Characterization and comparison of the cement produced using clam wreckage and limestone: Cement clinker, freeze–thaw resistance, and hydration products

Limestone accounts for more than 85 wt% raw materials for cement production. Clam wreckage, a calcareous residual, brings serious harm to the environment, such as attracting mosquitoes and releasing unpleasant odors after decay. This work produced a cement (lime coefficient: 0.97, silica coefficient: 2.04, and alumina coefficient: 1.37) using the clam wreckage as an alternative to limestone and done a comparison with the cement produced with limestone in the calcined temperature of production, mineral phases, freeze–thaw resistance, and hydration products and their formation amount and microstructures. Results show that clam wreckage contains more calcite than limestone so that the addition of clam wreckage to cement production is lower than that of limestone at the same clinker coefficient. The optimum calcined temperature for the production of cement using clam wreckage is 1350 °C, leading to a reduction of 100 °C comparing to the cement using limestone. The mineral phases of the two cements are the same, but the clam wreckage promotes the formation of C3A, and C4AF as well as the conversion of C2S into C3S, at 1350 °C. The hydration products are all the virgulate 3CaO·Al2O3·3CaSO4·32H2O, petal-like sheet Ca(OH)2, and close-grained and glazed C-S-H; but their formation amount in cement produced with 78.98 wt% clam wreckage are higher than that with 85.81 wt% limestone, leading to the cement with clam wreckage shows better freeze–thaw resistance at the same curing ages compared to that with limestone. This work is helpful to the upcycling of clam wreckage and provides an alternative to limestone in cement production.