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ACT Grouts practice questions

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Question 1Grout Materials and Mix Design

Which property of cementitious grout is most directly improved by lowering the water-to-cementitious-materials ratio within a workable range?

  1. Compressive strength Correct answer.
  2. Bleed rate
  3. Initial set time
  4. Coefficient of thermal expansion

Explanation

Reducing water content lowers porosity in the hardened paste, which increases compressive strength. Workability decreases as water is removed, so the ratio is kept as low as placement allows. Bleed and set time are affected but are not the primary property sought by lowering the ratio.

Question 2Grout Materials and Mix Design

In grout mix design, what is the primary function of a superplasticizer?

  1. To compensate for shrinkage
  2. To accelerate the set
  3. To increase flow at a given water content Correct answer.
  4. To entrain air for freeze-thaw resistance

Explanation

Superplasticizers are high-range water reducers that disperse cement particles, raising flowability without adding water. This lets the designer keep a low water ratio while achieving pumpable or placeable consistency. They do not primarily accelerate set, entrain air, or offset shrinkage.

Question 3Grout Materials and Mix Design

Which cementitious material is commonly added to grout to improve sulfate resistance and reduce heat of hydration?

  1. Calcium chloride
  2. Type III portland cement
  3. Hydrated lime
  4. Fly ash Correct answer.

Explanation

Fly ash is a pozzolan that reacts with calcium hydroxide to form additional cementitious compounds, improving sulfate resistance and lowering heat of hydration. It also improves workability and reduces permeability. Type III cement raises early heat, calcium chloride accelerates, and hydrated lime is used for plasticity, not sulfate resistance.

Question 4Grout Materials and Mix Design

What does the term 'bleeding' describe in a cementitious grout mix?

  1. Migration of water to the surface after placement Correct answer.
  2. Loss of entrained air during mixing
  3. Segregation of coarse aggregate from paste
  4. Formation of laitance on the surface

Explanation

Bleeding is the upward migration of mixing water as solid particles settle before the paste sets. Excessive bleed water raises the effective water ratio at the top and weakens the bond there. It is distinct from air loss or aggregate segregation.

Question 5Grout Materials and Mix Design

Which unit is conventionally used to express the flowability of a cementitious grout measured with a flow cone?

  1. Millimeters of slump
  2. Seconds Correct answer.
  3. Pounds per cubic yard
  4. Percent air content

Explanation

Flow cone testing measures the time in seconds for a fixed volume of grout to flow through a standard orifice. Shorter times indicate higher fluidity. Slump, air content, and unit weight are different measures entirely.

Question 6Grout Materials and Mix Design

Why is silica fume sometimes incorporated into high-performance grout mixes?

  1. To reduce compressive strength for flexibility
  2. To increase the water demand for easier mixing
  3. To raise permeability and improve drainage
  4. To refine the pore structure and boost strength Correct answer.

Explanation

Silica fume consists of very fine amorphous silica particles that fill voids and react pozzolanically, refining the pore structure. This raises strength and lowers permeability. It also increases water demand, so superplasticizers are typically needed.

Question 7Grout Materials and Mix Design

Which factor most strongly governs the initial setting behavior of a neat cement grout?

  1. The cement chemistry and any set-controlling admixtures Correct answer.
  2. The type of mixing paddle used
  3. The ambient relative humidity alone
  4. The color of the mix water

Explanation

Setting is driven by the hydration reactions of the cement compounds, which are modified by set accelerators or retarders. Mixing method and environment influence workability but do not define the intrinsic set chemistry. Water color is irrelevant to set.

Question 8Grout Materials and Mix Design

In grout specification terminology, what does 'neat cement grout' mean?

  1. Grout containing sand and gravel
  2. Grout with entrained air
  3. Grout with polymer modifiers
  4. Grout containing only cement and water Correct answer.

Explanation

Neat cement grout is a mixture of hydraulic cement and water without aggregate. Adding sand produces a sanded grout, and other additives define separate categories. The term refers specifically to the absence of aggregate.

Question 9Grout Materials and Mix Design

A grout mix design specifies a water-to-cementitious-materials ratio of 0.45 by mass. If 100 kg of cementitious material is used, how much water is required?

  1. 145 kg
  2. 45 kg Correct answer.
  3. 22.5 kg
  4. 55 kg

Explanation

The water ratio is water mass divided by cementitious mass, so water equals ratio times cementitious mass. Multiplying 0.45 by 100 kg gives 45 kg. The other values reflect dividing by two, subtracting, or adding the ratio rather than applying it.

Question 10Grout Materials and Mix Design

A grout exhibits excessive bleed water and segregation shortly after placement. Which adjustment is most appropriate in the mix design?

  1. Remove the superplasticizer entirely
  2. Add more coarse aggregate
  3. Increase the water content
  4. Reduce the water content or add a viscosity modifier Correct answer.

Explanation

Bleeding and segregation indicate insufficient water retention and particle suspension. Reducing water and using a viscosity-modifying admixture improve cohesion and stability. Adding water or coarse solids worsens the problem.

Question 11Grout Materials and Mix Design

Why is a shrinkage-compensating component sometimes included in a grout mix?

  1. To increase bleed water for lubrication
  2. To slow the hydration reaction indefinitely
  3. To reduce early-age volume loss that can cause cracking or loss of contact Correct answer.
  4. To lower the compressive strength

Explanation

Shrinkage-compensating grouts expand slightly during curing to offset drying shrinkage, helping maintain contact with the substrate and reducing cracking. They do not aim to increase bleed or reduce strength, and they do not halt hydration.

Question 12Grout Materials and Mix Design

A designer wants to compare the fluidity of two grout batches at equal water content. Which test result would indicate the more flowable mix?

  1. A shorter flow-cone time Correct answer.
  2. A longer flow-cone time
  3. A higher unit weight
  4. A greater initial set time

Explanation

Flow-cone time decreases as fluidity increases, so the shorter time indicates the more flowable mix. Unit weight and set time do not directly measure flowability. Longer flow times indicate a stiffer mix.

Question 13Grout Materials and Mix Design

Which combination of ingredients best describes a typical sanded cementitious grout for structural support applications?

  1. Cement, water, and fine aggregate Correct answer.
  2. Cement and water only
  3. Cement, water, and coarse gravel
  4. Resin and hardener only

Explanation

Sanded grout combines hydraulic cement, water, and fine aggregate to control shrinkage and add body. Neat grout omits aggregate, resin grouts are polymer-based, and coarse gravel is not typical of grout.

Question 14Grout Materials and Mix Design

What is the main purpose of adding an air-entraining admixture to a grout that will be exposed to freezing and thawing?

  1. To create small, evenly spaced voids that relieve ice pressure Correct answer.
  2. To reduce the water demand
  3. To raise the density of the hardened grout
  4. To increase the set time

Explanation

Air entrainment produces a network of tiny, closely spaced bubbles that give expanding ice room to relieve pressure, improving freeze-thaw durability. It does not primarily reduce water demand, retard set, or increase density.

Question 15Grout Materials and Mix Design

A grout mix is found to be too stiff to pump even though the water ratio is at its maximum allowable value. Which approach best preserves the design water ratio while restoring pumpability?

  1. Add more water beyond the maximum
  2. Reduce the mixing time
  3. Add an accelerator
  4. Add a high-range water reducer Correct answer.

Explanation

A high-range water reducer increases flow without adding water, preserving the specified water ratio and strength. Exceeding the water maximum compromises strength, accelerators affect set not flow, and shorter mixing reduces uniformity.

Question 16Grout Materials and Mix Design

Which measurement best characterizes the density of a freshly mixed grout for quality control purposes?

  1. Unit weight in mass per unit volume Correct answer.
  2. Flow-cone time in seconds
  3. Bleed percentage
  4. Initial set time in hours

Explanation

Unit weight expresses mass per unit volume and directly reflects the density of the fresh mix, useful for verifying proportions and air content. Flow time, set time, and bleed measure other properties.

Question 17Grout Materials and Mix Design

Which statement about the role of water in a cementitious grout mix is accurate?

  1. Water prevents all shrinkage
  2. Water lubricates the mix and reacts with cement during hydration Correct answer.
  3. Water acts only as a filler and has no chemical role
  4. Water reduces strength at any content

Explanation

Water serves two functions: it provides workability by lubricating particles and it participates chemically in cement hydration. Only water beyond that needed for workability and hydration dilutes the paste and reduces strength. Water does not prevent shrinkage.

Question 18Grout Materials and Mix Design

A grout specification requires a minimum 28-day compressive strength. Which mix change would most reliably raise the expected 28-day strength?

  1. Lowering the water ratio while maintaining workability with an admixture Correct answer.
  2. Increasing the water ratio
  3. Adding more bleed water
  4. Extending the mixing time only

Explanation

Lowering the water ratio reduces porosity and raises strength, and an admixture maintains workability so the mix remains placeable. Adding water or bleed water dilutes the paste and lowers strength, and mixing time alone does not reliably raise strength.

Question 19Grout Materials and Mix Design

Which pozzolanic material reacts with calcium hydroxide to form additional cementitious compounds in a grout mix?

  1. Portland cement
  2. Ground granulated blast-furnace slag
  3. Silica fume Correct answer.
  4. Calcium chloride

Explanation

Silica fume is a highly reactive pozzolan that consumes calcium hydroxide to form calcium silicate hydrate, refining the pore structure. Portland cement is the primary binder, calcium chloride is an accelerator, and slag is a latent hydraulic material rather than a classic pozzolan.

Question 20Grout Materials and Mix Design

A grout is placed in a deep, confined anchor hole where complete filling is critical. Which mix characteristic matters most for achieving full encapsulation?

  1. High early stiffness
  2. Low flowability
  3. High fluidity with low bleed Correct answer.
  4. High air content

Explanation

Complete filling of a confined space requires high fluidity so the grout reaches all voids and low bleed so water does not collect and create gaps. High stiffness or low flow prevents filling, and high air content introduces voids.

Question 21Grout Materials and Mix Design

Two grout mixes have the same water ratio, but one includes a viscosity-modifying admixture. What is the most likely observable difference during placement?

  1. The modified mix will have higher air content by definition
  2. The modified mix will resist segregation and hold solids in suspension Correct answer.
  3. The modified mix will segregate more readily
  4. The modified mix will set faster

Explanation

Viscosity-modifying admixtures increase the mix's ability to hold particles in suspension, reducing segregation and bleeding at the same water ratio. They do not inherently change set time or air content. They reduce, rather than increase, segregation.

Question 22Grout Materials and Mix Design

A grout mix is proportioned with a high water ratio to maximize flow. What is the most likely combined consequence for the hardened grout?

  1. Higher strength and higher permeability
  2. Lower strength and lower permeability
  3. Higher strength and lower permeability
  4. Lower strength and higher permeability Correct answer.

Explanation

Excess water increases porosity in the hardened paste, which lowers compressive strength and raises permeability. Strength and permeability move in opposite directions relative to water content. The other combinations contradict this relationship.

Question 23Grout Materials and Mix Design

An engineer must choose between a neat cement grout and a sanded grout for filling a wide, unconfined void where shrinkage control is important. Which choice is most appropriate and why?

  1. Sanded grout, because fine aggregate reduces shrinkage and adds body Correct answer.
  2. Neat grout, because aggregate increases shrinkage
  3. Neat grout, because it shrinks less than sanded grout
  4. Either is equivalent because aggregate has no effect on shrinkage

Explanation

Fine aggregate in sanded grout restrains volume change and reduces shrinkage while adding body for wider placements. Neat grout tends to shrink more and is better suited to narrow, confined spaces. Aggregate does influence shrinkage, so the two are not equivalent.

Question 24Grout Materials and Mix Design

A grout batch is mixed and found to have a flow-cone time far above the specified maximum, yet the water ratio is correct. Which factor is the most plausible cause that should be investigated first?

  1. The bleed rate is too low
  2. The grout has been over-retarded
  3. The cementitious materials have partially hydrated or the admixture dose is too low Correct answer.
  4. The unit weight is too high

Explanation

Excessive flow time at a correct water ratio suggests the paste has stiffened from premature hydration or that the water-reducing admixture dose is insufficient. Over-retardation would tend to keep the mix fluid longer, not stiffen it. Unit weight and low bleed do not explain high flow time.

Question 25Grout Materials and Mix Design

Which statement best explains why a low water ratio alone does not guarantee high strength in a grout mix?

  1. Water ratio has no effect on strength
  2. Strength is determined solely by aggregate size
  3. Strength depends only on water content
  4. Insufficient water can prevent full hydration and reduce workability, so consolidation matters too Correct answer.

Explanation

A very low water ratio can leave cement unhydrated and make the mix too stiff to consolidate, trapping voids that reduce strength. Strength therefore depends on both the water ratio and adequate compaction and curing. Water ratio clearly affects strength, and aggregate size is not the sole determinant.

Question 26Grout Materials and Mix Design

Which property of a cementitious grout is most directly improved by lowering its water-to-cementitious-materials ratio?

  1. Setting time
  2. Permeability
  3. Bleeding rate
  4. Compressive strength Correct answer.

Explanation

A lower water-to-cementitious-materials ratio reduces the capillary porosity of the hardened paste, which increases compressive strength. While bleeding and permeability may also be reduced, the most direct and reliable improvement is in strength.

Question 27Grout Materials and Mix Design

Which material is commonly used as a mineral filler in grout to reduce cost and improve dimensional stability?

  1. Fly ash
  2. Limestone powder Correct answer.
  3. Hydrated lime
  4. Silica fume

Explanation

Limestone powder is often added as an inert filler to increase yield and reduce shrinkage, without significantly altering the cementitious reactions. It is not a pozzolan and does not contribute to strength development.

Question 28Grout Materials and Mix Design

What is the primary function of a superplasticizer in a grout mix?

  1. To compensate for shrinkage
  2. To accelerate setting time
  3. To entrain air for freeze-thaw resistance
  4. To reduce water demand while maintaining flow Correct answer.

Explanation

Superplasticizers are high-range water reducers that disperse cement particles, allowing the grout to achieve a given flow at a lower water content. This enables lower water-to-cementitious-materials ratios and higher strength.

Question 29Grout Materials and Mix Design

Which type of grout is typically used to fill the annular space between a tunnel lining and the surrounding ground?

  1. Neat cement grout
  2. Sanded cementitious grout Correct answer.
  3. Bentonite grout
  4. Chemical grout

Explanation

Sanded cementitious grouts are commonly used for annular void filling because the sand provides bulk and reduces shrinkage, while the cementitious binder provides strength and cohesion. Neat cement grout is more prone to shrinkage and is less economical for large volumes.

Question 30Grout Materials and Mix Design

A grout mix contains 50 kg of cement, 50 kg of fly ash, and 25 kg of water. What is the water-to-cementitious-materials ratio by mass?

  1. 0.25 Correct answer.
  2. 0.50
  3. 0.33
  4. 0.20

Explanation

The water-to-cementitious-materials ratio is the mass of water divided by the total mass of cementitious materials (cement plus fly ash). Here, water = 25 kg, cementitious materials = 50 + 50 = 100 kg, so the ratio is 25/100 = 0.25.

Question 31Grout Materials and Mix Design

Which test method is commonly used to evaluate the flowability of a cementitious grout in the field?

  1. Slump test
  2. Flow cone test Correct answer.
  3. Compression test
  4. Vicat test

Explanation

The flow cone test measures the time for a given volume of grout to flow through a standard cone, providing an indication of fluidity and consistency. It is specifically suited to grouts, which are often too fluid for the slump test.

Question 32Grout Materials and Mix Design

Which constituent of a cementitious grout mix primarily contributes to early-age strength development?

  1. Silica fume
  2. Portland cement Correct answer.
  3. Limestone powder
  4. Fly ash

Explanation

Portland cement reacts relatively quickly with water to form calcium silicate hydrates, which are responsible for early strength gain. Supplementary cementitious materials like fly ash and silica fume contribute more to later-age strength.

Question 33Grout Materials and Mix Design

A grout is specified to have a minimum 28-day compressive strength of 35 MPa. Which change to the mix design is most likely to achieve this without adversely affecting other properties?

  1. Increase the water-to-cementitious-materials ratio
  2. Increase the cement content while maintaining the water-to-cementitious-materials ratio Correct answer.
  3. Replace a portion of cement with fly ash without adjusting the water content
  4. Add more sand while keeping the cement content constant

Explanation

Increasing the cement content while holding the water-to-cementitious-materials ratio constant increases the amount of cementitious binder, which generally raises strength. Other options either reduce strength or have uncertain effects.

Question 34Grout Materials and Mix Design

Which of the following is a typical function of bentonite in a grout mix?

  1. To increase compressive strength
  2. To improve stability and reduce bleed Correct answer.
  3. To entrain air
  4. To accelerate setting time

Explanation

Bentonite is a thixotropic clay that absorbs water and swells, increasing the viscosity and stability of the grout, which helps prevent bleeding and segregation. It does not significantly contribute to strength or setting.

Question 35Grout Materials and Mix Design

In a grout mix design, what is the primary purpose of adding a shrinkage-compensating admixture?

  1. To offset the volume reduction that occurs as the grout cures Correct answer.
  2. To increase the flowability of the grout
  3. To improve freeze-thaw resistance
  4. To accelerate the setting time

Explanation

Shrinkage-compensating admixtures expand slightly during curing to counteract the shrinkage of the grout, reducing the risk of cracking and improving bond. They do not primarily affect flowability, setting time, or freeze-thaw resistance.

Question 36Grout Materials and Mix Design

A grout mix has a water-to-cementitious-materials ratio of 0.40 and contains 10% silica fume by mass of cementitious materials. Which property is most likely to be enhanced compared to a mix without silica fume?

  1. Bleeding
  2. Permeability Correct answer.
  3. Density
  4. Workability

Explanation

Silica fume particles fill the voids between cement grains and react pozzolanically to refine the pore structure, significantly reducing permeability. It typically reduces workability and bleeding rather than enhancing them.

Question 37Grout Materials and Mix Design

Which statement about the use of recycled concrete aggregate (RCA) as a filler in grout is accurate?

  1. RCA has lower water absorption than natural sand.
  2. RCA always improves the compressive strength of grout.
  3. RCA is not permitted in any grout applications.
  4. RCA can increase the water demand of the grout due to its porosity. Correct answer.

Explanation

Recycled concrete aggregate is more porous than natural sand and therefore absorbs more water, which can increase the water demand of the grout mix. This must be accounted for in mix design to maintain the desired water-to-cementitious-materials ratio.

Question 38Grout Materials and Mix Design

A grout mix is being designed for a project requiring high early strength. Which adjustment is most appropriate?

  1. Add a retarder
  2. Increase the water-to-cementitious-materials ratio
  3. Increase the fly ash content
  4. Use a Type III cement Correct answer.

Explanation

Type III cement is a high-early-strength cement that is ground finer than Type I, leading to faster hydration and higher early strength. Increasing fly ash or water ratio, or adding a retarder, would delay strength development.

Question 39Grout Materials and Mix Design

Which of the following best explains why the water-to-cementitious-materials ratio is a key parameter in grout mix design?

  1. It sets the maximum aggregate size.
  2. It dictates the type of mixing equipment required.
  3. It determines the color of the hardened grout.
  4. It controls the balance between workability and strength. Correct answer.

Explanation

The water-to-cementitious-materials ratio directly affects both the fresh workability and the hardened strength and durability of the grout. A higher ratio increases flow but reduces strength and increases permeability.

Question 40Grout Materials and Mix Design

A grout mix contains 400 kg of cement, 100 kg of fly ash, and 200 kg of water. If the fly ash has a reactivity that contributes to strength at 28 days, what is the effective water-to-cementitious-materials ratio?

  1. 0.40 Correct answer.
  2. 0.44
  3. 0.50
  4. 0.57

Explanation

The effective water-to-cementitious-materials ratio includes all cementitious materials (cement + fly ash). Total cementitious = 400 + 100 = 500 kg. Water = 200 kg. Ratio = 200/500 = 0.40. The reactivity of fly ash does not change the mass-based ratio.

Question 41Substrate Preparation and Surface Conditions

Before placing grout, a concrete substrate that has been power-troweled to a hard, glassy finish should generally be treated by which method?

  1. Sealing to lock in the finish
  2. Applying a bond breaker
  3. Scarifying or grinding to open the surface Correct answer.
  4. Wet-sponging to soften the surface

Explanation

A dense, trowel-burnished surface resists grout penetration and bonding, so mechanical abrasion such as scarifying or grinding is used to open the pores and expose sound aggregate. Chemical or water treatments do not remove the glazed layer.

Question 42Substrate Preparation and Surface Conditions

A concrete slab is being prepared for grout. What does the term 'sound substrate' most nearly mean?

  1. The slab has fully cured for at least one year
  2. The concrete is free of loose, weak, or delaminated material Correct answer.
  3. The surface is damp to the touch
  4. The concrete has been painted a uniform color

Explanation

A sound substrate is structurally intact, with no loose, crumbling, or hollow material that could detach and take the grout with it. Soundness is about integrity, not moisture, color, or age.

Question 43Substrate Preparation and Surface Conditions

Which surface condition must be removed before grout can develop a reliable bond?

  1. Dust, oil, and curing compound residue Correct answer.
  2. A properly saturated surface-dry condition
  3. A light, uniform concrete texture
  4. A slightly roughened profile

Explanation

Contaminants such as dust, oil, grease, and curing compound form a barrier between grout and substrate and must be removed. A rough, clean, properly moistened surface is desirable, not a defect.

Question 44Substrate Preparation and Surface Conditions

What is the purpose of achieving a saturated surface-dry (SSD) condition on a concrete substrate prior to grouting?

  1. To prevent the substrate from drawing mix water out of the grout Correct answer.
  2. To speed up the curing of the grout
  3. To make the concrete easier to sand
  4. To keep the grout from sticking to the concrete

Explanation

A dry, absorbent substrate can pull water from fresh grout, leaving it stiff and weak near the interface. Saturating the pores first and removing standing water gives a stable moisture balance.

Question 45Substrate Preparation and Surface Conditions

A substrate has a visible film of form-release oil on its surface. Which action is appropriate before grouting?

  1. Wet the surface until the oil floats away
  2. Cover the oil with a thin layer of sand
  3. Remove the oil with an appropriate degreaser and rinse Correct answer.
  4. Proceed, since grout bonds through thin films

Explanation

Form-release agents are bond breakers by design and must be chemically removed and rinsed so no residue remains. Simple wetting or covering does not eliminate the contaminant.

Question 46Substrate Preparation and Surface Conditions

Why is it important to remove laitance from a new concrete surface before grouting?

  1. It is too rough and creates voids
  2. It is too hard and dulls grinding tools
  3. It is radioactive and hazardous
  4. It is a weak, porous layer that prevents a strong bond Correct answer.

Explanation

Laitance is a thin layer of weak, cement-rich fines that rises to the surface during placement; it has low strength and must be removed to reach sound concrete. Leaving it in place gives the grout a weak layer to bond to.

Question 47Substrate Preparation and Surface Conditions

What is the recommended surface texture for a concrete substrate receiving grout?

  1. Smooth with visible trowel marks
  2. Covered with a thin layer of dust
  3. Rough and open, like medium-grit sandpaper Correct answer.
  4. Polished and glassy

Explanation

An open, roughened profile provides mechanical keying so the grout can grip the substrate. Glassy or dusty surfaces offer little mechanical interlock.

Question 48Substrate Preparation and Surface Conditions

Which tool is commonly used to mechanically prepare a large concrete floor for grouting?

  1. A hand trowel
  2. A wet mop
  3. A paint roller
  4. Diamond grinding or shot blasting equipment Correct answer.

Explanation

Diamond grinders and shot blasters are standard mechanical preparation tools that remove laitance and contaminants and create profile. Hand tools, rollers, and mops do not achieve this.

Question 49Substrate Preparation and Surface Conditions

After mechanical preparation, a concrete surface is swept but still has fine dust. What should be done before grouting?

  1. Grout immediately to save time
  2. Dampen the dust so it becomes part of the mix
  3. Blow the dust into the corners
  4. Vacuum the surface thoroughly and confirm it is clean Correct answer.

Explanation

Fine dust left on the surface acts as a bond breaker, so it must be removed, typically by vacuuming. Simply wetting it or moving it around leaves contamination in the bond zone.

Question 50Substrate Preparation and Surface Conditions

A technician is preparing a substrate that will receive a cementitious grout. The concrete is very dry and absorbent. Which sequence best protects the grout?

  1. Grout dry, then mist the surface afterward
  2. Pre-wet until puddles remain, then grout
  3. Pre-wet to SSD, remove standing water, then grout Correct answer.
  4. Apply a sealer first, then grout

Explanation

Pre-wetting to SSD keeps the substrate from stealing mix water, while removing standing water prevents dilution of the grout. Grouting dry or leaving puddles both harm the water balance.