The river sand in the Santo Tomas River area of the Philippines is a kind of volcanogenic sand. The sand is fine sand with a fineness modulus of 2.2, an apparent density of 2380 kg/m3, a bulk density of 1320 kg/m3, a mud content of 6.7%, a methylene blue value of 1.2, a soluble chloride ion content of 0.00071%, and a light-matter content of up to 12.2%, which does not meet the requirements of the three-zone grading. Based on a series of experiments, this paper systematically studies and compares the workability, mechanical properties, and durability of two kinds of concrete with the river sand in the Santo Tomas River area and natural river sand in Beijing, China as fine aggregates, respectively. In addition, volcanogenic sand in the Philippines is technically optimized for the purpose of in-depth study. After optimization, such sand reaches the standard of Zone II-graded medium sand and is comprehensively improved in performance, which is evidenced by a fineness modulus of 2.4, an apparent density of 2570 kg/m3, a bulk density of 1550 kg/m3, a light-matter content of 6.0%, and a mud content of 6.7%. Study results show that in terms of mechanical properties, the concrete made of the optimized river sand in the Santo Tomas River area is superior to that made from the natural river sand in the Beijing area. In addition, separated light matter can be used as a natural light aggregate, which has a bulk density of 960 kg/m3, a cylindrical compressive strength of 2.5 MPa, and a 1 h water absorption of 8.2%, respectively.
Keywords: concrete; fine aggregate; lightweight aggregate; optimization; volcanogenic sand.