understanding crushed stone grades | ozinga

understanding crushed stone grades | ozinga

These grades are determined based on the size of the stone after it has been crushed, and they let you know the best applications for the specific stone. It is important to note that some gradations will have a range of stone sizes in that particular gradation. For example, a CA11 or CA7 (generally ) gradation may include individual stone sizes of 1 down to .

This form is for communication purposes and should not be considered an official order or order change request. All requests for changes to existing concrete or material orders need to be made through dispatch. Be aware delivery schedules fill up quickly, so its recommended that you place your order two or three days in advance.

Ozinga provides quality bulk materials and diverse concrete solutions delivered where you need it, when you need it with our extensive network of transportation services including truck, rail, barge and ship terminals across the Midwest and South Florida regions.

aggregates specifications|ontario sand, stone & gravel association

aggregates specifications|ontario sand, stone & gravel association

Specifications for construction aggregates have been developed for a variety of construction applications. The most important construction materials specifications for aggregates are for roadway and pavement construction (including hot-mix asphalt, granular base and granular sub-base), and for concrete materials used in buildings, civil engineering structures and infrastructure construction. In Ontario, specifications for aggregates used in road/pavement and infrastructure construction are presented in the Ontario Provincial Standard Specifications (OPSS; OPSS.MUNI for municipal and OPSS.PROV for MTO) and related special provisions developed by the Ministry of Transportation (MTO). These special provisions may override OPSS in contracts, and are not addressed in this document. In addition, specifications for aggregates used in concrete materials are covered within OPSS or the Canadian Standards Association (CSA) A23.1-14 specification. Agencies may also have their own specific requirements based on local experience or material availability.

Aggregate is usually described as either coarse aggregate (retained 4.75 mm) or fine aggregate (passing 4.75 mm). Aggregates generally make up about 95 percent of the total mass of hot-mix asphalt mixtures and 80 percent by mass of concrete - aggregate properties are, therefore, critical for quality hot-mix asphalt or concrete. Typically, hot-mix asphalt mixtures consist of 50 percent coarse aggregate and 50 percent fine aggregate, whereas conventional concrete and concrete products typically require about 55 percent coarse aggregate and 45 percent fine aggregate. Aggregates may be produced by processing sand and gravel or by blasting and crushing bedrock materials or select by-product materials, including recycled/reclaimed materials, such as concrete, asphalt, blast furnace slag, glass and ceramics, etc. Crushed stone and processed sand and gravel are interchangeable for many applications, but not all. Aggregates consisting of 100 percent crushed, angular particles are desirable for heavily loaded, high traffic roadway/highway applications where aggregate interlock is necessary to develop adequate shear strength and resistance to deformation (rutting). The most important specification parameters are particle size and distribution, particle shape and texture, and physical and chemical properties to assess aggregate strength and durability.

The gradation of the aggregates used in bituminous and concrete materials is very important to developing the required engineering properties of the materials and for economical production. Specifications generally permit a fairly broad range in gradation (gradation band) but a high degree of consistency is required during production for mix quality and uniformity. In concrete, the colour and texture of the finished product is also largely a function of the aggregate and, particularly, the fine aggregate.

In fine aggregates, the gradation is one of the most important quality factors. If it is controlled, the material is usually acceptable. However, it must be noted that more recent specifications, including the MTO special provisions and Superpave mix design method, place greater emphasis on the physical properties of fine aggregate, including micro-Deval abrasion and angularity.

In coarse aggregate, the desired gradation can generally be controlled by appropriate processing (screening) and the degree of crushing, but many physical and chemical properties must also be satisfied. Various deleterious materials, such as chert, shale and siltstone, may be present in a pit or quarry face, which may restrict or totally preclude the use of such materials.

Figure 1 illustrates a typical cross-section of an asphalt road. Figure 2 illustrates a typical cross-section of a concrete road. The thickness and composition of each layer will depend on the volume and composition of traffic (mainly amount of truck and bus traffic) expected for the road, as well as the nature of the ground (subgrade soils type(s) and drainage conditions), and climatic conditions.

As well as providing support for the pavement structure, the granular subbase layer provides drainage for the pavement structure and hence must be relatively free-draining. The granular base provides resistance to shear stresses transferred through the asphalt pavement surfacing and crushed particles are required to develop adequate aggregate interlock and strength to resist deformations. A well-graded material results in greater interlock between particles thereby increasing the shear strength and load-bearing capacity of the road.

There are a number of mix types, including Dense Friction Course (DFC), HL 1, Open Friction Course (OFC), Superpave 12.5 FC1 & FC2 and Stone Mastic Asphalt (SMA) 9.5, 12.5 & 19.0, which require premium surface course aggregates from the MTO Designated Sources for Materials List.

HL 2, HL 3, HL 3F, HL 4, HL 4F, Superpave 4.75, 9.5, 12.5 surface course mixes; HL 4, HL 8, Medium Duty Binder Course (MDBC) and Heavy Duty Binder Course (HDBC), Superpave 19.0, 25.0 & 37.5 binder course do not require the use of designated source aggregates, but, in some cases, do require that minimum crushed aggregate percentage and source type requirements are met. As well, other agency specific mixes may be specified on a contract basis with non-typical aggregate type requirements.

Open Graded Drainage Layer (OGDL) consists of open-graded aggregates bound with about 1.8 percent asphalt cement and is used as a drainage layer below concrete and deep-strength asphalt pavements. Secondary highways with speeds less than about 80 km/hr and lower traffic volumes typically specify HL 3, HL 4 or Superpave 9.5 or 12.5 surface course mixes. For proper placement and compaction, the asphalt lift thickness should be at least 2.5 to 3.0 times the maximum particle diameter. HL 3 aggregates have a nominal maximum size of 13.2 mm, requiring a minimum mat thickness of at least 35 mm. HL 4 is a slightly coarser mix with aggregates of a nominal maximum size of 16 mm, and hence requiring a minimum mat thickness of at least 40 mm.

On highways with speeds in excess of 80 km/hr and higher traffic volumes, premium surface course mixes are specified that provide adequate frictional resistance for safe vehicle operation and to resist permanent deformation (rutting). The types of asphalt mixtures used are designated as HL 1, DFC, OFC Superpave 12.5 (Friction Course) FC1 & FC2.

OFC is an open-graded mix, allowing internal drainage through the matrix rather than over the pavement surface, reducing the potential for hydroplaning on wet roads. It is also used on high-volume urban highways because of lower tire noise characteristics.

Stone Mastic Asphalt (SMA) is a gap-graded premium surface course mix with high frictional resistance, enhanced rutting resistance, water spray reduction and a potential for noise reduction. SMA consists of two parts: a coarse aggregate skeleton and an asphalt binder rich mortar. The mix has a gap-graded aggregate skeleton with coarse aggregate stone-on-stone contact. SMA is used on very high-volume urban highways or very high-volume, slow-moving traffic to resist rutting.

Aggregates for HL 3, HL 4 and Superpave 4.75, 9.5 and 12.5 surface course mixes do not have specific requirements for frictional properties, except for northern Ontario. In this region, most of the locally available aggregates are of igneous or metamorphic origin, with hard, wear-resistant minerals. These aggregates generally give good frictional properties in contrast to pavements made with carbonates of low wear resistance.

Aggregates used in concrete are governed by OPSS 1002 and/or CSA specification CSA A23.1-14. The desirable properties for concrete aggregates being essentially clean and uncoated, and consisting of properly shaped particles of strong, durable material. They should satisfactorily resist changes, such as cracking, swelling, softening, leaching, or chemical alteration, and should not contain deleterious materials, which might contribute to the deterioration, loss of strength, or unsightly appearance of the concrete.

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