The Maryneal Plant has been approved to construct a third 22,000 MT clinker storage silo for 2018. The necessity of adding a third clinker silo is two-fold. First, the two identical existing silos have a combined live capacity of 44,000 MT; one being for class C clinker and one for being for Type I/II clinker. During periods of high shipment demand this storage volume would then equate to two weeks of cement shipment capacity. As a result, any plant outage lasting more than two weeks could exhaust the clinker inventory. Second, during periods of low cement demand, the additional silo can act as a buffer to keep the plant in operation.

The structural and mechanical portion of the project was designed by the engineering group in Casale. Clinker Silo No. 3 is being built in the area previously occupied by the recently decommissioned 3 kiln lines that operated prior to the most recent plant expansion. The presence of deep pockets at the old kiln piers made the excavation challenging. The excavation proceeded to solid rock and 2,000 psi lean concrete was then used as a base for the new silo, followed by a pour of 4,000 psi for the foundation and finally constructing the silo slip-rings and roof using a 5,000 psi concrete mix.

All concrete utilized was provided by Ingram Concrete using an onsite batch plant. The tight schedule required that concrete placement begin in t67891he unpredictable west Texas winter months. The early foundation pours did face freezing temperature challenges and some initial pouring delays occurred due to the colder than expected weather.

A comprehensive approach was taken with the concrete preparation for the slipform. A team consisting of Borton, LC as the prime contractor, Ingram Concrete & Aggregates, Buzzi Unicem USA Inc., and Alamo Concrete set out to design the mix. An important issue was the type of aggregate to be utilized.  In the slip pours for the first two silos, smooth river rock was used.  However, this was thought to be one of the factors causing plugs in the pumping lines as was experienced during the initial silo projects. A decision was made to then use crushed aggregate this time.

In order to estimate the time needed for the concrete to set up properly, the contractor conducted a series of trial forms that simulated the slip form.  Different additives were added to each test batch to determine the additive products which gave the best setting properties.  With a final mix design decided, a single pump truck was then used to transfer the concrete to a central hopper on the deck of the slip. From there, concrete was moved to the slip form using small "buggies".  While seeming rudimentary, this is the technique of choice by the contractor and turned out to be very successful. The system worked well and the crews were able to maintain the desired pace. Concrete trucks were scheduled such that there was always a gap of several minutes between the time one finished and the next truck arrived.

The slipform started the morning of Thursday, March 1 2018 and finished the morning of Thursday, March 8, traveling a height of 186 feet in 167 hours. The slipform process went smoothly with only a few obstacles. On March 4th the main crane handling rebar had a failure of a hydraulic valve that caused it to stop operating. Luckily, the plant maintenance crane was located and with the jib boom extended it was able to function as a replacement until the main crane could be repaired.

Once the slipform was completed the contractor installed the roof beams, decking, and poured the roof. Buzzi Unicem provided all the mechanical process equipment for this project so the contractor was only required to fabricate structural steel, chutes, and ductwork. A bridge was installed to connect the new Silo No. 3 with existing Silo No. 2, which was modified to accept a new drag chain conveyor to feed Silo No. 3. A drag chain takeaway conveyor was installed in the silo withdraw tunnel that discharges into a new bucket elevator which feeds the existing transfer belt conveyors to the finish mill system.  

The construction was completed in November 2018.