SPECIFICATION RC-1. Broken Stone and Sand for One-course Portland Cement Concrete Pavement. BROKEN STONE FOR COARSE AGGREGATE. The broken stone shall consist of fragments of clean durable crushed General. rock, free from soft, thin, elongated or laminated pieces, disintegrated stone, vegetable, or other deleterious matter. The stone shall meet the following requirements: Toughness, not less than_____ Physical When tested by means of laboratory screens the broken stone for coarse Grading. aggregate shall meet the following requirements: The sand shall consist of clean, hard, durable, uncoated stone particles, General. preferably siliceous, free from lumps of clay, soft or flakey particles, loam, and all organic matter. It shall be well graded from coarse to fine, and when tested by means Grading. of laboratory screens and sieves shall meet the following requirements: Not more than 3 per cent by weight shall be removed by the elutriation test. When the sand is mixed with Portland cement in the proportion of 1 Mortar Strength Test. part of cement to 3 parts of sand, by weight, according to standard methods of making 1:3 mortar briquets, the resulting mortar at the age of 7 and 28 days shall have a tensile strength of at least 100 per cent of that developed in the same time by mortar of the same proportions and consistency, made of the same cement and Ottawa sand. Preliminary acceptance samples shall be subjected to both 7 and 28 day tests, and acceptance based thereupon. Samples tested during the progress of the work will be accepted on the basis of the 7-day test. Tests of the physical properties of the rock, the grading or mechanical Methods of analysis of broken stone and sand, and of the mortar tensile strength of Testing. sand shall be made in accordance with the following methods: 1. Toughness: U. S. Department of Agriculture Bulletin 347, page 15. 2. Grading of Broken Stone: U. S. Department of Agriculture Bulletin 555, page 32. 3. Mechanical Analysis of Sand: U. S. Department of Agriculture Bulletin 555, page 33. 4. Elutriation Test for Sand: U. S. Department of Agriculture Bulletin 555, page 32. 5. Mortar Tensile Strength Test for Sand: A. S. T. M. Standard Test C9-17. This specification provides for coarse and fine aggregate to be used in the construction of a one-course Portland cement concrete pavement. While a coefficient of hardness of not less than 16 for the stone for coarse aggregate might well be included under physical properties, a requirement for French coefficient of wear has been used instead, owing to the fact that few laboratories are equipped with a Dorry hardness machine. The 15 per cent of coarse aggregate passing the 1-inch screen, which is allowed, is permissible only upon the assumption that General. Grading. General. Grading. construction specifications will be based upon a fixed proportion of cement to combined coarse and fine aggregate and that the relative amounts of broken stone and sand will be varied as directed by the engineer so as to approximate definite proportions of coarse and fine aggregate. Thus the concrete should be composed of 1 part of Portland cement and 4 parts of fine and coarse aggregate, each measured separtely and accurately by volume. The concrete should approximate a 1:13:3 mix, but the engineer should vary the relative proportions of fine and coarse aggregate, depending upon their exact grading so as to obtain a concrete of maximum density. The concrete should be mixed in a batch mixer for not less than 14 minutes and the water should be reasonably clear, free from oil, acid, alkali, or vegetable substance, and neither brackish nor salt. Sufficient water should be used to produce a concrete which will flatten out and quake when deposited in place, but not enough to cause it to flow or to separate mortar and coarse aggregate. SPECIFICATION RC-2. Broken Stone or Gravel, and Sand for Portland Cement Concrete Base. The broken stone or gravel for coarse aggregate shall consist of clean, hard, tough, durable stone. It shall be free from soft, thin, elongated, or laminated pieces, disintegrated stone, vegetable, or other deleterious matter. When tested by means of laboratory screens the coarse aggregate shall meet the following requirements: Passing 3-inch screen, not less than___ Retained on 1-inch screen, not less than. SAND FOR FINE AGGREGATE, Per cent. 95 40 to 75 85 The sand shall consist of clean, hard, durable, uncoated stone particles. preferably siliceous, free from lumps of clay, soft or flakey particles, loam, and all organic matter. It shall be well graded from coarse to fine, and when tested by means of laboratory screens and sieves shall meet the following requirements Passing 1-inch screen-- Total passing 20-mesh sieve, not less than. Per cent 10 5 1 Mortar Strength Not more than 5 per cent by weight shall be removed by the elutriatio test. When the sand is mixed with Portland cement in the proportion of part of cement to 3 parts of sand, by weight, according to standar methods of making 1:3 mortar briquets, the resulting mortar at t age of 7 and 28 days shall have a tensile strength of at least 75 per ce of that developed in the same time by mortar of the same proportion and consistency, made of the same cement and Ottawa sand. Preliminary acceptance samples shall be subjected to both 7 and day tests, and acceptance based thereupon. Samples tested during t progress of the work will be accepted on the basis of the 7-day test. Tests of the grading or mechanical analysis of broken stone or gravel, Methods of and sand, and of the mortar tensile strength of sand shall be made in Testing. accordance with the following methods: 1. Grading of broken stone or gravel, U. S. Department of Agriculture Bulletin 555, p. 32. (8) 2. Mechanical analysis of sand, U. S. Department of Agriculture Bulletin 555, p. 33. 3. Elutriation test for sand, U. S. Department of Agriculture Bulletin 555, p. 32. 4. Mortar tensile strength test for sand, A. S. T. M., Standard Test C9-17. This specification provides for coarse and fine aggregate to be used in the construction of a Portland cement concrete base. The 15 per cent of coarse aggregate passing the 1-inch screen which is allowed is only permissible upon the assumption that construction specifications will be based upon a fixed proportion of cement to combined coarse and fine aggregate and that the relative amounts of broken stone or gravel and sand will be varied as directed by the enginer so as to approximate definite proportions of coarse and fine aggregate. Thus the concrete should be composed of 1 part of Portland cement and 9 parts of fine and coarse aggregate, each measured separately and accurately by volume. The concrete should approximate a 1:3:6 mix, but the engineer should vary the relative proportions of fine and coarse aggregate depending upon their exact grading, so as to obtain a concrete of maximum density. The concrete should be mixed in a batch mixer for not less than 1 minute and the water should be reasonably clear, free from oil, acid, alkali, or vegetable substance, and neither brackish nor salt. Sufficient water should be used to produce a concrete which will flatten out and quake when deposited in place, but not enough to cause it to flow or to separate mortar and coarse aggregate. General. Quality. Method of SPECIFICATION GW-1. Gravel for Water-bound Gravel Roads. The gravel shall be composed of fragments of hard, durable rock, of high resistance to abrasion, together with sand and clay or other binding material, and shall be free from thin or elongated pieces. Cementing value of material under 1-inch mesh shall be not 1. For base course: (a) The gravel, when tested by means of laboratory screens, (b) The material retained on the 1-inch screen is known as Total retained on 11-inch screen.. (c) The material passing the 1-inch screen is known as fine Total passing 200-mesh sieve---- 2. For wearing course: (a) The gravel, when tested by means of laboratory screens, Passing a 2-inch screen, not less than. (b) The material retained on the 1-inch screen is known as Total retained on 1-inch screen-- (c) The material passing the 3-inch screen is known as fine Total passing 200-mesh sieve__. Tests of the quality and grading of the gravel shall be made in accordance with the folowing methods: Cementing value, U. S. Department of Agriculture Bulletin 345, p. 19. This specification covers the quality and grading of a sandclay-gravel suitable for use in the construction of a water-bound gravel road. It applies to gravels composed mainly of fragments of quartz or other nonbinding rock types. In cases where the gravel is composed essentially of limestone or other materials which will bond under traffic, considerably less material under 200-mesh may be allowed. The sizes specified contemplate a base course of at least 4 inches, and a wearing course of at least 3 inches in thickness after consolidation. The relative proportions of the various intermediate sizes have been drawn so as to exclude only gravels of manifestly poor grading. In cases where the gravel, although otherwise acceptable, is deficient in sand or clay, such materials, if available, and of a suitable character, may be added in sufficient quantities to bring the grading and cementing value of the gravel to within the limits specified. This should be done by spreading the sand or clay uniformly over the loose gravel surface and thoroughly harrowing with a spike-tooth harrow, after which the surface is consolidated. In maintaining roads of this type, material as nearly the same as that composing the road surface should be used. In patching, care should be taken that the finished surface after consolidation is smooth and continuous. SPECIFICATION GBC-2. Gravel, Sand, and Filler for Coarse Aggregate Bituminous Concrete GRAVEL. The gravel shall be composed of sound, hard, durable fragments of General. rock of high resistance to abrasion and shall contain no particles of shale, slate, coal, or other materials which easily disintegrate. It shall be free from vegetable or other deleterious matter, and shall contain no soft, thin, or elongated pieces. The pea gravel, when tested by means of laboratory screens, shall Pea Gravel. meet the following requirements: Passing 1-inch screen, not less than__-. Retained on 1-inch screen, not less than--‒‒‒‒‒ Per cent. 95 85 The coarse aggregate, when tested by means of laboratory screens, Coarse shall meet the following requirements: Passing 1-inch screen, not less than.. Retained on 1-inch screen, not less than_. SAND. Aggregate. Per cent. 95 25 to 75 85 The sand for fine aggregate shall be composed of sound, durable stone General. particles, free from a coating of clay or loam. When tested by means of laboratory screens and sieves, the sand shall Grading. meet the following requirements: Passing-inch screen Total passing 40-mesh sieve--- Retained on 200 mesh sieve, not less than- MINERAL FILLER. Per cent. 30 to 70 90 The mineral filler shall consist of limestone dust, dolomite dust, Port- General. land cement, or natural cement. It shall be free from foreign or other objectionable material. When tested by means of laboratory sieves, the mineral filler shall Fineness. meet the following requirements: Per cent. Passing 30 mesh sieve--- Total passing 200 mesh sieve, not less than_-_ 100 Tests of the grading of the gravel, sand, and filler shall be made in Methods of accordance with the following methods: Testing. Grading of Gravel, U. S. Department of Agriculture Bulletin 555, p. 32. This specification is intended to cover the mineral constituents of a roughly proportioned bituminous concrete consisting of from 45 to 60 per cent gravel or coarse aggregate, from 30 to 45 per cent sand or fine aggregate, from 3 to 5 per cent mineral filler, and from 5 to 8 per cent bitumen. This mixture should preferably be 58683°-18-Bull. 704—————3 |