Calcium carbide sludge activated fly ash mixture for offshore construction and its crack repair using seawater-mixed bioslurry cement

Abstract

This paper reports a mixture based on the calcium carbide sludge (CCS) activation of fly ash. The formed calcium silicate hydrate (C–S–H) gel binds sands and gravel particles to synthesize pozzolanic-lime mortars and concretes. In both seawater and tap water, Ca(CO3), Ca(OH)2, and C–S–H were the main phases of hydration, as determined by powder X-ray diffraction. The optimal mixture was obtained using a CCS to FA ratio of 0.8 and curing time of 14 d. The surface morphology of spherical FA in the tap water mixed pozzolanic-lime materials had relatively loose rod-like, flower-like, and block structures, which were different from the irregular and dense block structure in the seawater mixed pozzolanic-lime mixture. For the fiber-reinforced mortar, the optimal content of polypropylene fiber was 0.1%. The surfaces of the fiber reinforced pozzolanic-lime mortars prepared using seawater were more compact than those prepared using tap and distilled water. The strengths of the fiber-reinforced specimens soaked in both seawater and tap water were maintained after 14, 28, 60, 90, and 120 d. The water permeability of pozzolanic-lime mixture with cracks was effectively reduced by spraying a seawater-mixed bioslurry cement. This work demonstrates the potential of a seawater-mixed pozzolanic-lime mortar as an offshore road base material and a bioslurry cement as its crack repairing material.