What kind of material can I pump to raise concrete? Jen Mazur Oct 11, 2011 0000 HMI Manufactures Polyurethane Material Designed to Raise Concrete Polyurethane concrete lifting uses material specifically designed to fill voids and raise concrete. Available for purchase directly from HMI, the reaction of this two part material expands with enough force to fill voids and raise concrete. There are multiple formulas designed for different applications. Polyurethane for raising highway slabs, sidewalk slabs or filling voids. Receive a free catalog! The original term mudjacking comes from using topsoil mixed with cement (mud). However, topsoil has organic properties that will eventually break down and may cause the concrete slabs to resettle. The most readily available material throughout the country is agricultural lime mixed with cement and water. Other slabjacking materials are pond sand, river sand, lime screenings, and fly ash. A good test for mudjacking material is to mix the base material with water to the consistency of a thick milkshake. Let the jar sit briefly. If the material has settled and separated from the water, it will may not make a good mudjacking material. However, additive may be introduced to the mixture to improve its pumpability. All HMI slabjacking pumps are designed to pump a 3/8” minus pea gravel concrete. We recommend that the mix design be at least an 8 bag mix with 400 to 600 pounds of pea stone. This mix design can vary depending on the coarseness and shape of the pea stone and sand that is used.