Stone products that are used for modern architectural construction are mainly consisted of two kinds,i.e.slab and irregular parts.Aiming to meet requirements to construction,stone decoration should attain such goals as，first, aesthetical appearance; second, safety; third, ware-well, i.e.strong enough to resist against natural weathering; forth, convenient to be constructed; and fifth, easy to be repaired.

1.      Slab

As to construction of architectural decoration and garden floor paving,slab is widely used for plane paving,Hence,there is a big demand for slab. Here we’ll not lay emphasis on common standardized slab due to that there are many criteria in both China and abroad.This book focuses on the quality for stone processing that ensures the requirement to decorative quality and appearance in pratical projects of stone installation, There are a large number of slab varieties for decoration, such as grantie,marble,artificial granite-imitated stone and artificial marble-imitates stone (commercially they are called as mini-crystal stone or –mini-granite or mini-artificial slab,etc),etc.,and massive natural slate that can be directly exploited.As far as construction is concerned,the requirements to slab are the same. There are different requirements to slab. For example, the slabs used for base floor and ground paving requires a relatively higher standard than that for decorating tall buildings and wall.

            Technical requirements to stone products in engineering design

1.1.1 Different technical indexes of stone products meet different requirements to construction. Among them,paving on floor requires a certain standard on resistance to pressure and fold, to which European criteria can be made for refernce. For example,the thickness of slab used for paving floor should be over 30mm.

1.1.2 Slab used for toilet is required to be low rate of water absorbing.so as to keep toilet clean without watery trail under moist condition.

1.1.3 Tall building requires relatively light materials.Hence,ultra-thin slab and light mulriple stone meet the requirement to modern stone processing.

1.1.4 Surface handling on stone is to make the building functioning for daily life or work,or to beautify a building.

1.2 Requirements to the procesion of slab specification

In terms of the production style, granite and marble slab can be classified as two kinds,i.e.regular slab(square or quadrate shape)andirregular slab(other shapes).In order to ensure the effects fo order joint, smooth surface,convenien operation and secured safety afer paving or fixing the slabs, China’s National Standard stipulates the tolerance of granite and marble slabs at size,flatness and angle.

1.2.1 Explanation of standardized size: The utmost tolerant error of a slab is ±1.0mm when the thickness of slab is ≤15mm,which means that it can be thinner or thicker within the tolerance of 1mm.otherwise it will be substandard;while the utmost tolerant error will be ±2.00mm when the thickness of slabs is >15mm.The length and widh should not be more but could be slightly less than standardized values. When measuring the standardized size, a steel rEler with 1.0mm scale is used for measuring the Length and width;while a vernier caliper with scale 0.1mm is used for measuring the thickness of slab. Thus, we can make sure the directness of segmentation line and the flatness of paved surface when we conduct decoration project with stone slab.

1.2.2 The utmost tolerant error of flatness: the flatness indicates the flat extent of slab,which directly influences the flatness of surface after being paved slab.When measuring, a standardized steel reler is closely put on the two diagonals of the slab plane to be measured.Since a slab is impossible to be absolutely flat, an aperture that can be measured with a filling reler appears between the measuring surface and slab surface. In case the length of diagonal exceeds 1000mm,it can be measured with a 1000mm ruler.

1.2.3 For the jointed slab under the tolerant angle, the angle between the face and side should not exceed 90°.For the irregular slabs, the tolerance of angle can be negotiated by both supplier and client.The angle that means that of the two bordering sides on the slabs surface should be 90°.When measuring,a standardized 90°steel ruler is used,with its long side clinging to the long side of slab, and the short side to be short side.Then using a filling ruler to measure the size of the gap between the long and short side.Four angles of slab are measured as regulated,from which the maximum gap size could be as the utmost tolerant angle.

2.      Requirement to irregular parts

Irregular stone is important ingreient making the finishing point in the whole decorative construction.Normally it means are surface slab,engraved line,solid pillar,and various construction parts such as window,gatepost and all of engraved  parts for decoration.They require a principle of regulation is to ensure the gap size between the irregular parts and decorated surface and parts as little as possible,and to accomplishe a good decorative effect.

Decorative stone is made of natural stone.Hence,the quality of slab is not noly depending on the quality of block,but also the process.An excellent project should be made from the period of quarrying to processing.

3.      Stone of low quality can be mainly categorized as follows

3.1 Being not artistic in texture and color.

For the decorative stone, people pay more attention to the effect after decorating,Stone of high quality appears good in texrure and color,some are artistic in good taste,some are natural and graceful,some look like natural and smooth flowing,and some look like star twinkling,shining and splendor,making the decoration effects the best.On the contrary,stone of bad quality appears littery texture and dismal color that can not be aesthetically enjoyed,Therefore,the texture and color of stone appeared on surface are important indexes to evaluate the quality.Just as the above-mentioned colorful texture marble produced in Dali,Yunnan province of China, is regarded as the top grade stone among marbles because of its rare and precious texture and color.

3.2Bad quality slab in appearance after processing.

The exterior character of natural stone appears after being cutting,sawing,rubbing,and polished,etc.Some visual defects appear on surface when stone is processed.For example,marble slab may appears such defects as warp,flaw,tinyhole,concave spot,splash,stained spot and imperfect edges and corners,etc.:while grantie slab may appears such defects as imperdect edges and corners,splash,stained spot and pit,etc.In case the visual defects exceed the tolerance stipulated by National Standard,theproduct is judged as reject.The decoration effect will not be satisfied if we decorate with the bad quality stone.Consequently,in addition to the texture and color to be considered,the exterior quality must also be taken ino consideration.

3.3Exceeding tolerance of specification.

Decorative stone is used after being processed.When operation,such technologies as install-paving(for floor)and install-gluing/fixing are adopte.In order to ensure ordered and level-up decoration,the National Standard stipulates the tolerance to the flatness,obverse angle and side angle,as well as the tolerance to the length,width and thickness of slab.The size error of slab of bad quality,with its bad precision in processing,exceeds the tolerance.If we decorate with such quality of stone, the paved or fixed surface will appear disordering,dissatisfied juncture,and especially for vertical decoration,twist decoration line,which are bad for effect.

3.4Bad physical and chemical indexes.

For stone,its decorative performance and characteristics,such as the texture,color,luster,and appearance,are placed as the indexes for selection of material.Beside of them,however,when we evaluate the quality of stone,we should further study other quality indexes,such as intensity of resistance to pressure,intensity of resistance to fold,enduring ability,resistance to frozen,resistance to wearing and rigidity,etc.Only can those stones that have good physical and chemical indexes perfor well in withstanding the influential factors from environment and ensure the effect and long-use when used.On the contrary ,stones of bad quality,with their bad physical and chemical performance,cannot be ensured to meet above-mentioned requirements.

To sum up,when we evaluate the quality of stone,we should take full consideration,not only the decorative performance,but also the utility performance,instead of being restrained in one aspect.

4.      The utility effect of stone affected by processing

Generally,machinery are adopted in modern stone production,from the processing of block,to slab,and to irregular shaped stone(such as engraved stone).Therefore,theprecision extent of machinery used will affect the quality of products.Another important factor influencing the quality of products is the so-called man-made factor,such as the extent of designing precision,and whether the design has been restrictedly followed in the processing period,etc.

In  conclusion,an excellent decorative project with stone is deeply affected and determined by the whole process,from selection of material to design,precision  processing, reasonable operation,and sound materialized surroundings where a building is situated.