Estudo de viabilidade técnica da produção de blocos de concreto de alta resistência com uma blenda de PE+PET para uso em pavimentação intertravada

Abstract

Differently from foreign countries such as South Africa, the applications of Concrete Paving Blocks (CBP’s) on urban streets and rural roads are still fairly limited. This may be attributed to the lack of reliable technical data about the performance of such blocks as wearing surfaces of pavements, as well as cultural aspects. One of the most critical problems of research is the identification of the most appropriate amounts and types of plastics for use on highly-resistant concretes, since these plastics typically lead to reductions in the compressive strength of the concrete (fpk) and their presence may avoid the application of CBP’s on pavements subjected to light traffic (minimum fpk of 35 MPa) and heavy traffic (minimum fpk of 50 MPa). In an attempt to solve such issues and encourage the recycling of plastics and the construction of pavements with CBP’s, the present investigation aimed at evaluating the technical feasibility of the addition of an industrially processed PE+PET blend on an ordinary Portland cement concrete trace T0 and at contents equal to 1, 2, 3, 4, 5 and 10% by volume (T1, T2, T3, T4, T5 and T6 traces, respectively). This replacement was made on the fine fraction of the aggregates, and the dosage of the trace T0 was made according to American standards. The basic laboratory tests performed on the CBP’s and established by the Brazilian NBR 9781 standard included the compressive strength and the water absorption (Ab), both after 28 days of curing. The CBP’s are classified as “Type I” and “16-faces” according to this same standard. Gnaisse aggregates and with a Los Angeles abrasion of 20.9% were selected, and the PE+PET blend was provided as pellets. Despite the approximately linear reductions in fpk with increasing PE+PET content, there were no great impacts on the outcomes of the T1 and T2 traces (fpk decreased from about 44 MPa to 39 MPa), and this could allow their use on pavements subjected to light traffic. With respect to the water absorption, all the results of Ab are placed below the máximum limit of 6%, and they suggest that the CBP’s would be able to deal with freezingthawing cycles without causing significant damage to the resistance of the concrete. In addition, the presence of PE+PET did not cause marked increases or decreases in Ab because the results varied from 2.1 to 3.2% for all the traces studied here. Therefore, it can be observed that the use of plastic aggregates on CBP’s is technically feasible, provided that the correct type of plastic is selected and its contents be compatible with the minimum required resistances for the concrete.