Cracks in cement-based mortar, putty and cracks are common problems. In many years of research and practice, the author believes that the cracks of plastering mortar, putty on exterior wall and the causes of cracks mainly come from "internal" and "external" aspects.

　　1、“內因”方面

　　1. Internal Causes

　　“內因”方面主要是由于一些抹面砂漿、膩子產品的干縮性大、干縮快，產生較大內應力破壞了砂漿結構而引起裂紋的，裂紋的表現一般呈不規則的龜裂狀，也就是常說的龜裂紋，主要是一些生產廠家對原材料性質、作用與技術原理上了解不充分，所用原材料不符合要求，配方不科學，導致產品質量不穩定、抗裂性能差，施工后不久就出現大面積龜裂、空鼓、脫落問題。

　　"Internal cause" is mainly due to the drying shrinkage of some plastered mortar and putty products, which causes cracks due to the destruction of mortar structure by large internal stress. The cracks generally show irregular tortoise cracks, that is to say, tortoise cracks. The main reason is that some manufacturers do not fully understand the nature, function and technical principles of raw materials, and the raw materials used do not conform to each other. According to the requirements, unscientific formulation leads to unstable product quality and poor crack resistance. Large area cracking, empty drum and shedding problems occur shortly after construction.

　　水泥砂漿的強度、防裂效果都與水有重要關系，水泥的水化與凝結硬化是一個漸進式、連續性過程，先水化，后凝結，凝結硬化結果如何，要取決于水化條件，水化的越充分、水養護的越好、水養護的時間越長，強度就會越高，收縮性就越小，防裂效果就越好；水泥的水化與凝結硬化速度受環境溫度的影響也是明顯的，即環境溫度高，水化與硬化速度就快，環境溫度低時，水泥的水化與凝結硬化的速度相應就慢些。凡是早干、早硬、早強的水泥砂漿，因保水不好、自養護能力差，會產生收縮過快、收縮力過強、容易產生大面積龜裂。在研究與實踐中，早干、早硬、早強的水泥砂漿的后期強度及穩定性、抗裂性均比晚干、晚硬、晚強的水泥砂漿要差，這也是水泥作為無機水硬性膠凝材料的特殊性所決定的。

　　The strength and anti-cracking effect of cement mortar are closely related to water. The hydration and condensation hardening of cement are a gradual and continuous process. The results of hydration first, then, and condensation hardening depend on the hydration conditions. The more fully hydration, the better water curing and the longer water curing time, the higher the strength, the smaller the shrinkage and the better the anti-cracking effect. The rate of cement hydration and setting hardening is also obviously affected by environmental temperature, that is, the rate of hydration and hardening is faster when the environmental temperature is high, and the rate of cement hydration and setting hardening is slower when the environmental temperature is low. The cement mortar with early drying, early hardening and early strength will shrink too fast, shrink too strongly and easily crack in large area due to poor water retention and poor self-curing ability. In research and practice, the late strength, stability and crack resistance of early-drying, early-hardening and early-strength cement mortar are worse than those of late-drying, late-hardening and late-strength cement mortar, which is also determined by the particularity of cement as inorganic hydraulically cementing material.

　　龜裂紋的產生，主要與水泥有關，不論是什么類型的水泥，都存在干縮問題，從試驗情況看，硫鋁酸鹽水泥、白水泥等水泥品種的后期強度及穩定性、抗裂性就不及普通硅酸鹽水泥好，主要是這些產品本身的收縮性大，干縮較快、收縮力較強、容易產生龜裂紋。普通硅酸鹽水泥在我國建筑工程上的應用很普遍，有好幾十年的歷史，它的性能是很好的，經研究與試驗，只要水化充分、水養護條件較好，幾年后、甚至十年后其強度還會有所提高。目前，聚合物砂漿、水泥類膩子仍以普通硅酸鹽水泥為主，所使用的型號為32.5R或42.5R，其在聚合物抹面砂漿、水泥類膩子產品中的配方量一定要掌握好。

　　The crack of tortoise is mainly related to cement. No matter what type of cement, there is drying shrinkage problem. From the test results, the strength, stability and crack resistance of sulphoaluminate cement, white cement and other cement varieties are not as good as ordinary Portland cement. The main reason is that these products have larger shrinkage, faster drying shrinkage, stronger shrinkage force and are prone to tortoise crack. Ordinary Portland Cement is widely used in China's construction engineering. It has a history of several decades. Its performance is very good. Through research and test, as long as the hydration is sufficient and the water maintenance condition is good, its strength will be improved in a few years or even ten years. At present, polymer mortar and cement putty are still based on ordinary Portland cement. The type used is 32.5R or 42.5R. The formulation of polymer plastering mortar and cement putty products must be well controlled.

　　2、“外因”方面

　　“外因”方面，主要是施工工藝、地基和自然環境引起的。通常情況下，建筑設計施工不科學和不合理，地基沉降、偏離，施工時一次性抹的太厚、施工前基底已經出現明顯裂縫、地震、大的風壓產生的應力、施工后連續性的高溫干旱天氣等，都會引起裂縫的產生，裂縫、裂紋的表現一般以裂縫為多，形狀有橫線式、豎線式或呈不規則式。

　　The external causes are mainly caused by construction technology, foundation and natural environment. Usually, unscientific and unreasonable architectural design and construction, settlement and deviation of foundation, excessive thickness of one-time plastering during construction, obvious cracks in basement before construction, earthquake, stress caused by large wind pressure, continuous high temperature and drought weather after construction, etc., will cause cracks. Cracks and cracks are generally manifested in the form of horizontal lines and vertical lines. Type or irregular.

　　3、水泥砂漿與水泥基膩子的裂紋裂縫的另一個特征是：無論抹多厚或抹多薄，其裂紋裂縫都是從面一直裂到底，這也是建筑物發生滲漏水的根本原因。裂紋裂縫有大小之分，大的裂紋裂縫可以很容易看到，小的裂紋裂縫肉眼不一定看得出來，但只要往干燥的墻面上潑灑水，微細的裂紋裂縫就能清楚地看到。

　　3. Another characteristic of crack in cement mortar and cement-based putty is that no matter how thick or thin it is, the crack always cracks from the surface to the end, which is also the most fundamental reason for water leakage in buildings. Cracks can be divided into different sizes. Large cracks can be easily seen. Small cracks may not be visible to the naked eye, but as long as water is sprinkled on the drying wall, fine cracks can be clearly seen.

　　4、只要出現裂紋、裂縫，基本上沒有什么可靠的材料和技術手段可以徹底修復，其結果會給建筑裝飾、裝修、防水工程以及今后的維修工作造成極大的困難，這是因為外墻裂縫、裂紋在隨著外部所處的環境條件(地基沉降、地震等)和較大溫差、干濕度變化的同時，其縫隙大小、形狀也在隨之不停地變化，即冬季低溫與夏季高溫時縫隙大小會變化，就是在同一季節下雨天與晴朗天，縫隙大小也會發生變化，總之每天24小時都處于變化之中，這也是裂縫、裂紋在屋面、墻面、地下防水工程及維修實踐中，也是令人頭痛的事，經常是修好后，不到一年甚至是幾個月內，又開始滲漏。只要沒有任何裂紋裂縫，一般情況下建筑物是不會發生滲漏水的，凡了解水泥水池的人，就明白只要沒有任何裂紋裂縫，水泥水池是不會發生滲漏水的。

　　4. As long as cracks and cracks occur, there is basically no reliable material and technical means to repair them thoroughly. The result will cause great difficulties in building decoration, decoration, waterproof engineering and future maintenance. This is because cracks and cracks in external walls are accompanied by environmental conditions (foundation settlement, earthquakes, etc.) and at the same time with large temperature difference and dry humidity change. The size and shape of cracks are constantly changing, that is, the size of cracks will change when the temperature is low in winter and high in summer. Even in rainy and sunny days in the same season, the size of cracks will change 24 hours a day. This is also the most headache of cracks and cracks in roof, wall, underground waterproof Engineering and maintenance practice. Often it starts to leak again in less than a year or even a few months after repair. As long as there are no cracks, the building will not leak water in general. Anyone who knows the cement pool knows that as long as there are no cracks, the cement pool will not leak water.