1.裂縫

1. Cracks

水泥穩(wěn)定碎石裂縫是水泥穩(wěn)定碎石基層混合料水泥固化以及水分散發(fā)后在表面產(chǎn)生的細微開裂，然后向深部與橫向擴展，貫通整個基層。裂縫的寬度約為1cm~3cm，嚴重可達4cm~5cm，裂縫的產(chǎn)生一定程度導(dǎo)致上破壞基層的板的整體受力狀態(tài)，如果裂縫進一步發(fā)展會產(chǎn)生反射裂縫，造成路面面層也相應(yīng)產(chǎn)生裂縫或者斷板情況的出現(xiàn)。

Cement stabilized crushed stone cracks refer to the subtle cracks that occur on the surface of the cement stabilized crushed stone base mixture after cement solidification and moisture dissipation, and then extend deep and horizontally, penetrating the entire base layer. The width of the cracks is about 1cm~3cm, and the severity can reach 4cm~5cm. The generation of cracks to a certain extent leads to the overall stress state of the board that damages the base layer. If the cracks further develop, reflection cracks will occur, causing cracks or broken boards in the road surface layer.

水穩(wěn)層產(chǎn)生裂縫原因有：

The causes of cracks in the water stable layer include:

1）水泥穩(wěn)定碎石混合料含水量高于佳含水量很多，水泥穩(wěn)定碎石基層干縮應(yīng)變隨混合料的含水量增加而增大；

1) The moisture content of cement stabilized crushed stone mixture is much higher than the optimal moisture content, and the dry shrinkage strain of cement stabilized crushed stone base increases with the increase of moisture content of the mixture;

2）水泥品種的選擇；

2) Selection of cement varieties;

3）水泥劑量用量偏大與級配不好；

3) Excessive cement dosage and poor grading;

4）水泥穩(wěn)定碎石養(yǎng)生不及時或養(yǎng)生不規(guī)范化；

4) The curing of cement stabilized crushed stone is not timely or standardized;

5）溫差原因。

5) Reason for temperature difference.

預(yù)防措施：

Preventive measures:

1）重視原材料的選用以保證有良好的級配，在滿足設(shè)計強度的前提下，降低水泥劑量；

1) Pay attention to the selection of raw materials to ensure good gradation, and reduce cement dosage while meeting the design strength;

2）水泥的選擇：不同品種的水泥干縮性不同，普通硅酸鹽水泥干縮性很小，火山灰質(zhì)硅酸水泥次之，礦渣水泥較大。因此，選用合適的水泥在一定程度上能減少干縮裂縫；

2) Selection of cement: Different types of cement have different dry shrinkage properties. Ordinary Portland cement has very low dry shrinkage, followed by volcanic ash silicate cement, and slag cement has a larger dry shrinkage. Therefore, selecting appropriate cement can to some extent reduce dry shrinkage cracks;

3）控制細集料量，細集料＜0.075mm顆粒的含量盡量小于5%~7%；

3) Control the amount of fine aggregate, and try to minimize the content of particles with fine aggregate<0.075mm to less than 5%~7%;

4）控制含水量，要嚴格按水泥穩(wěn)定碎石配合比設(shè)計控制含水量，使其與佳含水量接近，減少用水量不當(dāng)而人為造成裂縫；

4) To control the water content, it is necessary to strictly follow the design of the cement stabilized crushed stone mix ratio to control the water content, making it close to the optimal water content and reducing the risk of cracks caused by improper water use;

5）合理選擇施工時間，施工時間好選擇在夏季高溫季節(jié)來臨之前，如在夏季高溫季節(jié)施工，盡量在上午或夜間施工；

5) Reasonably choose the construction time, preferably before the arrival of the summer high temperature season. If construction is carried out during the summer high temperature season, it is advisable to do so in the morning or at night;

6）加強養(yǎng)生，因為干燥收縮的破壞發(fā)生在早期，所以及時的采用土工布，麻袋布或薄膜覆蓋進行良好的養(yǎng)生，可以防止水泥穩(wěn)定碎石層混合料內(nèi)部發(fā)生水化作用和水分的過分蒸發(fā)引起表面的干縮裂縫現(xiàn)象。如施工條件許可，及時鋪筑瀝青面層是減少干縮裂縫的一種好的辦法；

6) Strengthening health preservation, as the damage caused by dry shrinkage occurs in the early stages, timely use of geotextile, burlap cloth or film covering for good health preservation can prevent hydration and excessive evaporation of water inside the cement stabilized crushed stone layer mixture, which can cause surface dry shrinkage cracks. If construction conditions permit, timely laying of asphalt surface layer is a good way to reduce dry shrinkage cracks;

7）在水穩(wěn)層碎石基層中摻加粉煤灰（占集料重量的10%~20%），可以延緩水穩(wěn)層混合料的凝結(jié)，增加混合料的搞凍能力和改善混合料的形變性能。

7) Adding fly ash (accounting for 10% to 20% of the aggregate weight) to the water stable layer crushed stone base can delay the setting of the water stable layer mixture, increase the freezing ability of the mixture, and improve the deformation performance of the mixture.

2.取不出完整的芯樣

2. Unable to extract complete core samples

按照技術(shù)規(guī)范要求，水泥穩(wěn)定碎石層齡期7d~10d，應(yīng)能取出完整的鉆件，可實際情況是部分路段因為松散，不能取出完整的芯樣。其原因是：

According to the technical specifications, the age of the cement stabilized crushed stone layer should be between 7d and 10d, and complete drilling pieces should be able to be taken out. However, in reality, some sections of the road cannot take out complete core samples due to looseness. The reason is:

1）水泥用量偏少造成骨料之間膠結(jié)不好，達不到強度；

1) Insufficient cement usage results in poor bonding between aggregates and inability to achieve strength;

2）沒有完全按照規(guī)范要求進行養(yǎng)護，按規(guī)范要求每一段碾壓完成并經(jīng)壓實度檢查合格后，應(yīng)立即養(yǎng)生，宜采用濕砂進行養(yǎng)生，砂層厚度為7cm~10cm.也可采用瀝青乳液進行養(yǎng)生，無述條件時，也可用灑水車結(jié)常灑水進行養(yǎng)生。養(yǎng)生期不宜少于7天；

2) The curing is not carried out in full accordance with the requirements of the specification. After each section of rolling is completed according to the requirements of the specification and the compactness is checked to be qualified, it should be cured immediately. Wet sand should be used for curing. The thickness of the sand layer is 7cm~10cm. Asphalt lotion can also be used for curing. If there is no such condition, the watering cart can also be used for curing. The health period should not be less than 7 days;

3）水泥穩(wěn)定碎石層原材料級配不好；

3) Poor grading of raw materials for cement stabilized crushed stone layer;

4）含水量不合適，以于水泥不能在混合料中完全水化和水解，水泥對碎石的穩(wěn)定作用沒發(fā)揮，影響水泥穩(wěn)定碎石的強度；

4) The moisture content is inappropriate, so that cement cannot fully hydrate and hydrolyze in the mixture, and the stabilizing effect of cement on crushed stone is not fully exerted, which affects the strength of cement stabilized crushed stone;

5）水泥選用不當(dāng)，普通硅酸鹽水泥，礦渣硅酸鹽水泥和火山灰質(zhì)硅酸鹽水泥都可用水泥穩(wěn)定碎石，但應(yīng)選用初凝時間3h以上和終凝時間較長（宜在6h以上）。不宜使用快硬水泥，早強水泥以及已受潮變質(zhì)的水泥；

5) Improper selection of cement. Ordinary Portland cement, slag Portland cement, and volcanic ash Portland cement can all be stabilized with cement crushed stone, but the initial setting time should be more than 3 hours and the final setting time should be longer (preferably more than 6 hours). It is not advisable to use fast hardening cement, early strength cement, and cement that has been damp and deteriorated;

6）拌合得不均勻，且沒在佳含水量下充分壓實，以及施工碾壓時間拖的過長，破壞了已結(jié)硬的水泥膠凝，使其強度下降。

6) Uneven mixing and insufficient compaction at optimal moisture content, as well as prolonged construction compaction time, have damaged the hardened cement binder and reduced its strength.