Compressive Strength and Bulk Density of Concrete Hollow Blocks (CHB) with Polypropylene (PP) Pellets as Partial Replacement for Sand

Abstract

Plastics are non-biodegradable and the increasing generation of plastics creates a problem of disposal. One promising approach to address this problem is to find other uses for plastics after they are used. While studies on the incorporation of waste materials in concrete abound, little attention has been given to the incorporation of plastic wastes in concrete. Also, these few studies have focused on cylindrical concrete specimens -none in online published articles, to the authors' knowledge, has focused on concrete hollow blocks. The present study narrowed that gap by shifting the focus of research from the conventional cylindrical specimen to concrete hollow block. Thus, the main objective of the study was to assess the potential of concrete hollow blocks with PP pellets as partial replacement for sand. Polypropylene (PP), which is a subset of these plastics, were pelletized and incorporated in concrete hollow blocks as partial replacement for sand. Five batches of specimens, each with 0%, 10%, 20%, 30%, 40% PP replacement (by volume) were molded and cured for 28 days. The compressive strength and bulk density of the specimens from these batches were determined and compared. Results showed that, generally, compressive strength and bulk density decrease as percent replacement increases; however, it was observed that the compressive strength of the specimens from batch with 10% PP replacement were higher compared to batches with 0% PP replacement.

Compressive Strength and Bulk Density of Concrete Hollow Blocks (CHB) Infused with Low-density Polyethylene (LDPE) Pellets

“…However, an increase in compressive strength was observed at 10% LDPE replacement. The increase in compressive strength was also observed in the study by Lasco et al, where PP pellets where used as partial replacement for sand in CHB [26]. At lower concentrations, the pellets may have contributed to the compressive strength of the hollow block.…”

“…LDPE has a compressive strength of 9-10 MPa [30], which is stronger than the compressive strength of all the specimens without LDPE replacement (Batch A). However, increasing the concentration of replacement could lead to higher probability of creating areas with closely clustered LDPE pellets, which could lead to localized failure [26]. A similar trend of increase in compressive strength at low percentage of plastic aggregates was also observed in the separate studies of Azdharpour et al, and Hameed and Ahmed [17,20].…”

“…The research design of this study was derived from the research by Lasco et al [26], as summarized in Figure 2. Preliminary tests were done to determine the specific gravity of the materials as well as the fineness modulus of sand.…”

“…Its specific gravity ranges from 0.91 to 0.93 [30], which is lighter compared to the typical aggregates used in mortar production, thus has the potential to create a lightweight CHB. This study builds on the previous research by Lasco et al [26] by investigating the feasibility of incorporating pelletized LDPE into the widely-used CHB. This innovation may provide an environment-friendly, novel means to repurpose plastic wastes in the Philippines while improving the properties of the material.…”

“…Although incorporating different types of plastic wastes in CHB is already being done, the practice has not been extensively tested and documented in published journals. In one study that does so, the effect of using polypropylene pellets (PP) as partial replacement for sand on the compressive strength and bulk density of CHB [26]. The authors of this study observed that the bulk density of CHB decreases with increasing PP replacement.…”