行业资讯
水泥稳定碎石基层施工质量控制要点
水泥稳定材料(cement stabilized material)是以水泥为结合料,通过加水与稳定材料共同拌和形成的混合料。包括水泥稳定级配碎石、水泥稳定级配砾石、水泥稳定石屑、水泥稳定土、水泥稳定砂等。将此混合物经摊铺、碾压和养生后,可作为路面的基层或底基层。水泥稳定碎石,是将水泥、级配碎石、石屑和水按一定比例混合搅拌,摊铺碾压后形成的一种半刚性结构层,在压实和养生后,其无侧限抗压强度符合规定的要求。
Cement stabilized material is a mixture formed by mixing cement as a binder and stabilizing material with water. Including cement stabilized graded crushed stone, cement stabilized graded gravel, cement stabilized stone chips, cement stabilized soil, cement stabilized sand, etc. After paving, rolling, and curing, this mixture can be used as the base or sub base of the road surface. 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. After compaction and curing, its unconfined compressive strength meets the specified requirements.
水泥稳定碎石作为路面基层材料具有良好的力学性能和整体性、稳定性、耐久性、抗冻性以及与面层能够很好地结合的技术特点,在公路路面基层或底基层得到广泛的应用。为了充分发挥其优良的材料功能特点,必须切实做好水泥稳定碎石的施工工艺和管理各项要求,控制好整个施工管理的各个环节,达到规范规定的各项质量要求。
Cement stabilized crushed stone, as a pavement base material, has good mechanical properties, integrity, stability, durability, frost resistance, and technical characteristics that can be well combined with the surface layer. It has been widely used in highway pavement base or subbase. In order to fully utilize its excellent material functional characteristics, it is necessary to effectively carry out the construction process and management requirements of cement stabilized crushed stone, control all aspects of the entire construction management, and meet the quality requirements specified in the specifications.
1 水泥稳定碎石作用原理水泥稳定碎石是以级配碎石作为集料,原材料质量控制要求水泥、集料的相关参数要达到规范要求,采用一定数量的胶凝材料和足够的灰浆体积填充骨料的空隙,按嵌挤原理摊铺压实。其压实度接近于密实度,强度主要靠碎石间的嵌挤锁结原理,同时有足够的灰浆体积来填充骨料的空隙。它的初期强度高,并且强度随龄期而增加很快结成板体,因而具有较高的强度、抗渗度和抗冻性较好。混合料的组成设计按照水泥稳定粒料保湿养生6d、浸水1d无侧限抗压强度3~5MPa的标准,确定水泥剂量和混合料的含水量。水泥用量一般为混合料3%~6%,7d的无侧限抗压强度控制以5MPa为宜,实际配合比控制强度为4~4.5MPa,较其他路基材料高。水泥稳定碎石成活后遇雨不泥泞,表面坚实,是路面的理想基层材料。
The principle of cement stabilized crushed stone is to use graded crushed stone as aggregate, and the quality control of raw materials requires that the relevant parameters of cement and aggregate meet the specification requirements. A certain amount of cementitious material and sufficient mortar volume are used to fill the gaps of the aggregate, and it is spread and compacted according to the principle of interlocking. Its compaction degree is close to that of compactness, and its strength mainly relies on the interlocking principle between crushed stones, while having sufficient mortar volume to fill the voids of the aggregate. Its initial strength is high, and its strength increases rapidly with age to form a board, thus it has high strength, good impermeability, and frost resistance. The composition design of the mixture is based on the standard of 3-5MPa unconfined compressive strength after 6 days of moisture retention and 1 day of immersion of cement stabilized aggregates, and the optimal cement dosage and moisture content of the mixture are determined. The cement dosage is generally 3% to 6% of the mixture, and the unconfined compressive strength for 7 days should be controlled at 5MPa. The actual mix ratio control strength is 4 to 4.5MPa, which is higher than other roadbed materials. Cement stabilized crushed stone, after survival, does not become muddy in the rain and has a solid surface, making it an ideal base material for high-grade road surfaces.
2 材料的质量控制
Quality control of materials
2.1 水泥
2.1 Cement
(1)水泥作为结合料的一种稳定剂,其质量控制是很重要的。可采用普通硅酸盐水泥、矿渣硅酸盐水泥、火山灰质硅酸盐水泥,强度等级为32.5或42.5。为使水泥稳定碎石有足够的时间进行拌和、运输、摊铺、碾压以及保证其具有足够的强度,不应使用快凝水泥、早强水泥以及受潮变质水泥。
(1) The quality control of cement, as a stabilizer for binders, is crucial. Ordinary Portland cement, slag Portland cement, and volcanic ash Portland cement can be used, with a strength grade of 32.5 or 42.5. In order to allow sufficient time for mixing, transportation, paving, rolling, and ensuring sufficient strength of cement stabilized crushed stone, fast setting cement, early strength cement, and moisture damaged cement should not be used.
(2)所用水泥初凝时间应大于3h,终凝时间应大于6h且小于10h。
(2) The initial setting time of the cement used should be greater than 3 hours, and the final setting time should be greater than 6 hours and less than 10 hours.
(3)采用散装水泥,在水泥进场入罐后要停放7天,安定性合格后才能使用;夏季高温作业时,水泥入罐温度不能高于50℃,否则,应采用降温措施。
(3) Bulk cement is used, and it must be stored for 7 days after entering the tank. It can only be used after its stability is qualified; During high-temperature operations in summer, the temperature of cement entering the tank should not exceed 50 ℃, otherwise cooling measures should be taken.
2.2 粗集料
2.2 Coarse aggregate
(1)碎石的粒径一般为31.5mm,宜按粒径19~31.5mm、9.5~19mm、4.75~9.5mm和0~4.75mm四种规格备料。建议采用坚硬、洁净、无杂质的玄武岩、石灰岩或辉绿岩。
(1) The maximum particle size of crushed stone is generally 31.5mm, and it is recommended to prepare materials in four specifications: 19-31.5mm, 9.5-19mm, 4.75-9.5mm, and 0-4.75mm. It is recommended to use hard, clean, and impurity free basalt, limestone, or diabase.
(2)石子压碎值、针片状颗粒含量、0.075mm以下粉尘含量、软石含量均应符合规范要求。
(2) The crushing value of stones, the content of needle shaped particles, the content of dust below 0.075mm, and the content of soft stones should all meet the requirements of the specifications.
2.3 细集料(1)细集料应洁净、干燥、无风化、无杂质,并有适当的级配。
2.3 Fine aggregate (1) Fine aggregate should be clean, dry, free from weathering, impurities, and have appropriate gradation.
(2)细集料砂当量≥50%。实践证明,利用级配良好的碎石拌和的基层混合料强度高、稳定性好。2.4 水符合现行《生活饮用水卫生标准》GB 5749—2022的饮用水可直接作为基层、底基层材料拌和与养生用水。
(2) Fine aggregate sand equivalent ≥ 50%. Practice has proven that the base mixture mixed with well graded crushed stones has high strength and good stability. 2.4 Water that meets the current "Sanitary Standards for Drinking Water" GB 5749-2022 can be directly used as mixing and health water for base and sub base materials.
3 配合比设计3.1 集料的比例和级配
3 Mix proportion design 3.1 Proportion and gradation of aggregates
(1)用于二级及二级以上的公路基层和底基层的级配碎石和砾石,应由少4种规格的材料掺配而成。
(1) Graded crushed stone and gravel used for secondary and above highway base and subbase should be mixed with at least four specifications of materials.
(2)级配碎石或砾石细集料的塑性指数应不大于12。不满足要求时,可掺加石灰、无塑性的砂和石屑。
(2) The plasticity index of graded crushed stone or gravel fine aggregate should not exceed 12. When the requirements are not met, lime, non plastic sand, and stone chips can be added.
(3)从料场选择有代表性的试样进行筛分,通过试算法(正规方程法)或图解法确定各档集料的掺配比例。
(3) Select representative samples from the material yard for screening, and determine the mixing ratio of each grade of aggregate through trial and error algorithm (regular equation method) or graphical method.
(4)级配碎石用作基层时,高速公路和一级公路公称粒径应不大于26.5mm,二级及二级以下公路公称粒径应不大于31.5mm;用作底基层时,公称粒径应不大于37.5mm。
(4) When graded crushed stone is used as base course, the nominal maximum particle size of expressway and first-class highway shall not be greater than 26.5mm, and the nominal maximum particle size of roads of Class II and below shall not be greater than 31.5mm; When used as a base layer, the nominal maximum particle size should not exceed 37.5mm.
建议基层混合料设计级配曲线在C-B-1级配范围优选,宜落在级配范围中离下限曲线稍近的位置,并控制19mm、9.5mm、4.75mm、2.36mm、0.6mm、0.075mm这些关键筛孔的通过率在级配范围之内,
It is recommended to optimize the gradation curve of the grassroots mixture design within the C-B-1 gradation range, which should be located slightly closer to the lower limit curve in the gradation range, and focus on controlling the pass rate of key sieve holes such as 19mm, 9.5mm, 4.75mm, 2.36mm, 0.6mm, and 0.075mm within the gradation range,
31.5mm通过率要求100%,26.5mm筛上允许有不超过3%的颗粒含量。水泥稳定碎石中0.075mm以下的含量较高时,将影响混合料的收缩性能,容易开裂,应控制在5%以下;同时,为了保证混合料具有良好的抗疲劳性能,0.075mm以下含量的下限控制在2%。
The pass rate of 31.5mm requires 100%, and a particle content of no more than 3% is allowed on the 26.5mm sieve. When the content of cement stabilized crushed stone below 0.075mm is high, it will affect the shrinkage performance of the mixture and is prone to cracking. It should be controlled below 5%; At the same time, in order to ensure that the mixture has good fatigue resistance, the lower limit of the content below 0.075mm is controlled at 2%.
3.2 水泥剂量水泥的剂量对水泥稳定层质量起着关键作用。剂量太小,不能确保水泥稳定碎石基层施工质量;而剂量太大,既不经济,还会使基层的裂缝增多、增宽,从而引起面层相对应的反射裂缝。考虑到施工时各种损耗,工地实际施工采用的水泥剂量应比试验室内确定的剂量增加0.5%~1%,以确保水泥稳定基层的质量,但应控制不超过6%。
The dosage of cement plays a crucial role in the quality of the cement stabilized layer. The dosage is too small to ensure the construction quality of cement stabilized crushed stone base; However, excessive dosage is not only uneconomical, but also increases and widens the cracks in the base layer, causing corresponding reflection cracks in the surface layer. Considering various losses during construction, the actual cement dosage used in the construction site should be increased by 0.5% to 1% compared to the dosage determined in the laboratory to ensure the quality of the cement stabilized base, but should not exceed 6%.
3.3 含水量如果含水量过大,会影响基层的压实度,也会影响混合料的干缩性,使结构层容易产生干缩裂缝;含水量过小,混合料不易碾压成型,也会影响基层的压实度和强度。施工过程中要根据天气情况和运输距离等因素及时调整含水量的大小,使混合料在碾压时达到含水量。根据路面基层施工技术规范及施工经验,一般情况下实际拌和的含水量应比含水量略高0.5%~1%。若气温较高或运输距离较长时应提高1%~1.5%,以弥补混合料运输、摊铺和碾压过程中水分的损失,确保混合料的含水量。
3.3 Optimal moisture content: If the moisture content is too high, it will affect the compaction degree of the base layer and also affect the drying shrinkage of the mixture, making it easy for the structural layer to produce drying shrinkage cracks; If the moisture content is too low, the mixture is not easy to compact and shape, which can also affect the compaction degree and strength of the base layer. During the construction process, the moisture content should be adjusted in a timely manner according to factors such as weather conditions and transportation distance, so that the mixture can reach the optimal moisture content during compaction. According to the technical specifications and construction experience of pavement base construction, the actual mixed moisture content should generally be slightly higher than the optimal moisture content by 0.5% to 1%. If the temperature is high or the transportation distance is long, it should be increased by 1% to 1.5% to compensate for the loss of moisture during the transportation, paving, and rolling of the mixture, ensuring the optimal moisture content of the mixture.
3.4 干密度干密度直接影响着两个重要的质量技术指标,即7天无侧限抗压强度和现场压实度。混合料在工地现场实际达到的干密度与室内标准干密度的比值就是水泥稳定碎石基层的压实度。干密度是水泥稳定级配碎石施工过程中的重要质量控制参数,直接决定基层压实度的大小,而压实度是反映基层内在质量的关键指标。若基层压实度不够,会导致基层的抗压能力不足,主要表现为基层开裂,裂缝反射到沥青面层上,导致沥青路面开裂,大大降低路面的使用性能。
3.4 The maximum dry density directly affects two important quality technical indicators, namely the 7-day unconfined compressive strength and on-site compaction degree. The ratio of the actual dry density achieved by the mixture on the construction site to the maximum indoor standard dry density is the compaction degree of the cement stabilized crushed stone base. The maximum dry density is an important quality control parameter in the construction process of cement stabilized graded crushed stone, which directly determines the compaction degree of the base layer. Compaction degree is a key indicator reflecting the inherent quality of the base layer. If the compaction degree of the base layer is not sufficient, it will lead to insufficient compressive strength of the base layer, mainly manifested as cracking of the base layer, which will reflect onto the asphalt surface layer, causing cracking of the asphalt pavement and greatly reducing the performance of the pavement.
4 混合料的拌和
Mixing of 4 mixtures
(1)水泥稳定碎石优先使用振动搅拌,就是在搅拌的同时施以振动作用,使混合料中的水泥颗粒处于颤动状态,从而破坏黏聚的水泥团单元体,使水泥颗粒得以快速均匀地分布。与普通静力搅拌相比,振动搅拌可以提高水泥稳定碎石中水泥石与粗集料界面过渡区的微观结构,改善水泥浆体的外观和水泥稳定碎石的孔隙率和孔结构分布,从而提高水泥稳定碎石耐久性和力学性能。
(1) Vibration mixing is preferred for cement stabilized crushed stone, which means applying vibration while mixing to make the cement particles in the mixture vibrate, thereby breaking the cohesive cement aggregates and allowing the cement particles to be quickly and evenly distributed. Compared with ordinary static mixing, vibration mixing can improve the microstructure of the transition zone between cement stone and coarse aggregate in cement stabilized crushed stone, enhance the appearance of cement slurry and the porosity and pore structure distribution of cement stabilized crushed stone, thereby improving the durability and mechanical properties of cement stabilized crushed stone.
(2)各料仓、水泥电子秤在使用前须经有资质的检测单位进行标定,使用前还需进行动载试验校核,确保计量准确。
(2) Each silo and cement electronic scale must be calibrated by a qualified testing unit before use, and dynamic load testing and verification must be conducted before use to ensure accurate measurement.
(3)开盘前,应预先抽样检测粗、细骨料的含水率,计算当天的施工配合比,以控制整个搅拌过程中的用水量。实际生产过程中要达到“手握成团,落地开花”的状态,用此经验方法检测含水率方便实用、简单易行。
(3) Before the opening, the moisture content of coarse and fine aggregates should be sampled and tested in advance, and the construction mix ratio for the day should be calculated to control the water consumption during the entire mixing process. In the actual production process, it is necessary to achieve the state of "holding hands and forming clusters, falling to the ground and blooming". This empirical method is convenient, practical, and simple to use for detecting moisture content.
(4)水泥稳定碎石出料搅拌完成的经验标准是混合料色泽一致,没有灰条、灰团和花面,没有粗细集料“窝”,且水分合适均匀。
(4) The experience standard for the completion of cement stabilized crushed stone discharge mixing is that the color of the mixture is consistent, there are no gray bars, gray lumps, or flower surfaces, there are no coarse or fine aggregate "pits", and the moisture content is appropriate and uniform.
(5)生产过程中,应对成品料及时进行取样分析,检查混合料的级配情况以及含水率的均匀性,用EDTA滴定法及时测量水泥剂量。为保证混合料的质量,需经常进行取样分析并及时调整。
(5) During the production process, the finished materials should be sampled and analyzed in a timely manner to check the gradation and uniformity of the moisture content of the mixture. The cement dosage should be measured in a timely manner using EDTA titration method. To ensure the quality of the mixture, it is necessary to conduct regular sampling analysis and make timely adjustments.
5 混合料的运输和摊铺
Transportation and paving of 5 mixtures
(1)运输车辆一定要满足拌和出料与摊铺的进度,并略有富余。
(1) Transport vehicles must meet the schedule of mixing, discharging, and paving, with a slight surplus.
(2)车上的混合料应覆盖,减少水分损失。当车内混合料不能在水泥初凝时间内运到工地摊铺压实时,必须予以废弃。
(2) The mixture on the car should be covered to reduce moisture loss. When the mixture in the vehicle cannot be transported to the construction site for paving and compaction within the initial setting time of cement, it must be discarded.
(3)摊铺前做好施工放样工作,根据试验路段确定的松铺系数进行挂线,以保证水泥稳定基层的设计厚度。
(3) Before paving, carry out construction layout work and hang lines based on the loose paving coefficient determined by the test section to ensure the design thickness of the cement stabilized base layer.
(4)下承层表面应平整、坚实、干净,施工前对下承层洒水润湿。
(4) The surface of the lower layer should be flat, solid, and clean, and the lower layer should be moistened with water before construction.
(5)基层施工宜采用多台摊铺机全幅摊铺,摊铺机的规格、型号要一致,前后间距5~10m,摊铺时摊铺机摊铺速度设定为1~1.5m/min。
(5) It is advisable to use multiple pavers for full width paving during grassroots construction. The specifications and models of the pavers should be consistent, with a distance of 5-10m between them. The paving speed of the pavers should be set at 1-1.5m/min during paving.
(6)前后两台摊铺机重叠50~100mm,中缝辅以人工修整。摊铺机在摊铺过程中应连续、均匀、不间断摊铺。
(6) The front and rear pavers overlap by 50-100mm, and the middle seam is manually adjusted. The paver should spread continuously, evenly, and uninterrupted during the paving process.
(7)尽量减少摊铺机收放料斗,在摊铺机前后设专人粗细集料离析现象,特别应铲除粗料料窝,然后用新拌混合料填补,以确保配合比稳定统一。
(7) Try to minimize the collection and discharge hopper of the paver, and assign a dedicated person to eliminate the segregation of coarse and fine aggregates before and after the paver. Especially, the coarse material pit should be removed, and then filled with fresh mixed material to ensure a stable and uniform mix proportion.
6 混合料的压实
Compaction of mixture 6
(1)要及时进行碾压。碾压过程中,混合料表面应始终保持湿润,如水分蒸发过快,应及时喷洒少量水;宜先用轻型两轮压路机跟在摊铺机后及时碾压,后用重型振动压路机继续碾压,经拌和的水泥混合料宜在2小时以内碾压完成,并达到要求的密实度。
(1) Timely compaction is necessary. During the rolling process, the surface of the mixture should always be kept moist. If the water evaporates too quickly, a small amount of water should be sprayed in a timely manner; It is advisable to first use a lightweight two wheeled roller to follow the paver for timely rolling, and then use a heavy-duty vibratory roller to continue rolling. The mixed cement mixture should be rolled within 2 hours and achieve the required density.
(2)压路机碾压时的速度,宜控制在第1~2遍为1.5~1.7km/h,以后各遍应为1.8~2.2km/h,且碾压时应重叠1/2轮宽。
(2) The speed of the road roller during rolling should be controlled at 1.5-1.7km/h for the first and second passes, and 1.8-2.2km/h for each subsequent pass, with an overlap of 1/2 wheel width during rolling.
(3)碾压过程中,如有“弹簧”、“松散”、“起皮”等现象时,应及时翻开重新拌和或用其他方法处理。
(3) During the rolling process, if there are phenomena such as "spring", "looseness", "peeling", etc., they should be promptly opened and re mixed or treated with other methods.
(4)基层应采用分层施工方法,分层压实厚度不宜超过20cm,小不应小于16cm,压实厚度宜为18~20cm。
(4) The base layer should adopt a layered construction method, and the maximum compacted thickness of each layer should not exceed 20cm, the minimum should not be less than 16cm, and the compacted thickness should be 18-20cm.
(5)碾压原则:先轻后重,先慢后快,尽量缩短从拌和、摊铺到碾压之间的延迟时间。
(5) Rolling principle: light before heavy, slow before fast, try to shorten the delay time from mixing, paving to rolling as much as possible.
(6)为了及时指导现场压实工作,碾压过程中,可用核子仪初查压实度,不合格时,重复再压(注意检测压实时间),碾压完成后用灌砂法检测压实度。另外,在碾压过程中应进行标高、平整度的及时跟踪检测,如发现严重超标,应及时修整。
(6) In order to provide timely guidance for on-site compaction work, a nuclear gauge can be used to initially check the compaction degree during the compaction process. If it is not qualified, it can be repeatedly compacted (pay attention to checking the compaction time). After compaction is completed, the compaction degree can be checked using the sand filling method. In addition, timely tracking and testing of elevation and flatness should be carried out during the rolling process. If serious exceedances are found, they should be rectified in a timely manner.
(7)碾压应达到要求的压实度,并没有明显的轮迹。7 水泥稳定碎石的养生(1)水泥稳定碎石底基层、基层在碾压完成后并经压实度检查合格后,应立即开始养生。(2)养生方法:应将麻布或透水无纺土工布湿润,然后人工覆盖在碾压完成的基层(底基层)顶面。覆盖2~3h后,再用洒水车洒水,在养护期内应保持基层(底基层)处于湿润状态。养生结束后,应将覆盖物干净
(7) Rolling should achieve the required compaction degree without obvious wheel marks. 7. Curing of Cement Stabilized Crushed Stone (1) After the completion of compaction and passing the compaction degree inspection, the curing of cement stabilized crushed stone subbase and base should be started immediately. (2) Health preservation method: The hemp cloth or permeable non-woven geotextile should be moistened, and then manually covered on the top surface of the compacted base layer (sub base layer). After covering for 2-3 hours, use a sprinkler truck to water again. During the maintenance period, the base layer (sub base layer) should be kept moist. After the health preservation is over, the covering should be cleaned thoroughly
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