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.

Design storm hyetographs are synthetic temporal rainfall patterns used as input for flood modeling studies, drainage design and hydrodynamic modeling. In practice, the Philippines adopts the alternating block (AB) method to derive hyetographs using PAGASA-synthesized rainfall intensity-duration-frequency (RIDF) curves. In this study, six other methods- AB from actual RIDF curve, actual normalized 24-hour storms and four different patterns derived by Huff (1967)- were tested using the tipping-bucket raingauge records of a local weather station. Nonparametric statistical tests were employed to determine the significant difference between and among distributions. Moreover, Chi-squared goodness-of-fit test was used to compare the hyetographs with data from actual storms. The PAGASA AB hyetographs, while accurate in some instances, do not always represent actual storms well. Furthermore, other methods may have better fits for other storms. This study recommends further research in establishing design hyetographs in the Philippines.

Infusing plastic waste to concrete and masonry structures is an increasingly common industry practice that has the potential to create an environment-friendly material that can improve some of the material’s properties, craft a novel means to repurpose plastic waste, and reduce the need for mining aggregates in the environment. This concept has been studied extensively in different forms of concrete, as shown by several studies; however, there is a dearth of studies focusing on the incorporation plastic waste in concrete hollow blocks (CHB). In this study, we aim to fill that gap by investigating on the effects of incorporating low-density polyethylene (LDPE), a commonly used plastic material, to CHB on its compressive strength and bulk density. Samples of varying percentages of LDPE replacement by volume (0, 10, 20, 30 and 40%) were fabricated and tested. Results showed a general trend of decreasing compressive strength and bulk density upon increasing the amount of LDPE pellets in CHB, which was also observed in previous studies. However, the compressive strength of CHB increased at 10% LDPE replacement, a result similar to a previous study. It was inferred that the strength of the plastic material could have a direct contribution to the compressive strength of CHB at low percentage of aggregate replacement. Statistical analysis showed that the mix with 10% LDPE pellets as replacement to sand was the best among the samples tested. It was shown that CHB infused with LDPE pellets has a higher compressive strength than what is normally used in the Philippines. It was concluded that based on compressive strength and bulk density, LDPE pellets is a viable material to use as partial replacement to sand in non-load bearing CHB.

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