The eruption of Mt. Pinatubo has ejected billions of cubic meters of pyroclastic materials into surrounding rivers in Tarlac, Pampanga and Zambales. Although sandy, they are not deemed suited for construction because its chemical content and large amount of silt has a profound effect on the quality of concrete mixture. Chemical analysis made by various researches has confirmed that the silt of Lahar sand is pozzolanic and there are several researches made to maximize it’s potential in the construction industry. In TUP, Lejano (2000) has been able to develop a modular panel for low cost housing using what is primarily lahar sand. DPWH (Krirk et al 1999) has also made several studies in which they utilized lahar aggregates and sand as road base and asphalt mix. But it should be noted that good quality sand being quarried from Tarlac, Pampanga and Zambales also came from Mt. Pinatubo. This finding suggests that as time goes on the content of what we consider as lahar sand will gradually become washed sand. This research determined if how long will it take to wash the silt away from the sand. This research has found out that the amount of silt by weight has been reduced from 14% in 1998 to 10% in 2007. While there was still presence of small pumice aggregates from the sample, it was remarkable reduced from visual inspections made 10 years ago. The pumice is also light and light has the tendency to float away specially when the water level in the river is high and the flow is fast.
This research looked into the potential of lahar sand as stabilizer for compressed earth blocks. The presence of various types of soil has given a potential to a very old technology in construction that can be revived using compressed earth. There are various mixtures of soil, clay, silt and sand presented in various literatures of rammed earth and compressed earth block construction and they have a common ingredient, which is sand. In various experiments conducted, the sample that contained 80% clay and 20% lahar sand by weight performed very well in compression testing which gave strength of 300 psi, which is the minimum, set by the earthen building industry in the US. While this mixture performs well in the compression tests the true effect of the silt, which is deemed pozzolanic, has yet to be seen because there is not enough time to dry cure that samples