Aggregate tests Northstone Materials（总测试Northstone材料）.pdfVIP

© NORTHSTONE (NI) Ltd. QUARRY ASPHALT DIVISION AGGREGATE TESTS Why do we need to test rocks? Have you ever wondered why stone quarries tend to be found in hilly and mountainous regions of the country? Hills and mountains exist because they are composed of hard rocks resistant to erosion. Thats why quarrymen look to these areas to find suitable rock to quarry. Valleys often form in areas of weaker rocks that are more easily eroded away. It is essential that aggregates used in construction purposes are strong and durable. Think of bricks, blocks, concrete, coated materials – the largest single component in all of these construction materials is aggregate. It would be disastrous to construct houses or bridges or roads with building materials made with weak rock. This is why quarrymen need to test the rocks that they quarry – they need to know if the rock is strong and suitable for the end-use it is to be put to. They need to know if there are any weak strata (rock layers) in the quarry that would be detrimental to the quality of the stone. For instance, where basalt lavas are being quarried, the quarryman needs to take care to exclude any soft red rock that is often found between lava flows. He also needs to avoid any basalt that has weathered, or that contains excessive amounts of vesicles (gas cavities formed during the emplacement of the flow), or amygdales (cavities filled with soft white minerals called zeolites). In gritstone quarries, bands of soft shale have to be excluded from aggregate production. Soft rocks The following are some rock types that are generally too soft, friable (crumbly) or fissile (composed of weak platy layers) for use as aggregates in construction: • Marl (calcium carbonate • Mudstone