SPECIFICATION FOR LAYING INDASCO BITUMEN EMULSION IN COACHES AND DIESEL CARS
Thanks to Mark Brinton

This comes from a letter from Swindon Works dated 23/12/1958 which was contained within the Class 117 build specification.

(1). Specification of Mix.

Coaches:
1sq yd of flooring 5/8in thick
24lbs of 1/8" granite chippings
16lbs of course sand
10lbs of cement
11lbs of Indasco

Diesel cars:
1sq yd of flooring 1 1/4in thick
34lbs of 1/8" granite chippings
20lbs of course sand
11lbs of cement
17lbs of Indasco

(2). Method of mixing
Add 1/8" granite chippings, course sand and cement together in the mixer, and allow to mix in a dry state. Add the Indasco Emulsion and allow to mix until the mastic is of uniform colour and free from lumps. Then add a small quantity of water to achieve the desired working consistency.

(3). Preparation of Base.

Surfaces to which Indasco are to be applied must be clean, firm and free from dust and loose particles, and in the case of steel, rust, scale etc.

(4). Method of Laying.

Apply a wash coat, consisting of one part Indasco and one part clean cold water, and allow to dry. Over this dry wash coat, brush on neat Indasco and lay the flooring mix before the neat emulsion dries out. The surface should then be brought to a smooth finish with a wooden float.

After about two hours, a fine finish can be obtained by the use of a steel float.

Note added 8/6/59:

"For PS only, specification of bitumen-granite floors to be Bitumen 1 part by weight, Granite dust 3 parts by weight. See ref DY.3612/PS 3/6/59."

The Class 107 build specification (Section 11/5) quotes the use of 170lb of brown bitumen mixed with 476lb of granite dust to coat 55sq ft 1" thick.
The Class 122 build specification (Section 11) quotes the use of 195lb of brown bitumen mixed with 585lb of granite dust to coat 65sq ft 1" thick

If its a red concrete like substance then beware it may contain asbestos.