Lehigh Hanson, Leeds Alabama, cement plant decision to construct a new three chamber 20,000 MT silo, 240 feet tall with an 80ft diameter along with automatic truck loading. The thought of using C1157 and C989 SLAG Cement and being green, was far from anyone’s mind.
ASTM C1157 is manufactured under a Performance Specification in contrast to the prescriptive C150 Portland Cement specification. This allows for a target of 10% calcium carbonate (limestone) and a lower CO2 footprint.
To give the new silo the longest possible life cycle, SLAG CEMENT was introduced to the concrete design. The concrete proposed for the silo was 60% C1157 and 40% Slag cement with a low water cement ratio. A hundred year durable concrete can be expected with this combination of cementitious materials. The C1157 from Leeds is a Type HE, MS (High Early, Moderate Sulfate) cement.
All this was proposed to the slip form contractor TEI (T.E. ibberson Company). TEI is an experienced slip form contractor, but had no familiarity with doing a complicated slip form with this combination of cementitious materials. A support team was formed that included the concrete supplier, Sherman Industries, TEI, and Heidelberg Technology Center (HTC), to monitor the concrete performance of the slip.
The results of the first phase of the silo were a successful slip form concrete placement of 1554 cubic yards at an average rate of 11 vertical inches per hour. This rate of placement is considered good for the complexity of the formwork and reinforcing. Hydraulic pump pressures that “jack the slip” formwork were reported to be low normal and the concrete had no tendency for stickiness.
The combination C1157 and C989 hydraulic cements produce a durable, environmentally sound structural concrete with a long service life.