Madelyn Marrero

A Spanish model for quantification and management of construction waste

Currently, construction and demolition waste (C&D waste) is a worldwide issue that concerns not only governments but also the building actors involved in construction activity. In Spain, a new national decree has been regulating the production and management of C&D waste since February 2008. The present work describes the waste management model that has inspired this decree: the Alcores model implemented with good results in Los Alcores Community (Seville, Spain). A detailed model is also provided to estimate the volume of waste that is expected to be generated on the building site. The quantification of C&D waste volume, from the project stage, is essential for the building actors to properly plan and control its disposal. This quantification model has been developed by studying 100 dwelling projects, especially their bill of quantities, and defining three coefficients to estimate the demolished volume (CT), the wreckage volume (CR) and the packaging volume (CE). Finally, two case studies are included to illustrate the usefulness of the model to estimate C&D waste volume in both new construction and demolition projects.

High fire resistance in blocks containing coal combustion fly ashes and bottom ash

Fire resistance recycled blocks, containing fly ash and bottom ash from coal combustion power plants with a high fire resistance, are studied in this paper by testing different compositions using Portland cement type II, sand, coarse aggregate and fly ash (up to 50% of total weight) and bottom ash (up to 30% of total weight). The fire resistance, physical-chemical (density, pH, humidity, and water absorption capacity), mechanical (compressive and flexural strength), and leaching properties are measured on blocks made with different proportions of fly ash and bottom ash. The standard fire resistance test is reproduced on 28cm-high, 18cm-wide and 3cm-thick units, and is measured as the time needed to reach a temperature of 180°C on the non-exposed surface of the blocks for the different compositions. The results show that the replacement of fine aggregate with fly ash and of coarse aggregate with bottom ash have a remarkable influence on fire resistance and cause no detriment to the mechanical properties of the product. Additionally, according to the leaching tests, no environmental problems have been detected in the product. These results lead to an analysis of the recycling possibilities of these by-products in useful construction applications for the passive protection against fire.

Numerical behavior of time domain BEM for three-dimensional transient elastodynamic problems

The present paper deals with the time domain formulation of the boundary element method for three-dimensional elastodynamic problems and its actual implementation for the solution of transient problems relative to bounded domains with any geometry. Particular attention is paid to stability and accuracy of the computed solutions. The numerical approach is based on a constant velocity prediction algorithm and the combination of the integral representation for several time steps. Quadratic boundary elements are considered. A subdivision of the elements is introduced for integration in order to preserve the causality condition and to improve the accuracy of the solution. As opposite to previously published techniques, the present approach is tested for finite 3D bodies with actual values of the elastic constants (non-zero Poissons ratio). The obtained results show the stability and accuracy of the approach for a wide enough range of time step size and non-uniform meshes.

The building cost system in Andalusia: application to construction and demolition waste management

During the last 25 years, a building cost system (BCS) has been developed in Andalusia, Spain. The first step was to generate the Andalusia construction information classification system (ACICS). Not only is ACICS valid as an estimation of cost, but it also provides a common method to manage information during the design and construction of buildings. Another important innovation is that this BCS defines the cost structure which distinguishes between direct and indirect cost and thereby allows a clear definition of all costs for each project type. Its most extended usage is for estimating cost in building projects and it is mandatory in public developments in Andalusia. This is the first time that this system is presented internationally and compared to others. Furthermore, the latest additions to ACICS are explained, and these take into account the waste management of reused and recycled materials in the budget estimate through a new division in the classification: Waste Management. Finally, a new way to address the cost related to construction and demolition waste management is explained which increases precision and generates an estimate independent from the general budget.

Recycled blocks with improved sound and fire insulation containing construction and demolition waste

The environmental problem posed by construction and demolition waste (C&D waste) is derived not only from the high volume produced, but also from its treatment and disposal. Treatment plants receive C&D waste which is then transformed into a recycled mixed aggregate. The byproduct is mainly used for low-value-added applications such as land escape restoration, despite the high quality of the aggregate. In the present work, the chemical composition properties and grading curve properties of these aggregates are defined. Furthermore, the resulting recycled concrete with a high proportion of recycled composition, from 20% to 100% replacement of fine and coarse aggregate, is characterized physically and mechanically. An environmental study of the new construction material when all aggregates are substituted by C&D waste shows a low toxicity level, similar to that of other construction materials. The new material also has improved properties with respect to standard concrete such as high fire resistance, good heat insulation, and acoustic insulation.

Methodology for Determining the Carbon Footprint of the Construction of Residential Buildings

With the increasing activity in the building sector in the last decade, construction has become a major consumer of natural resources. This resource consumption has been traditionally accounted for through life cycle assessment and similar approaches. In this chapter, a methodology to apply the carbon footprint indicator to a building project is proposed in order to predict the emissions generated by the construction work. The methodology takes into account the resources used and the waste generated. Thus, a number of factors involved in the calculations are first defined, followed by the methodology to determine the carbon footprint for each of the elements into which it is divided (i.e., energy, water, food, mobility, construction materials, and waste). Finally, the methodology is applied to a case study corresponding to the urbanization and building construction of a representative building type in Andalusia (Spain) when the building is in the planning stage.

Solid-particle erosion of in situ reinforced Si3N4

Abstract Steady-state solid-particle erosion has been investigated on in situ reinforced Si 3 N 4 and the “equivalent” fine-grained hot-isostatically-pressed Si 3 N 4 whose R-curve behaviors are quite different, having K IC values in the long-crack limit of 8.3 and 5.6 MPa m p 1 2 respectively. Experiments were carried out at 20 °C, using SiC abrasives, whose diameters ranged from 42 to 1035 μm, varying the angle of impact from 15 to 90° and the velocity from 50 to 100 to 150 m s −1 . The erosion rates of the two materials were, within a factor of two, the same, indicating that the long-crack-length-limit toughness is not an indication of erosion resistance, for the range of particle sizes and velocities studied.

Demolition Waste Management in Spanish Legislation

In 2008, a legal frame was established in Spain for construction and demolition waste management. The new control model, called the Alcores model, presents a waste management closed loop and was previously tested in Seville in order to demonstrate its viability. In current demolition projects, specific barriers arise which limit the frame implementation. Until recently, demolition was considered a low technical process. The contractors main goals were quick demolition and disposal of the debris, usually uncontrolled, into landfills. No special measures for separating different material types were taken due to their incompatibility with the work time-span required. The present work establishes a simplified procedure in order to fulfill Spains legal frame. This procedure determines the management of demolition waste quantities and costs following the Andalusia Construction Information Classification System. The procedure also generates the demolition waste management plan, which includes: previous work, waste quantification, hazardous waste inventory, waste prevention action plans, reuse, valorisation and disposal plan, separation plan, technical drawings, technical instructions, and budget. Finally, as an example, the procedure is applied to a school demolition project.

Schedule and Cost Control in Dwelling Construction Using Control Charts

Methods to monitor the schedule and to control cost in dwelling construction projects are numerous and varied but commonly constitute an obstacle to a fast and agile response by construction managers, whose decisions require in- formation to be comprehensive and summarized. A simple model to monitor these projects is proposed that can easily be implemented within control systems that are already in place. For the first time, process control charts are combined with cost control in dwelling construction in order to prevent overruns in terms of time and/or cost. The model facilitates the production supervision of construction contracts by regularly providing information on the work completed and the in- curred cost of the production processes per period, through charting and/or summarizing this information in a manner con- sistent with statistical control charts. Finally, the manager can easily identify those processes which are off target by con- sulting control charts.

Time-domain BEM for three-dimensional fracture mechanics

Abstract The present paper deals with time-domain analysis of three-dimensional transient dynamic crack problems. The time-domain formulation of the boundary element method for 3-D elastodynamic problems is used. Quarter-point and singular quarter-point elements represent displacements and tractions, respectively, near the crack front. Special attention is paid to integration and algorithms to preserve stability. Cracks in finite and unbounded regions under single and mixed mode dynamic loading conditions are studied. To the authors’ knowledge, no previous BE approach for 3-D elastodynamic crack problems based on the time-domain displacement representation exists.