一、水泥稳定碎石作用原理及强度机理

　　1、 Principle and strength mechanism of cement stabilized crushed stone

　　1、作用原理?

　　1. Working principle?

　　水泥稳定碎石是以级配碎石为骨料， 辅以胶凝材料和水泥浆体按照嵌挤原理进行摊铺压实，该种工艺的初期强度高， 强度随龄期延长而增加， 其抗渗性能较高， 该工艺的水泥用量为混合料的3%～6%， 施工后7d无侧限抗压强度可达2MPa～4MPa， 其施工质量优劣将直接影响路面的使用性能和寿命。?

　　Cement stabilized crushed stone is made of graded crushed stone as aggregate, supplemented with cementitious materials and cement slurry, and spread and compacted according to the principle of interlocking. This process has high initial strength, which increases with age and has high impermeability. The cement dosage of this process is 3% to 6% of the mixture, and the unconfined compressive strength can reach 2MPa to 4MPa after 7 days of construction. The quality of its construction will directly affect the performance and service life of the road surface.?

　　2、 强度机理?

　　2. Strength mechanism?

　　（1）嵌挤作用?

　　(1) Squeezing effect?

　　该工艺采用的骨料是由颗粒组成， 施工后小粒径颗粒可填充大粒径颗粒空隙， 应按照一级填补一级的原则进行， 摊铺后在外力作用下， 大小颗粒可紧密的嵌锁在一起， 颗粒间的嵌挤和摩阻作用而形成内模阻力可提高其强度和稳定性。?

　　The aggregate used in this process is composed of particles. After construction, small particles can fill the gaps between large particles, and the principle of filling one level at a time should be followed. After paving, under external force, the large and small particles can be tightly interlocked, and the internal mold resistance formed by the interlocking and friction between particles can improve its strength and stability.?

　　（2）水泥硬化?

　　(2) Cement hardening?

　　施工后水泥内矿物质和水将发生水解和水化反应， 最终产物为Ca（OH）2和其他水化物， 部分水化物可自行硬化生成水泥石骨架， 部分则与碎石内的其他矿物质发生硬凝反应和碳酸化作用，该类产物可增加水泥稳定碎石基层强度。?

　　After construction, minerals and water in the cement will undergo hydrolysis and hydration reactions, and the final products are Ca (OH) 2 and other hydrates. Some hydrates can self harden to form a cement stone skeleton, while others undergo hardening and carbonation reactions with other minerals in the crushed stone. These products can increase the strength of cement stabilized crushed stone base.?

　　二、水泥稳定碎石在公路工程中的应用

　　2、 Application of cement stabilized crushed stone in highway engineering

　　二、水泥稳定碎石在公路工程中的应用　　1、原材料控制?

　　2、 Application of cement stabilized crushed stone in highway engineering 1. Raw material control?

　　水泥碎石稳定基层结构属于半刚性结构，对原材料要求比较严，严把材料质量关是保证工程质量的基础和重要环节。水泥稳定碎石路面基层的原材料主要有水泥、粗集料、细集料、矿粉。?

　　The cement crushed stone stabilized base structure belongs to a semi-rigid structure, which has strict requirements for raw materials. Strictly controlling the quality of materials is the foundation and important link to ensure the quality of the project. The raw materials for the cement stabilized crushed stone pavement base mainly include cement, coarse aggregate, fine aggregate, and mineral powder.?

　　（1）水泥?

　　(1) Cement?

　　水泥作为稳定剂，是控制水泥碎石稳定基层质量的关键所在。水泥选用初凝时间3h 以上和终凝时间较长的低标号水泥，各项技术指标必须满足技术规范的要求，同时水泥初终凝时间是确定水泥稳定碎石的施工控制时间的重要依据。在施工过程中，为了保证水泥的质量，我们对进场水泥每批次都进行水泥强度、初凝时间、终凝时间、安定性和细度指标的检验。?

　　Cement, as a stabilizer, is the key to controlling the quality of cement stabilized crushed stone base. Low grade cement with an initial setting time of more than 3 hours and a longer final setting time must be selected for cement. All technical indicators must meet the requirements of technical specifications. At the same time, the initial and final setting time of cement is an important basis for determining the construction control time of cement stabilized crushed stone. During the construction process, in order to ensure the quality of cement, we conduct inspections on cement strength, initial setting time, final setting time, stability, and fineness indicators for each batch of cement that enters the site.?

　　（2）集料?

　　(2) Aggregate?

　　粗集料的质量控制指标主要是根据结构层性能确定出碎石的强度和级配。细集料主要是控制好石屑的颗粒组成和掺加量，保证级配连续。为了把好原材料质量关，工地试验室加强对各类原材料的料源进行提前确定和检查，在使用过程中按规定频率抽样检验，不合格的材料不能用于工程中。?

　　The quality control indicators of coarse aggregate mainly determine the strength and gradation of crushed stone based on the performance of the structural layer. Fine aggregate mainly controls the particle composition and dosage of stone chips to ensure continuous gradation. In order to ensure the quality of raw materials, the on-site laboratory strengthens the pre determination and inspection of various raw material sources, and conducts sampling inspections at the prescribed frequency during use. Unqualified materials cannot be used in the project.?

　　2、混合料组成及配合比设计?

　　2. Composition and mix design of the mixture?

　　级配选择。各种不同粒径的集料，按照一定比例搭配起来，才能达到较高的密实度和较大的摩擦力。因此，要求碎石集料有一定的级配。但施工时所用碎石集料颗粒不均匀，所以，原材料选定后，要对集料进行级配设计和级配调整，使其合成级配尽量满足设计级配的要求。?

　　Grading selection. Various aggregates of different particle sizes can only be combined in a certain proportion to achieve higher density and greater friction. Therefore, it is required that the crushed stone aggregate has a certain grading. However, the crushed stone aggregate particles used during construction are uneven. Therefore, after selecting the raw materials, it is necessary to design and adjust the gradation of the aggregate to ensure that its composite gradation meets the requirements of the design gradation as much as possible.?

　　其他路用性能检验。初步拟定配合比后，综合考虑混合料的抗拉性、刚度、耐久性、抗疲劳性、抗裂性等路用性能，得出最佳水泥掺量，从而确定最佳配合比。?

　　Other road performance tests. After preliminary formulation of the mix proportion, the optimal cement dosage is determined by comprehensively considering the road performance such as tensile strength, stiffness, durability, fatigue resistance, and crack resistance of the mixture.?

　　最佳级配确定。在确定最佳水泥剂量后，变化集料级配，通过混合料路用性能验证，分析规范中三种典型级配对混合料路用性能的影响，得出最佳级配。?

　　Determine the optimal grading. After determining the optimal cement dosage, changing the aggregate gradation, verifying the road performance of the mixture, analyzing the influence of three typical gradation pairs in the specifications on the road performance of the mixture, and obtaining the optimal gradation.?

　　3、混合料的拌和?

　　3. Mixing of mixtures?

　　摊铺用料搅拌前, 应检查场内各处集料的含水量, 计算当天的配合比, 外加水与天然含水量的总和要比最佳含水量略高。实际的水泥剂量可以大于混合料组成设计时确定的水泥剂量约0.5%, 但是实际采用的水泥剂量和现场抽检的水泥剂量应小于5.5%。同时在充分估计施工富余强度时要从缩小施工偏差入手, 不得以提高水泥用量的方式提高路面基层强度; 每天开始搅拌之后, 出料时要在拌和机投料运输带上取样检查是否符合设计的配合比, 进行正式生产之后, 每1 h～2 h 检查一次拌和情况, 检验其配比、集料级配、含水量是否变化。高温作业时, 早晚与中午的含水量要有区别, 要按温度变化及时调整; 拌和机出料不允许采取自由跌落式的落地成堆、装载机装料运输的办法。一定要配备带活门漏斗的料仓, 由漏斗出料直接装车运输, 装料时运输车辆必须前后移动, 最少分3 次装料, 避免混合料离析。?

　　Before mixing the paving materials, the moisture content of the aggregates in each part of the site should be checked, and the mix ratio for the day should be calculated. The total moisture content of the external water and natural water should be slightly higher than the optimal moisture content. The actual cement dosage can be about 0.5% higher than the cement dosage determined during the design of the mixture composition, but the actual cement dosage used and the cement dosage sampled on site should be less than 5.5%. At the same time, when fully estimating the surplus strength of construction, we should start with reducing construction deviations and not increase the strength of the pavement base by increasing the amount of cement used; After starting mixing every day, samples should be taken from the feeding conveyor belt of the mixer to check if they meet the designed mix ratio. After formal production, the mixing situation should be checked every 1-2 hours to check if the mix ratio, aggregate gradation, and moisture content have changed. When working in high temperatures, there should be a difference in moisture content between morning, evening, and noon, and adjustments should be made in a timely manner according to temperature changes; The discharge of the mixer is not allowed to adopt the method of free falling and stacking on the ground, or loading and transporting by the loader. It is necessary to equip a silo with a valve funnel, and the material should be directly loaded and transported from the funnel. When loading, the transport vehicle must move forward and backward, and the material should be loaded at least three times to avoid segregation of the mixture.?

　　4、 混合料的摊铺?

　　4. Spread the mixture?

　　为了控制好水泥稳定碎石基层的高程与平整度，采用自动找平摊铺机摊铺。将水泥稳定碎石混合料通过自卸汽车直接卸入摊铺机料斗内，由摊铺机均匀摊铺，摊铺均匀的料应立即碾压，在摊铺过程中要注意集料的离析。在摊铺机后设专人消除粗细集料离析现象，特别应该铲除局部粗集料带，并用新拌混合料填补。使用摊铺机铺筑水泥稳定土混合料时，必须严格遵守操作技术规程，才能达到较好的平整度。一次铺筑的厚度不超过25cm，分层摊铺时，上层厚度取10cm；工程计划应尽量减少横向接缝；做好横向接缝，应立即用直尺检验；经常检验控高钢丝和传感器；经常用直尺检验表面；保持摊铺机在良好的工作状态。?

　　In order to control the elevation and flatness of the cement stabilized crushed stone base, an automatic leveling and paving machine is used for paving. The cement stabilized crushed stone mixture is directly unloaded into the hopper of the paver by a dump truck, and evenly spread by the paver. The evenly spread material should be immediately compacted, and attention should be paid to the segregation of aggregates during the paving process. After the paver, a dedicated person should be assigned to eliminate the segregation of coarse and fine aggregates, especially to remove the local coarse aggregate belt and fill it with fresh mixed material. When using a paver to lay cement stabilized soil mixture, it is necessary to strictly follow the operating technical regulations in order to achieve good flatness. The thickness of a single paving shall not exceed 25cm. When paving in layers, the thickness of the upper layer shall be taken as 10cm; The engineering plan should minimize horizontal joints as much as possible; Horizontal joints should be inspected immediately with a ruler; Regularly inspect the height control steel wire and sensors; Regularly inspect the surface with a ruler; Keep the paver in good working condition.?

　　5、压实?

　　5. Compaction?

　　混合料经摊铺机摊铺成型后，即可用压路机碾压，碾压长度需根据施工现场的实际情况确定，如果实测混合料的含水量高于最佳含水量，且气温较低时可适当延长碾压长度，如果混合料已接近最佳含水量且温度较高蒸发快时，应缩短碾压长度，确保在最佳含水量时进行碾压。?

　　After the mixture is spread and formed by the paver, it can be rolled by a roller. The rolling length should be determined according to the actual situation of the construction site. If the measured moisture content of the mixture is higher than the optimal moisture content and the temperature is low, the rolling length can be appropriately extended. If the mixture is close to the optimal moisture content and evaporates quickly at high temperatures, the rolling length should be shortened to ensure that rolling is carried out at the optimal moisture content.?

　　从开始加水拌和到完成压实的延迟时间，对水稳的密实度和强度有很大影响。间隔时间过长，水泥会部分结硬，一方面影响水稳的压实度，而压实度对强度的影响很大；另一方面将破坏已结硬水泥的胶凝作用，使水稳的强度下降。?

　　The delay time from the start of water mixing to the completion of compaction has a significant impact on the compactness and strength of water stability. If the interval time is too long, the cement will partially harden, which on the one hand affects the compaction degree of water stability, and the compaction degree has a significant impact on strength; On the other hand, it will destroy the cementing effect of already hardened cement, causing a decrease in the strength of water stability.?

　　碾压过程中的质量控制∶试验人员在现场检测混合料含水量及配合比，发现问题，反馈信息，及时纠正。现场技术人员在压实过程中，跟踪检测松铺厚度、摊铺宽度等各项指标，确保成型后的基层各项几何尺寸符合要求。?

　　Quality control during rolling process: Testing personnel inspect the moisture content and mix proportion of the mixture on site, identify problems, provide feedback, and promptly correct them. On site technicians track and detect various indicators such as loose paving thickness and paving width during the compaction process to ensure that the geometric dimensions of the formed base meet the requirements.?

　　每次摊铺结束后，暂留30～40m路段，将摊铺机驶离混合料末端（注意应将摊铺机内存料清理干净），然后人工将末端混合料弄整齐，使之与路中心线垂直，再进行碾压。待摊铺新的混合料之前，将末端不符合要求的混合料铲除，末端切齐，使之与路中心线垂直并成垂直向下的断面，然后再摊新铺的混合料。?

　　After each paving is completed, leave a section of 30-40m for the paver to drive away from the end of the mixture (note that the material stored in the paver should be cleaned up), and then manually tidy the end of the mixture to be perpendicular to the centerline of the road before rolling it. Before laying the new mixture, remove the mixture that does not meet the requirements at the end, cut the end evenly, make it perpendicular to the centerline of the road and form a vertical downward section, and then lay the new mixture.?

　　6、养生?

　　6. Health preservation?

　　在下基层碾压成型并经压实度检验合格后, 即采用复合材料养生膜覆盖进行保湿养生。上基层碾压结束表面稍干随即洒布透层沥青和摊铺稀浆封层进行养生。薄膜覆盖养生可以保证有充足的水分让水泥充分水化, 并且可以防止因失水过多而引起干缩裂缝。养生期间, 应封闭交通。如不能封闭交通, 应禁止重车通行, 其他车辆的车速不得超过30 km/ h, 并避免在主车道上集中行驶。上基层采用透层油和稀浆封层养生时, 透层油采用慢裂、渗透性好的洒布型乳化沥青, 稀浆封层采用慢裂快凝的拌和型乳化沥青。气温低于10°或大风、即将降雨时, 不得喷洒透层油。?

　　After the lower base layer is compacted and passes the compaction degree inspection, composite material curing film is used to cover it for moisturizing and curing. After the compaction of the upper base layer is completed, the surface should be slightly dry, and then a prime coat of asphalt and a slurry seal layer should be sprayed for curing. Thin film coverage for health preservation can ensure sufficient moisture to fully hydrate cement and prevent shrinkage cracks caused by excessive water loss. During the period of health preservation, traffic should be closed off. If traffic cannot be closed, heavy vehicles should be prohibited from passing, and the speed of other vehicles should not exceed 30 km/h, and concentrated driving on the main lane should be avoided. When using permeable oil and slurry seal for curing the upper base layer, the permeable oil should be a slow cracking and permeable spray type emulsified asphalt, and the slurry seal layer should be a slow cracking and fast setting mixed emulsified asphalt. When the temperature is below 10 ° C or there is strong wind or imminent rainfall, it is not allowed to spray the penetrating oil.?

　　总之，影响水泥稳定碎石基层质量的因素很多, 在施工中, 不仅要严格执行有关规范, 还应结合具体情况进行相应的调节、控制。实践证明, 在施工中只要加强对混合料含水量、材料组成比例的控制, 有效防止混合料离析, 选择合适的压实机械, 采取适当的压实工艺并注意混合料养生, 就能够提高工程质量。?

　　In summary, there are many factors that affect the quality of cement stabilized crushed stone base. During construction, it is not only necessary to strictly comply with relevant regulations, but also to make corresponding adjustments and controls based on specific circumstances. Practice has proven that in construction, as long as the control of the moisture content and material composition ratio of the mixture is strengthened, the segregation of the mixture is effectively prevented, suitable compaction machinery is selected, appropriate compaction processes are adopted, and attention is paid to the curing of the mixture, the quality of the project can be improved.?

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