12-06-2014, 11:17 AM
Use of Recycled Brick Masonry Aggregate and Recycled Brick Masonry Aggregate Concrete in Sustainable Construction
Use of Recycled Brick Masonry.pdf (Size: 302.03 KB / Downloads: 31)
Abstract:
Use of recycled aggregates in portland cement concrete (PCC) construction can offer benefits associated with both economy and sustainability. Testing performed to date indicates that recycled brick masonry aggregate (RBMA) can be used as a 100% replacement for conventional coarse aggregate in concrete that exhibits acceptable mechanical properties for use in structural and pavement elements, including satisfactory performance in some durability tests. Recycled brick masonry aggregate concrete (RBMAC) is currently not used in any type of construction in the United States. However, use of RBMAC could become a viable construction strategy as sustainable building practices become the norm. This paper explores the feasibility of use of RBMAC in several types of sustainable construction initiatives, based upon the findings of previous work with RBMAC that incorporates RBMA produced from construction and demolition waste from a case study site. A summary of material properties of RBMAC that will be useful to construction professionals are presented, along with a discussion of advantages and impediments to use. Several quality assurance and quality control techniques that could be incorporated into specifications are identified.
INTRODUCTION
A significant challenge facing the construction industry is management of construction and demolition (C&D) waste. Often, C&D waste is landfilled, consuming space that is becoming increasingly costly and scarce. An alternative to landfilling C&D waste is recycling and reuse. Conservation of landfill space, reduction of the environmental impact of producing new materials [1], and the reduction of overall project expenses can all be realized by recycling C&D waste [2]. Additionally, recycling of C&D waste can potentially create new jobs [3].
One means of recycling hardscape and structural C&D waste is by crushing it into aggregates. Depending on the recycled aggregate’s physical properties, recycled aggregates can be used in a variety of construction applications and can reduce dependence on natural aggregates [4]. For aggregates used in portland cement concrete (PCC), use of recycled C&D waste in new concrete construction results in a decrease in both the amount of waste landfilled and the amount of primary aggregate extracted, thus reducing the environmental impact of the new construction [5].
Demolition
UNC Charlotte personnel monitored the demolition process of the brick masonry walls, loading and transport to a local crushing yard, and final transport to UNC Charlotte laboratories. Additional details on the demolition process at this case study site, as well as a discussion on incentives and impediments to use of recycled aggregates from demolition waste, are presented by Tempest et al. [6]
ANALYSIS OF CASE STUDY
In order to obtain the “cleanest‟ demolished brick masonry that can be achieved via readily employable source separation techniques, RBMA was made from brick masonry obtained from a single demolition site, Idlewild Elementary School, located in Charlotte, North Carolina. This case study site was selected for use in a United States Department of Energy (DOE) research grant, in which UNC Charlotte researchers found reuse for several types of demolition waste. Findings of this study are presented in Weggel et al. [3]. As part of this study, several brick masonry walls that were demolished were utilized to produce RBMA, which was then used as a replacement for conventional coarse aggregates in RBMAC [10]
POTENTIAL ISSUES
In many cases, recycling only takes place when use of C&D waste provides economic advantages to stakeholders. This occurs when beneficial reuse is cheaper than landfilling, and (in the case of recycled aggregates) when users of construction aggregates find recycled aggregates of similar quality cheaper than newly quarried aggregates [1]. Potential costs incurred by design and construction professionals desiring to use RBMA and RBMAC include costs associated with crushing (using either a mobile crushing unit or hauling/crushing at a recycled aggregate producer), with storage of the demolished masonry and/or RBMA, with characterization of whole brick and RBMA, and with development and testing of RBMAC.
CONCLUSIONS
Use of recycled aggregates in PCC can offer benefits associated with both economy and sustainability. Significant research has been performed on use of RCA in concrete elements, but until recently, use of RBMA has not been studied in the United States. As landfill space becomes increasingly scarce, and tipping fees continue to rise, the need to find alternative uses for demolition waste becomes more pronounced. RBMA has been shown to be a viable material for use in structural and pavement grade concrete, possessing mechanical properties similar to those of PCC with conventional aggregates.
Potential advantages of using RBMAC include reduction in the use of virgin aggregates, lower embodied energies of concrete elements, and possibly, project cost savings and creation of jobs. However, due to risks inherent in using this (and any) waste material in new construction, guidance in the form of standards and specifications is important. A quality program should be developed prior to initiating work at the site in order to ensure that adequate QA/QC measures related to RBMA and RBMAC production are utilized during all stages of the project. The suggested provisions for specifications, as presented in this paper, should assist stakeholders interested in utilizing RBMA and RBMAC in sustainable construction projects.