A resin-coated substrate composition includes a resin-coated substrate comprising a particulate substrate coated with a polymer resin, and an additive comprising bentonite or a zeolite. A method of preparing a resin-coated substrate composition includes heating a particulate substrate, and mixing the heated substrate with a polymer resin and an additive such as bentonite or a zeolite. In some embodiments, a foundry sand composition includes the resin-coated substrate composition. In some embodiments, a proppant sand composition includes the resin-coated substrate composition.