水泥穩(wěn)定碎石是將水泥、級配碎石、石屑和水按一定比例混和攪拌，攤鋪碾壓后形成的一種半剛性結(jié)構(gòu)層。廣泛地應(yīng)用于各級公路的基層，它具有良好的板體性和水穩(wěn)性，對于保證道路的使用功能，具有很重要的作用。它作為瀝青面層的下承層，是連接瀝青面層與路基的紐帶，是車輛荷載的主要承擔(dān)者，其主要承擔(dān)瀝青面層傳遞而來的行車垂直荷載，并將荷載均勻地分散在路基中。瀝青面層所發(fā)生的許多病害，都與其有直接的關(guān)系，下面分別介紹水泥穩(wěn)定碎石基層開裂、離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、開裂現(xiàn)象及防治措施

　　1、 Cracking phenomenon and prevention measures

　　水泥穩(wěn)定碎石基層經(jīng)常發(fā)生開裂現(xiàn)象，其裂縫形狀一般沿道路縱向呈規(guī)則分布的橫向裂縫，間距一般為5m～10m，裂縫寬度一般為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

　?。?）干縮性裂縫：即基層施工完畢后，隨著水分的蒸發(fā)，基層的濕度將明顯降低，就會產(chǎn)生干縮應(yīng)力，從而導(dǎo)致干縮裂縫。

　　(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.

　?。?）溫縮性裂縫：也就是熱脹冷縮產(chǎn)生的裂縫。水泥穩(wěn)定碎石基層屬半剛性基層，具有熱脹冷縮的性質(zhì)。水泥無機結(jié)合料內(nèi)部的不同礦物顆粒組成的固相、液相和氣相體，在溫差作用中必然會使其產(chǎn)生熱脹冷縮的體積變化，從而引起溫縮性裂縫。?

　　(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）控制水穩(wěn)基層的水泥劑量，一般控制在3%—6%，因為水泥劑量偏大時，水泥的水化熱會使基層內(nèi)外產(chǎn)生溫差，從而導(dǎo)致開裂現(xiàn)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.

　?。?）嚴(yán)格選擇水泥品種及水泥強度等級，水泥是影響水泥穩(wěn)定碎石質(zhì)量的關(guān)鍵，一般選用普通硅酸鹽水泥，水泥強度等級一般為32.5MPa，因為水泥活性成分過多或強度等級過高，會產(chǎn)生大量的水化熱，從而導(dǎo)致開裂現(xiàn)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，碾壓含水量不宜超過最佳含水量的1%，因含水量越大，則水泥穩(wěn)定碎石蒸發(fā)散失的水分越多，形成的裂縫就越大。

　　(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.

　?。?）加強基層的養(yǎng)護，基層施工完畢后，養(yǎng)生時間不少于7天，在養(yǎng)護期內(nèi)應(yīng)保持基層處于濕潤狀態(tài)，切忌或干或濕，從而避免干縮裂縫的產(chǎn)生。28天內(nèi)正常養(yǎng)護。最好在基層施工完畢一星期后即進行下封層或噴灑透層油，隨后盡早鋪筑瀝青面層，保證基層不繼續(xù)失水，引起干縮裂縫，這期間禁止車輛通行。

　　(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.

　?。?）適當(dāng)分割水穩(wěn)基層，對水穩(wěn)基層表面進行縮縫切割的辦法，人工提前消除基層所產(chǎn)生的收縮應(yīng)力，從而使基層的收縮應(yīng)力提前釋放。以消除溫縮和干縮裂縫的形成。方法是用切割機沿道路縱向每隔5m切割一道縮縫，縫寬3mm，縫深5—8mm，然后在縫內(nèi)灌以乳化瀝青。?

　　(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、離析現(xiàn)象及防治措施

　　2、 Separation phenomenon and prevention measures

　　水穩(wěn)基層經(jīng)常發(fā)生離析現(xiàn)象，所謂離析即粗細料集中現(xiàn)象，也即級配變異現(xiàn)象，離析還造成水穩(wěn)基層的強度不均勻，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

　　水穩(wěn)混合料在攪拌過程中發(fā)生的放料離析，在運輸過程中發(fā)生的顛簸離析，在卸料過程中發(fā)生的卸料離析，在攤鋪過程中發(fā)生的攤鋪離析，在找平過程中發(fā)生的找平離析等。

　　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）水穩(wěn)混合料在攪拌站輸出時，應(yīng)盡量降低出料高度，成品倉應(yīng)設(shè)置攪拌裝置，并能間歇放料。

　　(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）成品倉放料口距運料車廂的垂直距離不宜大于 2m，運料車應(yīng)及時移動前后位置，保證均勻裝料，以降低每次裝料的堆體高度。

　　(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）運料車輛在運輸過程中，應(yīng)勻速行駛，起步剎車要平穩(wěn)，路況差時應(yīng)慢行，避免強烈的顛簸振動。

　　(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.

　?。?）運料車輛在向攤鋪機受料斗卸料時，應(yīng)緩慢均勻地提升車廂，切忌速度太快。同時車廂的傾斜角度應(yīng)控制在30度之內(nèi)。

　　(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.

　?。?）攤鋪過程中，攤鋪機的螺旋布料器應(yīng)有三分之二埋入混合料中，應(yīng)使螺旋布料器均勻地運轉(zhuǎn)，切忌或快或慢。在攤鋪機后面應(yīng)設(shè)專人消除細集料離析現(xiàn)象，特別應(yīng)該鏟除局部粗集料“窩”，并用新拌混合料填補。

　　(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.

　?。?）人工找平時，應(yīng)扣鍬布料，切忌揚鍬遠拋，同時，刮爬拖動的次數(shù)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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