Phase oj lmprovement Prol of Calaveras Cemen

Bv \7. E. Trauf{er Reprinted lrom Pit und Ouutry, Janua

At San Andreas. Cal.. in the heart of the Mother Lode Country, from which centuries of er'osion washed gold-bearing gravel into the creek and river beds, is the plant of the Calaveras Cement Co. Built in 1926, this plant has long been rated one of the most efficient operations in the cement industry, but in the last two years it has been so improved that it is now one of the sl-rorv places of the industry on the Pacific Coast. Every department of the plant {rom the quarries to the pack-house has been modernized lvith the result that a wide variety of cements can now be made. The products of this plant include: standard Portland cement, white Portland cement, pumicite or P'ortland-puzzttctlan cement, -plastic early-hardening cement, and modified or low-heat Portland cement.

The history oi the quarries which supply this plant would alone make an interesting article. When the plant went into operation in June, 1926, the stone and shale required were cleliverecl from Quarry No. 1, which is about Y, rr'i. from the plant. Quarries No. 2 and 4 were later opened but most of the stone now used is obtained from Quarry No. 1. The stone in this quarry will average about 7O pet cent calcium carbonate. The shale is quarried with the limestone from the same quarry.

A gasoline and a Diesel locomotive were used to haul stone and shale to the plant until 1935. when this method was abandoned in favor of motor truck haulage' Quarry No' 4, which was openecl in 1935, contains a very pure limestone averaging 95 per 'cent calcium carbonate or better' This quarry has been developed to a point rvhere it is able to supply a large part of the raw material for the plant when needed. There is a S%-mi. roadway from this quarry to the plant. Its construction required the excavation of 200,C00 cu. yd. of material and the erection of three trestles; one of them has in it a concrete overpass crossing the scenic Mother Lode Highu'ay. At no point does the grade exceed 1 per cent, and all the curves were designed for possible future railway haulage. The rvhite clay used in the manufacture of white cement is obtained from a near source, as

Above: The two rcw-grinding compcrtmenl mills in closed circuit with Iour vibrcting screens. ThJ slurry-pump- lines crre shown' Center: Sev"rcl ol th1 cir-aepsrctors in tlie linish-grinding dep<rriment with 1f,"" "ia ieeders <rbo-ve. Below: The three clinker-grinding compart-."f -iii" *ith teed bins in bcckground, cnd some ol the cir-eeptrrctors used in closed circuii'