Resources, Conservation and Recycling 56 (2011) 66–70 Contents lists available at SciVerse ScienceDirect Resources, Conservation and Recycling journal homepage: www.elsevier.com/locate/resconrec Review Effect of volcanic ash on the properties of cement paste and mortar Rafat Siddique ∗ Department of Civil Engineering, Thapar University, Patiala, Punjab 147004, India article info Article history: Received 6 August 2011 Accepted 9 September 2011 Keywords: Cement Compressive strength Consistency Electrical resistivity Hydration Mortar Setting times Volcanic ash Workability abstract Volcanic ash (VA) is formed during volcanic eruptions. Volcanic glass is relatively high in silica, and its physical and chemical properties could be referenced with ASTM C618-93, a Standard Specification for ‘Fly Ash and Raw or Calcinated Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete’. This paper presents comprehensive details of the physical, chemical properties of volcanic ash, and its micro-structure and hydration products. It also covers effect of volcanic ash on consistency, setting times, workability, compressive strength, electrical resistivity of cement paste and mortar. © 2011 Elsevier B.V. All rights reserved. Contents 1. Introduction ............................................................................................................................................. 66 2. Properties of volcanic ash .............................................................................................................................. 67 2.1. Physical properties .............................................................................................................................. 67 2.2. Chemical composition .......................................................................................................................... 67 3. Uses of volcanic ash ..................................................................................................................................... 67 4. Properties of blended cement containing volcanic ash ................................................................................................ 68 4.1. Consistency and setting times .................................................................................................................. 68 4.2. Compressive strength ........................................................................................................................... 68 4.3. Microstructure of hydration products .......................................................................................................... 68 4.4. Alkali–silica reaction and autoclave expansion ................................................................................................ 69 4.5. Electrical resistivity ............................................................................................................................. 70 4.6. Total pore volume (TPA) ........................................................................................................................ 70 5. Conclusions ............................................................................................................................................. 70 References .............................................................................................................................................. 70 1. Introduction Volcanic ash (VA) is formed during volcanic eruptions. Ash is cre- ated when solid rock shatters and magma (molten rock) separates into minute particles during explosive volcanic activity. The usually violent nature of an eruption involving steam (phreatic eruption) results in the magma and solid rock surrounding the vent is torn into particles of clay to sand size. ∗ Tel.: +91 175 239 3207; fax: +91 175 239 3005. E-mail address: siddique 66@yahoo.com The plum that is generally seen above an erupting volcano is composed primarily of ash and steam. The very fine particles maybe carried away for miles together, settling out as a dust-like layer across the landscape. This is known as ‘ash fall’. The commonly used term for any material explosively thrown out from a vent is tephra, also known as pyroclasstic debris. If liquid magma is ejected as spray, the particles will solidify in the air to small fragments of volcanic glass. Tephra particles of gravel are termed cinders. The ejection of large quantities of ash will produce an ash cone. A layer of volcanic ash tends to become cemented together to form a solid rock called ‘tuff’. The size of ash particles, which fall on the ground decreases exponentially with increasing distance from a volcano. Also, the 0921-3449/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.resconrec.2011.09.005