水泥稳定碎石是将水泥、级配碎石、石屑和水按一定比例混和搅拌，摊铺碾压后形成的一种半刚性结构层。广泛地应用于各级公路的基层，它具有良好的板体性和水稳性，对于保证道路的使用功能，具有很重要的作用。它作为沥青面层的下承层，是连接沥青面层与路基的纽带，是车辆荷载的主要承担者，其主要承担沥青面层传递而来的行车垂直荷载，并将荷载均匀地分散在路基中。沥青面层所发生的许多病害，都与其有直接的关系，下面分别介绍水泥稳定碎石基层开裂、离析病害原因及防治措施。

　　Cement stabilized crushed stone is a semi-rigid structural layer formed by mixing cement, graded crushed stone, stone chips, and water in a certain proportion, paving and rolling. Widely used in the grassroots of various levels of highways, it has good flatness and water stability, and plays an important role in ensuring the functional use of roads. As the lower layer of the asphalt surface layer, it is the link between the asphalt surface layer and the roadbed, and is the main carrier of vehicle loads. It mainly bears the vertical load transmitted from the asphalt surface layer and evenly distributes the load in the roadbed. Many diseases that occur on the asphalt surface layer are directly related to it. The following introduces the causes and prevention measures of cracking and segregation diseases on cement stabilized crushed stone base.

　　一、开裂现象及防治措施

　　1、 Cracking phenomenon and prevention measures

　　水泥稳定碎石基层经常发生开裂现象，其裂缝形状一般沿道路纵向呈规则分布的横向裂缝，间距一般为5m～10m，裂缝宽度一般为3mm～5mm左右。

　　The cement stabilized crushed stone base often experiences cracking, and the crack shape is generally horizontally distributed in a regular pattern along the longitudinal direction of the road, with a spacing of generally 5m to 10m and a crack width of generally 3mm to 5mm.

　　1原因分析

　　Reason analysis

　　（1）干缩性裂缝：即基层施工完毕后，随着水分的蒸发，基层的湿度将明显降低，就会产生干缩应力，从而导致干缩裂缝。

　　(1) Dry shrinkage cracks: After the completion of the base construction, as the moisture evaporates, the humidity of the base will significantly decrease, resulting in dry shrinkage stress and leading to dry shrinkage cracks.

　　（2）温缩性裂缝：也就是热胀冷缩产生的裂缝。水泥稳定碎石基层属半刚性基层，具有热胀冷缩的性质。水泥无机结合料内部的不同矿物颗粒组成的固相、液相和气相体，在温差作用中必然会使其产生热胀冷缩的体积变化，从而引起温缩性裂缝。?

　　(2) Thermal shrinkage cracks: cracks caused by thermal expansion and contraction. Cement stabilized crushed stone base is a semi-rigid base with thermal expansion and contraction properties. The solid, liquid, and gas phases composed of different mineral particles inside the inorganic binder of cement will inevitably undergo volume changes due to thermal expansion and contraction under the action of temperature difference, thereby causing thermal shrinkage cracks.?

　　2防治措施

　　2 Prevention and control measures

　　（1）控制水稳基层的水泥剂量，一般控制在3%—6%，因为水泥剂量偏大时，水泥的水化热会使基层内外产生温差，从而导致开裂现象。

　　(1) The cement dosage for controlling the water stable base layer is generally controlled at 3% -6%, because when the cement dosage is too high, the hydration heat of cement will cause a temperature difference between the inside and outside of the base layer, leading to cracking.

　　（2）严格选择水泥品种及水泥强度等级，水泥是影响水泥稳定碎石质量的关键，一般选用普通硅酸盐水泥，水泥强度等级一般为32.5MPa，因为水泥活性成分过多或强度等级过高，会产生大量的水化热，从而导致开裂现象。

　　(2) Strictly select the type and strength grade of cement. Cement is the key factor affecting the quality of cement stabilized crushed stone. Ordinary Portland cement is generally used, with a strength grade of 32.5MPa. Due to excessive active ingredients or high strength grades in cement, a large amount of hydration heat will be generated, leading to cracking.

　　（3）控制含水量，碾压含水量不宜超过最佳含水量的1%，因含水量越大，则水泥稳定碎石蒸发散失的水分越多，形成的裂缝就越大。

　　(3) Control the moisture content, and the rolling moisture content should not exceed 1% of the optimal moisture content, because the higher the moisture content, the more water evaporates and dissipates from cement stabilized crushed stone, resulting in larger cracks.

　　（4）加强基层的养护，基层施工完毕后，养生时间不少于7天，在养护期内应保持基层处于湿润状态，切忌或干或湿，从而避免干缩裂缝的产生。28天内正常养护。最好在基层施工完毕一星期后即进行下封层或喷洒透层油，随后尽早铺筑沥青面层，保证基层不继续失水，引起干缩裂缝，这期间禁止车辆通行。

　　(4) Strengthen the maintenance of the grassroots. After the completion of grassroots construction, the maintenance time should not be less than 7 days. During the maintenance period, the grassroots should be kept in a moist state, avoiding dryness or wetness, in order to avoid the occurrence of shrinkage cracks. Normal maintenance within 28 days. It is best to carry out the sub sealing layer or spray the prime coat oil one week after the completion of the base construction, and then lay the asphalt surface layer as soon as possible to ensure that the base does not continue to lose water and cause shrinkage cracks. During this period, vehicle traffic is prohibited.

　　（5）适当分割水稳基层，对水稳基层表面进行缩缝切割的办法，人工提前消除基层所产生的收缩应力，从而使基层的收缩应力提前释放。以消除温缩和干缩裂缝的形成。方法是用切割机沿道路纵向每隔5m切割一道缩缝，缝宽3mm，缝深5—8mm，然后在缝内灌以乳化沥青。?

　　(5) The method of appropriately dividing the water stable base layer and cutting shrinkage joints on the surface of the water stable base layer can manually eliminate the shrinkage stress generated by the base layer in advance, thereby releasing the shrinkage stress of the base layer in advance. To eliminate the formation of thermal and dry shrinkage cracks. The method is to use a cutting machine to cut a shrinkage joint every 5m along the longitudinal direction of the road, with a width of 3mm and a depth of 5-8mm, and then pour emulsified asphalt into the joint.?

　　二、离析现象及防治措施

　　2、 Separation phenomenon and prevention measures

　　水稳基层经常发生离析现象，所谓离析即粗细料集中现象，也即级配变异现象，离析还造成水稳基层的强度不均匀，表面不平整等病害。

　　The phenomenon of segregation often occurs in the water stable base layer, which refers to the concentration of coarse and fine materials, that is, the variation of gradation. Segregation also causes uneven strength and uneven surface of the water stable base layer.

　　原因分析

　　Cause analysis

　　水稳混合料在搅拌过程中发生的放料离析，在运输过程中发生的颠簸离析，在卸料过程中发生的卸料离析，在摊铺过程中发生的摊铺离析，在找平过程中发生的找平离析等。

　　The material segregation that occurs during the mixing process of water stable mixtures, the bouncing segregation that occurs during transportation, the unloading segregation that occurs during unloading, the spreading segregation that occurs during paving, and the leveling segregation that occurs during leveling.

　　防治措施

　　Preventive measures

　　（1）水稳混合料在搅拌站输出时，应尽量降低出料高度，成品仓应设置搅拌装置，并能间歇放料。

　　(1) When the water stable mixture is output from the mixing plant, the discharge height should be minimized as much as possible. The finished product warehouse should be equipped with a mixing device and able to discharge intermittently.

　　（2）成品仓放料口距运料车厢的垂直距离不宜大于 2m，运料车应及时移动前后位置，保证均匀装料，以降低每次装料的堆体高度。

　　(2) The vertical distance between the discharge port of the finished product warehouse and the transport carriage should not be greater than 2 meters. The transport carriage should move its front and rear positions in a timely manner to ensure uniform loading and reduce the height of each loading pile.

　　（3）运料车辆在运输过程中，应匀速行驶，起步刹车要平稳，路况差时应慢行，避免强烈的颠簸振动。

　　(3) During transportation, the material transport vehicle should drive at a constant speed, brake smoothly when starting, and drive slowly when the road conditions are poor to avoid strong bumps and vibrations.

　　（4）运料车辆在向摊铺机受料斗卸料时，应缓慢均匀地提升车厢，切忌速度太快。同时车厢的倾斜角度应控制在30度之内。

　　(4) When the material transport vehicle unloads from the receiving hopper of the paver, the carriage should be slowly and evenly lifted, and the speed should not be too fast. At the same time, the inclination angle of the carriage should be controlled within 30 degrees.

　　（5）摊铺过程中，摊铺机的螺旋布料器应有三分之二埋入混合料中，应使螺旋布料器均匀地运转，切忌或快或慢。在摊铺机后面应设专人消除细集料离析现象，特别应该铲除局部粗集料“窝”，并用新拌混合料填补。

　　(5) During the paving process, two-thirds of the spiral distributor of the paver should be buried in the mixture, and the spiral distributor should operate evenly, avoiding either too fast or too slow. A dedicated person should be assigned behind the paver to eliminate the segregation of fine aggregate, especially to remove local coarse aggregate "pits" and fill them with fresh mixed material.

　　（6）人工找平时，应扣锹布料，切忌扬锹远抛，同时，刮爬拖动的次数不大于2次。

　　(6) When manually searching, the shovel should be used to remove the fabric, and the shovel should not be thrown far away. At the same time, the number of scraping, crawling, and dragging should not exceed 2 times.

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