voter model. When 0 ≤ p < 1/2, agents with higher k–values are less persuasive, and the system approaches exponentially fast to the consensus state of the initial majority opinion. The mean consensus time τ appears to grow logarithmically with the number of agents N , and it is greatly decreased relative to the linear behavior τ ∼ N found in the standard voter model. When 1/2 < p ≤ 1, agents with higher k–values are more persuasive, and the system initially relaxes to a state with an even coexistence of opinions, but eventually reaches consensus by finite-size fluctuations. The approach to the coexistence state is monotonic for 1/2 < p < po 0.8, while for po ≤ p ≤ 1 there are damped oscillations around the coexistence value. The final approach to coexistence is approximately a power law t −b(p) in both regimes, where the exponent b increases with p. Also, τ increases respect to the standard voter model, although it still scales linearly with N. The p = 1 case is special, with a relaxation to coexistence that scales as t −2.73 and a consensus time that scales as τ ∼ N β , with β 1.45

Assessing the Degree of Polish on Hardened Concrete Air Void Parameters

This study provides much needed insight regarding how the degree of polish on a concrete sample affects the hardened air void parameters. As required by ASTM C457, each hardened concrete sample assessed by any of its three procedures needs to be polished until light reflects off of the surface. However, there is currently little to no insight as to how various degrees of polish will affect the concrete air void parameters. This research aims to fill the gap in the literature by providing a step-by-step procedure, materials necessary, and most importantly, the effect of the degree of polish on the hardened air void system parameters. Four target air void percentages (control at 2%, low at 3 – 5%, medium at 5 – 7%, and high at &gt;8%) were investigated. Two different polishing mediums (silicon carbide and diamond) were investigated at six different polishing pad grit sizes. The results show that the most economical and preferred polishing method uses diamond polish pads. The results also indicate that the first polishing step is crucial in producing a suitable surface for further analysis, which requires using the coarsest polishing medium. Therefore, the results indicate that any further polishing (at finer degrees of polish) is negligible in obtaining the hardened air void parameters following ASTM C457 procedures. The average percent difference across each polish pad grit size investigates was 3.8%. This value amounted to an average hardened air void difference of only 0.1 across all samples. Comparing the average hardened air void percentage across all polish pad grit sizes to the ASTM C231 fresh air percentage reveals an average difference of 6.7%, which constituded a difference of 0.3. Therefore, the results show non-statistically significant variations between any of the degrees of polish investigated, especially between the coarsest polishing medium and the finest polishing medium, which produces the reflective surface as stipulated in ASTM C457

Investigating the Rheological Properties of Ultra High Strength Concrete Made with Various Superplasticizers

Ultra-High Strength Concrete (UHSC) is a high-strength and highly ductile material formulated to provide compressive strengths exceeding 130MPa. UHSC materials typically have a very low water-to-cementitious ratio (w/cm), which requires the use of superplasticizers to disperse the fine particles and to make the material workable for placing, handling and consolidating. Common examples of superplasticizer compositions include Polynaphthalene Sulfonate (PNS), Polymelamine Sulfonate (PMS) and Polycarboxylate Ether (PCE) based polymers. This study focuses on assessing the impact of various superplasticizers on the compressive strength and rheological performance of a UHSC mixture. Four different types of superplasticizers were used; two different PCE based superplasticizers from a leading manufacturer, one PNS superplasticizer, and one PCE superplasticizer, both of which were provided by a local chemical provider. Specific properties assessed were the superplasticizers' viscosity, concrete workability through the mortar-spread test, concrete rheology, and 7, 14, and 28 day compressive strengths. Two mixtures were produced with two w/cm (0.20 and 0.15), which would subsequently increase the amount of HRWRA needed, from 34.7L/m3 to 44.5L/m3. The results show that both name brand PCE superplasticizers produce a higher spread, lower viscosity, and a higher compressive strength at all ages tested up to 28 days than the two local superplasticizers. Additionally, the rheology test demonstrated that the name brand PCE superplasticizers, and UHSC produced with such superplasticizers, had a lower viscosity at all angular speeds than the local superplasticizers counterparts

An Alternative Test Method for Determining Hardened Air Void Parameters for Concrete Pavement

This research has developed an alternative test method for determining hardened air void parameters that follows ASTM C457 Procedure C, but does not require image analysis software or the required training and skills to develop or use one. Instead, the alternative technique uses a sophisticated microscope that has on-board counting and measuring capabilities, that are easy to use and easy to repeat. The technique was developed and tested on concrete mixtures with four target air void percentages (control at 2%, low at 3 – 5%, medium at 5 – 7%, and high at &gt;8%) and compared to ASTM C457 Procedure A and B. The concrete produced was a conventional pavement mixture, which was a straight cement mixture with a target 3” slump. The results show that the alternative technique is not only just as accurate as the other methods, but it reduces the analysis time, human judgment calls, and the development and maintenance of a sophisticated image analysis program, which are all typical issues with any of the three procedures described in ASTM C457. Additionally, the alternative technique produces all hardened air void parameters that ASTM C457 provides. This study also demonstrates new potential issues that could result in erroneous hardened air void results when following ASTM C457. Lastly, this study provides a detailed description of the equipment necessary to produce the alternative method including a very detailed list of steps required to obtained the hardened air void parameters